ArticlePDF Available

Late Ordovician biostratigraphy of the northern Rockley–Gulgong Volcanic Belt, and Ordovician stratigraphy of the northern Molong Volcanic Belt - new facts and figures.

February 1999

February 1999
108:1-7, 8-27

Authors:

Geological Survey of New South Wales

Previously published age determinations for Ordovician formations in the Sofala–Mudgee– Gulgong–Dunedoo region have, with rare exceptions (a record of late Darriwilian conodonts, and identifications of Bolindian graptolites), supported deposition of these strata largely in the Gisbornian. Revision of a conodont fauna from the Sofala Volcanics has led to recognition of diagnostic late Eastonian species, in agreement with the age of associated corals. Similar conodont and coral faunas from the Tucklan Formation, and from allochthonous limestones within the Burranah Formation, suggest the main episode of Late Ordovician sedimentation in the northern Rockley–Gulgong Volcanic Belt was younger than previously believed. There is a high degree of similarity between these faunas and those from limestones in the basal Malongulli Formation of the Molong Volcanic Belt to the west.

b N.S.W.

…

Geological map of the " Wahringa " area, 26-28 km south of Wellington (mapping by Ian Percival and Martin Scott) (for location see pages 14-15).

…

Diagrammatic stratigraphic column for the Ordovician succession west of the Neurea Fault at "Wahringa", showing occurrences of significant fossils.

…

Figures - uploaded by Ian G. Percival

Content may be subject to copyright.

Content uploaded by Ian G. Percival

Content may be subject to copyright.

Late Ordovician biostratigraphy of the

northern Rockley–Gulgong Volcanic Belt

Ian G. Percival

ABSTRACT

Previously published age determinations for Ordovician formations in the Sofala–Mudgee–

Gulgong–Dunedoo region have, with rare exceptions (a record of late Darriwilian conodonts,

and identifications of Bolindian graptolites), supported deposition of these strata largely in the

Gisbornian. Revision of a conodont fauna from the Sofala Volcanics has led to recognition of

diagnostic late Eastonian species, in agreement with the age of associated corals. Similar

conodont and coral faunas from the Tucklan Formation, and from allochthonous limestones

within the Burranah Formation, suggest the main episode of Late Ordovician sedimentation in

the northern Rockley–Gulgong Volcanic Belt was younger than previously believed. There is a

high degree of similarity between these faunas and those from limestones in the basal

Malongulli Formation of the Molong Volcanic Belt to the west.

Keywords:

Late Ordovician, conodonts, corals, Rockley–Gulgong Volcanic Belt, Sofala

Volcanics, Tucklan Formation, Burranah Formation

INTRODUCTION

The first indication of the presence of Late

Ordovician strata in the northern Rockley–Gulgong

Volcanic Belt (figure 1) was provided by the

occurrence of poorly preserved graptolites in the

lower or middle part of the Sofala Volcanics. These

were identified by Packham (1968, 1969) as being

comparable with

Glyptograptus teretiusculus

which suggested an age at least as old as Gisbornian

(early Late Ordovician). Pickett (1978) confirmed

his age determination with recognition of conodonts

(discussed below), the alga

Vermiporella

V. canadensis

, and tabulate coral

Plasmoporella

in limestones within the Sofala Volcanics,

supposedly from very near to the top of the

formation. A similar macrofossil assemblage was

obtained from limestones in the upper part of the

Cudgegong Volcanics (now equated with the Sofala

Volcanics) by Pickett (1982). The stratigraphic

context of this sample was discussed by Pemberton

(1989). The underlying ‘Lue beds’, now Adaminaby

Group (Colquhoun et al 1997), which represent a

deepwater turbidite facies, include chert from

which Stewart and Fergusson (1995) identified the

conodont

Pygodus serra

in thin sections. They

concluded that the age of this horizon was most

likely late Darriwilian (Da3-Da4), or latest Middle

Ordovician.

Remapping of the Dubbo 1:250 000 map sheet

(Morgan et al 1999) by the Geological Survey of

New South Wales and the Australian Geological

Survey Organisation has resulted in the revision of

ages of some strata previously mapped as Devonian

on the first edition of the map (Offenberg et al 1971).

Allochthonous limestones in the Burranah Formation

yielded

Plasmoporella

and

Vermiporella

, the former

indicative of the Late Ordovician (Pickett 1995).

This paper revises the previous dating of the upper

Sofala Volcanics, now recognised as including late

Eastonian (middle Late Ordovician) clasts, and

documents a conodont fauna of Eastonian age

recovered from the Burranah Formation and the

Tucklan Formation. A biostratigraphic synthesis

incorporating these results is presented (figure 2),

with suggested correlations to strata on the Molong

Volcanic Belt to the west.

REVISION OF CONODONT FAUNA FROM THE

SOFALA VOLCANICS

The original determinations of conodonts from a

sample of the Sofala Volcanics (Pickett 1978)

were made prior to the advent of multielement

terminology. Of the elements he illustrated, the

form-species

Eobelodina occidentalis

(Pickett 1978,

cover photograph 1 and 2) is (as Pickett surmised)

the eobelodiniform element attributable to the same

Belodina

apparatus to which the grandiform element

(Pickett 1978, cover photograph 7 and 8) belongs.

Panderodus compressus

, illustrated by Pickett

(1978, cover photograph 5 and 6) remains a valid

species. Of greatest biostratigraphic significance

is the occurrence of the late Eastonian index

Taoqupognathus tumidus

(Pickett 1978, cover

photograph fig 4, referred to as gen. unident; see

No 108

NEW SOUTH WALES

February 1999

Quarterly Notes 108, 1999

also figure 3.5 herein), which Zhen and

Webby (1995) recognised as suggesting

a younger age than was interpreted by

Pickett (1978).

Four samples in the Geological Survey

Micropalaeontological Collection (C012,

C014, C015 and C033) contain residues

from the same location (Surface Hill,

6 km southwest of Sofala; Figure 1b) as

Pickett’s (1978) illustrated conodonts. All

samples were taken from allochthonous

limestone blocks within an agglomerate.

The last of these residues was prepared

about a year after Pickett’s (1978) paper

appeared, and contains a more diverse

and relatively abundant suite of conodont

elements, identified and illustrated below

(figure 3).

Conodont sample C033

(figure 3.1-3.3, 3.6-3.10)

GR 751958E 6332329N Sofala 1:50 000

map

Conodonta

Belodina confluens

Sweet, 1979

Belodina

sp F Trotter & Webby, 1995

Panderodus

Phragmodus

Plectodina

Scabbardella

Taoqupognathus tumidus

Trotter &

Webby, 1995

Yaoxianognathus

This fauna is unquestionably late

Eastonian (Ea3) in age, as indicated

by the occurrence of

Taoqupognathus

tumidus

, first described from (and

apparently otherwise restricted to) the

lower Malongulli Formation in the

Cliefden Caves area, south of Orange,

by Trotter and Webby (1995). Most of

the other genera in sample C033 are

also present in the Malongulli Formation.

Pickett (1978) based his Gisbornian

age determination on identification of

Belodina monitorensis

Ethington &

Schumacher 1969 and correlations with

the North American succession in which

this species occurs. The element

illustrated by Pickett as

B. monitorensis

has the stout appearance of that species,

with a strong costa paralleling the

Figure 1. Locality map showing sample sites

and distribution of Late Ordovician

rock units on the northern Rockley–

Gulgong Volcanic Belt, based on

Raymond et al (1998) and Morgan

et al (1999).

Turon

River

23086

Sofala

Wattle Flat

Bathurst

Gulgong

Mudgee

Dunedoo

REFERENCE

Town, Village

Roads

Limestone clast

Fossil locality

CAINOZOIC

Alluvium

Basalt

Undifferentiated

TRIASSIC

PERMIAN

Intrusions

CARBONIFEROUS

sedimentary rocks

Undifferentiated

sedimentary rocks

Undifferentiated

DEVONIAN

Mafic intrusions

sedimentary rocks

Undifferentiated

SILURIAN

ORDOVICIAN

Tucklan Formation

Burranah Formation

Sofala Volcanics

SYDNEY

33° 10’

149° 50’

149° 40’

33° 00’

32° 05’

32° 10’

32° 20’

32° 15’

5 km0

Fig 1a

Fig 1b

N.S.W.

(in limestone clast)

C1500

C1420

C1421

C1462

C1467

C1459

C033

32° 30’

149° 20’

(a)

(b)

C015

149° 30’

Quarterly Notes 108, 1999

anterolateral margin. However, as

Zhen and Webby (1995) found with

the younger species

B. confluens

, the

local range does not entirely agree

with that in North America. Trotter

and Webby (1995) discussed and

illustrated a species from the lower

Malongulli Formation (late Eastonian)

which they informally referred to

. sp F, while noting its similarity

to the eobelodiniform element of

B. monitorensis

. The same species

occurs in the Sofala Volcanics, as well

as in the Burranah Formation samples

discussed below.

This reassessment of the conodont

fauna agrees with age implications of

the presence of the coral

Plasmoporella

at the same horizon in the upper Sofala

Volcanics. This coral is representative

of Webby’s (1969) coral/stromatoporoid

Fauna III, also of late Eastonian age.

Hence the Sofala Volcanics (at the

Surface Hill locality, at least) appears

not to extend into the latest stage

(Bolindian) of the Late Ordovician,

unless the age of the matrix enclosing

the allochthonous limestone clasts is

substantially younger than the clasts

themselves. This is a possibility, given

that poorly preserved late Bolindian

(Bo3) graptolites have been identified

by A.H.M. VandenBerg (in Rickards et

al 1998) from within the Sofala

Volcanics at a locality (GR 756500E

6373600N, Broombee 1:25 000 map)

near Windamere Dam, southeast of

Mudgee. Unfortunately, the stratigraphic

level of this graptolite assemblage is

unknown.

NEW MICROFAUNAS FROM THE

BURRANAH FORMATION

Three samples from the Burranah

Formation in the Mudgee region, details

of which are given below, produced

low yields of conodont elements which

had been subject to varying degrees

of geothermal heating. However, the

presence of age-diagnostic species

enabled useful conclusions to be

reached. Sample C1420 is from a

limestone occurring as allochthonous

blocks in volcaniclastic conglomerate.

Hence (as with the Sofala Volcanics

sample) the age of deposition of the

matrix may be either contemporaneous

with the age of the conodont fauna, or

somewhat younger. The stratigraphic

context of the other samples is not

known.

Conodont Sample C1420

(figure 3.20-3.22)

GR 739220E 6395930N Mudgee

1:50 000 map

Conodonta

Belodina confluens

Sweet, 1979

Belodina hillae

Savage, 1990

Belodina

B. monitorensis

Ethington

& Schumacher, 1969

Drepanoistodus

sp cf

D. suberectus

(Branson & Mehl, 1933)

Oistodus

sp cf

O. venustus

Stauffer,

1935

Panderodus

Most species identified in sample

C1420 are long-ranging. However,

Belodina hillae

is only known from

the early Eastonian Cliefden Caves

Limestone Subgroup in the Molong

Volcanic Belt. One very large fragment,

referred to

Belodina

B. monitorensis

due to its robust appearance, could

also be closely related to

. sp F of

Trotter and Webby (1995) from the

late Eastonian Malongulli Formation.

Figure 2. Late Ordovician stratigraphic framework, northern Rockley–Gulgong Volcanic Belt, with

suggested correlations to formations on the Molong Volcanic Belt. Note that the left-hand

stratigraphic column is composite; the Fairbridge Volcanics is overlain in the northern MVB

by the Reedy Creek Limestone (correlative of the Cliefden Caves Limestone Subgroup) and

the Cheesemans Creek Formation (Malongulli Formation equivalent), but palaeontological

similarity is greater between the Malongulli Formation and strata on the Rockley–Gulgong

Volcanic Belt.

Cliefden Caves

Limestone Subgroup

Yuranigh Limestone Member

Wahringa Limestone Member

23088

ORDOVICIAN

MIDDLE LATE

SILURIAN

Da1

Da2

Da3

Da4

Gi1

Gi2

Ea1

Ea2

Ea3

Ea4

Bo1

Bo2

Bo3

Bo4

Bo5

Malongulli Formation

Angullong Formation

FAIRBRIDGE VOLCANICS

SOFALA VOLCANICS

MOLONG

VOLCANIC BELT VOLCANIC BELT

ROCKLEY – GULGONG

Adaminaby Group

(formerly ‘Lue Beds’)

Tucklan Formation

(and allochthonous

limestone in

Burranah formation)

Quarterly Notes 108, 1999

31 30

29 28 27

123

910

Quarterly Notes 108, 1999

Conodont Sample C1421

(figure 3.15-3.17, 3.19)

GR 739260E 6397100N Mudgee

1:50 000 map

Conodonta

Belodina confluens

Sweet, 1979

Belodina

hillae

Savage, 1990

Belodina

B. monitorensis

Ethington

& Schumacher, 1969

Belodina

sp E Trotter & Webby, 1995

Panderodus

Yaoxianognathus

sp nov

None of the conodont elements

recovered from the above sample is

indicative of more than a generalised

Late Ordovician age.

Belodina

B. monitorensis

could well be

conspecific with

. sp E, described

from the late Eastonian Malongulli

Formation (Trotter & Webby 1995).

The fauna is very similar to that from

sample C1420, but has been subject to

much higher temperatures and greater

deformation.

Conodont Sample C1500

(figure 3.11-3.14, 3.18)

GR 736270E 6397140N Mudgee

1:50 000 map

Conodonta

Belodina

sp cf

B. monitorensis

Ethington & Schumacher, 1969

Drepanoistodus

Panderodus gracilis

(Branson & Mehl,

1933)

Taoqupognathus

Yaoxianognathus

The high Conodont Alteration Index

(CAI greater than 5, indicated by the

black colour of elements in C1500) is

most like the assemblage in C1421, and

suggests a comparable thermal history

for these two samples. The presence

Taoqupognathus

(in particular the

diagnostic Sc3 element, although

incomplete) indicates that the age of

sample C1500 is Eastonian, based on

the occurrence of three species of this

genus on the Molong Volcanic Belt

(Savage 1990; Trotter & Webby 1995;

Zhen & Webby 1995).

NEW MICROFAUNAS FROM THE

TUCKLAN FORMATION

Three samples from the Tucklan

Formation south of the Dunedoo

area were analysed for microfossils.

Of these, two contained

biostratigraphically useful faunas.

The aspect of both the conodont

assemblages and the associated

brachiopod fauna is strongly

reminiscent of the Late Ordovician

(late Eastonian to early Bolindian)

Malongulli Formation of the Molong

Volcanic Belt.

Conodont Sample C1459

(figure 3.23-3.29)

GR 724681E 6445350N Dunedoo

1:50 000 map

Conodonta

Belodina confluens

Sweet, 1979

Drepanoistodus

suberectus

(Branson & Mehl, 1933)

Panderodus

Taoqupognathus

Yaoxianognathus

Y. wrighti

Savage,

1990

Yaoxianognathus

Brachiopoda

acrotretide pedicle valve

(cf ?

Hisingerella

)

Orbiculoidea

new genus of ?craniopsid

The most diagnostic conodont in the

above fauna is

Taoqupognathus

, but

unfortunately the sole specimen is

embedded in a flake of insoluble

matrix which obscures the critical

morphological distinction between the

older

T. philipi

(Ea1 age),

T. blandus

(Ea2 age) and the younger

T. tumidus

(Ea3 age). Although

Yaoxianognathus

wrighti

is restricted to Ea1 and Ea2

strata on the Molong Volcanic Belt, the

genus is now known to range into Ea3.

The presence of the new ?craniopsid

genus is especially interesting. This

undescribed brachiopod was previously

known only from the lower part of

the Malongulli Formation and its

equivalents along the Molong Volcanic

Belt (Percival, unpublished data). The

age range indicated for sample C1459

is therefore most likely late Eastonian

(Ea3).

Conodont Sample C1462

(figure 3.30-3.31)

GR 730300E 6425100N Goolma

1:50 000 map

Conodonta

Taoqupognathus

Panderodus

The conodont yield from this sample

was meagre and poorly preserved, but

fortunately included a single element

Taoqupognathus

. Either an early

Eastonian (Ea2) or late Eastonian (Ea3)

age is indicated for sample C1462,

based on

T. blandus

studied by Zhen

and Webby (1995) from the Cliefden

Caves Limestone Subgroup of the

southern Molong Volcanic Belt, and

T. tumidus

described by Trotter and

Webby (1995) from the overlying

Malongulli Formation.

Figure 3. Representative Late Ordovician conodonts from the Sofala Volcanics (3.1-3.10), Burranah Formation (3.11-3.22) and Tucklan

Formation (3.23-3.31).

3.1

Taoqupognathus tumidus

, Sc3 element, x90; 3.2

Taoqupognathus tumidus

, ?Sc element, x60; 3.3

Yaoxianognathus

sp,

Pa element, x90; 3.4 ?

Phragmodus

sp, x110; 3.5

Taoqupognathus tumidus

, P element, x90; 3.6

Belodina

sp F Trotter & Webby

1995, compressiform element, x 50; 3.7

Belodina confluens

, compressiform element, x 50; 3.8

Belodina confluens

eobelodiniform element, x90; 3.9 ?

Plectodina

sp, x90; 3.10

Plectodina

sp, Sc element, x110. 3.4-3.5 from conodont sample

C0015; all others from conodont sample C0033.

3.11

Belodina

B. monitorensis

, compressiform element, x60; 3.12

Belodina

B. monitorensis

, x90; 3.13

Belodina

B. monitorensis

, eobelodiniform element, x90; 3.14

Panderodus gracilis

, x60; 3.15

Yaoxianognathus

sp nov, x90;

3.16

Belodina

sp E Trotter & Webby 1995, compressiform element, x90; 3.17

Belodina

B. monitorensis

, ?compressiform

element, x60; 3.18 ?

Yaoxianognathus

sp, x45; 3.19

Belodina ?hillae

, x60; 3.20

Belodina hillae

, compressiform element x60;

3.21

Belodina hillae

, grandiform element, x90; 3.22

Belodina

B. monitorensis

, x90. 3.11-3.14 and 3.18 from conodont

sample C1500; 3.15-3.17 and 3.19 from conodont sample C1421; 3.20-3.22 from conodont sample C1420.

3.23 ?

Yaoxianognathus

sp, P element, x60; 3.24

Yaoxianognathus

Y. wrighti

, x60; 3.25

Drepanoistodus

suberectus

, x60;

3.26

Taoqupognathus

sp, x80; 3.27

Yaoxianognathus

Y. wrighti

, P element, x60; 3.28

Belodina confluens

, grandiform

element?, x40; 3.29

Belodina confluens

, x60; 3.30

Panderodus

sp, x45; 3.31

Taoqupognathus

sp, Sc element, x100. Last two

specimens from C1462; 3.23-3.29 from C1459.

▲

Quarterly Notes 108, 1999

Conodont Sample C1467

GR 730800E 6425200N Goolma

1:50 000 map

Conodonta

2 indeterminate coniform elements

The more complete conodont element

in the above sample is laterally

compressed and has a deep continuous

furrow down its inner side, with a

posteriorly extended heel. There is

insufficient material to be certain

of the identification — it could either

be a species of

Panderodus

such as

P. panderi

, or alternatively is referable

Protopanderodus

. Both genera

range through the Middle and Late

Ordovician.

CORAL FAUNAS FROM THE

SOFALA VOLCANICS, BURRANAH

FORMATION AND TUCKLAN

FORMATION

A well-preserved example of

Plasmoporella

from the Sofala

Volcanics (same locality as conodont

sample C033, listed above) was

illustrated by Pickett (1978). Compared

to the

Plasmoporella

illustrated from

the Burranah Formation (Pickett 1995),

the Sofala Volcanics example has

slightly larger cystose dissepiments,

but otherwise appears to be identical.

Burranah Formation

(identifications by John Pickett)

GR 739150E 6396160N Mudgee

1:50 000 map

Coelenterata

Heliolites

sp A

Nyctopora

Plasmoporella

Algae

Vermiporella

Tucklan Formation

One locality in the Tucklan Formation,

from the same site and horizon as

conodont sample C1459 (described

previously), also yielded a coral fauna,

listed below, and illustrated in figure 4.

GR 724681E 6445350N Dunedoo

1:50 000 map

Coelenterata

Heliolites

sp B

Plasmoporella

indeterminate ?heliolitid

indeterminate solitary rugosan

Whereas in typical

Plasmoporella

the

tabulae are distinctly convex, those in

the specimens questionably referred to

the genus from the Tucklan Formation

are only very gently domed to flat or

gently concave; occasionally the tabulae

are axially depressed. In this respect

the species is similar to

Propora

. The

tabularia are narrower and more widely

spaced than in

Plasmoporella

from the

Sofala Volcanics and the Burranah

Formation.

There are also differences in the

Heliolites

in the Burranah Formation,

distinguishing it from that in the

Tucklan Formation. The latter, informally

referred to

Heliolites

sp B, has more

crowded tabulae, and closer transverse

diaphragms crossing the tubuli, than

does

. sp A from the Burranah

Formation (although only a single

longitudinal section is available of this

form).

Despite slight differences noted in

the coral species, there is a general

similarity in faunas (and floras) from

the three formations. The presence of

Plasmoporella

suggests correlation

with Fauna II (Ea2 age) or Fauna III

(Ea3) of the Molong Volcanic Belt

coral/stromatoporoid biozonation.

Heliolites

appeared late in Fauna I (Ea1),

then diversified and became prominent

in Fauna II (Webby & Kruse 1984).

Hence a mid-Eastonian age is

suggested by the coral fauna examined

from the Sofala Volcanics, Burranah

Formation and Tucklan Formation.

SYNTHESIS — REVISED LATE

ORDOVICIAN BIOSTRATIGRAPHY

OF THE NORTHERN ROCKLEY–

GULGONG VOLCANIC BELT

With reassessment of the age of the

Cliefden Caves Limestone Subgroup to

Eastonian rather than Gisbornian (Zhen

& Webby 1995), similarities in coral

and conodont faunas from the northern

Rockley–Gulgong Volcanic Belt imply

a comparable revision. There was

widespread sedimentation in middle to

late Eastonian time over much of the

area from Sofala to Dunedoo, including

the Tucklan Formation to the northwest,

the Burranah Formation in the vicinity

of Gulgong–Mudgee, and the Sofala

Volcanics to the south (figure 1). It is

likely that these formations are lateral

equivalents, at least in part (figure 2).

The unfossiliferous Coomber Formation

in the Botobolar–Lue district east of

Mudgee has been correlated with the

Sofala Volcanics on the basis of similar

radiometric signatures (Fergusson &

Colquhoun 1996) and may also be of

comparable age.

Based on the presence of a faunal

association directly comparable with

that in limestone clasts in the basal

Malongulli Formation (Molong Volcanic

Belt), which were initially deposited on

the slopes of volcanic islands below

the shelf edge, limestones in the

Tucklan Formation were also probably

deposited in relatively deep water. This

Figure 4. Late Ordovician tabulate corals

from the Tucklan Formation.

4.1

Heliolites

sp B, transverse

section, x3.8;

4.2 ?

Plasmoporella

sp, transverse

section, x4.1;

4.3 ?

Plasmoporella

sp,

longitudinal section, x3.8.

All from conodont locality C1459.

4.1

4.2

4.3

Quarterly Notes 108, 1999

faunal similarity between deeper water

deposits on the Molong Volcanic Belt

and Rockley–Gulgong Volcanic Belt

supports the contention of Fergusson

and Colquhoun (1996) that the source

area for the Late Ordovician sediments

of the Sofala Volcanics and Coomber

Formation (and presumably their

correlatives) lay to the west — either

the Molong Volcanic Belt itself, or

intervening volcanic islands (now

covered or eroded).

Limestones in the Burranah Formation

and Sofala Volcanics are definitely

allochthonous, and hence the apparent

ages are maxima. The older age limit

of the Sofala Volcanics remains poorly

constrained by the record of possible

late Darriwilian to Gisbornian graptolites

(Packham 1968). The occurrence of

Pygodus serra

in cherts of the “Lue

beds” (Stewart & Fergusson 1995),

now Adaminaby Group (Colquhoun

et al 1997), provides the sole well-

established age (late Darriwilian) for

the underlying strata (figure 2).

Dating of the remainder of the Sofala

Volcanics is based on proven late

Eastonian conodont and coral faunas

(discussed herein), and a record of

poorly preserved graptolites of probable

late (but not latest) Bolindian age

(Rickards et al 1998). Although

Colquhoun et al (1997) claimed that

this latter sample was taken from well

below the formation top (thus allowing

the possibility that the Sofala Volcanics

spanned the Ordovician–Silurian

boundary), structural complications

and discontinuity of outcrop prevent

the level of the graptolitic horizon from

being precisely known. There is as yet

no conclusive evidence that deposition

on the Rockley–Gulgong Volcanic Belt

continued into the Early Silurian.

ACKNOWLEDGMENTS

I thank John Pickett, Barry Webby and

Dick Glen for their review of this paper,

and Richard Facer for his precision

in editing it. Gary Dargan processed

the conodont samples and prepared

the thin sections. Peter Cockle

photographed the conodonts; Yongyi

Zhen assisted with their identification.

Digital preparation of the conodont

illustrations was done by David Barnes

and Dora Lum. Samples, other than

those collected by John Pickett, were

obtained by members of the Geological

Survey of New South Wales Dubbo

1:250 000 mapping team (John

Watkins, Simone Meakin, Gary

Colquhoun). This is a contribution

to IGCP Project No. 410: The Great

Ordovician Biodiversification Event.

REFERENCES

COLQUHOUN G.P., MEAKIN N.S., KRYNEN J.P.,

WATKINS J.J., YOO E.K., HENDERSON

G.A.M. & JAGODZINSKI E.A. 1997.

Stratigraphy, structure and

mineralisation of the Mudgee

1:100 000 geological map sheet.

Geological Survey of New South

Wales, Quarterly Notes

102, 1-14.

FERGUSSON C.L. & COLQUHOUN G.P. 1996.

Early Palaeozoic quartz turbidite

fan and volcaniclastic apron,

Mudgee district, northeastern

Lachlan Fold Belt, New South

Wales.

Australian Journal of Earth

Sciences

43, 497-507.

OFFENBERG A.C., ROSE D.M. & PACKHAM

G.H. 1971

. Dubbo 1:250 000

geological series sheet SI/55-04

Geological Survey of New South

Wales, Sydney.

MORGAN E.J., CAMERON R.G., COLQUHOUN

G.P., MEAKIN N.S., RAYMOND O.L.,

SCOTT M.M., WATKINS J.J., BARRON

L.M., HENDERSON G.A.M., KRYNEN

J.P., POGSON D.J., WARREN A.Y.E.,

WYBORN D., YOO E.K., GLEN R.A. &

JAGODZINSKI E.A. 1999 in prep.

Dubbo 1:250 000 Geological

Sheet SI/55-4.

(second edition).

Geological Survey of New South

Wales, Sydney/Australian

Geological Survey Organisation,

Canberra.

PACKHAM G.H. 1968. The lower and

middle Palaeozoic stratigraphy

and sedimentary tectonics of

the Sofala–Hill End–Euchareena

region, N.S.W.

Linnean Society of

New South Wales

Proceedings

93, 111-163.

PACKHAM G.H. ed. 1969. The geology of

New South Wales.

Geological

Society of Australia

Journal

16,

1-654.

PEMBERTON J.W. 1989. The Ordovician-

Silurian stratigraphy of the

Cudgegong-Mudgee district, New

South Wales.

Linnean Society of

New South Wales

Proceedings

111, 169-200.

PICKETT J. 1978. Further evidence for

the age of the Sofala Volcanics.

Geological Survey of New South

Wales

Quarterly Notes

31, 1-4.

PICKETT J.W. 1982. Preliminary report

on conodont samples from the

Cudgegong area. Palaeontological

Report 82/10. Geological Survey

of New South Wales, Report

GS1982/197 (unpublished)

PICKETT J.W. 1995. Fossils make a

prospective link.

Minfo, New

South Wales Mining and

Exploration Quarterly

No. 49, 53.

RAYMOND O.L., POGSON D.J., et al [14

others] 1998.

Bathurst

1:250 000 Geological Sheet

SI/55-8.

(second edition).

Geological Survey of New

South Wales, Sydney/Australian

Geological Survey Organisation,

Canberra.

RICKARDS R.B., WRIGHT A.J. & PEMBERTON

J.W. 1998. Graptolite evidence for

the ages of the Sofala Volcanics

and Willow Glen Formation,

northern Capertee High, N.S.W.

Alcheringa

22, 223-230.

SAVAGE N.M. 1990. Conodonts of

Caradocian (Late Ordovician)

age from the Cliefden Caves

Limestone, southeastern

Australia.

Journal of Paleontology

64, 821-831.

STEWART I.R. & FERGUSSON C.L. 1995.

Ordovician conodonts from the

Lue Beds, Mudgee and Sunlight

Creek Formation, Goulburn, New

South Wales. p.164

Jell P.A. ed.

APC 94: Papers from the First

Australian Palaeontological

Convention.

Australasian

Association of Palaeontologists

Memoir

18.

TROTTER J.A. & WEBBY B.D. 1995. Upper

Ordovician conodonts from the

Malongulli Formation, Cliefden

Caves area, central New South

Wales.

AGSO Journal of Australian

Geology & Geophysics

15 (for

1994), 475-499.

WEBBY B.D. 1969. Ordovician

stromatoporoids from New

South Wales.

Palaeontology

12,

637-662.

WEBBY B.D. & KRUSE P.D. 1984. The

earliest heliolitines: a diverse

fauna from the Ordovician of New

South Wales.

Palaeontographica

Americana

54, 164-168.

ZHEN Y.Y. & WEBBY B.D. 1995. Upper

Ordovician conodonts from

the Cliefden Caves Limestone

Group, central New South

Wales, Australia.

Courier

Forschungsinstitut Senckenberg

182, 265-305.

Quarterly Notes 108, 1999

Ordovician stratigraphy of the northern Molong Volcanic Belt:

new facts and figures

Ian G. Percival, Elisabeth J. Morgan and Martin M. Scott

ABSTRACT

The oldest fossiliferous strata in the northern Molong Volcanic Belt of central New South Wales, overlying

the volcanogenic Mitchell Formation, are limestones and graptolitic beds in the Hensleigh Siltstone of early

Bendigonian (Early Ordovician) age. A significant time-break spanning approximately 15-20 Ma separates the

Hensleigh Siltstone from the overlying Fairbridge Volcanics, which includes in its lower part allochthonous

limestones with reworked Early Ordovician conodonts and Darriwilian (Middle Ordovician) brachiopods.

Autochthonous carbonate units newly-recognised at two levels within the Fairbridge Volcanics include the older

Wahringa Limestone Member of late Darriwilian to early Gisbornian age, and the Yuranigh Limestone Member

of late Gisbornian age. These successions predate the main phase of Late Ordovician carbonate deposition,

represented in the northern Molong Volcanic Belt by the Reedy Creek Limestone, of early Eastonian age.

Allochthonous and autochthonous limestones in the Oakdale Formation, deposited in deeper water to the east

of the volcanic belt, yield conodonts which span an age range equivalent to the Wahringa, Yuranigh and Reedy

Creek limestones. Similar offshore facies, including probable autochthonous limestones in both the Oakdale

Formation and the correlative Sourges Shale, are present on the western flank of the Molong Volcanic Belt,

but only Eastonian ages have been recorded for these strata. The northern Molong Volcanic Belt can be shown

to have had an Ordovician volcanogenic and sedimentological history closely comparable with that of the

Junee–Narromine Volcanic Belt to the west.

Keywords:

Ordovician, conodonts, graptolites, brachiopods, corals, Molong Volcanic Belt, Hensleigh Siltstone,

Wahringa Limestone Member, Yuranigh Limestone Member, Reedy Creek Limestone, Oakdale Formation, Sourges

Shale.

INTRODUCTION

The Molong Volcanic Belt (MVB) is a

prominent meridionally-aligned tectonic

feature of early Palaeozoic age within

the Lachlan Orogen of central New

South Wales. It extends through the

western area of the region covered by

the Bathurst and Dubbo 1:250 000

map sheets, which were recently

remapped by the Geological Survey

of New South Wales and the Australian

Geological Survey Organisation (AGSO)

(Raymond et al 1998; Morgan et al

1999). In the course of this work,

Geological Survey of New South Wales

geologists [Scott and Morgan]

recognised new fossiliferous strata

in the northern sector of the MVB,

between Orange and Wellington (figure

1). Palaeontological investigations

[Percival] on these strata have resulted

in significant advances to knowledge

of how Ordovician sequences correlate

across the region. This paper presents

definition of a new stratigraphic unit

(Wahringa Limestone Member), lists

fossils identified from new stratigraphic

horizons and localities, and discusses

implications of the biostratigraphic

discoveries for revised understanding

of the geological history of the MVB.

Description of the fauna will be

published elsewhere.

within the Goonumbla Volcanics below

the Late Ordovician Billabong Creek

Limestone Member. That was the first

indication that submarine volcanoes

had built up to shallow water depths

in central New South Wales during

the Middle Ordovician. The present

research has disclosed a much more

complex geological history than

previously envisaged, particularly

for the northern MVB, with multiple

limestones having been deposited in

the Early, Middle and Late Ordovician.

This has enabled accurate definition of

a major stratigraphic break between

the first (Early Ordovician, Lancefieldian

or older) and second (Darriwilian–

Gisbornian) phases, of the three

episodes of volcanicity that characterise

the Ordovician history of central New

South Wales.

Palaeontological data were collected

from four main areas: Bakers Swamp

(25 km south of Wellington), where the

stratigraphic sequence comprises the

Mitchell Formation, Hensleigh Siltstone,

Fairbridge Volcanics and Oakdale

Formation (figure 2); the area south of

Molong, including the Printhie property,

where the Fairbridge Volcanics are

overlain by the Reedy Creek Limestone

and Cheesemans Creek Formation

(figure 3); the Narrawa property, 15 km

REGIONAL SETTING

Previous models of the development

of the Lachlan Orogen in central New

South Wales (eg, Webby 1976)

commenced with an Early to Middle

Ordovician interval of basinal deposition

and intervening arc-related volcanism.

The volcanic islands thus formed

became emergent early in the Late

Ordovician. Around the flanks of the

islands, shallow water carbonates

developed along the MVB and Parkes

Platform (now identified as the Junee–

Narromine Volcanic Belt, or JNVB —

Glen et al 1998). These limestones were

succeeded by Late Ordovician deep

water clastic and interspersed volcanic

units, prior to a final episode of more

continuous volcanism which persisted

nearly to the end of the Ordovician.

The presence of Bendigonian (Early

Ordovician) graptolites, and deep-water

trilobites of probable Darriwilian (late

Middle Ordovician) age (Packham

1969), had been reported in the

basinal successions, but it is important

to note that in those syntheses, no in

situ carbonate horizons of pre-Late

Ordovician age were recognised in

the MVB.

In the JNVB to the west, however,

Pickett (1985) identified Middle

Ordovician conodonts from a level

Quarterly Notes 108, 1999

Figure 2. Geological map of the “Wahringa” area, 26-28 km south of Wellington (mapping by Ian Percival and Martin Scott)

(for location see pages 14-15).

78 41

"Wahringa"

Bakers Swamp

Mitchell

Highway

149°00’

32°45’

REFERENCE

Quaternary alluvium

Undifferentiated Devonian

Undifferentiated Silurian

Late

Ordovician

Oakdale Formation

limestone in

Oakdale Formation

late Middle

to early Late

Ordovician

Fairbridge Volcanics

allochthonous

limestones

Wahringa Limestone

Member

Ordovician

Early

Hensleigh Siltstone

Mitchell Formation

42 Dip, and strike

Syncline, with plunge

Anticline

23087

Fossil locality

Thrust fault

Road

0 1 2 km

Neurea

Fault

C1458

C1456

C1450

C1463

C1427, C1465, C1553

C1481

C1458

Type section

C1432

Quarterly Notes 108, 1999

west of Wellington, where fossiliferous

Oakdale Formation is exposed (figure

4); and the area immediately east of

Cumnock where the Sourges Shale is

fault-bounded (figure 5). Additional

samples from the Oakdale Formation

were collected from several localities

between Orange and Wellington (shown

on figure 1).

STRATIGRAPHIC SUCCESSION

Mitchell Formation

The Mitchell Formation, formerly the

‘Mitchell Grit’ of Kemezys (1959) and

‘Mitchell Breccia’ of Wolf et al (1968),

represents the oldest rocks in the MVB.

To the east its outcrop abuts the Neurea

Fault, while the top of the formation

is conformable with the Hensleigh

Siltstone (figure 6). The lithology and

geochemistry of the Mitchell Formation

is very similar to that of the Fairbridge

Volcanics of the Cabonne Group and,

without identification of the intervening

Hensleigh Siltstone, the two formations

would be difficult to differentiate. It is

possible that the Mitchell Formation is

more widespread but has been mapped

elsewhere as Cabonne Group. The

formation crops out only in the Bakers

Swamp area, 25 km south of Wellington

(figure 2). The type section for the

Mitchell Formation is modified from

that of Kemezys (1959) to exclude

what is now the overlying Hensleigh

Siltstone to the west. The revised

section now extends from the Neurea

Fault (at GR 679750E 6369250N,

Cumnock 1:50 000 map), west to the

Mitchell Highway (GR 679000 6369300)

and further west along a tributary

of Neurea/Bakers Swamp Creek to

GR 678500 6369900. This section

includes a syncline-anticline pair, with

an estimated minimum thickness for

the Mitchell Formation of 1 100 m.

The Mitchell Formation comprises latitic

volcaniclastic conglomerate and

sandstone with minor primary volcanic

(latite lava and monzodiorite intrusions)

and polymict sedimentary rocks. Poorly

sorted, massive to crudely bedded

and graded, latitic conglomerate is

the most common lithology. The

conglomerate includes rounded to

subangular clasts up to 20 cm in

diameter. The poorly sorted and

massive nature of the conglomerate,

together with the dominance of latite

clasts, suggests the material was

derived as a downslope mass flow

from a volcanic centre. Interbedded

sandstone units probably represent

turbidite deposits. No fossils have

been found in the Mitchell Formation

but it must be earliest Ordovician

(Lancefieldian) or older, as early

Bendigonian graptolites occur within

the overlying Hensleigh Siltstone

(Kemezys 1959; Packham 1969).

Hensleigh Siltstone

The Hensleigh Siltstone (Wolf et al

1968) conformably overlies the Mitchell

Formation (cf figure 7) and similarly

crops out only in the Bakers Swamp

area. The boundary between the

Figure 6. Diagrammatic stratigraphic column for the Ordovician succession west of the Neurea Fault at “Wahringa”, showing

occurrences of significant fossils.

23122

CATOMBAL

GROUP

Middle to Late

Devonian

WAHRINGA

LIMESTONE

MEMBER

MITCHELL

FORMATION

SILTSTONE

HENSLEIGH

early Gisbornian Gi1

- late Darriwilian Da4

C1463

C1427, C1465

C1553

C1481

C1458

C1456

C1450

Appalachignathus,

Pygodus, Phragmodus

Girvanella, Reutterodus, Drepanoistodus

first plectambonitoid brachiopods

Pendograptus, Didymograptus asperus,

Dichograptus maccoyi

Bergstroemognathus extensus, Juanognathus variabilis,

Jumudontus, Paracordylodus gracilis, Reutterodus,

Scolopodus, Prioniodus, Acodus, Walliserodus australis

Labechia banksi

Labechiella regularis

Belodina compressa

Periodon grandis

Sowerbyites

Belodina B. monitorensis

Periodon P. aculeata

Periodon aculeata, Phragmodus flexuosus

Maclurites, Calathium

abundant lithistid sponges

(no older than Darriwilian)

Bendigonian

Be1-Be2

FAIRBRIDGE VOLCANICS

sp nov

Quarterly Notes 108, 1999

Hensleigh Siltstone and the overlying

Fairbridge Volcanics is now recognised

as a low angular unconformity, although

locally the contact may be faulted, eg

at GR 678200E 6369800N (Cumnock

1:50 000 map). The type section of the

Hensleigh Siltstone is along a tributary

of Neurea/Bakers Swamp Creek and

partly on Neurea/Bakers Swamp Creek

itself, from GR 678500E 6369900N

to GR 678310E 6370150N (Cumnock

1:50 000 map). The Hensleigh Siltstone

is approximately 310 m thick.

The Hensleigh Siltstone consists of

buff to dark grey, laminated siltstone

and shale, minor volcaniclastic

sandstone and, at the base of the

formation, laminated calcareous

siltstone. Volcaniclastic detritus is

common in the basal units, presumably

being derived from the underlying

Mitchell Formation. Allochthonous

limestone blocks and scattered volcanic

clasts also occur locally within the

Hensleigh Siltstone. Limestone blocks

at GR 678600E 6370100N and

GR 678450E 6369700N consist of

partly bioturbated or burrowed, grey

wackestones to packstones bearing

sponge spicules and rare trilobite

moulds. Siltstone in the upper part

of the formation contains a narrow,

graptolite-rich band yielding early

Bendigonian forms, discussed

below.

Laminated calcareous siltstones at

the base of the Hensleigh Siltstone

at GR 678825E 6370300N (Cumnock

1:50 000 map) are believed to represent

undisturbed, in situ deeper water

sediments, and are quite distinct

lithologically from allochthonous

limestone pods emplaced slightly

higherstratigraphically in the Hensleigh

Siltstone. Both the autochthonous

laminated siltstones (sample C1536),

and the allochthonous limestones

(sample C1481), yielded a similar,

exceptionally rich, diverse, and very

well-preserved conodont fauna

(Conodont Alteration Index, CAI, of

1.5-2) of Early Ordovician age, which

indicates approximate contemporaneity

with the graptolitic siltstone succession.

Conodont Sample C1481

allochthonous limestone in Hensleigh

Siltstone

GR 678450E 6369700N, Cumnock

1:50 000 map

Conodonta (figure 8.1-8.2, 8.4-8.12)

Acodus deltatus

Lindström

Bergstroemognathus extensus

(Graves & Ellison)

Drepanodus arcuatus

Pander

Drepanodus

Drepanoistodus

Juanognathus variabilis

Serpagli

Jumudontus

brevis

Nicoll

Oistodus

Paracordylodus gracilis

Lindström

Paroistodus

Prioniodus

Protopanderodus

Reutterodus

andinus

Serpagli

Scandodus

Scolopodus rex

Lindström or

multicostatus

Barnes & Tuke

Stolodus

Tropodus

sweeti

(Serpagli)

“Walliserodus” australis

Serpagli

Within Australia, the Hensleigh

assemblage most closely resembles

that described by McTavish (1973)

from the Emanuel Formation of the

Canning Basin. Nicoll (in Shergold

et al 1995) subdivided the Emanuel

Formation into five conodont

assemblages, from A (oldest) to E

(youngest), spanning the equivalent

of late Lancefieldian (La3) to middle

Bendigonian (Be2).

Bergstroemognathus

extensus

appears in assemblage B,

together with

Jumudontus brevis

and

“Acodus” deltatus

, and

Paracordylodus

gracilis

first appears in assemblage D.

This early Bendigonian age accords

precisely with that indicated by

a graptolite fauna, including

Didymograptus asperus

Harris and

Thomas

, Dichograptus maccoyi

Harris

and Thomas, and

Pendograptus

sp,

from overlying beds in the upper part

of the Hensleigh Siltstone.

Fairbridge Volcanics

The Fairbridge Volcanics (Adrian 1971)

crops out in three meridional tracts in

the northern MVB (figure 1): a western

Figure 7. Diagrammatic stratigraphic column for the Ordovician succession at “Printhie”

and along strike, showing occurrences of significant fossils.

23123

Taoqupognathus blandus

Periodon grandis

Besselodus, Spinodus

Belodina confluens

Yaoxianognathus wrighti

Chirognathus cliefdenensis

Belodina confluens

Scabbardella, Staufferella

Sowerbyella, Dinorthis

Ishimia,

coral – stromatoporoid

Fauna II (Eastonian Ea2)

Fauna I (Eastonian Ea1)

coral – stromatoporoid

pre - Brachiopod Fauna A

(Gisbornian Gi2)

CHEESEMANS CREEK

FORMATION

REEDY CREEK

LIMESTONE

YURANIGH

LIMESTONE

MEMBER

FAIRBRIDGE VOLCANICS

C1377,

C1437

C1394

gastropds

Quarterly Notes 108, 1999

15 16

Quarterly Notes 108, 1999

belt extending 45 km along strike

from north of Borenore to west of

Cundumbul; a northern band of 5 km

strike length at Bakers Swamp; and a

largely fault-bounded eastern belt

approximately 7 km northwest of

Orange (not discussed in this paper).

The Fairbridge Volcanics in the western

belt, where the name originated, is

faulted at its base and, to the north,

also at the top. North and south of

Molong the formation is conformably

overlain by the Reedy Creek Limestone

and, where that formation is absent,

the Cheesemans Creek Formation. Two

autochthonous carbonate-dominated

units, the Wahringa Limestone Member

(formally defined below) in the Bakers

Swamp area, and the Yuranigh

Limestone Member (Scott & Pogson,

in Pogson & Watkins 1998) south of

Molong, are now recognised as units

within the Fairbridge Volcanics. During

remapping of the Bathurst 1:250 000

geological map sheet the Fairbridge

Volcanics was redefined to include

Stevens’ (1950) ‘Cargo Volcanics’ and

was placed in the newly introduced

Kenilworth Group (Pogson & Watkins

1998). However, additional information,

reported below, has led to a revision of

this assignment.

The Fairbridge Volcanics at Bakers

Swamp, formerly the ‘Blathery Creek

Volcanics’ of Kemezys (1959) and Wolf

et al (1968), overlie the Hensleigh

Siltstone with slight angular

discordance. This suggests a significant

but previously unrecognised Middle

Ordovician break in deposition on

the MVB. The top of the Fairbridge

Volcanics at Bakers Swamp is faulted

against the Oakdale Formation, while

to the west the Ordovician sequence is

unconformably overlain by the Late

Devonian Catombal Group.

Several allochthonous limestone pods,

including one described as an algal

bioherm by Wolf et al (1968), are now

known from the lower part of the

Fairbridge Volcanics. These limestones

are very significant as they yielded the

first biostratigraphic data from this

formation. Based on the Darriwilian

age indicated by the limestone fauna,

the maximum age of the Fairbridge

Volcanics is much younger than that

proposed by earlier workers. This major

revision to the stratigraphic position

of the Fairbridge Volcanics confirms

its inclusion within the Middle to Late

Ordovician Cabonne Group, as it

correlates in age with other units of

that group, including the Weemalla

Formation and Blayney Volcanics.

A type area for the Fairbridge Volcanics

has been nominated at Bakers Swamp

(Morgan, Scott & Percival, in Meakin

& Morgan in prep 1999) in three

composite sections: from the top of

the Hensleigh Siltstone to the base of

the Wahringa Limestone Member

along Bakers Swamp Creek (from

GR 678320E 6370150N to GR 677820E

6370750N, Cumnock 1:50 000 map);

through the Wahringa Limestone

Member from GR 678700E 6372000N

to GR 678600E 6372300N; and from

the top of the Wahringa Limestone

Member to the faulted top of the

formation from GR 679320E 6372800N

to 677970E 6375480N. The Fairbridge

Volcanics is estimated to be

approximately 2 750 m thick in the

type area, although this may be a low

estimate given that the top of the

formation is faulted. Adrian (1971)

gave an approximate thickness for the

formation of 1 500 m to 2 100 m east

of Molong.

Together with basaltic andesitic to

latitic lavas and intrusions which are

characteristic of the Fairbridge

Volcanics, massive to bedded limestone

breccia and conglomerate, calcareous

volcaniclastic sandstone and

allochthonous limestone blocks are

common in the formation in the Bakers

Swamp area. Breccia and conglomerate

units consist of unsorted, chaotically

mixed limestone clasts, including

blocks up to 5 m in diameter, as well

as fossil and volcaniclastic detritus.

Calcarenite beds are fine to coarse

grained, locally graded and polymict,

consisting of angular to rounded fossil,

lithic and crystal fragments in a

carbonate mud. Allochthonous

limestone blocks and clasts are massive

to bedded, grey, fine to coarse grained

packstone grading to grainstone and

wackestone. Grains are subangular to

rounded and consist mostly of fossil

debris, as well as oncolites, ooids and

minor lithic and crystal fragments. The

carbonate material is generally clean,

well-rounded and even-grained,

resembling beach sand.

The “algal bioherm” from which Wolf

et al (1968) described

Girvanella

, is

undoubtedly of allochthonous origin.

The limited outcrop, restricted to a

creek gully at GR 678020E 6370300N

(Cumnock 1:50 000 map), consists

of a limestone breccia which coarsens

upwards over 3 m stratigraphically

from rounded pebble-sized clasts at

the base to metre-sized blocks with

prominent calcimicrobial stromatolites

(figure 9.1). This outcrop is the oldest

datable sediment within the lower part

of the Fairbridge Volcanics. A limited

Figure 8. Selected conodonts typical of Ordovician strata on the northern Molong Volcanic Belt, including the Hensleigh Siltstone

(8.1-8.12), allochthonous limestones in the Fairbridge Volcanics (8.13, 8.14), Wahringa Limestone Member (8.15-8.20),

Yuranigh Limestone member (8.21), allochthonous limestones in the Oakdale Formation (8.22-8.23), and autochthonous

bedded limestone in the Oakdale Formation (8.24).

8.1

Bergstroemognathus extensus

Pa element, x35; 8.2

Bergstroemognathus extensus

Sd element, x60; 8.3

Bergstroemognathus extensus

Sa element, x55; 8.4

Acodus deltatus

, x 45; 8.5

Prioniodus

sp, x 65; 8.6

Reutterodus

R. andinus

, cone-like element x50; 8.7

Paracordylodus gracilis

, x120; 8.8

Stolodus

sp, x80; 8.9

Scolopodus

rex

, x55; 8.10

Tropodus

sweeti

, x45; 8.11

Juanognathus variabilis

, x70; 8.12

Drepanodus arcuatus

, x50; all from conodont sample C1481,

except 8.3 from C1536 (same horizon).

8.13

Reutterodus

sp, bipennate element, x105; from conodont sample C1427.

8.14

Phragmodus flexuosus

, S element, x75; from conodont sample C1463.

8.15

Phragmodus flexuosus

, S element, x60; 8.16

Periodon aculeata

, M element, x95; 8.17

Drepanodus

sp, x110; 8.18

Pygodus serra

, x70; 8.19

Ansella

sp, x120; 8.20

Belodina compressa

, compressiform element, x60; 8.15-8.18 from conodont

sample C1450; 8.19-8.20 from conodont sample C1458.

8.21

Belodina confluens

, compressiform element, x50; from conodont sample C1437.

8.22

Appalachignathus delicatulus

, Pa element, x60; 8.23

Appalachignathus delicatulus

, Sa element, x60; both from conodont

sample C1425.

8.24

Belodina confluens

, compressiform element, x80; from conodont sample C1388.

▲

Quarterly Notes 108, 1999

Wellington

Figure 4

01 km

"Narrawa"

C1491

Wellington

32°30’00"

Figure 4

Molong

REFERENCE

Quaternary alluvium

Tertiary basalt

Mesozoic volcanic and

sedimentary units

Undifferentiated Devonian

Undifferentiated Silurian

Silurian limestone

Sourges Shale

limestone member

latite member

Kabadah Formation

Cheesemans Creek Formation

Reedy Creek Limestone

Fairbridge Volcanics

limestone (allochthonous)

Yuranigh Limestone Member

Wahringa Limestone member

Hensleigh Siltstone

Mitchell Formation

Undifferentiated intrusions

Dip and strike

Syncline

Anticline

Thrust fault

Fossil locality

Road

Railway

City or town

Homestead

C1377

"Printhie"

limestone

Oakdale Formation

ORDOVICIAN

Figure 2

Fault, accurate

Fault, approximate

Molong

C1425

C1490

Type section

149°00’

32°30’

Dubbo

Quarterly Notes 108, 1999

Figure 1. Simplified geological map of the northern Molong Volcanic Belt, based on Raymond et al (1998) and Morgan et al in prep (1999),

showing locations of areas considered in greater detail in figures 2, 3, 4, and 5. For clarity, faults are not shown.

Figure 3. Geological map of the area south-east of Molong (compilation by Martin Scott).

Figure 4. Geological map of the “Narrawa” area, 15 km west of Wellington (mapping by Alice Warren).

Figure 5. Geological map of the area immediately east of Cumnock (compilation by Elisabeth Morgan).

Figure 3

0 50 km

23089

Cumnock

Cudal Fault

Figure 5

32°55’00"

01 km

1 km0

Figure 3

C1377

C1437

C1394

Orange

"Printhie"

C1519

C1547

Figure 5

Cumnock

Molong

C1388

C1414

148°45’

33°15’

Quarterly Notes 108, 1999

fauna recovered from residues of the

basal limestone clasts (sample C1553)

lacked conodonts, but included

incomplete specimens of a brachiopod

referred to ?

Anoptambonites

. Its

presence means that the age of the

basal clasts can be reasonably reliably

estimated as no older than Darriwilian.

No earlier occurrences of this genus,

or the family to which it belongs, are

known world-wide (Cocks & Rong

1989).

Conodonts recovered from the upper

part of this outcrop (samples C1427,

C1465) include one specimen (figure

8.13) of the distinctive bipennate

ramiform element (together with

numerous coniform elements) of the

Early Ordovician conodont

Reutterodus

(closely comparable with Serpagli 1974,

plate 28, fig 5)

Presumably the

limestone comprising the “bioherm”

was derived from the underlying

Hensleigh Siltstone succession,

which also includes limestones with

Reutterodus

(sample C1481), and

was incorporated into the Fairbridge

Volcanics during erosion and

redeposition.

Allochthonous limestones within

boulder and cobble size volcanic

conglomerates at a comparable level,

or perhaps slightly higher than the

“bioherm”, in the Fairbridge Volcanics

yielded elements of the Middle to early

Late Ordovician genera

Pygodus

and

Appalachignathus

(indicative of a

probable late Darriwilian age), together

with

Phragmodus

and

Panderodus

This composite sample (C1463;

GR 679150E 6371900N, Cumnock

1:50 000 map) was taken from several

small limestone clasts at the one

isolated stratigraphic level (in some

cases lying adjacent to each other),

though differing markedly in

appearance. Preservational differences

were also apparent in the conodont

fauna, which appears to include

reworked specimens. Wide variation

in the CAI of the elements, from 1.5

to approximately 5, confirms the

heterogeneity of the clasts.

Wahringa Limestone Member of

the Fairbridge Volcanics

The Wahringa Limestone Member [first

recognised by Scott during remapping

of the Dubbo 1:250 000 geological

map area (Morgan et al in prep 1999)],

is here formally defined. Although the

outcrop of this unit was initially plotted

as occurring within the ‘Cargo Andesite’

in a map compilation by Byrnes (in

Pickett 1982, fig 17; and also in

Lishmund et al 1986, fig 28), its

significance was not then recognised

and it has not been previously named

nor studied in detail. The member is

an autochthonous limestone lens

conformable within volcaniclastic

rocks in the lower part of the Fairbridge

Volcanics in the Bakers Swamp area

(figures 2, 6). The name is derived

from the Wahringa property on which

the member crops out, the Wahringa

homestead being located at

GR 680150E 6370750N, Cumnock

1:50 000 map. The Wahringa

Limestone Member is exposed

adjacent to Bakers Swamp Creek from

GR 677650E 6370350N northeast to

GR 679350E 6372800N, a strike

length of approximately 400 m. The

northeastern-most margin is not

exposed, while to the southwest the

member is overlain unconformably by

the Late Devonian Catombal Group.

The type section of the Wahringa

Limestone Member is just north of a

bend in Bakers Swamp Creek, and

extends from GR 678700E 6372000N

Figure 9. Selected macrofossils from limestones in the Fairbridge Volcanics on the northern

Molong Volcanic Belt.

9.1 Stromatolite, showing partially silicified calcimicrobial laminae comprised of

Girvanella

sp, x0.3; from allochthonous limestone at GR 678020E 6370300N

(Cumnock 1:50 000 map).

9.2 natural cross-section through gastropod

Maclurites

sp, x0.9; 9.3 longitudinal

cross-section through nautiloid ?

Michelinoceras

sp, x1.7; 9.4 unidentified crinoid

calyx, x1.9; 9.5 natural transverse section, and 9.6 natural longitudinal section, of

lithistid sponge referable to ?

Archaeoscyphia

sp (identification by John Pickett),

both x0.6; 9.2-9.6 from lower part of Wahringa Limestone Member in its type

section.

9.69.5

9.3

9.2 9.4

9.1

Quarterly Notes 108, 1999

to GR 678600E 6372300N, Cumnock

1:50 000 map. The limestone has been

measured in this section at 88 m in

thickness.

The Wahringa Limestone Member

consists of medium to thinly bedded

fossiliferous limestone, largely

grainstone, with lesser packstone

and wackestone, as well as calcareous

sandstone, breccia and siltstone.

Calcimicrobes are abundant throughout

the limestone, especially at the base

where many of the sedimentary grains

are oncolites, indicative of shallow,

well-circulated marine conditions.

The unit consists of three parts: lower

beds rich in oncolites, ooids and

volcaniclastic detritus; a middle part

that is muddy, thinly bedded and rich

in brachiopods; and an upper section

that is more massive.

The most common facies in the

lower part of the Wahringa Limestone

Member is a brown to grey, fine to

coarse grained, poorly to moderately

well-sorted, oncolitic skeletal

grainstone, locally grading to

packstone. Fossil grains are subangular

to rounded, frequently microbial-coated

and include echinoderms, gastropods,

trilobites, brachiopods, sponge

spicules,

Solenopora

and dasycladalean

algae. Large oncolites with well-

preserved

Girvanella

filaments, well-

defined cyanobacterial strands and

ooids are also abundant. Other

distinctive fossils at this level include

the large gastropod

Maclurites

, and

a receptaculitid similar to

Calathium

Minor detrital mineral fragments include

angular quartz, plagioclase, K-feldspar,

olivine, magnetite, epidote, apatite,

zircon, garnet, mica and ?fuchsite.

Rare porphyritic rhyolite, andesite and

chert clasts are also present.

Unsorted, medium to coarse grained,

bedded, skeletal, volcanolithic

calcareous sandstone and breccia also

occur in the lower part of the Wahringa

Limestone Member. These rocks

consist of well-rounded carbonate

grains, including oncolites, oolites,

echinoderm ossicles, and sparse

mollusc and brachiopod shells. Also

present are angular to subrounded

lithic fragments, including limestone

(wackestone and packstone),

calcareous sandstone, porphyritic

quenched trachyte, andesite and

latite, vitric felsic tuff, chert, and rare

?granite, metaquartzite, quartz-veined

metasiltstone and microdiorite. Detrital

angular minerals include quartz,

plagioclase, ?fuchsite, Ti-magnetite,

unidentified mafic minerals, epidote

and garnet (Larry Barron pers comm

1997). The matrix consists of micrite.

Some units are graded and exhibit relict

burrow structures. Rare fine to coarse

grained, latitic volcaniclastic sandstone

lacking organic material also occurs at

the base of the member. The presence

of ooids and the abundance of algae in

the basal Wahringa Limestone Member

indicate shallow, well-circulated marine

conditions.

The middle part of the Wahringa

Limestone Member is characterised

by a brown to brownish grey, fine to

coarse grained, skeletal grainstone,

dominated by remains of echinoderms,

brachiopods, dasycladalean algae,

molluscs, trilobites and ostracodes.

The unit is well-sorted, commonly

laminated and interbedded, with silty

layers, and grades between packstone

and wackestone. Beds may exhibit

burrows. The grainstone includes well-

rounded fossil fragments, some with

thin micritic rinds or microbial coatings;

sponge spicules; minor mineral grains

including quartz, feldspar, Ti-magnetite,

mafic grains and ?fuchsite; scattered

oncolites of

Girvanella

; and rare ooids.

Rare, rounded lithic clasts include

porphyritic and microlitic latite and

chert. The matrix consists of

microcrystalline micrite.

The most common lithology in the

upper part of the Wahringa Limestone

Member is brownish grey to light

brown, fine to coarse grained, skeletal,

oncolitic grainstone and lesser

packstone to wackestone with no

internal lamination. Grains are well-

washed and include ostracodes,

dasycladalean algae, rare ooids (some

with micritic rinds) and oncolites of

Girvanella

. Echinoderm and mollusc

fragments, as well as rare latite clasts,

are also present. Sparse detrital

mineral fragments include quartz,

magnetite, plagioclase and mafic

minerals. Irregular voids may be

infilled with spar and laminated

?marine cement. Minor brownish grey,

calcareous, volcaniclastic sandstone

and conglomerate — rich in shelly,

lithic and crystal detritus — also occur

at the top of the member. The beds

are poorly to moderately sorted and

are locally graded. Shelly debris

includes trilobites and ostracodes, with

fewer echinoderm ossicles and rare

stictoporoid bryozoans. Lithic clasts are

angular to rounded and include fine

grained wackestone, skeletal packstone,

porphyritic latite, porphyritic and

microlitic basaltic andesite and

microdiorite. Minor detrital quartz,

plagioclase, augite and hornblende

fragments are also present.

Biostratigraphy

The diversity, relative abundance, and

good preservation of the conodonts

in sample C1450 permits an accurate

age determination for the basal

Wahringa Limestone Member.

Periodon

aculeata,

which ranges through the

upper Middle Ordovician into the

basal Late Ordovician (Darriwilian

Da2 to Gisbornian Gi1), is the most

common species in the assemblage.

Co-occurrence with

Phragmodus

flexuosus

restricts the possible age of

this interval to Da3-Gi1. The presence

Pygodus serra

also supports a late

Darriwilian age.

Conodont Sample C1450

basal Wahringa Limestone Member

GR 678650E 6372000N Cumnock

1:50 000 map

Conodonta (figure 8.15-8.18)

Drepanoistodus

Erraticodon

Panderodus

Periodon aculeata

Hadding

Phragmodus flexuosus

Moskalenko

Prioniodus (Baltoniodus)

Protopanderodus

P. liripipus

Kennedy, Barnes & Uyeno

Pygodus serra

(Hadding)

Gastropoda (figure 9.2)

Maclurites

Nautiloidea (figure 9.3)

Michelinoceras

Brachiopoda

Multispinula

indeterminate lingulate fragments

acrotretide

Trilobita

pliomerinid cephalon and pygidium

Ostracoda (unidentified)

Echinodermata (figure 9.4)

unidentified crinoid calyx

Porifera (figures 9.5, 9.6)

several genera of lithistid sponges

Algae

Calathium

undetermined dasycladales

Quarterly Notes 108, 1999

Sample C1456, from slightly higher

in the Wahringa Limestone Member

(figure 6), is most likely latest Middle

Ordovician (Da4) or earliest Late

Ordovician (Gi1). Evidence for the age

derives from quite close similarities

to the conodont fauna described from

the Pratt Ferry Limestone of Alabama

by Sweet and Bergström (1962).

That formation is restricted in time to

the upper

Pygodus anserinus

Zone,

according to Ross et al (1982). The

co-occurrence of early species of

Belodina

with

Periodon aculeata

(or

.cf

aculeata

) in both the Pratt Ferry

and Wahringa limestones suggests

contemporaneity. Conodonts from

sample C1450 (figure 6) also include

P. aculeata

but lack

Belodina

, and

several other age-significant taxa

found in C1450 do not persist into

C1456. The fish scale found in the

latter is especially interesting, as

there are no previous records of

vertebrates (excluding conodonts)

from the Ordovician of the MVB.

Given the rarity of Ordovician fish

fossils, it is doubtful if it could be

identified to an age-diagnostic form.

Conodont Sample C1456

lower part of Wahringa Limestone

Member

GR 678675E 6372025N Cumnock

1:50 000 map

Conodonta

Belodina

B. monitorensis

Ethington

& Schumacher

‘Belodina’ alabamensis

Sweet &

Bergström

Drepanoistodus

Panderodus

Periodon

P. aculeata

Hadding

Walliserodus

Scolecodont

Gastropod steinkerns

Trilobite fragments

Lingulate brachiopod fragments

Echinoderm spines, with articulation

boss at base

Fish scale, ornamented with small

smooth elongate tubercles

A further conodont sample (C1458),

taken about midway stratigraphically

within the Wahringa Limestone

Member, has an entirely Gisbornian

aspect, including

Belodina compressa

and a younger species of

Periodon

P. grandis

. Co-occurrence of these

species indicates, according to Sweet

(1988), an age spanning the

Phragmodus undatus

–

Plectodina

tenuis

zones of the North American

Midcontinent Fauna.

Belodina

compressa

in North America ranges

through the early Late Ordovician

Amorphognathus tvaerensis

Zone of

the North Atlantic Fauna (equivalent to

the early Gisbornian to early Eastonian

interval in the Australian succession).

Zhen and Webby (1995) reviewed

previous records of

B. compressa

Australia, and concluded all were better

placed in

B. confluens

. However, the

abundant material available in the

Wahringa Limestone Member allows

an unequivocal identification of

B. compressa

, indicating that this unit

is older than any of the other East

Australian Late Ordovician limestones

bearing

B. confluens

Conodont Sample C1458

middle part of Wahringa Limestone

Member

GR 678700E 6372050N Cumnock

1:50 000 map

Conodonta (figure 8.19-8.20)

Ansella

Belodina compressa

(Branson &

Mehl)

Besselodus

Dapsilodus

Drepanoistodus

Panderodus unicostatus

(Branson &

Mehl)

Panderodus

panderi

(Stauffer)

Periodon grandis

(Ethington)

Protopanderodus

Pseudobelodina

Scabbardella

Yaoxianognathus

Brachiopoda

Leptellina

Sowerbyites

sp nov

indeterminate lingulates, all

fragmentary

Gastropoda

unidentifiable steinkerns (internal

moulds)

Ostracode

Echinoderm spines, with articulation

boss at base (cf C1456)

DISCUSSION

The Wahringa Limestone Member

conodont (and macrofossil) fauna

of sample C1458 bears no close

resemblance with faunal assemblages

found in the Cliefden Caves Limestone

Subgroup, or the equivalent Reedy

Creek Limestone, of early Eastonian

age. Hence the C1458 assemblage

is more likely to have an older

(Gisbornian) age. There is a marked

difference between the conodont fauna

of that level, and the stratigraphically

older sample C1450 (basal Wahringa

Limestone Member), which is

demonstrably late Darriwilian. While

C1450 and C1458 differ in facies,

having been deposited in different water

depths and turbulence conditions, this

is probably not the cause of the faunal

discrepancy. It seems probable that

the 88 m thick Wahringa Limestone

Member spans at least two zones,

from late Darriwilian (Da4) to early

Gisbornian (Gi1). Evidence supporting

correlation of the Wahringa Limestone

Member with the Tasmanian succession

(Banks & Burrett 1980, table 2) is

given by stromatoporoids in the middle

part of the section, identified by Barry

Webby (pers comm 1996) as similar

to those he described from the

Cashions Creek Limestone and

overlying

Lichenaria

unit in Tasmania

(Webby 1979). These levels contain

representatives of Faunal Assemblages

OT10 and OT11, which have been

correlated with Da3-Da4 and Gi1

intervals.

Yuranigh Limestone Member of the

Fairbridge Volcanics

The Yuranigh Limestone Member is an

autochthonous limestone up to 180 m

thick that lies conformably within the

upper part of the Fairbridge Volcanics,

approximately 1 300 m below the base

of the overlying Reedy Creek Limestone

(figure 7). The limestone, on Printhie

property, 3 km south of Molong was

named [by Scott] during remapping of

the Bathurst 1:250 000 geological map

area (Raymond et al 1998), and was

defined by Scott and Pogson (in

Pogson & Watkins 1998, pp 26-27).

The type section extends from

GR 675300E 6332800N to GR 674950E

6332800N, Molong 1:50 000 map

(figure 3).

The Yuranigh Limestone Member

consists of bioturbated limestone,

calcareous siltstone and lithic

sandstone. Basal beds are characterised

by coarse calcarenite grading into

lithic sandstone and volcaniclastic

pebble conglomerate, incorporating

detritus probably derived from

underlying volcanic strata. Macrofossils

from the lower part of the Yuranigh

Quarterly Notes 108, 1999

Limestone Member are dominated by

gastropods and brachiopods. New

brachiopod species constitute a distinct

pre-Brachiopod Fauna A (Percival 1992)

assemblage, although no definitive age

is indicated. Associated microfossils are

largely ostracodes, and few conodonts

have been recovered.

Upper beds of the Yuranigh Limestone

Member are marly carbonates of

wackestone to packstone lithology.

Conodonts are sparsely represented at

this horizon (samples C1377, C1437)

byelements attributable to four genera

(Pogson & Watkins 1998, appendix 1).

Of these,

Staufferella

is widespread in

Middle to Late Ordovician strata in

North America, and also occurs in the

Late Ordovician Fork Lagoons Beds of

central Queensland (Palmieri 1978),

but has not previously been recorded

from New South Wales. The element of

Staufferella

in sample C1377 is closely

comparable with that of a species from

the Late Ordovician Galena Formation

of Minnesota (Ethington 1959). Another

species identified in the Yuranigh

Limestone Member,

Belodina confluens

(figure 8.21), has been shown to be

much longer ranging in eastern

Australia than in the North American

succession (Zhen & Webby 1995),

with occurrences low in the Fossil Hill

Limestone at Cliefden Caves broadly

correlated with the

Phragmodus

undatus

Zone of the North American

Midcontinent Fauna. This Zone is of

latest Gisbornian to early Eastonian

age in Australia (Webby 1995; Zhen &

Webby 1995).

There is a disparity in faunal content

between the Yuranigh Limestone

Member and the succeeding Reedy

Creek Limestone (and its correlatives,

including the Fossil Hill Limestone).

Also, there is mutual exclusivity

to fossil assemblages in the older

Wahringa Limestone Member. Hence

it is reasonable to infer that the

Yuranigh Limestone Member occupies

the interval between those two levels,

and is of late Gisbornian (Gi2) age.

Reedy Creek Limestone

The Reedy Creek Limestone (Ross

1961, after Pritchard (1955) and Adrian

(1956)) crops out for over 24 km along

strike north and south of Molong

(figure 3). The formation was revised

during remapping of the Bathurst

1:250 000 geological map area

(Raymond et al 1998) and included in

the new Barrajin Group (Morgan, Scott

& Pogson in Pogson & Watkins 1998).

The limestone overlies the Fairbridge

Volcanics conformably or with slight

disconformity (Adrian 1971). North of

Molong, the formation is conformably

overlain by the Cheesemans Creek

Formation, while to the south of Molong

these Late Ordovician volcaniclastic

rocks interfinger with the limestone.

Maximum thickness of the unit is about

850 m (Morgan, Scott & Pogson in

Pogson & Watkins 1998).

During the remapping of the Molong

1:100 000 map area, extensive fossil

collection enabled identification of

many taxa not previously recorded

from the Reedy Creek Limestone. In

particular, a rich conodont fauna allows

precise correlation with other Late

Ordovician limestones on the MVB

along strike to the south. Macrofossils

from the Reedy Creek Limestone are,

in general, quite distinct from those in

the underlying Yuranigh Limestone

Member. However, occurrence of the

conodont species

Belodina confluens

in both units implies that a substantial

time gap does not separate the top

of the Fairbridge Volcanics and the

overlying Late Ordovician limestones,

at least in this area of the MVB.

The highly fossiliferous thinly-bedded

lower section of the Reedy Creek

Limestone has been dated as Late

Ordovician (Eastonian) on the basis

of macrofossils, such as corals and

stromatoporoids, indicative of Fauna I

in the local biostratigraphic scheme of

Webby (1969). That section is overlain

by an upper massive relatively poorly

fossiliferous limestone of previously

indeterminate age. There is usually

no development of a thin-bedded

conspicuously fossiliferous facies

above the massive limestone, such as

in the Cliefden Caves Limestone

Subgroup and the Regans Creek

Limestone, along strike to the south,

and the Bowan Park Limestone on the

western side of the MVB.

A Fauna II age conodont assemblage

has now been recovered from a thin-

bedded limestone in the Reedy Creek

Limestone, rich in shelly macrofossils

with a distinctive lithology reminiscent

of the Trilobite Hill Limestone Member

of the Cliefden Caves area. Conodonts

were abundant and diverse in this

sample (C1394), with diagnostic

species, such as

Periodon grandis

and

Taoqupognathus blandus

, well

represented. These are characteristic

of the “upper assemblage” of the

Cliefden Caves Limestone Subgroup

succession (Zhen & Webby 1995). The

range of the nautiloids

Cliefdenoceras

gregarium

, previously known only from

the Fossil Hill Limestone (Stait et al

1985), and

Trocholites costatum

, of

Fauna I age, now can be extended into

Fauna II as a result of their occurrence

with these conodonts. Unfortunately,

because sample C1394 is from an

isolated outcrop of the Reedy Creek

Limestone, a precise level within the

formation cannot be established. It is

significant in demonstrating that the full

section of the Late Ordovician carbonate

succession that developed on the

eastern flank of the MVB is also shown

to exist in the region north of Molong,

though considerably diminished in

thickness from that of the correlative

limestone formations to the south.

Conodont sample C1394

upper Reedy Creek Limestone

GR 679048E 6323222N Molong

1:50 000 map

Conodonta

Ansella

sp nov

Aphelognathus packhami

Savage

Aphelognathus webbyi

Savage

Aphelognathus

Belodina confluens

Sweet

Belodina

hillae

Savage

Besselodus

Chirognathus cliefdenensis

Zhen &

Webby

Chirognathus

Drepanoistodus suberectus

(Branson

& Mehl)

Panderodus gracilis

(Branson &

Mehl)

Periodon grandis

(Ethington)

Phragmodus

undatus

Branson &

Mehl

Plectodina tenuis

(Branson & Mehl)

Pseudobelodina

Pseudooneotodus mitratus

(Moskalenko)

Serraculodus

Spinodus

Taoqupognathus blandus

Yaoxianognathus tunguskaensis

(Moskalenko)

Yaoxianognathus

Porifera

anthaspidellid sponge

hexaxon spicule

Quarterly Notes 108, 1999

Coelenterata

indeterminate favositid

Bryozoa

Orbignyella

indeterminate stictoporoid

Brachiopoda

fragmentary small lingulides

Schizotreta

Hisingerella

Sowerbyites isotes

Percival

Wiradjuriella halis

Percival

Nautiloidea

Cliefdenoceras gregarium

Stait,

Webby & Percival

Trocholites costatum

Stait, Webby &

Percival

Trilobita

harpid fringe

Echinodermata

indeterminate ossicles

Problematica

byroniids

Algae

dasycladales, most likely

Vermiporella

Isolated limestone blocks near Eurimbla

(north of Molong) also contain the

Fauna II stromatoporoid

Ecclimadictyon

(Webby 1969). Farrell (in Talent 1995)

listed brachiopods from that area,

including

Doleroides

and

Sowerbyella

which appear identical to species of

Brachiopod Fauna B (= Fauna II) age

from the Cliefden Caves Limestone

Subgroup and the Bowan Park

Limestone. The Eurimbla blocks may

be allochthonous (Farrell 1996), or may

have been tectonically displaced, but

their most likely source is the Reedy

Creek Limestone which is the closest

in situ carbonate unit of Fauna II age.

Oakdale Formation

The Oakdale Formation (Strusz 1960;

Oakdale Group of Vandyke & Byrnes

1976) is the most extensive Ordovician

unit in the MVB (figure 1). The

formation occurs in two broad tracts,

the eastern belt extending from

Lucknow in the south to Golan in the

north, a distance of over 130 km, while

the western belt crops out in several

small fault slices between Bournewood

and Ponto localities, west of Wellington.

The Oakdale Formation was significantly

revised during remapping of the

Bathurst and Dubbo 1:250 000

geological map areas (Raymond et al

1998; Morgan et al in prep 1999) and

the term was extended to include the

Angullong Tuff (Packham 1968)

northwest and southeast of Orange;

undifferentiated strata (Offenberg et

al 1971) north of Wellington; and

undifferentiated rocks previously

considered Silurian in age (Bradley, in

Pickett 1982) west and southwest of

Wellington. The formation has been

included in the Late Ordovician

Cabonne Group (Pogson & Watkins

1998; Meakin & Morgan in prep 1999).

The base of the Oakdale Formation

in the eastern belt is almost always

faulted, an exception being to the east

of Lucknow where the formation

overlies the Byng Volcanics with

apparent conformity. In turn it is

unconformably overlain by rocks of

the late Early to Late Silurian Mumbil

Group and locally the Early Silurian

Waugoola Group. The base of the

Oakdale Formation is not exposed

west of Wellington. In this area the

formation is conformably overlain by

the Late Ordovician to Early Silurian

Kabadah Formation north of the

Bournewood locality, while near Ponto

the formation is unconformably overlain

by rocks of the Silurian Cudal Group.

The Oakdale Formation is dominated

by cherty and volcaniclastic siltstone

and sandstone turbidite sequences,

volcaniclastic mass flow conglomerate

and minor primary volcanic rocks —

as well as limestone and limestone

breccia. Units within the Oakdale

Formation are laterally discontinuous

and no complete section of the

formation has been found. The turbidite

sequences are well-bedded to

laminated, commonly graded and

are crystal- and lithic-rich. Siltstone

beds locally include graptolite-rich

bands. Well-bedded, dark coloured,

autochthonous limestones occur on

Barham Winchester property, 10 km

northeast of Molong. The conglomerate

horizons are massive to coarsely

bedded, clast- to matrix-supported,

poorly sorted and can commonly be

traced for over 2 km along strike.

They generally have a high magnetic

susceptibility (8 000 x 10-5 SI) and

exhibit a high potassium response

on airborne radiometric images.

Clasts range from millimetres to tens

of centimetres in diameter and are

dominantly andesitic to trachytic in

origin, with lesser sandstone, siltstone,

chert and limestone. Limestone blocks

up to 10 m in diameter occur

sporadically within conglomerate beds,

probably representing material that

slumped from a carbonate shelf on

the margins of the marine basin. The

depositional environment interpreted

for the Oakdale Formation is generally

deep-water, on the shelf-edge or further

offshore.

Conodonts recovered during this study

from several allochthonous limestone

clasts in the Oakdale Formation are

of late Darriwilian to early Gisbornian

age, whereas those extracted from

autochthonous limestone are Eastonian,

consistent with the age indicated

by graptolites from the enclosing

siltstones. Strusz (1960, 1961) reported

Late Ordovician (Eastonian) graptolites

from the Oakdale Formation in the

Wellington 1:100 000 map area,

between Neurea and Dripstone. From

nearby outcrops Webby (1973, 1974)

described the trilobites

Shumardia

and ?

Geragnostus

(now reidentified

by J. Laurie (pers comm 1990) as

Dividuagnostus

), and suggested

that these came from an older, possibly

Gisbornian, section (Webby et al 1981).

Vandyke and Byrnes (1976) listed

additional Late Ordovician graptolites

from the Oakdale Formation, and also

noted the occurrence in associated

limestones of the tabulate coral

Coccoseris speleana

Hill. The latter

is indicative of coral/stromatoporoid

Fauna I of the local biostratigraphic

scheme of Webby (1969), and Webby

and Kruse (1984). Sherwin (1994a)

identified three graptolite species

generally indicative of a late Eastonian

age from the Oakdale Formation, and

Sherwin (1994b) recorded brachiopods

and graptolites, some of the latter

suggesting an age straddling the

Eastonian–Bolindian boundary. Late

Ordovician conodonts had previously

been recovered from the Oakdale

Formation north of Wellington, by

Pickett (1972), who reported eight

form-species.

During the current mapping program,

two distinct faunas have been identified.

Allochthonous limestone blocks at

several widely scattered localities

yielded, inter alia, the shallow water

conodont

Appalachignathus delicatulus

type and only species of this distinctive

genus, which ranges through the upper

Pygodus serra

–

Pygodus anserinus

–

lower

Amorphognathus tvaerensis

zones of the North Atlantic faunal

succession (Bergström et al 1974).

Quarterly Notes 108, 1999

This range spans the North American

late Whiterockian-early Mohawkian

series, which Webby (1995) equated

with the late Darriwilian to early

Gisbornian interval.

Conodont Sample C1490

llochthonous limestone in Oakdale

Formation

GR 684000E 6361550N Cumnock

1:50 000 map

Conodonta

Ansella

Appalachignathus delicatulus

Bergström, Carnes, Ethington, Votaw

& Wigley

Bryantodina

Icriodella

Panderodus

Protopanderodus

Plectodina aculeata

Hadding

Gastropoda

Brachiopoda

lingulate fragments

Co-occurrence of

Appalachignathus

and

Plectodina aculeata

in sample

C1490 implies correlation with the

P. aculeata

and lower

Erismodus

quadridactylas

zones of the basal

Mohawkian in the North American

Midcontinent Fauna (cf Sweet 1988,

chart 1), approximately equivalent to

the upper half of the Gisbornian 1

stage in Australian usage (Nicoll &

Webby 1996). In Tasmania, Banks

and Burrett (1980) recorded

Appalachignathus

sp from their

assemblages OT10 and OT11,

correlated with the late Darriwilian

(Da3-Da4). The abundance of this

genus in widely separated localities

(C1414, C1425 and C1490) along the

northern MVB suggests derivation

from shallow-water carbonates of this

age (Wahringa Limestone Member

and equivalent units, now eroded or

covered). Those units presumably

accumulated on the crest or flanks of

the MVB, prior to their redeposition as

allochthonous blocks in deeper-water

younger clastic beds of the Oakdale

Formation.

Eastonian faunas — eastern belt

The second distinctive conodont

auna recovered from the Oakdale

Formation occurs in bedded, apparently

in situ limestones, probably deposited

in moderately deep water. Sample

C1388 (from Barham Winchester

property, 10 km northeast of Molong)

yielded

Belodina confluens

and

Yaoxianognathus tunguskaensis

indicative of the “lower assemblage”

(early Eastonian, Ea1) of Zhen and

Webby (1995).

Conodont Sample C1432

autochthonous limestone in the

Oakdale Formation

GR 681476E 6371233N Cumnock

1:50 000 map

Conodonta

Panderodus

Paroistodus

Periodon

Plectodina

Protopanderodus

Yaoxianognathus

Y. sesquipedalis

(Nowlan & McCracken)

Ostracoda

4 genera

Bryozoa

several genera, mainly trepostomes,

and a phylloporinid

Brachiopoda

lingulates (abundant but fragmentary)

2 articulate genera (1 is possibly

Christiania

)

Trilobita

remopleuridid

odontopleurid

Porifera

lithistid sponge

Late Eastonian graptolites confirm

the age given by the shelly fauna in

sample C1432 (listed above), which

strongly resembles the assemblage

obtained from limestone breccias in

the basal Malongulli Formation (Ea3)

near Cliefden Caves. Conodonts are not

abundant in the sample, but those that

occur appear identical (or nearly so)

with specimens illustrated from that

horizon by Trotter and Webby (1995).

Eastonian faunas — western belt

Conodont Sample C1491

Oakdale Formation

GR 669273E 6401756N Wellington

1:50 000 map

Conodonta

Belodina confluens

Sweet

Drepanoistodus

Panderodus

Periodon grandis

(Ethington)

Plectodina

Protopanderodus

sp cf

P. liripipus

Kennedy, Barnes & Uyeno

Brachiopoda

new orthiid, transitional between

Orthinae and Productorthinae

undescribed new genus of

?craniopsid

Multispinula

acrotretide

discinide

lingulate

Gastropoda

indeterminate opercula

Conulariida

2 fragments

Coelenterata

Quepora

Halysites praecedens

Webby & Semeniuk

Porifera

indeterminate cylindrical or

hemispherical sponge

Bryozoa

Homotrypa

stictoporoid

Trilobita

?new encrinurid genus of sub-family

Cybelinae

indeterminate proetiid genus

Problematica

byroniid

Only Eastonian ages have been

obtained for the Oakdale Formation

and equivalent offshore strata flanking

the west side of the northern MVB.

Many components of the diverse

assemblage in sample C1491 (listed

above), particularly the undescribed

?craniopsid brachiopod and

Multispinula

, occur also in the lower

Malongulli Formation (late Eastonian)

near Cliefden Caves. Comparable

similarities are noted with the Tucklan

Formation south of Dunedoo, which

also contains an Eastonian conodont

fauna (Percival 1998). The late

Eastonian age is supported by early

halysitid corals, which make their

first appearance in the New South

Wales succession in Fauna III. Webby

and Semeniuk (1969) described

Quepora calamus

from the upper

Cargo Creek Limestone (late Eastonian

Fauna III), and

Halysites praecedens

from a slightly younger horizon in

the Canomodine Limestone and the

upper part of the Clearview Limestone

Member of the Ballingoole Limestone

Quarterly Notes 108, 1999

at Bowan Park (also Fauna III). The

species from the Oakdale Formation

is morphologically a

Quepora

(lacking

microcorallites and septa), but displays

the growth habit of

H. praecedens

, with

open chains not surrounding lacunae.

Sourges Shale

The Sourges Shale (Offenberg et al

1971; Bradley, in Pickett 1982) crops

out in a fault- bounded, complexly

folded meridional belt east and

northeast of Cumnock (figure 5).

The formation has been substantially

redefined by Morgan (in Meakin &

Morgan in prep 1999; Morgan et al

in prep 1999) because its age is

significantly older than thought by

earlier workers (Maggs 1963; Offenberg

et al 1971; Bradley, in Pickett 1982).

The eastern margin of the Sourges

Shale lies just west of the boundary

shown by Bradley (in Pickett 1982)

and does not include his Late Silurian

graptolitic black cherts.

The type section for the Sourges

Shale extends along Sourges Creek

southeast of Brookvale homestead

from just west of the limestone

member at GR 665140E 6357200N

to GR 666550E 6357310N (Cumnock

1:50 000 map), where the shale is

faulted against the Hanover Formation.

Thickness of the formation is uncertain

due to complex internal folding and

faulting. The Sourges Shale comprises

pale grey to buff, well-bedded to

laminated shale, siltstone and fine

sandstone, rare latitic volcanic rocks,

and a prominent but discontinuous

limestone member. The latter is well-

bedded to massive, and is abundantly

fossiliferous. Two samples from the

limestone member yielded diverse

Late Ordovician (Eastonian) faunas.

Conodont Sample C1519

limestone member of Sourges Shale

GR 665280E 6354080N Cumnock

1:50 000 map

Conodonta

Belodina confluens

Sweet

Belodina

B. hillae

Savage

Panderodus

Paroistodus

Phragmodus

Serraculodus

Taoqupognathus philipi

Savage or

T. blandus

Yaoxianognathus wrighti

Savage

Yaoxianognathus tunguskaensis

(Moskalenko)

distinctive but unknown “fishhook”

element

Coelenterata–Tabulata

Bagjolia

Fletcheria stipulosa

Webby

Heliolites

Tetradium

T. tenue

Webby &

Semeniuk

Tetradium

cribriforme

(Etheridge)

Brachiopoda

Eodinobolus

Protozyga definitiva

Percival

Zygospira carinata

Percival

Gastropoda

Murchisonia

Lophospira

Trochonema

Holopea

The macrofauna in sample C1519

(listed above) matches precisely the

assemblage in the Gerybong Limestone

Member of the Daylesford Limestone

in the Bowan Park Limestone Subgroup.

The tabulate corals, particularly

Tetradium

tenue

and ?

Fletcheria

stipulosa

, closely resemble species

previously described solely from the

Gerybong Limestone Member. It is

also at this level that

Zygospira carinata

first appears, in Brachiopod Fauna AB

(Percival 1992). The depositional

environment of the Gerybong

Limestone Member has been

interpreted (Percival 1995) as ranging

from low intertidal (Benthic Assemblage

2) through shallow subtidal (BA 3).

This accords well with evidence for the

depth of deposition of the limestone

member in the Sourges Shale, as the

Eodinobolus

valves present are all

transported from their preferred BA 1-2

habitat and stacked in the outcrop as

if by storm or current activity. The

age indicated is early Eastonian (Ea1),

equivalent to Webby’s (1969) coral/

stromatoporoid Fauna I.

Conodont Sample C1547

limestone member of Sourges Shale

GR 665300E 6357360N Cumnock

1:50 000 map

Conodonta

Aphelognathus packhami

Savage

Belodina confluens

Sweet

Belodina hillae

Savage

Belodina

Panderodus gracilis

(Branson &

Mehl)

Panderodus panderi

(Stauffer)

Phragmodus undatus

Branson &

Mehl

Plectodina

tenuis

(Branson & Mehl)

Pseudooneotodus mitratus

(Moskalenko)

Taoqupognathus philipi

Savage

Yaoxianognathus wrighti

Savage

Yaoxianognathus tunguskaensis

(Moskalenko)

Coelenterata

Palaeophyllum

Plasmoporella

Algae

Girvanella

The age of sample C1547 (above) is

most likely middle Eastonian (probably

Ea2-Ea3), based on the occurrence

Phragmodus undatus

— which has

previously only been rarely recorded

from Fauna II, Ea2 age strata (Zhen &

Webby 1995) and is only common in

Fauna III (Ea3) (Trotter & Webby 1995).

This age determination is supported by

the presence of corals which, although

sparse and poorly preserved, appear to

be genera which only occur in Faunas II

and III. However, the conodont fauna

also contains several elements which

are restricted elsewhere to early

Eastonian (Ea1) strata. Examples

include

Aphelognathus packhami,

which

appears to be almost entirely confined

(with one exception) to Fauna I in the

lower part (Fossil Hill Limestone) of the

Cliefden Caves Limestone Subgroup

(Savage 1990; Zhen & Webby 1995).

Confirmatory evidence is provided

by co-occurrence of species such as

Yaoxianognathus wrighti

and potentially

Taoqupognathus philipi

(although the

diagnostic Sc3 element of the latter was

not recovered, and the species may

equally well be identified as

T. blandus

of Fauna II age).

REGIONAL TECTONIC SYNTHESIS

Our developing understanding of the

geological evolution of central New

South Wales during the Ordovician is

based on detailed mapping combined

with thorough palaeontological analysis,

which has confirmed a previously

recognised consistency between the

stratigraphic histories of the central

JNVB and northern MVB (Percival et

al 1997). The palaeontological data

presented herein also define the

Quarterly Notes 108, 1999

presence of a Middle to Late Ordovician

volcanic hiatus (Glen et al 1998) across

this region of the Lachlan Orogen.

The oldest dated formation in the JNVB

is the Yarrimbah Chert Member of the

Nelungaloo Volcanics, determined by

Sherwin (1979) as late Lancefieldian

to possibly early Bendigonian in age.

On the northern MVB, the Hensleigh

Siltstone contains early Bendigonian

graptolites and conodonts, and

overlies the volcaniclastic Mitchell

Formation. Above the graptolite

horizons in both volcanic belts, there

are no units that can be positively dated

until limestones with

Pygodus

conodont

assemblages of late Darriwilian (Da3-

Da4) age. This level appears to be of

regional significance, representing a

widespread cessation of shallow water

sedimentation in the volcanic belts —

throughout the Lachlan Orogen outcrop

in central New South Wales no fossils

have been reliably dated as between

middle Bendigonian (the minimum

age of the Hensleigh Siltstone) and

late Darriwilian (Percival et al 1997).

Conodont faunas documented by Nicoll

(1980), Pickett (1985), Stewart and

Glen (1986), Pickett (1992), Fowler

and Iwata (1995), Iwata et al (1995)

and Stewart and Fergusson (1995)

are all no older than Da3 (figure 10).

The maximum extent of the

stratigraphic break between the

Early Ordovician and late Middle

Ordovician volcanic episodes could

therefore encompass all of the

Chewtonian, Castlemainian and

Yapeenian stages. The basal Fairbridge

and time-equivalent Goonumbla

Volcanics probably commenced

accumulation during the early or middle

Darriwilian, and persisted (with

intermittent development of relatively

thin, shallow-water carbonates around

isolated emergent volcanic islands) into

Late Ordovician (late Gisbornian) time.

More widespread limestone deposition

then characterised the latest Gisbornian

to early Eastonian history of the MVB

and JNVB. Given the similarity now

recognised between their sedimentary

and volcanic histories during much

of the Ordovician (figure 10), it is

probable that these areas did not start

to become distinct entities until late in

the period, around late Eastonian time

at the earliest. Although the record

of Ordovician sedimentation in the

Rockley-Gulgong Volcanic Belt to

the east is comparatively incomplete,

deep water late Eastonian faunas in

that belt are identical with those of

the MVB (Percival 1999). This lends

further support to the arc-rifting

model of Glen et al (1998). Whereas

the thrust of this latter paper was

directed towards documentation of a

volcanic hiatus in the Lachlan Orogen,

our work has concentrated on

recognition and definition of significant

sedimentological breaks in the

depositional history of this region.

The two streams of research are related

by the dependence of fossiliferous

shallow-water sediments on emergent

(or nearly so) volcanic islands as loci

of formation; their presence in turn

allows age-dating of the volcanic

phases.

SUMMARY

In the Molong Volcanic Belt succession

of central New South Wales, the oldest

fossiliferous strata currently recognised

are found in the Hensleigh Siltstone,

where Early Ordovician conodonts

occur in limestones underlying beds

containing graptolites of early

Bendigonian age. These strata are most

similar in age to the late Lancefieldian–

early Bendigonian Yarrimbah Chert

Member in the Junee–Narromine

Volcanic Belt, and presumably shared

a comparable deep-water age

depositional environment.

A major time break of regional

significance, throughout the central

New South Wales region of the Lachlan

Orogen, spans the Chewtonian,

Castlemainian and Yapeenian stages.

It separates a earliest Ordovician phase

of volcanism and volcaniclastic

deposition (Mitchell Formation) and

subsequent deep water sedimentation

(Hensleigh Siltstone), from an episode

of Middle to early Late Ordovician

volcanism (represented in the study

area by the Fairbridge Volcanics).

The Fairbridge Volcanics contain

evidence at several levels of

allochthonous limestones derived

from local shallow-water carbonate

deposits. These algal-rich limestones

also include brachiopods and

conodonts indicative of an age no

older than Darriwilian (late Middle

Ordovician).

Autochthonous limestones are present

at two distinct stratigraphic levels in the

Fairbridge Volcanics. The older of these,

the Wahringa Limestone Member, has

a late Darriwilian–early Gisbornian

(Da4-Gi1) age which is well established

by the co-occurrence of

Periodon

aculeata, Phragmodus flexuosus

and

Pygodus

sp in the basal beds of the

member.

Belodina compressa

is also

abundant in the middle and upper part

of the Wahringa Limestone Member,

but this conodont species is absent

from the younger Yuranigh Limestone

Member of the upper Fairbridge

Volcanics.

Any time gap separating deposition of

the Yuranigh Limestone Member (most

likely of late Gisbornian, Gi2 age) and

the overlying Reedy Creek Limestone

was of relatively limited duration, as

the long-ranging conodont

Belodina

confluens

(which in North American

successions succeeds the occurrence

B. compressa

) is prominent at both

levels. The brachiopod fauna of the

Yuranigh Limestone Member differs

only at species level from those of the

Reedy Creek and equivalent Eastonian

limestones. The Reedy Creek Limestone

contains a typical Fauna I (of early

Eastonian, Ea1) age macrofossil and

microfossil assemblage in its lower,

thinly bedded section. Conodonts

identified in this study demonstrate

that the upper part of the formation

extends into Fauna II (Ea2 age).

The Oakdale Formation appears to

have been deposited from ?Gisbornian

to Eastonian or Bolindian time on the

eastern flank of the MVB, although

these sediments enclose allochthonous

limestones of late ?Darriwilian to

Eastonian age which were presumably

sourced from the Wahringa and

Yuranigh Limestone Members (or their

equivalents) and the Reedy Creek

Limestone, deposited on the crest of

the MVB to the west. Ages obtained

for the Oakdale Formation, and the

correlative Sourges Shale, on the

western flank of the MVB are restricted

to the Eastonian.

ACKNOWLEDGMENTS

Barry Webby, Gordon Packham, John

Pickett and Dick Glen are thanked for

their incisive reviews of this paper.

Gary Dargan assisted with thin section

preparation. SEM illustrations of the

conodonts were taken by Yongyi Zhen,

who also checked their identifications.

Macrofossil photographs were prepared

by David Barnes. Margaret McLaren

Quarterly Notes 108, 1999

Figure 10. Revised correlations through the Ordovician for selected regions across the Lachlan Orogen, from west (Cobar Trough)

to east (Monaro Trough, and accreted Narooma Terrane). Note the extent of the stratigraphic gap from the late Bendigonian

and Chewtonian, to the early Darriwilian.

Abbreviations in left-hand column refer to the standard subdivisions of the Victorian graptolite-based biostratigraphic

scheme.

Asterisks mark points of biostratigraphic control.

References for individual regions — Cobar Trough: Iwata et al (1995), Stewart &Glen (1986); Junee–Narromine Volcanic

Belt: Percival et al (1997), Pickett (1985), Sherwin (1979); Northern Molong Volcanic Belt: this paper; Rockley–Gulgong

Volcanic Belt: Fowler & Iwata (1995), Percival (1999), Stewart and Ferguson (1995); Monaro Trough: Jenkins (1982),

Nicoll (1980); Narooma Terrane: Stewart & Glen (1991).

La1

La1.5

La2

La3

Be1

Be2

Be3

Be4

Ch1

Ch2

Ca1

Ca2

Ca3

Ca4

Ya1

Ya2

Da1

Da2

Da3

Da4

Gi1

Gi2

Ea1

Ea2

Ea3

Ea4

Bo1

Bo2

Bo3

Bo4

Bo5

BILLABONG

CREEK

LIMESTONE

Gunningbland

Shale Mbr

GOONUMBLA VOLCANICS

MEMBER

CHEESE-

MANS CK

FAIRBRIDGE

VOLCANICS SOURGES

SHALE

GIRILAMBONE

GROUP

BALLAST

OAKDALE FORMATION

SOFALA VOLCANICS

ADAMINABY

GROUP

and

TRIANGLE

GROUP

PITTMAN FM

"MONGA

Turbidite

Sequence

WAGONGA GROUP

CAMBRIAN

JUNEE-

NARROMINE

VOLC. BELT

SILURIAN

23095

EARLY

REEDY

CREEK

LST

WAHRINGA

LST MBR

YURANIGH

TUCKLAN

and

BURRANAH

FORMATION

BEDS"

NAROOMA

CHERT

YARRIMBAH

CHERT

MEMBER

NELUNGALOO

VOLCANICS

MITCHELL

FORMATION

HENSLEIGH

SILTSTONE

ORDOVICIAN

MIDDLE LATE

*** *

NORTHERN

VOLCANIC BELT

MOLONG ROCKLEY-

VOLCANIC BELT

GULGONG MONARO

TROUGH NAROOMA

TERRANE

COBAR

TROUGH

WAGONGA GROUP

Quarterly Notes 108, 1999

and Cheryl Hormann skilfully drafted

the maps and diagrams. Richard Facer

improved the final presentation with his

attention to detail. This is a contribution

to IGCP Project No 410: The Great

Ordovician Biodiversification Event.

REFERENCES

ADRIAN J. 1956. Geology of the Molong

district. B.Sc. (Hons) thesis,

University of Sydney

(unpublished).

ADRIAN J. 1971. Stratigraphic units in

the Molong district, New South

Wales.

Geological Survey of

New South Wales, Records

13,

179-198.

BANKS M.R. & BURRETT C.F. 1980. A

preliminary Ordovician

biostratigraphy of Tasmania.

Geological Society of Australia,

Journal

26, 363-375.

BERGSTRÖM S.M., CARNES J.B., ETHINGTON

R.L., VOTAW R.B. & WIGLEY P.B .

1974.

Appalachignathus

, a new

multielement conodont genus

from the Middle Ordovician of

North America.

Journal of

Paleontology

48, 227-235.

COCKS L.R.M. & RONG J.Y. 1989.

Classification and review of

the brachiopod superfamily

Plectambonitacea.

British

Museum of Natural History,

Geology Series, Bulletin

45,

77-163.

ETHINGTON R.L. 1959. Conodonts from

the Ordovician Galena Formation.

Journal of Paleontology

33,

257-292.

FARRELL J.R. 1996. New data on Late

Ordovician, Silurian and Early

Devonian conodont faunas from

the Larras Lee and Wellington

districts, east-central New South

Wales.

SUCOGG Symposium

1996: The Geological Evolution

of Eastern Australia,

University

of Sydney, Abstracts, 20-21.

FOWLER T.J. & IWATA K. 1995. Darriwilian–

Gisbornian conodonts from the

Triangle Group, Triangle Creek

area, New South Wales.

Australian

Journal of Earth Sciences

42,

119-122.

GLEN R.A., WALSHE J.L., BARRON L.M. &

WATKINS J.J. 1998. Ordovician

convergent-margin volcanism

and tectonism in the Lachlan

sector of east Gondwana.

Geology

26, 751-754.

IWATA K., SCHMIDT B.L., LEITCH E.C., ALLAN

A.D. & WATANABE T. 1995.

Ordovician microfossils from the

Ballast Formation (Girilambone

Group) of New South Wales.

Australian Journal of Earth

Sciences

42, 371-376.

JENKINS C.J. 1982. Darriwilian (Middle

Ordovician) graptolites from

the Monaro Trough sequence

east of Braidwood, New South

Wales.

Linnean Society of New

South Wales

Proceedings

106,

173-179.

KEMEZYS K.J. 1959. Geology around

Bakers Swamp. B Sc (Hons)

thesis, University of Sydney

(unpublished).

LISHMUND S.R., DAWOOD A.D. & LANGLEY

W.V. 1986. The limestone

deposits of New South Wales.

Geological Survey of New South

Wales

Mineral Resources No.

25,

2nd Edition

, 373 pp.

MAGGS D.F. 1963. The stratigraphy of

the Yeoval–Cumnock–Manildra

region. Ph D thesis, University of

New South Wales, Sydney

(unpublished).

MCTAVISH R.A. 1973. Prioniodontacean

conodonts from the Emanuel

Formation (lower Ordovician) of

Western Australia.

Geologica et

Palaeontologica

7, 27-58.

MEAKIN N.S. & MORGAN E.J. in prep 1999.

Dubbo 1:250 000 Geological

Sheet SI/55-4: Explanatory Notes.

Geological Survey of New South

Wales, Sydney.

MORGAN E.J., CAMERON R.G., COLQUHOUN

G.P., MEAKIN N.S., RAYMOND O.L.,

SCOTT M.M., WATKINS J.J., BARRON

L.M., HENDERSON G.A.M., KRYNEN

J.P., POGSON D.J., WARREN A.Y.E.,

WYBORN D., YOO E.K., GLEN R.A. &

JAGODZINSKI E.A. in prep 1999.

Dubbo 1:250 000 Geological

Sheet SI/55-4 (second edition).

Geological Survey of New South

Wales, Sydney/Australian

Geological Survey Organisation,

Canberra.

NICOLL R.S. 1980. Middle Ordovician

conodonts from the Pittman

Formation, Canberra, ACT.

BMR

Journal of Australian Geology &

Geophysics

5, 150-153.

NICOLL R.S. & WEBBY B.D. 1996.

Ordovician (Chart 2) , pp 77-87.

Young G.C. & Laurie J.R. eds.

An Australian Phanerozoic

Timescale

. Section 2, Explanatory

notes on biostratigraphic charts.

Oxford University Press,

Melbourne, 279 pp.

OFFENBERG A.C., ROSE G.M. & PACKHAM

G.H. 1971.

Dubbo 1:250 000

Geological Series Sheet SI/55-4.

Geological Survey of New South

Wales, Sydney.

PACKHAM G.H. 1968. The lower and

middle Palaeozoic stratigraphy

and sedimentary tectonics of the

Sofala–Hill End–Euchareena

region, N.S.W.

Linnean Society of

New South Wales

Proceedings

93, 111-163.

PACKHAM G.H. ed. 1969. The geology of

New South Wales.

Geological

Society of Australia

Journal

16,

1-654.

PALMIERI V. 1978. Late Ordovician

conodonts from the Fork Lagoons

Beds, Emerald area, central

Queensland.

Geological Survey

of Queensland, Publication

369

(Palaeontological Paper 43),

31 pp.

PERCIVAL I.G. 1992. Ordovician

brachiopod biostratigraphy of

central-western New South Wales,

pp 215-229.

Webby B.D. &

Laurie J.R. eds.

Global

Perspectives on Ordovician

Geology

. A.A. Balkema,

Rotterdam, 513 pp.

PERCIVAL I.G. 1995. Ordovician

gastropods of New South Wales –

ecologic and biogeographic

relationships, pp 453-456.

Cooper J.D., Droser M.L. & Finney

S.C. eds.

Ordovician Odyssey:

short papers for the Seventh

International Symposium on the

Ordovician System, Las Vegas,

1995.

Pacific Section, Society for

Sedimentary Geology (SEPM),

Fullerton, California, 498 pp.

PERCIVAL I.G. 1999. Late Ordovician

biostratigraphy of the northern

Rockley–Gulgong Volcanic Belt.

Geological Survey of New South

Wales, Quarterly Notes

108, 1-8.

PERCIVAL I.G., WEBBY B.D. & ZHEN Y.Y.

1997. Revised Ordovician

biostratigraphy of New South

Wales.

Symposium on the

Quarterly Notes 108, 1999

Palaeobiogeography of

Australasian Faunas and Floras

(PAFF), University of Wollongong,

Geological Society of Australia,

Abstracts 48,

58-59.

PICKETT J.W. 1972. Late Ordovician

conodonts from Bodangora.

Palaeontological Report 72/17.

Geological Survey of New South

Wales, Report GS1972/219

(unpublished).

PICKETT J.W. 1982 ed. The Silurian

system in New South Wales.

Geological Survey of New South

Wales

Bulletin

29, 264 pp.

PICKETT J.W. 1985. Correlation of a mid

to late Ordovician section near

Parkes, New South Wales

Geological Survey of New

Zealand

Records

9, 77.

PICKETT J.W. 1992. Conodont

assemblages from limestones

north of “Millamolong”, via

Mandurama. Palaeontological

Report 92/11. Geological Survey

of New South Wales, Report

GS1992/356 (unpublished).

POGSON D.J. & WATKINS J.J. 1998.

Bathurst 1:250 000 Geological

Sheet SI/55-8: Explanatory Notes

Geological Survey of New South

Wales, Sydney, 430 pp.

PRITCHARD P.W. 1955. The geology of

the Molong district. B Sc (Hons)

thesis, University of Sydney

(unpublished).

RAYMOND O.L., POGSON D.J., et al [14

others] 1998.

Bathurst

1:250 000 Geological Sheet

SI/55-8

(second edition)

Geological Survey of New South

Wales, Sydney/Australian

Geological Survey Organisation,

Canberra.

ROSS J.P. 1961. Ordovician, Silurian,

and Devonian bryozoa of

Australia.

Bureau of Mineral

Resources, Geology and

Geophysics, Bulletin

50,

172 pp.

ROSS R.J. and 27 contributors 1982.

The Ordovician System in the

United States. Correlation Chart

and Explanatory Notes

International Union of Geological

Sciences, Publication No. 12,

73 pp.

SAVAGE N.M. 1990. Conodonts of

Caradocian (Late Ordovician)

age from the Cliefden Caves

Limestone, southeastern

Australia.

Journal of Paleontology

64, 821-831.

SERPAGLI E. 1974. Lower Ordovician

conodonts from Precordilleran

Argentina (Province of San Juan).

Bollettino della Societa

Palaeontologica Italiana

13 (1-2),

17-98.

SHERGOLD J., LAURIE J. & NICOLL R.S.

1995. Biostratigraphy of the

Prices Creek Group (Early

Ordovician, late Lancefieldian–

Bendigonian), on the Lennard

Shelf, Canning Basin, Western

Australia, pp 93-96.

Cooper

J.D., Droser M.L. & Finney S.C.

eds.

Ordovician Odyssey:

short papers for the Seventh

International Symposium on

the Ordovician System

. Pacific

Section, Society for Sedimentary

Geology (SEPM), Fullerton,

California, 498 pp.

SHERWIN L. 1979. Age of the

Nelungaloo Volcanics, near

Parkes.

Geological Survey of New

South Wales, Quarterly Notes

35,

15-18.

SHERWIN L. 1994a. Fossils from the

Orange 1:100 000 sheet No 2.

Palaeontological Report 94/04.

Geological Survey of New South

Wales, Report GS1994/101

(unpublished).

SHERWIN L. 1994b. Fossils from the

Molong 1:100 000 sheet.

Palaeontological Report 94/08.

Geological Survey of New South

Wales, Report GS1994/138

(unpublished).

STAIT B., WEBBY B.D. & PERCIVAL I.G.

1985. Late Ordovician nautiloids

from central New South Wales,

Australia.

Alcheringa

9, 143-157.

Stevens N.C. 1950. The geology of

the Canowindra district, N.S.W.

Part I. The stratigraphy and

structure of the Cargo–Toogong

district.

Royal Society of New

South Wales

Journal and

Proceedings

82, 319-337.

STEWART I.R. & FERGUSSON C.L. 1995.

Ordovician conodonts from the

Lue Beds, Mudgee and Sunlight

Creek Formation, Goulburn,

New South Wales.

Australasian

Association of Palaeontologists

Memoir

18, 164.

STEWART I.R. & GLEN R.A. 1986. An

Ordovician age for part of the

Girilambone Group at Yanda

Creek, east of Cobar.

Geological

Survey of New South Wales,

Quarterly Notes

64, 23-25.

STEWART I.R. & GLEN R.A. 1991. New

Cambrian and Early Ordovician

ages from the New South Wales

south coast.

Geological Survey

of New South Wales, Quarterly

Notes

85, 1-8.

STRUSZ D.L. 1960. The geology of

the Parish of Mumbil, near

Wellington, N.S.W.

Royal Society

of New South Wales

Journal and

Proceedings

93, 127-136.

STRUSZ D.L. 1961. Lower Palaeozoic

corals from New South Wales.

Palaeontology

4, 334-361.

SWEET W.C. 1988.

The Conodonta:

Morphology, Taxonomy,

Paleoecology, and Evolutionary

History of a Long-Extinct Animal

Phylum

. Clarendon Press, Oxford,

212 pp.

SWEET W.C. & BERGSTRÖM S.M. 1962.

Conodonts from the Pratt Ferry

Formation (Middle Ordovician) of

Alabama.

Journal of Paleontology

36, 1214-1252.

TALENT J.A. (co-ordinator) 1995.

Ordovician-Devonian of

Southeastern Australia. Excursion

guide, AUSCOS-1/Boucot pre-

conference excursion 1, 8 July-1

7 July, 1995. Macquarie University

Centre for Ecostratigraphy and

Palaeobiology, Sydney

(unpublished).

TROTTER J.A. & WEBBY B.D. 1995. Upper

Ordovician conodonts from the

Malongulli Formation, Cliefden

Caves area, central New South

Wales.

AGSO Journal of Australian

Geology & Geophysics

15 (for

1994), 475-499.

VANDYKE A. & BYRNES J.G. 1976.

Palaeozoic succession beneath

the Narragal Limestone, Oakdale

Anticline near Mumbil.

Geological

Survey of New South Wales

Records

17, 123-134.

WEBBY B.D. 1969. Ordovician

stromatoporoids from New

South Wales.

Palaeontology

12,

637-662.

WEBBY B.D. 1973.

Remopleurides

and

other Upper Ordovician trilobites

Quarterly Notes 108, 1999

from New South Wales.

Palaeontology

16, 445-475.

WEBBY B.D. 1974. Upper Ordovician

trilobites from central New

South Wales.

Palaeontology

17,

203-252.

WEBBY B.D., 1976. The Ordovician

system in south-eastern Australia,

pp 417-446.

Bassett M.G. ed.

The Ordovician System:

proceedings of a Palaeontological

Association symposium,

Birmingham, September 1974.

University of Wales Press and

National Museum of Wales,

Cardiff.

WEBBY B.D. 1979. The oldest

Ordovician stromatoporoids from

Australia.

Alcheringa

3, 237-251.

WEBBY B.D. 1995. Towards an

Ordovician time scale, pp 5-9.

Cooper J.D., Droser M.L. &

Finney S.C. eds.

Ordovician

Odyssey: short papers for the

Seventh International Symposium

on the Ordovician System

. Pacific

Section, Society for Sedimentary

Geology (SEPM), Fullerton,

California, 498 pp.

WEBBY B.D. & KRUSE P.D. 1984. The

earliest heliolitines: a diverse

fauna from the Ordovician of New

South Wales.

Palaeontographica

Americana

54, 164-168.

WEBBY B.D. & SEMENIUK V. 1969.

Ordovician halysitid corals from

New South Wales.

Lethaia

345-360.

WEBBY B.D., VANDENBERG A.H.M., COOPER

R.A., BANKS M.R., BURRETT C.F.,

HENDERSON R.A., CLARKSON P.D.,

HUGHES C.P., LAURIE J., STAI T B.,

THOMSON M.R.A. & WEBERS G.F.

1981.

The Ordovician System

in Australia, New Zealand and

Antarctica. Correlation chart

and explanatory notes

International Union of Geological

Sciences, Publication No 6,

64 pp.

WOLF K.H., FLUGEL E. & KEMEZYS K.J.

1968. Ordovician calcareous

algae from a bioherm, Blathery

Creek Volcanics, New South

Wales (Australia).

Review of

Palaeobotany and Palynology

147-153.

ZHEN Y.Y. & WEBBY B.D. 1995. Upper

Ordovician conodonts from

the Cliefden Caves Limestone

Group, central New South

Wales, Australia.

Courier

Forschungsinstitut Senckenberg

182, 265-305.

Note. Figure 8 in the Molong paper of this issue

was prepared in the "usual" way before digital

manipulation. Figure 3 in the Gulgong paper (and

figures 3 and 4 in the paper by I.G. Percival in

Quarterly Notes

No 107) were prepared directly

from digital data recorded by the SEM. Readers

may be interested in the comparison.

Quarterly Notes 108, 1999

Quarterly Notes of the

Geological Survey

of New South Wales

No 108

GUEST EDITOR:

Richard A. Facer

GEOLOGICAL EDITOR:

Ross Stewart

MANAGER PUBLISHING & MARKETING:

Peter Walker

CARTOGRAPHY:

Margaret McLaren

Cheryl Hormann

GRAPHIC DESIGN:

Val Grant

PUBLISHING ASSISTANT:

Dora Lum

CONTENTS

Late Ordovician biostratigraphy of the

northern Rockley–Gulgong Volcanic Belt .................... 1

I.G. Percival

Ordovician stratigraphy of the

northern Molong Volcanic Belt:

new facts and figures ............................................ 8

I.G. Percival. E.J. Morgan & M.M. Scott

NEXT ISSUE

Development of DIGS®

Digital Imaging GS (Geological Survey) System

G. Brookes, J. Mong, J. Xie, C. Bembrick, N. Aadil, G. Kouzmina,

B. Shi & S. Barry

from the text of this publication and copies of maps, figures, tables, etc

(excluding any subject to pre-existing copyright) may be used in scientific

articles, exploration reports and similar works provided that the source is

acknowledged and subject to the proviso that any excerpt used, especially in

a company prospectus, Stock Exchange report or similar, must be strictly fair

and balanced. Other than for the purposes of research or study the whole work

may not be reproduced without the permission in writing of the Department.

www.minerals.nsw.gov.au

Issued February 1999

ISSN 0155-3410

Published under the authority of the

Minister for Mineral Resources

1999

Inception and early evolution of the Ordovician Macquarie Arc of Eastern Gondwana margin: Zircon U-Pb-Hf evidence from the Molong Volcanic Belt, Lachlan Orogen

Article

Feb 2019
LITHOS

The Ordovician Macquarie Arc is faulted against and surrounded by coeval Gondwana-derived quartz turbidites, in the Lachlan Orogen of southeastern Australia. How these juvenile, island arc rocks were emplaced and structurally interleaved with continental margin sequences of eastern Gondwana is an ongoing debate. Understanding the inception of this arc is critical in building an accurate Early Paleozoic reconstruction for eastern Gondwana. However, the arc's inception and early evolution are poorly-constrained due to the lack of reliable geochronological data. Integrated field observations, zircon U-Pb-Hf, mineral and whole rock geochemistry are presented here for the oldest units of the Molong Volcanic belt, which is a central strand of the dissected Macquarie arc. Geochemistry indicates that these are calc-alkaline rocks with high-K (locally shoshonitic) to medium-K affinities. The stratigraphically-lowest mafic volcanic and volcano-sedimentary rocks of the Mitchell Formation have a unimodal earliest Ordovician zircon U–Pb age of 479.8 ± 3.8 Ma, with uniform depleted mantle like initial zircon εHf values of +12 to +13. The lack of pre-Ordovician zircons and the uniform positive initial εHf value indicate that the Macquarie arc was initiated in an intra-oceanic setting, far from the influence of eastern Gondwana. The stratigraphically overlying Fairbridge Volcanics includes some more evolved volcano-sedimentary components and has a polymodal, but mostly Ordovician, zircon U–Pb age population, with a youngest component at 444.3 ± 2.4 Ma. Overall, its Ordovician grains show a greater spread in initial εHf values from +14 down to +8 than the Mitchell Formation, which suggests some continental influence, at least 35 million years after the arc was initiated. The lack of any significant Gondwanan inheritance in Early Ordovician volcaniclastic rocks of the Macquarie Arc along with geochemical comparisons with modern island arcs, suggest that the arc evolved outboard of Gondwana probably as a result of steep, easterly-directed subduction. As the Macquarie arc approached eastern Gondwana there would have been increasing quantities of continent derived sediment subducted beneath the arc which may account for the decreasing and more variable zircon initial εHf values and the appearance of sparse Precambrian continental detritus at the arc's moribund stage. The collision of the Macquarie island arc with Gondwana initiated the Benambran Orogeny and reflects an important mechanism of episodic continental growth involving the addition of juvenile oceanic crust to a continental margin, which contrasts and alternates with periods of purely accretionary growth.

Ordovician rhipidognathid conodonts from Australia and Iran

Article

Jan 2001

Based on specimens from Australia and Iran, five species of rhipidognathid conodonts, Appalachignathus delicatulus Bergström, Carnes, Ethington, Votaw, and Wigley, 1974, Bergstroemognathus extensus (Graves and Ellison, 1941), B. hubeiensis An (MS) in An, Chen, and Li, 1981, B. kirki Stait and Druce, 1993, and Rhipidognathus ? yichangensis (Ni, 1981), are described and revised in terms of multielement morphology. All three genera comprising the Rhipidognathidae are interpreted as having a septimembrate apparatus, partially confirmed by bedding plane assemblages of B. extensus from Victoria. Occurrence of A. delicatulus in allochthonous limestones (about the Middle-Upper Ordovician boundary) of central New South Wales is the first record of the species outside North America. Recognition of Rhipidognathus ? yichangensis in Early Ordovician strata of the Canning Basin, reinforces biogeographic affinities of Australia and South China. The three described species of Bergstroemognathus are mainly restricted to late Early Ordovician strata. Bergstroemognathus extensus is widely distributed in North America, western Argentina (Precordillera), China, and Australia. Bergstroemognathus hubeiensis , described from east-central Iran, has been previously recorded only from China, while the slightly younger B. kirki seems endemic to central and northern Australia, where it was restricted to shallow, warm water environments. In contrast, B. extensus and B. hubeiensis inhabited a spectrum of water depths from shallow to deep.

Ordovician (Darriwilian–Katian) lingulate brachiopods from central New South Wales, Australia

Article

Full-text available

May 2016

This paper completes the systematic description of all known lingulate brachiopods from the Ordovician Macquarie Volcanic Province in central New South Wales, including a new genus and species, Psygmakantha malachiensis and the new species Acrosaccus scutatus, Apatobolus anoskelidion, Atansoria australis, Biernatia pseudoplana, Biernatia wrighti, Eoconulus puteus, Nushbiella kleithria and Scaphelasma quadratum. The oldest lingulates documented are from latest Middle Ordovician (Darriwilian) to early Upper Ordovician (Sandbian) limestones within the Fairbridge Volcanics, which yield Acrosaccus, Biernatia, Elliptoglossa, Ephippelasma and Nushbiella. Late Ordovician (Katian) lingulates described from the Fossil Hill Limestone (Benthic Assemblage 1-3) of the Cliefden Caves area include Acrosaccus, Plectoglossa and Pseudolingula?. Slightly younger, outer shelf to upper slope (BA 4-5) high diversity lingulate faunas, comprising most of the new taxa described herein, occur in allochthonous limestone breccias of the Malongulli Formation, in the Downderry Limestone Member of the Ballingoole Limestone, and in limestones redeposited in the Barnby Hills Shale and other Silurian strata. These deeper water faunas are dominated by acrotretoids, including species of Conotreta, Ephippelasma, Hisingerella, Rhysotreta?, Scaphelasma, Spondylotreta and Undiferina. Additional material of species previously described from graptolitic siltstones of the lower Malongulli Formation, including Elliptoglossa adela, Paterula malongulliensis and Hisingerella hetera, are figured by SEM photography for the first time. Biogeographic affinities of the lingulate faunas described here align most strongly with those from Kazakhstan, terranes along the perimeter of Laurentia, New Zealand, and to a lesser extent with South China.

Conodont faunas from the mid to late ordovician boundary interval of the Wahringa Limestone Member (Fairbridge Volcanics), Central New South Wales

Article

Full-text available

Jan 2004
J NEW MAT ELECTR SYS

Twenty-nine conodont species are documented from the Wahringa Limestone Member and other isolated limestone pods of the Fairbridge Volcanics, in the Bakers Swamp area between Wellington and Orange, central New South Wales. Three conodont assemblages are recognised within the Wahringa Limestone Member. The oldest is characterised by the occurrence of Pygodus protoanserinus and Pygodus serra, indicative of a late Darriwilian age (Da3 to early Da4). The overlying assemblage B, bearing Belodina monitorensis, probably ranges across the Mid to Late Ordovician boundary. Assemblage C with abundant Belodina compressa in the upper part of the Wahringa Limestone Member is of late Gisbomian (Gi2) age. The conodont faunas are significant in being the first described from the Lachlan Orogen in New South Wales spanning the Mid to Late Ordovician interval, although resolution of the actual boundary level is limited in the section measured.

Key features of the Macquarie Arc, eastern Lachlan Orogen; a 2007 summary

Article

Full-text available

Jan 2009

Ordovician marginal basin evolution near the palaeo-Pacific east Gondwana margin, Australia

Article

Full-text available

Sep 2014

Although the Ordovician Macquarie Arc, part of the eastern Lachlan Orogen of southeastern Australia, has long been considered to be an intra-oceanic arc within an accretionary orogen, key characteristics contrast with more typical examples of accreted arcs. Significantly, multiple stacked phases of mafic to intermediate volcanic rocks, with suprasubduction-zone chemistry, are flanked to the east and west by extensive, coeval continental margin turbidite, chert and black shale sequences. By analysing stratigraphic and contact relationships within and between the volcanic rocks, ophiolitic components (sensu lato) and turbidite sequences, constrained by precise biostratigraphy, we document a repeated cycle of uplift, upper-plate extension and collapse common to all sequences. This cycle is interpreted as resulting from localized extension (rifting or hyper-extension and lower-crustal delamination) within a continent-margin sequence developed upon an already established marginal or back-arc basin of probable middle to late Cambrian age. Our interpretation provides a counter-example to prevailing arc accretion models by inferring extensional tectonics at the palaeo-Pacific east Gondwana margin during the Ordovician with development of alkalic and calc-alkalic Cu-Au porphyry deposits away from an active arc system.

The Ordovician System in Australia and New Zealand

Article

Feb 2023

The stratigraphic overview presented in this chapter substantially updates and revises the last major review of the Ordovician rocks of Australia and New Zealand published forty years ago. In the western two-thirds of the present-day continent of Australia, Ordovician sedimentary rocks are restricted to intracratonic basins. The Canning Basin (Western Australia) and Amadeus Basin (central Australia) contain the best known Lower and Middle Ordovician shallow marine successions. The eastern third of the continent, known as the Tasmanides, comprises multiple orogens (i.e. Delamerian, Lachlan, New England, Thomson, Mossman) that formed along the convergent East Gondwana Margin. As a result, volcanic and intrusive rocks are much more common in these orogens than in the intracratonic basins. Their deep-water depositional environments span 31 graptolite biozones. Slope and basinal siliceous sedimentary rocks are constrained by a newly defined set of 12 conodont biozones, complementing the conodont biostratigraphic scheme refined for shallow-water environments from the basal boundary of the Ordovician to the latest Katian. In some places these conodont biozones are integrated with radiometric ages from tuff interbeds (e.g. Canning Basin). Ordovician graptolitic strata in the Buller Terrane of New Zealand share palaeogeographic links with those in the Bendigo Zone of the western Lachlan Orogen.

Late Ordovician conodont biozonation of Australia—current status and regional biostratigraphic correlations

Article

Mar 2017

Zhen, Y.Y. & Percival, I.G. March 2017. Late Ordovician conodont biozonation of Australia—current status and regional biostratigraphic correlations. Alcheringa 41, xxx–xxx. ISSN 0311-5518. Seven conodont biozones are recognized in the Upper Ordovician of Australia. The Pygodus anserinus, Belodina compressa and Phragmodus undatus–Tasmanognathus careyi biozones are successively represented in the Sandbian. Although the Erismodus quadridactylus Biozone of the late Sandbian North America Midcontinent succession was previously recognized in the Stokes Siltstone of the Amadeus Basin and the Mithaka Formation of the Georgina Basin in central-north Australia, we argue for a middle–late Darriwilian age for these two units. Four conodont biozones, from oldest to youngest the Taoqupognathus philipi, T. blandus, T. tumidus–Protopanderodus insculptus and Aphelognathus grandis biozones, are established in the Katian of eastern Australia. Taoqupognathus species are particularly useful in correlation of the lower–middle Katian successions of eastern Australia with contemporary rocks in other parts of eastern Gondwana and peri-Gondwana, such as with the three major terranes of North and South China and Tarim. These regions, together with Sibumasu and eastern Australia, were part of the Australasian Superprovince during the Late Ordovician, with a strong palaeobiogeographic identity signalled by domination of Taoqupognathus, Tasmanognathus and Yaoxianognathus. Longstanding difficulties for precise correlation with the well-established North American Midcontinent or Baltoscandian successions in the Late Ordovician, owing mainly to strong endemism of the Australian faunas particularly from shallow-water settings, have been resolved by integration of regional conodont biostratigraphic schemes. The conodont biozonation of the Australian Upper Ordovician reviewed herein also provides a crucial chronological reference for better constraining the temporal and spatial range of Late Ordovician tectonostratigraphic events across the intracratonic basins of northern and western Australia and orogenic belts of eastern Australia. Yong Yi Zhen* [yong-yi.zhen@industry.nsw.gov.au] and Ian G. Percival [ian.percival@industry.nsw.gov.au], Geological Survey of New South Wales, W.B. Clarke Geoscience Centre, 947–953 Londonderry Road, Londonderry NSW 2753, Australia.

Late Ordovician Conodonts and Brachiopods from near Greenvale in the Broken River Province, North Queensland

Article

Full-text available

Dec 2015
J NEW MAT ELECTR SYS

Late Ordovician conodonts and brachiopods are described from limestones (previously referred to the Carriers Well Formation) in the Wairuna Formation of the Broken River Province. The conodonts include the new genus and species Molloydenticulus bicostatus. Scabbardella altipes, Besselodus fusus sp. nov. and Protopanderodus liripipus dominate the conodont fauna of 24 species, which is typical of the Protopanderodus biofacies, with two large, robust species of Protopanderodus making up about one-quarter of recovered elements. Associated lingulate brachiopods include species of Acrosaccus, Atansoria, Biernatia, Conotreta, Elliptoglossa, Hisingerella, Nushbiella, Paterula and Scaphelasma, identical with those known from the Malongulli Formation and correlative units of the Macquarie Volcanic Province in central New South Wales. Many of the same conodont species found in allochthonous limestones in the basal Malongulli Formation also occur in the fauna from north Queensland, supporting its assignment to the Taoqupognathus tumidus–Protopanderodus insculptus conodont Biozone of late Eastonian age, equivalent to the middle Katian Stage. Subtle palaeoecological differences between the fauna of the deeper water Malongulli Formation limestones and that from the Broken River Province limestones indicate that the latter were likely originally deposited on or near the shelf edge. Recognition of this unstable depositional environment confirms interpretation of these limestones as allochthonous, having been reworked into younger basinal sediments of the Wairuna Formation.

Middle to Late Ordovician (Darriwilian-Sandbian) conodonts from the Dawangou section, Kalpin area of the Tarim Basin, northwestern China

Article

Full-text available

Nov 2011

Yong Yi Zhen

Forty-four conodont species are documented from the Dawangou section in the Tarim Basin, which spans the Darriwilian to Sandbian interval and is the global auxiliary stratotype for the base of the Upper Ordovician. Five conodont zones are recognized in this section, including the Yangtzeplacognathus crassus, Histiodella holodentata and H. kristinae zones in the upper part of the Dawangou Formation, the Pygodus anserinus Zone from the upper part of the Saergan Formation to the lower part of the Kanling Formation, and the Baltoniodus alobatus Zone in the upper part of the Kanling Formation. Presence of the P. serra Zone is based on occurrences of this species on shale bedding planes in the lower and middle Saergan Formation, but could not be confirmed in acid-leached samples studied from this interval. The Middle/Upper Ordovician boundary occurs within graptolitic black shale of the upper Saergan Formation. Although the boundary interval was intensively sampled, conodonts were very rare, probably due to stagnant or stratified basinal environments. This documentation of the conodont faunas and biostratigraphy of the Dawangou section is considered preliminary and more detailed conodont studies are required, but the remoteness of the site hinders the further extensive sample collection needed for this purpose.

The geology of the Canowindra district, N.S.W. Part I. The stratigraphy and structure of the Cargo-Toogong district

Article

Mar 1950

N C Stevens

The geology of the parish of Mumbil, near Wellington, N.S.W

Article

Mar 1960

Desmond Leslie Strusz

Upper Ordovician conodonts from the Malongulli Formation, Cliefden Caves area, central New South Wales

Article

Jan 1994

Thirty-seven spicule-dominated clasts from limestone breccia in the lower part of the Upper Ordovician Malongulli Formation of the Cliefden Caves area, central New South Wales, have yielded a collection of 2657 conodonts. These have been assigned to 48 species. This allochthonous assemblage is a mixture of North American Midcontinent and North Atlantic-type pelagic elements, reflecting derivation from warm shallow and cooler deeper zones of the low-latitude, offshore Malongulli site. The graptolite horizons are late Eastonian in age. There is little evidence of reworking of the conodonts from older horizons. Twelve species have close North American Midcontinent affinities and may be correlated, using graphic methods, with the lower half of the Zone of Oulodus velicuspis, i.e. within the North American mid-upper Edenian Stage. -from Authors

New Cambrian and Early Ordovician ages from the New South Wales south coast

Article

Jan 1991

Upper Ordovician trilobites from central New South Wales

Article

Jan 1974
Palaeontology

B.D. Webby

Remopleurides and other Upper Ordovician trilobites from New South Wales

Article

Jan 1973
Palaeontology

B.D. Webby

Conodonts of the Ordovician Galena Formation

Article

Jan 1959

Rahymond Lindsay Ethington

Classification and review of the brachiopod superfamily Plectambonitacea

Article

Jan 1989

All nominal plectambonitacean genera are reviewed, and 79 are accepted whilst 26 are placed in synonymy or rejected. new criteria for familial and subfamilial classification are established, in order of importance i) the nature of the cardinal process (simple, trifid or trifid and undercut), ii) the presence of a bema, and iii) the presence of side septa. These result in 10 families of which 6 have between two and five subfamilies: the Family Grorudiidae and the Subfamilies Pelonomiinae, Spanodontinae, Palaeostrophomeninae and Craspedeliinae are new. Three new genera are erected, Rurambonites, Jonesea and Cooperea. Lectotypes are here selected of Strophomena nubigena and S. aranea, both of Salter, in Salter & Blanford 1865, and now ascribed to Toquimia. -Authors

The lower and middle Palaeozoic stratigraphy and sedimentary tectonics of the Sofala-Hill End-Euchareena region

Article

Jan 1968
J NEW MAT ELECTR SYS

Gordon Packham

Lower Ordovician conodonts from Precordilleran Argentina (Province of San Juan)

Article

Jan 1974

Enrico Serpagli

Late Ordovician biostratigraphy of the northern Rockley–Gulgong Volcanic Belt, and Ordovician stratigraphy of the northern Molong Volcanic Belt - new facts and figures.

Abstract and Figures

Recommended publications

Late Ordovician trilobites from the Zhusilenghaierhan area, Ejin Banner, western Inner Mongolia, Chi...

Two new Ordovician lithostratigraphic units in Wushi County, Xinjiang, China. (in Chinese with Engli...

Biostratigraphy and palaeoecology of Middle–Late Ordovician conodont and graptolite faunas of the La...

Stratigraphy of the la valute area (Mt. Zermula Massif, Carnic Alps, Italy)