Tectonic trigger to the first major extinction of the Phanerozoic: The early Cambrian Sinsk event

Abstract

The Cambrian explosion, one of the most consequential biological revolutions in Earth history, occurred in two phases separated by the Sinsk event, the first major extinction of the Phanerozoic. Trilobite fossil data show that Series 2 strata in the Ross Orogen, Antarctica, and Delamerian Orogen, Australia, record nearly identical and synchronous tectono-sedimentary shifts marking the Sinsk event. These resulted from an abrupt pulse of contractional supracrustal deformation on both continents during the Pararaia janeae trilobite Zone. The Sinsk event extinction was triggered by initial Ross/Delamerian supracrustal contraction along the edge of Gondwana, which caused a cascading series of geodynamic, paleoenvironmental, and biotic changes, including (i) loss of shallow marine carbonate habitats along the Gondwanan margin; (ii) tectonic transformation to extensional tectonics within the Gondwanan interior; (iii) extrusion of the Kalkarindji large igneous province; (iv) release of large volumes of volcanic gasses; and (v) rapid climatic change, including incursions of marine anoxic waters and collapse of shallow marine ecosystems.

Full text

Myrow et al., Sci. Adv. 10, eadl3452 (2024) 29 March 2024
SCIENCE ADVANCES | RESEARCH ARTICLE
1 of 12
GEOLOGY
Tectonic trigger to the first major extinction of the
Phanerozoic: The early Cambrian Sinsk event
Paul M. Myrow1*, John W. Goodge2,3, Glenn A. Brock4, Marissa J. Betts5, Tae- Yoon S. Park6,7,
Nigel C. Hughes8, Robert R. Gaines9
The Cambrian explosion, one of the most consequential biological revolutions in Earth history, occurred in two
phases separated by the Sinsk event, the rst major extinction of the Phanerozoic. Trilobite fossil data show that
Series 2 strata in the Ross Orogen, Antarctica, and Delamerian Orogen, Australia, record nearly identical and syn-
chronous tectono- sedimentary shifts marking the Sinsk event. These resulted from an abrupt pulse of contrac-
tional supracrustal deformation on both continents during the Pararaia janeae trilobite Zone. The Sinsk event
extinction was triggered by initial Ross/Delamerian supracrustal contraction along the edge of Gondwana, which
caused a cascading series of geodynamic, paleoenvironmental, and biotic changes, including (i) loss of shallow
marine carbonate habitats along the Gondwanan margin; (ii) tectonic transformation to extensional tectonics
within the Gondwanan interior; (iii) extrusion of the Kalkarindji large igneous province; (iv) release of large vol-
umes of volcanic gasses; and (v) rapid climatic change, including incursions of marine anoxic waters and collapse
of shallow marine ecosystems.
INTRODUCTION
e Cambrian explosion, which records the rapid radiation of most
animal phyla, took place in two phases, separated by the rst major
extinction of the Phanerozoic, the early Stage 4 Sinsk event (1–3). is
event included extinction or near extinction of many characteristic
early Cambrian clades such as archaeocyathids and hyoliths, and a
subsequent radiation of less aected brachiopods and trilobites, as
well as changes in body sizes in various groups (4). e global increase
in the abundance of unbioturbated black shale and a shi from cou-
pled to uncoupled carbon and sulfur isotopic records all indicate that
a decline in global oceanic oxygen levels played a major role in the
extinction (1–3). However, the causes of these environmental and bi-
otic changes remain poorly understood.
e Sinsk event followed a long phase of Neoproterozoic to early
Paleozoic global tectonic reorganization, including breakup of the su-
percontinent Rodinia and reassembly of most cratonic masses into
Gondwana (5). Collisional suturing during the East African and
Kuunga orogenies culminated in amalgamation of East Gondwana
(modern Africa, Antarctica, Australia, and India) during the Cam-
brian (6). Gondwana supercontinent assembly included suturing
along the East African–Antarctic Orogen, broadly fusing East (Indo-
Antarctica) and West (Africa) Gondwana between ~600 and 540 Ma
(7–10). is, in turn, triggered geodynamic reorganization of the
peri- Gondwanan realm, including a shi to widespread development
of nascent convergent plate margins (10–12) and continental- margin
arc magmatism that drove climatic warming that was conducive to
evolutionary diversication (13, 14).
In Antarctica, this global tectonic reorganization primarily includ-
ed the transition from a passive margin to an Andean- type conver-
gent plate margin along the proto- Pacic edge of the East Antarctic
craton. ere, onset of subduction by ~590million years ago (Ma) led to
the Ross Orogeny, a protracted cycle of latest Neoproterozoic to Or-
dovician magmatism, metamorphism, deformation, and syn- tectonic
erosion and sedimentation that culminated between ~525 and 490 Ma
(Fig.1) (15). e Cambrian Ross orogenic activity is well- documented
in the central Transantarctic Mountains (16–18). e Delamerian
Orogen in South Australia, situated along strike to the north on the
Rodinian and Gondwanan margins, shows a similar tectonic history,
including well- dated igneous and metamorphic events from ~515 to
490 Ma (19–21).
Here, we present data from trilobites that constrain the timing and
nature of Ross Orogenic supracrustal deformation and its erosional
and depositional response. ese are compared with faunal data from
an age- equivalent record from Kangaroo Island, South Australia, to
reveal remarkable similarities in the sedimentary signal and a near-
synchronous, Cambrian mid–Series 2 timing of supracrustal events in
these two orogens, despite dierences in paleogeographic position,
timing of the onset of subduction- related magmatism, and structural
styles (foreland versus forearc deformation).
ese supracrustal plate- margin events were synchronous within
geochronologic and biostratigraphic constraints, with a correspond-
ing transition from compressional to extensional tectonics within the
interior of post- assembly Gondwana, suggesting a causal linkage.
Coupled drowning of shale basins along active plate margins and
loading of the atmosphere with CO2 by voluminous mantle upwelling
in the extending cratonic interior together likely led to ocean warm-
ing (14), sluggish oceanic turnover, and bottom water anoxia. Criti-
cally, the timing of these changes coincides with the rst major
extinction of the Phanerozoic, the early Cambrian Sinsk event, a bi-
otic crisis that included a major extinction that decimated archaeocy-
athids. is suggests that tectonics were acting with, and perhaps a
major driver of, the widespread paleoenvironmental eects of the
Sinsk event, including perturbations to the oceans, atmosphere, and
biosphere.
1Department of Geology, Colorado College, Colorado Springs, CO 80903, USA. 2De-
partment of Earth and Environmental Sciences, University of Minnesota, Duluth,
MN 55812, USA. 3Planetary Science Institute, Tucson, AZ 85719, USA. 4School of
Natural Sciences, Macquarie University, North Ryde, Sydney, NSW 2109, Australia.
5Palaeoscience Research Centre, School of Environmental and Rural Science, Uni-
versity of New England, Armidale, NSW 2351, Australia. 6Division of Earth Sciences,
Korea Polar Research Institute, Incheon 21990, Republic of Korea. 7Polar Science,
University of Science and Technology, Daejeon 34113, Republic of Korea. 8Depart-
ment of Earth and Planetary Sciences, University of California, Riverside, CA 92521,
USA. 9Geology Department, Pomona College, Claremont, CA 91711, USA.
*Corresponding author. Email: pmyrow@ coloradocollege. edu, m_hu@ colorado-
college. edu
Copyright © 2024 The
Authors, some rights
reserved; exclusive
licensee American
Association for the
Advancement of
Science. No claim to
original U.S.
Government Works.
Distributed under a
Creative Commons
Attribution
NonCommercial
License 4.0 (CC BY- NC).
Downloaded from https://www.science.org on March 29, 2024

Myrow et al., Sci. Adv. 10, eadl3452 (2024) 29 March 2024
SCIENCE ADVANCES | RESEARCH ARTICLE
2 of 12
RESULTS
e Ross Orogen, central Transantarctic Mountains (Fig.1), records
the transition from Neoproterozoic passive- margin to Cambrian
active- margin tectonics along the Austral- Antarctic periphery of
Gondwana. ere, Archean and Proterozoic crystalline basement is
overlain by the Neoproterozoic Beardmore Group, a ri- margin suc-
cession of sandstone, shale, carbonate, diamictite, and minor volca-
nic rocks (15, 18, 22).
e Beardmore Group is succeeded by the lowermost Paleozoic
Byrd Group, consisting of carbonate platform deposits and overlying
syn- tectonic clastic molasse. e lower Cambrian Shackleton Lime-
stone at the base is a thick carbonate unit with archaeocyathid–
calcimicrobial reefs (16, 23, 24). e top of the formation is marked
by intact reefs up to 38 m thick that are draped by a phosphatic
hardground interpreted as a sediment starvation surface produced by
rapid deepening and terminal drowning of the reef system (Fig.2)
Fig. 1. Tectonic setting of the Neoproterozoic and Cambrian systems in East Antarctica and Australia. Locations of Kangaroo Island (KI) and Nimrod Glacier area of
the central Transantarctic Mountains (CTM) shown with black stars; similar geologic relations occur in the Shackleton Range (SR), shown by a white star. Early Paleozoic
trench migrated oceanward between Cambrian (1, solid line) and Devonian time (2, dashed line). ARC, Adelaide Rift Complex; FP, Fleurieu Peninsula; LFB, Lachlan Fold Belt;
NVL, northern Victoria Land; PM, Pensacola Mountains; Tas, Tasmania. Reconstruction modeled from GPlates (88) and alignment of geophysical anomalies (89), with mid-
Cambrian equator from Scotese (90). Inferred eastern edge of Precambrian cratons (purple dashed line) from Goodge and Finn (91) in Antarctica and Tasman Line (TL) in
Australia. Distribution of sedimentary units after Foden et al. (19), Goodge (15), and Cox et al. (92). Extent of Ross and Delamerian orogens shown by horizontal ruling (15,
93). Inferred Neoproterozoic rift- margin faults from Preiss (30) and Goodge (15). West- dipping early Paleozoic marginal subduction zone (blue barbed line) was sinistral-
oblique in middle Cambrian time [line 1; (60)]; by late Cambrian, convergence was geometrically more complicated (line 2), including multiple arcs and back- arcs [see (10)
and (94)]. Dashed line separates two convergent margin domains—to the south in East Antarctica dominated by Andean- type continental- margin magmatic arc, and to
the north from northern Victoria Land into Australia dominated by accretionary supra- subduction zone volcanism and marginal- basin development.
Downloaded from https://www.science.org on March 29, 2024

Myrow et al., Sci. Adv. 10, eadl3452 (2024) 29 March 2024
SCIENCE ADVANCES | RESEARCH ARTICLE
3 of 12
(16). e hardground is overlain by the Holyoake Formation, a 5-
to 10- m- thick unit of dark shale and nodular carbonate that grades
upward into siltstone to pebbly sandstone of the Starshot Forma-
tion, the latter comprising inner shelf to shoreline deposits. Both
the Holyoake and Starshot formations locally onlap uppermost
Shack leton reefs [see gure10 of (16)].
e Starshot Formation grades upward into the Douglas Con-
glomerate, a thick and coarse sedimentary wedge that is laterally
equivalent to (and locally both underlain and overlain by) sandstone
of the Starshot. e Douglas contains uvial and alluvial fan cobble
to boulder conglomerate, sandstone, and minor shale (16). Con-
glomeratic channels of the Douglas cut down into reefs of the upper
Fig. 2. Stratigraphic comparison of Cambrian Series 2, Stage 4 strata on Kangaroo Island and central Transantarctic Mountains. Inset shows location of sections
in the restored continents (Fig.1) and in Delamerian and Ross orogens. Stratigraphic units described in Results. The sections record ve stages, from platform buildup
through tectonic response to post- tectonic subsidence, although relative thicknesses and lithotypes vary. SS, sandstone; Sh, shale; Slst, siltstone; FS, ne sandstone; Carb,
carbonate; Cgl, conglomerate.
Downloaded from https://www.science.org on March 29, 2024

Myrow et al., Sci. Adv. 10, eadl3452 (2024) 29 March 2024
SCIENCE ADVANCES | RESEARCH ARTICLE
4 of 12
Shackleton, and their lls contain archaeocyathid- bearing limestone
boulders up to 2 m across (16, 23, 24). Overall, the succession indi-
cates reef drowning followed by shoaling from deeper water mud
through shoreline sand to subaerial coarse- grained uvial and alluvial
fan deposits.
Age constraints on the Byrd Group come from trilobites (25), ar-
chaeocyathids (26), and other fossils (27–29). Trilobite (25) and bra-
chiopod (28) assemblages and a positive carbon isotopic excursion at
the base (16) suggest that the Shackleton Formation is Cambrian Se-
ries 2, Stage 3 to lowermost Stage 4 (Atdabanian to lowermost Boto-
man equivalent) in age. Myrow et al. (16) assigned the overlying
Holyoake and Starshot formations to Stage 4, or late(?) Tsanglang-
puian/Botoman, based on preliminary trilobite data. We herein re-
port trilobite data from our subsequent work (eld collection in 2011)
to provide a more rened age for these units. Trilobites from these
units include Meniscuchus cf. M. menetus, Pagetides (Discomesites)
sp., and Hsuaspis cf. H. bilobata (= Estaingia bilobata) (Fig.3), the lat-
ter occurring as part of a diverse assemblage in the Pararaia janeae
Zone near the base of Stage 4. us, these data constrain the timing of
the abrupt switch from platform carbonate deposition to supracrustal
deformation processes during Stage 4.
e Delamerian Orogeny resulted in deformation of a thick Neo-
proterozoic to early Cambrian ri- margin succession in South Aus-
tralia (20, 30). e Cambrian strata include carbonate of the Kulpara
and Parara formations (31), succeeded by ne- grained siliciclastic
deposits, an unnamed shale unit in the eastern part of its outcrop
area and the Mt. McDonnell Formation in the western part (Fig.2)
(31–33). ese strata are overlain by the Kangaroo Island Group, an
alluvial fan to shallow marine Cambrian succession that crops out in
a small area on the northeastern coast of Kangaroo Island, southwest
of the Fleurieu Peninsula (Fig.1). It is approximately equivalent in age
to the Kanmantoo Group, a metamorphosed deep- water succession
that extends from Kangaroo Island northward to the eastern side of
the Fleurieu Peninsula (34, 35). Previous workers interpreted the
Kangaroo Island Group as alluvial fan to shallow marine deposits on
the northern margin of an active ri basin (34, 36–39), tectonically
linked to the Stansbury Basin (40).
Basal units of the Kangaroo Island Group are the White Point
Conglomerate and coeval Stokes Bay Sandstone (41). e White Point
is up to 580- m thick and contains a lower member of sandstone with
minor siltstone and shale (31, 32, 36) and an upper conglomerate
member with clasts up to 1.5 m across (31). e angular to subround-
ed clasts of the conglomerate are polymictic with basement and sedi-
mentary cover lithologies represented (32, 37). Abundant carbonate
clasts contain Cambrian archaeocyathids and small shelly fossils be-
longing to the P. janeae trilobite Zone, which sets a lowermost Stage 4
maximum depositional age for the unit (34). Pinch- out of the con-
glomerate to the south (31, 41) and clast imbrication (32) suggest
southward fan delta progradation with a source to the north. Clasts in
the White Point were likely derived from the underlying Koolywurtie
Limestone Member of the Parara Limestone, which is intersected in
numerous drill cores and exposed as outcrop 100 km to the north on
Yorke Peninsula (35, 42).
Overlying deposits consist of the Marsden Sandstone, an
unconformity- bound shoaling succession with a lower mudstone
member, followed by mudstone and sandstone of the Emu Bay Shale,
and sandstone of the Boxing Bay Formation (Fig.2). Together, these
units record pulses of marine transgression following deposition of
the White Point Conglomerate (31). P. janeae Zone trilobites from the
basal Marsden and from the Emu Bay indicate a Stage 4 age for these
marine strata (43). us, strata from the Koolywurtie Limestone
through the Emu Bay Shale all date to the P. janeae Zone, including
the White Point Conglomerate, indicating a nearly identical timing of
supracrustal deformation in this part of Australia with the central
Transantarctic Mountains deformation, which we discuss below.
DISCUSSION
Strata from the central Ross and Delamerian orogens indicate notable
similarities. Both sections record: (i) drowning of a carbonate
Fig. 3. Trilobites recovered from the Holyoake Formation (82°13.185′S, 160°16.122′E). (A and B) Estaingia bilobata; CMCIP 88140 and CMCIP 88142, respectively.
(C and D) Meniscuchus cf. M. menetus; CMCIP 88138 and CMCIP 96988, respectively. (E and F) Pagetides (Discomesites) sp.; CMCIP 88139 and CMCIP 96989, respectively.
Downloaded from https://www.science.org on March 29, 2024

Myrow et al., Sci. Adv. 10, eadl3452 (2024) 29 March 2024
SCIENCE ADVANCES | RESEARCH ARTICLE
5 of 12
platform containing archaeocyathid- bearing reefs, (ii) an overlying
shoaling succession of mud to sand, and (iii) continued shoaling to
coarse gravel alluvial fan deposits with carbonate clasts. In Antarctica,
the clastic succession represents tectonically induced subsidence as-
sociated with a major phase of supracrustal deformation during the
Ross Orogeny (16). e timing of this deformational and erosional
event is here rened to the P. janeae Zone of basal Cambrian Stage 4.
A nearly identical sedimentary record of deformation onset, tectonic
upli, erosion, and conglomeratic deposition in South Australia also
took place in the P. janeae Zone, as described above. Further evidence
linking the geologic histories of these areas is provided by dated igne-
ous and metamorphic events (Fig.4). Punctuated magmatic- arc in-
trusive activity in both areas extended from at least 550 to 490 Ma (17,
19, 21, 44), indicating active plate convergence through this period.
Metasedimentary 40Ar/39Ar mineral and slate cooling ages range
from ~512 to 476 Ma (Fig. 4) and record progressive cooling in
response to upli and erosion within the deeper orogen (17, 20, 45).
is activity corresponds closely in time with the surcial response to
deformation and upli. us, the depositional, igneous, and meta-
morphic events recorded in the central Ross and southern Delameri-
an orogens provide evidence for remarkable synchroneity in a late
early- Cambrian tectonic pulse during long- lived plate convergence.
e base of the as- yet- undened Cambrian Stage 4, and the
P. janeae Zone, is known to be younger than 514.45±0.36 Ma (46).
e pulse of contractional deformation, upli, and erosion along the
Austral- Antarctic margin of Gondwana described here clearly took
place within the lower part of the P. janeae Zone. A radiometric age of
511.87±0.14 Ma (47) from a volcanic tu in the Billy Creek Forma-
tion of the Flinders Range dates the middle to upper P. janeae Zone.
e Billy Creek is correlated with trilobites to the Marsden Sandstone
and Emu Bay Shale on Kangaroo Island, which rests above the syn-
tectonic White Point Conglomerate. ese relationships indicate that
Fig. 4. Time correlation diagram comparing Cambrian events in central Ross and Delamerian orogens. Timescale shows series and stages, and Atdabanian and
Botoman trilobite divisions for comparison. Schematic stratigraphic columns show primary depositional relations between biostratigraphically designated units (16, 17,
31, 32, 36), and colored bars denote time span of key events constrained by geochronological data (18–21, 44, 45). Note similar successions of archaeocyathid reefal car-
bonate, to black shale, and shallow- water sandstone, all down- cut and overlain by carbonate- clast conglomerate. Orogenic magmatism occurred through this period, but
punctuated termination of carbonate deposition, shoaling, and overlap by prograding alluvial fanglomerate marks onset of supracrustal deformation in both areas. Syn-
to post- orogenic cooling of micas and slates in metasedimentary lithologies mark metamorphism associated with structural shortening and thickening. Fm, Formation;
Ls, Limestone.
Downloaded from https://www.science.org on March 29, 2024

Myrow et al., Sci. Adv. 10, eadl3452 (2024) 29 March 2024
SCIENCE ADVANCES | RESEARCH ARTICLE
6 of 12
(i) the deformation, as constrained by fossil ages and thermochronol-
ogy, (ii) the base of Stage 4 (however dened), and (iii) the associated
Sinsk event, all took place between ~514 and~512 Ma.
e orogenic assembly of Gondwana was largely concluded by
~540 to 530 Ma, although some deformation and metamorphism
continued aerward (48). Assembly was quickly followed by orogenic
collapse, lithospheric extension, plutonism, and tectonic basin forma-
tion both along the East African–Antarctic Orogen and within in-
tracratonic areas of Africa and Australia (9, 49–52). As discussed
below, key geologic events signifying post- orogenic collapse within
Gondwana’s interior are dated to 518 to 510 Ma. Several examples of
crustal extension of the interior of Gondwana are known, including
migmatites and granitoids containing late- stage, post- collisional ex-
tensional structures in the Lurio Belt of Mozambique that formed be-
tween 518 and 514 Ma (53). ere, Neoproterozoic clastic rocks of the
Mecubúri Group were deposited in small fault- bounded intermon-
tane basins formed during early stages of post- collisional orogen col-
lapse (52). Overlying siliciclastic strata have a maximum depositional
age of ~530 Ma based on detrital zircon analysis, and they were sub-
ject to medium- grade metamorphism and migmatization by 514 Ma
(52). ese rocks are, in turn, intruded by ~510- Ma granitoids (50).
Younger mineral cooling ages indicate a long period of slow cooling
attributed to mantle upwelling triggered by lithospheric delamination
following Gondwana consolidation (53). e elevated temperatures,
cooling age patterns, and extensional features together point to local-
ized late- stage collapse by reactivation along orogenic structures
formed during lithospheric thickening. Similarly, metamorphic gran-
ulites in Madagascar record high- temperature/low- pressure cooling
trajectories as young as 510 Ma, attributed to orogenic collapse and
crustal extension following earlier collision within the East African
Orogen (9).
In the Dronning Maud Land area of East Antarctica, Pan- African
convergence marking collisional orogenesis between East and West
Gondwana was likewise followed by crustal extension, thought to
represent orogenic collapse (49). In this region, referred to broadly
as the East African–Antarctica Orogen, the post- collisional re-
sponse is dated to ~530 to 510 Ma and is characterized by large- scale
extensional structures and intrusion of voluminous granitoids. Em-
placement of late syn- to post- tectonic intrusions coincided with
retrograde metamorphism characterized by simultaneous cooling
and decompression during extensional exhumation, probably trig-
gered by the collapse of overthickened crust. Similar deep- crustal
responses to orogenic collapse are known from other parts of the
East African Orogen, such as in western Madagascar and the north-
ern Arabian- Nubian Shield (9).
Another signature of post- orogenic lithospheric extension is de-
velopment of large igneous provinces (LIPs). Magmatic activity in
western Australia within the Kalkarindji continental ood basalt
province included intrusion of dikes and diabase sills associated with
the Ocer, Wiso, and Georgina basins, dated by baddeleyite and zir-
con U- Pb to ~511 Ma (54), and eruption of subalkaline ood basalts
of the Antrim Plateau Volcanics with 40Ar/39Ar ages of 513 to 498 Ma
(55). Geochemical modeling of melt compositions in the Antrim Pla-
teau and Table Hill volcanics indicates that a mantle plume was not
required to induce melting but rather that post- orogenic thinning of
Gondwana lithosphere may have triggered decompression melting of
subcontinental lithospheric mantle and focused edge- driven astheno-
spheric convection into cratonic keels formed between higher- level
basins (56). Other magmatism at this time included emplacement of
dikes and minor volcanic rocks in western Australia at 513 to 508 Ma
(55, 57) and elsewhere in the North Australian Craton (58). Together,
a decompressional melting scenario requires that extension leading to
this middle Cambrian magmatism occurred before ~510 Ma.
e tectonic, magmatic, and depositional activity outlined here
signies a period of widespread lithospheric extension associated
with orogenic collapse of the Gondwana interior that began nearly
synchronously with the pulse of supracrustal contractional deforma-
tion along the peri- Gondwana margin described above that is bio-
stratigraphically dated to ~514 to ~512 Ma. e erosional response to
this deformation is also associated with the demise of carbonate plat-
forms along much of its length. We therefore argue here for a causal
linkage between post- orogenic extension in the hinterland interior of
Gondwana driven by gravitational collapse of over- thickened litho-
sphere and a pulse and/or acceleration of shortening in the external
convergent- margin realm. e body forces associated with supercon-
tinent amalgamation, collision, over- thickening, collapse, and region-
al lithospheric extension documented within contiguous parts of
Gondwana provide both a mechanism and the timing to explain the
episode of active- margin deformation described here. us, we posit
that an abrupt tectonic regime change within Gondwana’s interior
triggered a shi in convergent- margin deformation and magmatism
along nearly the entire Australian and Antarctic outer margins. Fur-
thermore, these tectonic responses are also linked to widely recog-
nized paleoenvironmental changes and a biotic crisis in shallow water
Cambrian settings.
e Ross and Delamerian orogens record W- dipping Gondwana-
margin plate convergence by at least 550 Ma in the latest Neoprotero-
zoic (Fig.1) (10, 15, 19, 20, 59), yet a major change occurred in the
early Cambrian. By this time, both the Ross and Delamerian systems
were characterized by le- oblique, continental- margin plate con-
vergence, dominantly I- type arc magmatism, medium- pressure Bar-
rovian metamorphism, and Cambrian Stage 3 carbonate platform
deposition (Fig.4) (10, 15, 18, 20, 59, 60). ese areas straddled the
mid–Series 2 tropics (Fig. 1), promoting carbonate growth in shallow
forearc settings that may have fostered shallow- water biotic radiation
(33, 61). Deformation in Antarctica between 550 and 515 Ma was lim-
ited to inboard magmatism and incipient thickening of ri- margin
deposits. In both areas, separated by ~1800 km at the time, an abrupt
and simultaneous pulse of contractional deformation took place in
active- margin supracrustal successions deposited originally within
ri- margin and platformal settings (Figs. 2 and 4). A distinctive
change in Cambrian plate- margin tectonic patterns is particularly
well- preserved in Antarctica where abrupt cessation of carbonate de-
position and drowning of archaeocyathid–microbial reefs reected a
pulse of subsidence, driven by thrust loading of crust from the west
(Fig.5). Subsequent development of coarse alluvial fans included ini-
tial erosion of basement sources and later erosion of deformed car-
bonate strata and the contemporaneous magmatic arc to the west
(Fig.5). Syn- to post- orogenic cooling ages of muscovite, biotite, and
slate that range into the Ordovician document the response to crustal
shortening and thickening (Fig.4). A similar record is preserved in
the Kangaroo Island succession and other parts of the Delamerian
Orogen as discussed above, yet deformation there is west- vergent (34).
Despite their dierences in deformation pattern, eastward forearc-
directed thrusting in the Transantarctic Mountains (17) versus cra-
tonward foreland thrusting on Kangaroo Island (34), both areas
record near- synchronous (within a specic biostratigraphic zone)
supracrustal shortening, a surcial response to punctuated tectonism
Downloaded from https://www.science.org on March 29, 2024

Myrow et al., Sci. Adv. 10, eadl3452 (2024) 29 March 2024
SCIENCE ADVANCES | RESEARCH ARTICLE
7 of 12
Fig. 5. Model depicting sedimentary and structural evolution of central Ross Orogen during Cambrian late Series 2. (A) Reef and shoal deposition phase,
dominated by carbonate buildup (Shackleton Limestone) over older siliciclastic strata. Undierentiated basement includes metamorphic rocks and Neoproterozoic
Beardmore Group. Outboard subduction operated at this time (14). S.L., sea level. (B) Initial thrusting phase, in which inland basement was uplifted and eroded, and
marine platform underwent initial tectonically induced subsidence, resulting in deepening and development of a capping phosphatic hardground (heavy brown line).
(C) Ongoing oceanward thrust displacement led to further crustal loading and deposition of a clastic shoaling succession, including nodular shale (Holyoake Forma-
tion) and shallow- marine sandstone (Starshot Formation). Subaerial alluvial- fan deposits sourced from inland thrust sheets were dominated by basement debris.
(D) Mature thrust propagation phase, in which forward- propagating thrusts cut into Shackleton Limestone, producing carbonate- clast debris containing archaeocy-
athid fossils. Ongoing erosion, transport, and alluvial deposition led to accumulation of coarse alluvial- fan deposits (Douglas Conglomerate). Narrow vertical rectan-
gle in (D) corresponds to stratigraphic section in Fig.2. Primary eld relations, sedimentation patterns, faunal occurrences, and geochronological constraints provided
by earlier studies (16, 17, 23, 95).
Downloaded from https://www.science.org on March 29, 2024

Myrow et al., Sci. Adv. 10, eadl3452 (2024) 29 March 2024
SCIENCE ADVANCES | RESEARCH ARTICLE
8 of 12
that precisely captures the rapid onset of accelerated plate- margin
convergence. Both areas later evolved toward younger upper- plate ex-
tension from ~500 to 480 Ma (15, 19, 59).
Beyond the coincident timing, however, contrasting structural
styles in these two areas provide insight into their respective respons-
es. Dierences in sedimentation and deformation patterns in the two
areas are likely due to the primary conguration of the Neoprotero-
zoic ri margin, with the southern Australian margin developed as a
broader basin system constructed upon extended Paleoproterozoic
cratonic basement, whereas the Antarctic ri margin was narrower,
and its sedimentary succession was less voluminous (Fig.1). During
subsequent plate- margin deformation, the Ross Orogen in the central
Transantarctic Mountains behaved as a cratonal promontory, whereas
the Delamerian belt evolved in a trough- like reentrant resembling an
aulacogen at the edge of a long- lived Neoproterozoic basin (15, 30,
34). ese inherited continental margin geometries led to earlier ter-
mination of Ross deformation by ~480 Ma, whereas progressively
outboard orogenic activity persisted in the outer Tasmanides between
~485 and 340 Ma in the Lachlan Fold Belt (Fig.1) (62). In addition to
duration, plate margin activity also diered in character, in which the
southern to central coast of Antarctica was dominated by Andean-
type continental- margin magmatism with pronounced crustal thick-
ening and high- pressure metamorphism (from at least 540 to 515 Ma)
(15), while the region from northern Victoria Land northward into
Australia was dominated by early Paleozoic supra- subduction–zone
arc volcanism and marginal- basin development typical of accretion-
ary orogens between at least 515 to 340 Ma (Fig.1) (62). Despite these
dierences, the synchronous early Cambrian sedimentary patterns in
these disparate areas attest to a near- simultaneous surcial response
to tectonism across the broader Ross- Delamerian system.
e events highlighted here may also be expressed in a cryptic
Cambrian succession in the Shackleton Range (Fig. 1), where con-
glomerate of the Mount Wegener Formation contains carbonate clasts
with P. janeae Zone archaeocyathids, indicating syn- orogenic erosion
and deposition during early Stage 4 or younger (<514 Ma) (63). Al-
though the platform source for the limestone clasts is not exposed,
conglomerate deposition is linked to collisional convergence of East
and West Gondwana during closure of the Mozambique Ocean, con-
sistent with Gondwana supercontinent consolidation as the cause of
erosion, sedimentation, and marine habitat loss. e coincident tim-
ing of events in the Shackleton Range suggest that much of the
Austral- Antarctic margin was marked by regional tectonic disruption
of Series 2 carbonate depositional systems.
It is not possible to make a direct kinematic link between tectonic
events of the Austral- Antarctic margin and eastern Gondwanan inte-
rior, as discussed here, and other Cambrian events on the western
Gondwanan margin, yet several events recognized in west Gondwana
have similar timing and may represent far- eld tectonic responses of
the former. ese include (i) termination of the Pampean Orogeny
~515 Ma (64) and (ii) both initiation of subduction beneath West
Ganderia [~515 Ma; (65)] and associated back- arc extension within
that continent, causing ri separation of Ganderia and Amazonia
during opening of the Rheic Ocean at ~510 Ma (66). Together, these
events likely reect supercontinental responses to post- Gondwana
global tectonic reorganization in the Cambrian that have recognizable
paleoenvironmental and paleobiological eects.
e timing of the tectonic event that we document here for the
Austral- Antarctic margin of Gondwana corresponds with that of the
Sinsk event (2, 3). We posit that tectonic transformation involving
inversion from collisional supercontinent assembly to lithospheric-
scale orogenic collapse and extension triggered a series of cascading
environmental and biotic processes during the Sinsk event. Wide-
spread extension during this transformation, possibly associated with
lithospheric delamination and/or mantle upwelling (56), was likely
linked to a synchronous and/or immediately subsequent extrusion of
the oldest LIP of the Phanerozoic in north- central Australia, the
Kalkarindji continental basalts. Geochronological data constrain the
onset of Kalkarindji eruptions to mid–Series 2. Zircon and baddeley-
ite U- Pb ages of 510.7±0.6, 511±5, and 508±5 Ma were obtained
from Kalkarindji dikes (54, 57). Plagioclase 40Ar/39Ar ages, including
some recalculated results, from Kalkarindji dikes and volcanics of
the Antrim Plateau Volcanic rock suite range from 512.8± 1.6 to
508.7±4.3 Ma (55). Given reported uncertainties, the oldest possible
magmatic ages are 516 to 514 Ma. Published radiometric ages and as-
sociated uncertainties for the Kalkarindji LIP indicate that emplace-
ment took place through much of Cambrian Series 2, with many dates
in the range of 514 to 508 Ma (54, 55). Integration of all ages indicates
that initial Kalkarindji LIP emplacement likely took place as early as
514 to 513 Ma (see the Supplementary Materials). is is in the same
age range as the tectonic transition of the Austral- Antarctic margin of
Gondwana described here, during which time the Kalkarindji mag-
matism may plausibly have contributed volatile and aerosol emis-
sions, aecting atmospheric change in Cambrian Series 2. e eroded
remains of the Kalkarindji basalt province cover 55,000 km (2, 58, 67,
68). Its estimated volume of ~1.5×105 km (3, 69) could have released
as much as ~2% of the Cambrian atmospheric CO2 load (58), and,
coupled with the simultaneous release of large amounts of CH4 and
SO2 emissions, it led to rapid climatic changes and environmental
pressures (54, 70), specically expressed as the Sinsk event.
Climate change at this time is supported by two major perturba-
tions of the carbon cycle, namely, (i) a negative δ (13) Ccarb shi near
or at the base of Stage 4, the Botoman- Toyonian Extinction (BTE)
interval, and the events outlined in this study; and (ii) isotope
anomaly ROECE, which corresponds with the Series 2–Miaolingian
boundary Redlichiid–Olenellid Extinction (71–76) and the main
phase of Kalkarindji volcanism at ~509 Ma (67–70). Two dierent iso-
topic features have been placed at the base of Stage 4: the Archaeocy-
athid Extinction Carbon Isotope Excursion negative excursion (73)
and the initiation point of the underlying MICE positive excursion
(72). Regardless of which is best placed at the base of Stage 4, that
isotopic feature and the BTE interval correspond to the Sinsk event (1,
2), the rst major extinction of the Cambrian. e Sinsk records a
global genus- level reduction in diversity of ~45% (77), reduction of
body sizes of many marine invertebrate groups (4), a major extinction
of archaeocyathan reefs (78), elevated sea surface temperatures (79), a
global greenhouse climate (2, 80), extensive deposition of evaporites
(81), and spread of anoxic deep waters into shallow- water environ-
ments (1–3, 82). is is reected in the rapid demise of archaeocy-
athid species in South Australia from 100+ reef- building species on
carbonate platforms during Stages 3 to 4 (83) to only three to four
species before their nal extinction in late Stage 4 shallow water car-
bonate (84). Although authors have opined on causalities between the
Kalkarindji LIP, climate change, and extinction (54, 70), some have
been hesitant to link the LIP to extinction (58). One possible link is
that warming caused by the release of volatile emissions through vol-
canism may have elevated sea surface temperatures and led to reduced
oceanic turnover, stratication, and bottom water anoxia, the latter
causing dysoxia and elevated rates of extinction (85). A sea level rise,
Downloaded from https://www.science.org on March 29, 2024

Myrow et al., Sci. Adv. 10, eadl3452 (2024) 29 March 2024
SCIENCE ADVANCES | RESEARCH ARTICLE
9 of 12
starting at the base of Stage 4 (86), could also have been an important
factor in the extinction, particularly as sea level rise produced by ele-
vated atmospheric and ocean temperatures could have led to drown-
ing of continental interiors with oxygen- decient waters.
Our hypothesis that the initiation of supracrustal Ross Orogenic
activity, Sinsk event extinction, and initial Kalkarindji LIP extrusion
and associated eects were nearly synchronous is highly dependent
on the precision of the absolute age constraints for these events. e
tectonic activity and the Sinsk event both took place within the
P. janeae trilobite Zone (Fig.6). eir age is bracketed by strata from
upper Stage 3 in Britain (W. Avalonia), below the P. janeae Zone,
which yielded an age of 514.45±0.36 Ma (46), and a radiometric date
on strata from the middle to upper P. janeae Zone (Billy Creek Forma-
tion of Australia) that places an upper constraint for these events at
511.87±0.14 Ma (47).
Age models for the Sinsk event (3, 87) rest largely on radiometric
dates, chemostratigraphic curves, and estimates of accumulation
rates. e timing of the Sinsk event will be close to, or at, the base of
Stage 4 (and the P. janeae Zone); however, the stage boundary is
ultimately dened. e event is recorded in strata directly above a
sequence boundary at the base of the Sinsk Formation in Siberia. e
amount of time represented by that sequence boundary is unknown,
so the Sinsk could be a million years or more younger than the
514.45±0.36 Ma (46) radiometric date. As a result, the dates (with
errors) of initial LIP activity are well within the range of possible
dates for the Sinsk event. Our suggestion that tectonics triggered a
series of events that resulted in the Sinsk extinction is a hypothesis
that can be tested with future geochronologic data, although the
present overlap of geochronologic ages for LIP initiation (514 to
513 Ma) and the maximum age for upper Stage 3 (~514.5 Ma)
strongly supports the hypothesis. In addition to the eects of wide-
spread oceanic anoxia on marine fauna during the Sinsk event, we
suggest that onset of supracrustal tectonic deformation led to wide-
spread loss of shallow water carbonate habitats of eastern Gondwana
(Australian and Antarctic margins) and possibly much of the pe-
rimeter of the supercontinent. is occurred through both initial
thrust- loading–induced marine subsidence, focused at the convergent
plate boundary, and subsequent upli and erosion of carbonate
platforms. Such loss of habitat may have added to the overall biotic
stresses of the Sinsk event and to global extinction patterns, given the
Fig. 6. Time diagram for the Cambrian, showing the oldest and youngest possible age of the Sinsk event and the Stage 3 to 4 boundary (black arrows with ra-
diometric dates). The base of Stage 4 and the P. janeae Zone is younger than 514.45±0.36 Ma; the date of 511.87±0.14 from the middle to upper P. janeae Zone is the
upper limit for both the Sinsk and the supracrustal deformation event described herein. Dated units from the Kalkarindji LIP in Australia are shown as gray squares with
error bars. Two ages from both the Kalkarindji dikes/volcanics and Antrim basalt represent minimum and maximum ages. The time span during which tectonic shortening
occurred along the Ross- Delamerian margin of Antarctica and Australia, and during which the Sinsk event took place, is shown as a horizontal gray band. Sources of age
data cited in Discussion.
Downloaded from https://www.science.org on March 29, 2024

Myrow et al., Sci. Adv. 10, eadl3452 (2024) 29 March 2024
SCIENCE ADVANCES | RESEARCH ARTICLE
10 of 12
extensive carbonate shelves around the supercontinent Gondwana that
were potentially aected by the tectonic transition documented herein.
In summary, the tectono- sedimentary events along the Austral-
Antarctic margin were part of a supercontinent- wide transformation
that led to shallow- water carbonate habitat loss along equatorial
Gondwana. ese events were also geodynamically linked to a broad
inversion from collisional supercontinental assembly to extensional
tectonics associated with lithospheric- scale orogenic collapse within
the interior of Gondwana, the latter including eruption of the Kalkar-
indji LIP. e Kalkarindji LIP eruptions released considerable levels of
atmospheric CO2 and associated CH4 and SO2 emissions, all of which
caused a series of cascading environmental processes that resulted in
ocean warming, reduced oceanic turnover, widespread bottom- water
anoxia in marginal and epicontinental seas, and, ultimately, the Sinsk
extinction.
MATERIALS AND METHODS
Specimens of trilobites were collected insitu from the Holyoake For-
mation during expeditions in 2000 and 2011. ose preserved in
mudstone (Fig.3, A and C to F) are weakly distorted with moderate
convexity, while the one preserved in grainstone (Fig.3B) is pre-
served with original convexity. e specimens of eodiscoids (Fig.3,
C to F) are external molds and latex casts were prepared. All speci-
mens are reposited in the Cincinnati Museum, prexed with CMC
IP. Mechanical preparation of the E. bilobata specimens was done
with an AUTOMEL Electric Engraver (Dong Yang Electric Co.).
Trilobite specimens were coated with magnesium oxide smoke.
The specimens of E. bilobata were photographed with a Canon
EOS 6D using a Canon EF 100 mm f/2.8 L IS USM macro lens.
e eodiscoid fossils were photographed with a Leica M205C mi-
croscope equipped with a Leica DFC550 camera using the z-
stacking method.
Supplementary Materials
This PDF le includes:
Supplementary Materials
REFERENCES AND NOTES
1. A. Y. Zhuravlev, R. A. Wood, Anoxia as the cause of the mid- Early Cambrian (Botomian)
extinction event. Geology 24, 311–314 (1996).
2. A. Y. Zhuravlev, R. A. Wood, The two phases of the Cambrian Explosion. Sci. Rep. 8, 16656
(2018).
3. T. He, M. Zhu, B. J. W. Mills, P. M. Wynn, A. Y. Zhuravlev, R. Tostevin,
P. A. E. Pogge von Strandmann, A. Yang, S. W. Poulton, G. A. Shields, Possible links
between extreme oxygen perturbations and the Cambrian radiation of animals. Nat.
Geosci. 12, 468–474 (2019).
4. A. Y. Zhuravlev, R. A. Wood, Dynamic and synchronous changes in metazoan body size
during the Cambrian Explosion. Sci. Rep. 10, 6784 (2020).
5. P. A. Cawood, R. A. Strachan, S. A. Pisarevsky, D. P. Gladkochub, J. B. Murphy, Linking
collisional and accretionary orogens during Rodinia assembly and breakup: Implications
for models of supercontinent cycles. Earth Planet. Sci. Lett. 449, 118–126 (2016).
6. J. G. Meert, A synopsis of events related to the assembly of eastern Gondwana.
Tectonophysics 362, 1–40 (2003).
7. R. J. Stern, Arc assembly and continental collision in the Neoproterozoic East- African
Orogen: Implications for the consolidation of Gondwanaland. Annu. Rev. Earth Planet. Sci.
22, 319–351 (1994).
8. J. Jacobs, C. M. Fanning, F. Henjes- Kunst, M. Olesch, H. J. Paech, Continuation of the
Mozambique Belt into East Antarctica: Grenville- age metamorphism and polyphase
Pan- African high- grade events in Central Dronning Maud Land. J. Geol. 106, 385–406
(1998).
9. H. Fritz, M. Abdelsalam, K. A. Ali, B. Bingen, A. S. Collins, A. R. Fowler, W. Ghebreab,
C. A. Hauzenberger, P. R. Johnson, T. M. Kusky, P. Macey, S. Muhongo, R. J. Stern, G. Viola,
Orogen styles in the East African Orogen: A review of the Neoproterozoic to Cambrian
tectonic evolution. J. Afr. Earth Sci. 86, 65–106 (2013).
10. P. A. Cawood, Terra Australis Orogen: Rodinia breakup and development of the Pacic
and Iapetus margins of Gondwana during the Neoproterozoic and Paleozoic. Earth- Sci.
Rev. 69, 249–279 (2005).
11. P. M. Myrow, N. C. Hughes, N. R. McKenzie, Cambrian–Ordovician orogenesis in
Himalayan equatorial Gondwana. Geol. Soc. Am. Bull. 128, 1679–1695 (2016).
12. P. M. Myrow, N. C. Hughes, N. R. McKenzie, Reconstructing the Himalayan margin prior to
collision with Asia: Proterozoic and lower Paleozoic geology and its implications for
Cenozoic tectonics in P.J. Treloar, M.P. Searle, Eds. Himalayan Tectonics: A Modern Synthesis.
J. Geol. Soc. (London, U. K.) Spec. Pub.483, 39–64 (2019).
13. N. R. McKenzie, N. C. Hughes, B. C. Gill, P. M. Myrow, Plate tectonic inuences on
Neoproterozoic–Early Paleozoic climate and animal evolution. Geology 42, 127–130
(2014).
14. T. W. Wong Hearing, A. Pohl, M. Williams, Y. Donnadieu, T. H. P. Harvey, C. R. Scotese,
P. Sepulchre, A. Franc, T. R. A. Vandenbroucke, Quantitative comparison of geological data
and model simulations constrains early Cambrian geography and climate. Nat. Commun.
12, 3868 (2021).
15. J. W. Goodge, Geological and tectonic evolution of the Transantarctic Mountains, from
ancient craton to recent enigma. Gondw. Res. 80, 50–122 (2020).
16. P. M. Myrow, M. C. Pope, J. W. Goodge, W. Fischer, A. R. Palmer, Depositional history of
pre- Devonian strata and timing of Ross Orogenic tectonism in the central Transantarctic
Mountains. Antarctica. Geol. Soc. Am. Bull. 114, 1070–1088 (2002).
17. J. W. Goodge, P. Myrow, D. Phillips, C. M. Fanning, I. S. Williams, Siliciclastic record of rapid
denudation in response to convergent-margin orogenesis, Ross Orogen, Antarctica, in
M. Bernet, C. Spiegel, Eds. Detrital Thermochronology—Provenance Analysis, Exhumation,
and Landscape Evolution of Mountain Belts. Geol. Soc. Am. Spec. Paper Boulder, Colorado
378, 101–122 (2004a).
18. J. W. Goodge, I. S. Williams, P. Myrow, Provenance of Neoproterozoic and lower Paleozoic
siliciclastic rocks of the Central Ross Orogen, Antarctica: Detrital record of rift- ,
passive- and active- margin sedimentation. Geol. Soc. Am. Bull. 116, 1253–1279 (2004).
19. J. Foden, M. A. Elburg, J. Dougherty- Page, A. Burtt, The timing and duration of the
Delamerian Orogeny: Correlation with the Ross Orogen and implications for Gondwana
assembly. J. Geol. 114, 189–210 (2006).
20. J. Foden, M. Elburg, S. Turner, C. Clark, M. L. Blades, G. Cox, A. S. Collins, K. Wol, C. George,
Cambro- Ordovician magmatism in the Delamerian orogeny: Implications for tectonic
development of the southern Gondwanan margin. Gondw. Res. 81, 490–521 (2020).
21. S. Turner, T. Ireland, J. Foden, E. Belousova, G. Wörner, J. Keeman, A comparison of granite
genesis in the Adelaide Fold Belt and Glenelg River Complex using U–Pb, Hf and O
isotopes in zircon. J. Petrol. 63, egac102 (2022).
22. J. W. Goodge, P. Myrow, I. S. Williams, S. A. Bowring, Age and provenance of the
Beardmore Group, Antarctica: Constraints on Rodinia supercontinent breakup. J. Geol.
110, 393–406 (2002).
23. M. N. Rees, A. J. Rowell, E. D. Cole, Aspects of the late Proterozoic and Paleozoic geology
of the Churchill Mountains, southern Victoria Land. Antarct. J. U. S. 22, 23–25 (1988).
24. M. N. Rees, B. R. Pratt, A. J. Powell, Early Cambrian reefs, reef complexes, and associated
lithofacies of the Shackleton Limestone, Transantarctic Mountains. Sedimentology 36,
341–361 (1989).
25. A. R. Palmer, A. J. Rowell, Early Cambrian trilobites from the Shackleton Limestone of the
central Transantarctic Mountains. J. Paleontol. 69, 1–28 (1995).
26. F. Debrenne, P. D. Kruse, Shackleton Limestone archaeocyaths. Alcheringa 10, 235–278 (1986).
27. T. M. Claybourn, S. M. Jacquet, C. B. Skovsted, T. P. Topper, L. E. Holmer, G. A. Brock,
Mollusks from the upper Shackleton Limestone (Cambrian Series 2), Central
Transantarctic Mountains, East Antarctica. J. Paleontol. 93, 437–459 (2019).
28. T. M. Claybourn, C. B. Skovsted, L. E. Holmer, B. Pan, P. M. Myrow, T. P. Topper, G. A. Brock,
Brachiopods from the Byrd group (Cambrian Series 2, Stage 4) central transantarctic
mountains, East Antarctica: biostratigraphy, phylogeny and systematics. Pap. Palaeontol.
6, 349–383 (2020).
29. T. M. Claybourn, C. B. Skovsted, M. J. Betts, L. E. Holmer, L. Bassett- Butt, G. A. Brock,
Camenellan tommotiids from the Cambrian Series 2 of East Antarctica: Biostratigraphy,
palaeobiogeography, and systematics. Acta Palaeontol. Pol. 66, 207–229 (2021).
30. W. V. Preiss, The Adelaide Geosyncline of South Australia and its signicance in
Neoproterozoic continental reconstruction. Precambrian Res. 100, 21–63 (2000).
31. J. G. Gehling, J. B. Jago, J. R. Paterson, D. C. García- Bellido, G. D. Edgecombe, The
geological context of the ower Cambrian (Series 2) Emu Bay Shale Lagerstätte and
adjacent stratigraphic units, Kangaroo Island, South Australia. Aust. J Earth Sci. 58,
243–257 (2011).
32. P. D. Kruse, E.- E. Moreno, Archaeocyaths of the White Point Conglomerate, Kangaroo
Island, South Australia. Alcheringa 38, 1–64 (2014).
33. G. A. Brock, M. J. Engelbretsen, J. B. Jago, P. D. Kruse, J. R. Laurie, J. H. Shergold, G. R. Shi,
J. E. Sorauf, Palaeobiogeographic anities of Australian Cambrian faunas. Mem. Assoc.
Australas. Palaeontol. 23, 1–61 (2000).
Downloaded from https://www.science.org on March 29, 2024

Myrow et al., Sci. Adv. 10, eadl3452 (2024) 29 March 2024
SCIENCE ADVANCES | RESEARCH ARTICLE
11 of 12
34. T. Flöttmann, P. Haines, J. Jago, P. James, A. Belperio, J. Gum, Formation and reactivation
of the Cambrian Kanmantoo Trough, SE Australia: implications for early Palaeozoic
tectonics at eastern Gondwana’s plate margin. J. Geol. Soc. 155, 525–539 (1998).
35. M. J. Betts, T. M. Claybourn, G. A. Brock, J. B. Jago, C. B. Skovsted, J. R. Paterson, Early
Cambrian shelly fossils from the White Point Conglomerate, Kangaroo Island. Acta
Palaeontol. Pol. 64, 489–522 (2019).
36. B. Daily, P. S. Moore, B. R. Rust, Terrestrial–marine transition in the Cambrian rocks of
Kangaroo Island, South Australia. Sedimentology 27, 379–399 (1980).
37. D. I. Gravestock, C. G. Gatehouse, The Geology of South Australia, Volume 2, The
Phanerozoic. Geol. Surv. S. Aust. Bull. 54, 5–19 (1995).
38. R. J. F. Jenkins, M. Sandiford, Observations on the tectonic evolution of the southern
Adelaide Fold Belt. Tectonophysics 214, 27–36 (1992).
39. C. Nedin, Taphonomy of the Early Cambrian Emu Bay Shale Lagerstätte, Kangaroo Island,
South Australia. Bull. Nation. Mus. Nat. Sci. 10, 133–141 (1997).
40. A. P. Belperio, M. Fairclough, C. Gatehouse, J. Hough, W. Preiss, J. C. Gum, Tectonic and
metallogenic framework of the Cambrian Stansbury Basin- Kanmantoo Trough, South
Australia. AGSO J. Aust. Geol. Geophys. 17, 183–200 (1998).
41. J. B. Jago, C. J. Bentley, J. R. Paterson, J. D. Holmes, T. R. Lin, X. W. Sun, The stratigraphic
signicance of early Cambrian (Series 2, Stage 4) trilobites from the Smith Bay Shale near
Freestone Creek, Kangaroo Island. Aust. J. Earth Sci. 68, 204–212 (2021).
42. J. R. Paterson, C. B. Skovsted, G. A. Brock, J. B. Jago, An early Cambrian faunule from the
Koolywurtie Limestone Member (Parara Limestone), Yorke Peninsula, South Australia and
its biostratigraphic signicance. Mem. Assoc. Australas. Palaeontol. 34, 131–146 (2007).
43. J. R. Paterson, D. C. García- Bellido, J. B. Jago, J. G. Gehling, M. S. Y. Lee, G. D. Edgecombe,
The Emu Bay Shale Konservat- Lagerstätte: a view of Cambrian life from East Gondwana. J.
Geol. Soc. 173, 1–11 (2016).
44. J. W. Goodge, C. M. Fanning, M. D. Norman, V. C. Bennett, Temporal, isotopic and spatial
relations of early Paleozoic Gondwana- margin arc magmatism, central Transantarctic
Mountains, Antarctica. J. Petrol. 53, 2027–2065 (2012).
45. S. P. Turner, S. P. Kelley, A. H. M. VandenBerg, J. D. Foden, M. Sandiford, T. Flöttmann, Source
of the Lachlan fold belt ysch linked to convective removal of the lithospheric mantle and
rapid exhumation of the Delamerian- Ross fold belt. Geology 24, 941–944 (1996).
46. T. H. P. Harvey, M. Williams, D. J. Condon, P. R. Wilby, D. J. Siveter, A. W. A. Rushton,
M. J. Leng, S. E. Gabbott, A rened chronology for the Cambrian succession of southern
Britain. J. Geol. Soc. 168, 705–716 (2011).
47. M. B. Betts, J. R. Paterson, S. M. Jacquet, A. S. Andrew, P. A. Hall, J. B. Jago, E. A. Jagodzinski,
W. V. Preiss, J. L. Crowley, S. A. Birch, C. P. Mathewson, D. C. García- Bellido, T. P. Topper,
C. B. Skovsted, G. A. Brock, Early Cambrian chronostratigraphy and geochronology of
South Australia. Earth- Sci. Rev. 185, 498–543 (2018).
48. P. A. Cawood, C. Buchan, Linking accretionary orogenesis with supercontinent assembly.
Earth Sci. Rev. 82, 217–256 (2007).
49. J. Jacobs, R. Klemd, C. M. Fanning, W. Bauer, F. Colombo, Extensional collapse of the late
Neoproterozoic- early Palaeozoic East African- Antarctic Orogen in central Dronning Maud
Land, East Antarctica. Geol. Soc. Spec. Pub. 206, 271–287 (2003).
50. J. Jacobs, B. Bingen, R. J. Thomas, W. Bauer, M. T. D. Wingate, P. Feitio, Early Palaeozoic
orogenic collapse and voluminous late-tectonic magmatism in Dronning Maud Land and
Mozambique: insights into the partially delaminated orogenic root of the East
African-Antarctic Orogen? In: M. Satish-Kumar, Y. Motoyoshi, Y. Osanai, Y. Hiroi, K.
Shiraishi, Eds. Geodynamic Evolution of East Antarctica: A Key to the East–West Gondwana
Connection. Geol. Soc. Lon. Spec. Pub. 308, 69–90 (2008).
51. G. Viola, I. H. C. Henderson, B. Bingen, R. J. Thomas, M. A. Smethurst, S. de Azavedo,
Growth and collapse of a deeply eroded orogen: Insights from structural, geophysical,
and geochronological constraints on the Pan- African evolution of NE Mozambique.
Tectonics 27, TC5009 (2008).
52. R. J. Thomas, J. Jacobs, M. S. A. Horstwood, K. Ueda, B. Bingen, R. Matola, The Mecubúri
and Alto Benca Groups, NE Mozambique: Aids to unravelling ca. 1 and 0.5Ga events in
the East African Orogen. Precambrian Res. 178, 72–90 (2010).
53. K. Ueda, J. Jacobs, R. J. Thomas, J. Kosler, F. Jourdan, R. Matola, Delamination- induced
late- tectonic deformation and high- grade metamorphism of the Proterozoic Nampula
Complex, northern Mozambique. Precambrian Res. 196- 197, 275–294 (2012).
54. F. Jourdan, K. Hodges, B. Sell, U. Schaltegger, M. T. D. Wingate, L. Z. Evins, U. Söderlund,
P. W. Haines, D. Phillips, T. Blenkinsop, High- precision dating of the Kalkarindji large
igneous province, Australia, and synchrony with the Early–Middle Cambrian (Stage 4–5)
extinction. Geology 42, 543–546 (2014).
55. P. E. Marshall, A. M. Halton, S. P. Kelley, M. Widdowson, S. C. Sherlock, New40Ar/39Ar
dating of the Antrim Plateau Volcanics, Australia: clarifying an age for the eruptive phase
of the Kalkarindji continental ood basalt province. J. Geol. Soc. 175, 974–985 (2018).
56. B. D. Ware, F. Jourdan, R. Merle, M. Chiaradia, K. Hodges, The Kalkarindji Large Igneous
Province, Australia: Petrogenesis of the oldest and most compositionally homogenous
province of the Phanerozoic. J. Petrol. 59, 635–665 (2018).
57. F. A. Macdonald, M. T. D. Wingate, K. Mitchell, Geology and age of the Glikson impact
structure, Western Australia. Aust. J. Earth Sci. 52, 641–651 (2005).
58. P. E. Marshall, L. E. Faggetterand, M. Widdowson, Was the Kalkarindji continental ood
basalt province a driver of environmental change at the dawn of the Phanerozoic?, in
Large Igneous Provinces: A Driver of Global Environmental and Biotic Changes. , R. E. Ernst, A.
J. Dickson, A. Bekker, Eds. (Geophysical Monograph Series, American Geophysical Union,
Washington D.C., 2021), pp.435–447.
59. A. I. S. Kemp, C. J. Hawkesworth, W. J. Collins, C. M. Gray, P. L. Blevin, Isotopic evidence for
rapid continental growth in an extensional accretionary orogen: The Tasmanides, eastern
Australia. Earth Planet. Sci. Lett. 284, 455–466 (2009).
60. J. W. Goodge, V. L. Hansen, S. M. Peacock, B. K. Smith, N. W. Walker, Kinematic evolution of
the Miller Range shear zone, central Transantarctic Mountains, Antarctica, and
implications for Neoproterozoic to Early Paleozoic tectonics of the East Antarctic Margin
of Gondwana. Tectonics 12, 1460–1478 (1993).
61. I. W. D. Dalziel, Cambrian transgression and radiation linked to an Iapetus- Pacic oceanic
connection? Geology 42, 979–982 (2014).
62. R. A. Glen, The Tasmanides of eastern Australia, In: A. P. M. Vaughan, P.T. Leat, R.J.
Pankhurst, Eds. Terrane Processes at the Margins of Gondwana. Geol. Soc. Lon. Spec. Pub.
246, 23–96 (2005).
63. M. Rodríguez- Martínez, W. Buggisch, S. Menéndez, E. Moreno- Eiris, A. Perejón,
Reconstruction of a Ross lost Cambrian Series 2 mixed siliciclastic–carbonate platform
from carbonate clasts of the Shackleton Range, Antarctica. Earth Environ. Sci. Trans. R. Soc.
Edinburgh 113, 175–226 (2022).
64. V. A. Ramos, M. Escayola, P. Leal, M. M. Pimentel, J. O. S. Santos, The late stages of the
Pampean Orogeny, Córdoba (Argentina): Evidence of postcollisional Early Cambrian slab
break- o magmatism. J. South Am. Ear th Sci. 64, 351–364 (2015).
65. C. R. van Staal, S. M. Barr, J. W. F. Waldron, D. I. Schoeld, A. Zagorevski, C. E. White,
Provenance and Paleozoic tectonic evolution of Ganderia and its relationships with Avalonia
and Megumia in the Appalachian- Caledonide orogen. Gondw. Res. 98, 212–243 (2021).
66. H. Sandeman, V. McNicoll1, D. T. W. Evans, U- Pb geochronology and lithogeochemistr y of
the host rocks to the Reid gold deposit, Exploits Subzone- M ount Cormack subzone
boundary area, central Newfoundland. Current Research Newfoundland and Labrador
Department of Natural Resources Geological Survey Report 12- 1, 85–102 (2012).
67. R. J. Bultitude, The Antrim Plateau Volcanics, Victoria River District, Northern Territory. Bur.
Mineral Resources, Geol. Geophys. 1971/69, (1971).
68. R. J. Bultitude, The Geology and Petrology of the Helen Springs, Nutwood Downs, and
Peaker Piker Volcanics. Bur. of Mineral Resources, Geol. Geophys. 1972/74, (1972).
69. P. E. Marshall, M. Widdowson, D. T. Murphy, The Giant Lavas of Kalkarindji: Rubbly
pāhoehoe lava in an ancient continental ood basalt province. Palaeogeogr.
Palaeoclimatol. Palaeoecol. 441, 22–37 (2016).
70. L. M. Glass, D. Phillips, The Kalkarindji continental ood basalt province: A new Cambrian
large igneous province in Australia with possible links to faunal extinctions. Geology 34,
461–464 (2006).
71. I. P. Montañez, J. L. Banner, D. A. Osleger, L. E. Borg, P. J. Bosserman, Integrated Sr isotope
variations and sea- level histor y of Middle to Upper Cambrian platform carbonates:
Implications for the evolution of Cambrian seawater 87Sr/86Sr. Geology 24, 917–920
(1996).
72. M. Y. Zhu, L. E. Babcock, S. C. Peng, Advances in Cambrian stratigraphy and paleontology:
Integrating correlation techniques, paleobiology, taphonomy and paleoenvironmental
reconstruction. Palaeoworld 15, 217–222 (2006).
73. C. Chang, W. Hu, X. Wang, H. Yu, A. Yang, J. Cao, S. Yao, Carbon isotope stratigraphy of the
lower to middle Cambrian on the eastern Yangtze Platform, South China. Palaeogeogr.
Palaeoclimatol. Palaeoecol. 479, 90–101 (2017).
74. L. E. Faggetter, “Environmental change, trilobite extinction and massive volcanism at the
Cambrian Series 2- Series 3 boundary” thesis, University of Leeds (2017).
75. L. E. Faggetter, P. B. Wignall, S. B. Pruss, D. S. Jones, S. Grasby, M. Widdowson, R. J. Newton,
Mercury chemostratigraphy across the Cambrian Series 2- Series 3 boundar y: Evidence for
increased volcanic activity coincident with extinction? Chem. Geol. 510, 188–199 (2017).
76. Y. Ren, D. Zhong, C. Gao, T. Liang, H. Sun, D. Wu, X. Zheng, High- resolution carbon isotope
records and correlations of the lower Cambrian Longwangmiao formation (stage 4,
Toyonian) in Chongqing, South China. Palaeogeogr. Palaeoclimatol. Palaeoecol. 485,
572–592 (2017).
77. J. J. Sepkoski, Patterns of Phanerozoic extinction: A perspective from global data bases, in
Global Events and Event Stratigraphy in the Phanerozoic (Springer, 1996), pp. 35–51.
78. M. D. Brasier, The basal Cambrian transition and bio- events (from terminal Proterozoic
extinctions to Cambrian biomeres), in Global Events and Event Stratigraphy in the
Phanerozoic (Springer, 1996), pp. 113–138.
79. T. Wotte, C. B. Skovsted, M. J. Whitehouse, A. Kouchinsky, Isotopic evidence for temperate
oceans during the Cambrian Explosion. Sci. Rep. 9, 6330 (2019).
80. T. W. Hearing, T. H. P. Harvey, M. Williams, M. J. Leng, A. L. Lamb, P. R. Wilby, S. E. Gabbott, A.
Pohl, Y. Donnadieu, An early Cambrian greenhouse climate. Sci. Adv. 4, eaar5690 (2018).
81. M. Keller, J. D. Cooper, O. Lehnert, Sauk megasequence supersequences, southern Great
Basin: second- order accommodation events in the southwest Cordilleran margin
platform. Am. Assoc. Petrol. Geol. Memoir 98, 873–896 (2012).
Downloaded from https://www.science.org on March 29, 2024

Myrow et al., Sci. Adv. 10, eadl3452 (2024) 29 March 2024
SCIENCE ADVANCES | RESEARCH ARTICLE
12 of 12
82. A. Y. Ivantsov, A. Y. Zhuravlev, A. V. Leguta, V. A. Krassilov, L. M. Melnikova,
G. T. Ushatinskaya, Palaeoecology of the early Cambrian Sinsk biota from the Siberian
platform. Palaeogeogr. Palaeoclimatol. Palaeoecol. 220, 69–88 (2005).
83. P. D. Kruse, F. Debrenne, Ajax Mine archaeocyaths: A provisional biozonation for the
upper Hawker Group (Cambrian stages 3- 4), Flinders Ranges South Australia. Australasian
Palaeontological Memoirs 53, 1–238 (2020).
84. P. D. Kruse, Cyanobacterial- archaeocyathan- radiocyathan bioherms in the Wirrealpa
Limestone of South Australia. Can. J. Earth Sci. 28, 601–615 (1991).
85. R. Wood, A. G. Liu, F. Bowyer, P. R. Wilby, F. S. Dunn, C. G. Kenchington, J. F. H. Cuthill,
E. G. Mitchell, A. Penny, Integrated records of environmental change and evolution
challenge the Cambrian Explosion. Nat. Ecol. Evol. 3, 528–538 (2019).
86. B. U. Haq, S. R. Schutter, A chronology of Paleozoic sea- level changes. Science 322, 64–68
(2008).
87. A. Y. Zhuravlev, R. A. Wood, F. T. Bowyer, Cambrian radiation speciation events driven by
sea level and redoxcline changes on the Siberian Craton. Sci. Adv. 9, eadh2558 (2023).
88. R. D. Müller, J. Cannon, X. Qin, R. J. Watson, M. Gurnis, S. Williams, T. Pfaelmoser,
M. Seton, S. H. J. Russell, S. Zahirovic, GPlates: Building a virtual Earth through deep time.
Geochem. Geophys. Geosyst. 19, 2243–2261 (2018).
89. A. R. A. Aitken, D. A. Young, F. Ferraccioli, P. G. Betts, J. S. Greenbaum, T. G. Richter,
J. L. Roberts, D. D. Blankenship, M. J. Siegert, The subglacial geology of Wilkes Land, East
Antarctica. Geophys. Res. Lett. 41, 2390–2400 (2014).
90. C. R. Scotese, “PALEOMAP PaleoAtlas for GPlates and the PaleoData Plotter Program”
(PALEOMAP Project, Tech. Rep. 56, 2016).
91. J. W. Goodge, C. A. Finn, Glimpses of East Antarctica: Aeromagnetic and satellite magnetic
view from the central Transantarctic Mountains of East Antarctica. J. Geophys. Res. 115, (2010).
92. S. C. Cox, B. Smith Lyttle, S. Elkind, C. Smith Siddoway, P. Morin, G. Capponi, T. Abu- Alam,
M. Ballinger, L. Bamber, B. Kitchener, L. Lelli, J. Mawson, A. Millikin, N. Dal Seno,
L. Whitburn, T. White, A. Burton- Johnson, L. Crispini, D. Elliot, S. Elvevold, J. Goodge,
J. Halpin, J. Jacobs, A. P. Martin, E. Mikhalsky, F. Morgan, P. Scadden, J. Smellie, G. Wilson, A
continent- wide detailed geological map dataset of Antarctica. Sci. Data 10, 250 (2023).
93. J. M. Miller, D. Phillips, C. J. L. Wilson, L. J. Dugdale, Evolution of a reworked orogenic zone:
the boundary between the Delamerian and Lachlan fold belts, southeastern Australia.
Aust. J. Earth Sci. 52, 921–940 (2005).
94. S. Rocchi, L. Bracciali, G. di Vincenzo, M. Gemelli, C. Ghezzo, Arc accretion to the early
Paleozoic Antarctic margin of Gondwana in Victoria Land. Gondw. Res. 19, 594–607
(2011).
95. A. J. Rowell, M. N. Rees, R. A. Cooper, B. R. Pratt, Early Paleozoic history of the central
Transantarctic Mountains: evidence from the Holyoake Range, Antarctica. N. Z. J. Geol.
Geophys. 31, 397–404 (1988).
Acknowledgments
Funding: We acknowledge support from National Science Foundation grants EAR- 1849968 to
P.M.M. and EAR- 1849963 to N.C.H. Author contributions: R.R.G. and M.J.B. completed eld
work in Australia. T.- Y.S.P. and N.C.H. prepared, photographed, and analyzed the trilobite
specimens. All authors contributed to the development of scientic arguments and the writing
and editing of the text. Competing interests: The authors declare that they have no
competing interests. Dating and materials availability: All data needed to evaluate the
conclusions in the paper are present in the paper and/or the Supplementary Materials. P.M.M.,
J.W.G., and G.A.B. completed eld work in Antarctica, including sampling for trilobite fossils.
Submitted 12 October 2023
Accepted 26 February 2024
Published 29 March 2024
10.1126/sciadv.adl3452
Downloaded from https://www.science.org on March 29, 2024