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Comment on Gold et al. “The biostratigraphic record of Cretaceous to Paleogene tectono-eustatic relative sea-level change in Jamaica, Journal of south American Earth Sciences (2018), doi: 10.1016/j.jsames.2018.06.011”
Abstract
Gold et al. (2018) present a mid Cretaceous-early Cenozoic relative sea-level curve for Jamaica based on sedimentological and biostratigraphic data from spot samples made from Jamaican outcrop localities and well/corehole samples. They base their work on 200 samples from field outcrops and 600 samples from hydrocarbon exploration wells (many of the latter with cuttings contaminated with extensive cavings)/coreholes, of which 266 were assigned a depositional setting, palaeobathymetry and biostratigraphic age. Gold et al. (2018) use this dataset to revise the sequence stratigraphy of Jamaica, develop a relative sea-level curve and compare this with global sea-level curves. The paper by Gold et al. (2018) includes numerous errors of fact and doubtful interpretations. In this comment I highlight some of these problems based on my own, and my research students’ research over the last 22 years, my own collection of 20,000 + samples from Jamaica, and a thorough understanding of the literature.
This paper provides new data on the Cretaceous geology together with existing data to define four terranes for the Cretaceous of Jamaica. The Northeast Blue Mountain Terrane (NEBMT) contains a shallow-water pile of Campanian basaltic and andesitic lavas interbedded with shallow-water, rudist-bearing limestones. The Southeast Blue Mountain Terrane (SEBMT) contains plume-related basalts attributed to the Caribbean Large Igneous Province (CLIP) of Turonian–Coniacian age overlain by interbedded cherts, limestones and basalts with CLIP affinity of Coniacian–Campanian age; the overlying succession is provisionally attributed to the late Campanian to Maastrichtian. The Western Blue Mountain Terrane (WBMT) contains a suite of Campanian arc rocks intruded by granodiorites which have tectonic contacts with metamorphic rocks (high pressure–low temperate blueschists, amphibolites and greenschists). The Western Jamaica Terrane (WJT) contains a suite of volcanic arc rocks in the Valanginian–Hauterivian, Barremian, Turonian, Santonian to Campanian, and Maastrichtian to Paleocene. These rocks are interbedded with thick to very thick (up to several kilometres) sedimentary sequences which occur at outcrop and in hydrocarbon exploration wells. Three major unconformities are present in the WJT, at the bases of the Crofts Synthem (earliest Campanian), Kellits Synthem (late Campanian to early Maastrichtian) and Yellow Limestone (late Paleocene to early Eocene). The NEBMT and SEBMT are separated from the WBMT and WJT by a NE–SW, left-lateral transform fault that defined the edge of the Caribbean Plate from the early(?) Cretaceous to the mid Eocene and allowed the Cuban oceanic arc and eastern Jamaican terranes to be emplaced between the Americas. Metamorphism in the WBMT indicates the existence of a northeasterly dipping subduction zone which allowed the subduction of CLIP lithosphere in the Campanian. Rudist bivalves suggest an affinity between Jamaica and the Siuna (Chortis) and Guerrero (Mexico) terranes in the Lower Cretaceous, suggesting that these arcs were close together. Subsequently, the three unconformities record interactions between the Jamaican arc segment and the Chortis Block and finally the collision with the Jamaican arc segment with the Maya Block in the Paleocene. The petroleum geology of each Cretaceous terrane is reviewed in the context of source and reservoir rocks. Possible source rocks exist in the Jurassic under northern Jamaica, the Albian to Turonian interval, which is associated with oceanic anoxic events, and the Maastrichtian, which contains thin units of organic-rich shales. Reservoirs are largely confined to limestones which preserve porosity in the body chambers of rudist bivalves and which have also been locally dolomitized and fractured (increasing both porosity and permeability). Oil-associated gas seeps present at outcrop, and oil shows of Jurassic and Cretaceous age from exploration wells indicate the existence of active petroleum systems, but not necessarily of economic hydrocarbon accumulations.
The lithostratigraphy of the Central Inlier is revised based on a complete geological map of the entire inlier. Nomenclature problems from previous schemes are reviewed, the Crofts Synthem is changed rank to Crofts Group, and the Back River Formation is corrected to Black River Formation. The following new units are described: Bellas Gate Formation, Dry Hill Formation; Corn Hill Member (Thomas River Formation); Yankee River Member, Two Meeting Member and Moravia Member (Guinea Corn Formation); and Bronte Tuff Member (Mahoe River Formation, Summerfield Group). The age and lateral relationships of the units are illustrated.
The Jamaican Stratigraphic Committee at a meeting held on the 25 th November 2015, came to the following decisions with regard to the naming of stratigraphic units in Jamaica: The names Yellow Limestone Group, White Limestone Group and Coastal group were formally adopted because of their historical use and to maintain terms in common usage. The name Popkin Formation needs to be replaced.
The geology of the Jerusalem Mountain Inlier is revised based on geological mapping. Five Cretaceous formations are recognized: Mint Formation (new name); Thicket River Formation; Belleisle Formation (new name); Jerusalem Formation; Masemure Formation. The Mint Formation is introduced for what has previously been called the Moreland Formation. Descriptions of the formations and locations of the type sections are indicated. In terms of structure, the inlier shows only gentle folding and does not represent an anticline as previously interpreted.
Previously unrecorded ichnotaxa from the Palaeogene Richmond Formation, namely Cosmorhaphe cf. gracilis, Helminthoida crassa, Paleodictyon? isp. and Taenidium cameronensis, are described. The ichnotaxa are assigned to a previously defined deep-water Scolicia ichnocoenosis characteristic of turbiditic strata. The general exclusion of graphoglyptids in these strata is believed to reflect a combination of the relatively shallow-water depths in which the turbiditic strata accumulated, the abundant organic matter available for biological consumption, and the existence of fluctuating dysaerobic/anoxic and oxygenated conditions at, or immediately below, the sediment-water interface. -Authors
Jamaica is located on a restraining bend on the E-trending, left-lateral plate boundary between the Gonave microplate and Caribbean plate. Deformation in southern Jamaica occurs on two reactivated and simultaneously active fault sets: NNW-striking reverse faults and E-striking strike-slip faults. Movement on NNW-striking reverse faults forms fault-propagation folds that are expressed topographically as the Don Figuerero, Santa Cruz, and Brisco Mountains. The NNW-trending ranges (and faults) of southern Jamaica terminate against the E-W-oriented strike-slip faults. The two dominant E-striking, left-lateral strike-slip faults are the South Coast fault zone in the south and the central Jamaica fault system (Cavaliers fault, Rio Minho-Crawle River fault, and the Siloah fault system) in the central part of the island. We propose that the restraining bend is the result of reactivated, interacting fault arrays in southern Jamaica. The two fault systems inherited from Cretaceous and Paleogene deformation are reactivated to accommodate current deformation. The NNW-striking reverse faults accommodate E-W shortening, and the E-striking strike-slip faults accommodate both the plate motion and the differential motion of the fault blocks bounded by the NNW-striking reverse faults. This geometry results in topographic highs and lows along strike of the strike-slip faults, as a result of vertical displacement on the NNW-striking reverse faults.
We present an updated synthesis of the widely accepted 'single-arc Pacific-origin' and 'Yucatan-rotation' models for Caribbean and Gulf of Mexico evolution, respectively. Fourteen palaeogeographic maps through time integrate new concepts and alterations to earlier models. Pre-Aptian maps are presented in a North American reference frame. Aptian and younger maps are presented in an Indo-Atlantic hot spot reference frame which demonstrates the surprising simplicity of Caribbean-American interaction. We use the Muller et al. (Geology 21: 275-278, 1993) reference frame because the motions of the Americas are smoothest in this reference frame, and because it does not differ significantly, at least since c. 90 Ma, from more recent 'moving hot spot' reference frames. The Caribbean oceanic lithosphere has moved little relative to the hot spots in the Cenozoic, but moved north at c. 50 km/Ma during the Cretaceous, while the American plates have drifted west much further and faster and thus are responsible for most Caribbean-American relative motion history. New or revised features of this model, generally driven by new data sets, include: (1) refined reconstruction of western Pangaea; (2) refined rotational motions of the Yucatan Block during the evolution of the Gulf of Mexico; (3) an origin for the Caribbean Arc that invokes Aptian conversion to a SW-dipping subduction zone of a trans-American plate boundary from Chortis to Ecuador that was part sinistral transform (northern Caribbean) and part pre-existing arc (eastern, southern Caribbean); (4) acknowledgement that the Caribbean basalt plateau may pertain to the palaeo-Galapagos hot spot, the occurrence of which was partly controlled by a Proto-Caribbean slab gap beneath the Caribbean Plate; (5) Campanian initiation of subduction at the Panama-Costa Rica Arc, although a sinistral transform boundary probably pre-dated subduction initiation here; (6) inception of a north-vergent crustal inversion zone along northern South America to account for Cenozoic convergence between the Americas ahead of the Caribbean Plate; (7) a fan-like, asymmetric rift opening model for the Grenada Basin, where the Margarita and Tobago footwall crustal slivers were exhumed from beneath the southeast Aves Ridge hanging wall; (8) an origin for the Early Cretaceous HP/LT metamorphism in the El Tambor units along the Motagua Fault Zone that relates to subduction of Farallon crust along western Mexico (and then translated along the trans-American plate boundary prior to onset of SW-dipping subduction beneath the Caribbean Arc) rather than to collision of Chortis with Southern Mexico; (9) Middle Miocene tectonic escape of Panamanian crustal slivers, followed by Late Miocene and Recent eastward movement of the 'Panama Block' that is faster than that of the Caribbean Plate, allowed by the inception of east-west trans-Costa Rica shear zones. The updated model integrates new concepts and global plate motion models in an internally consistent way, and can be used to test and guide more local research across the Gulf of Mexico, the Caribbean and northern South America. Using examples from the regional evolution, the processes of slab break off and flat slab subduction are assessed in relation to plate interactions in the hot spot reference frame.
Single-channel seismic reflection data from the margins of lowrelief (150-250 m, measured from edge of bank to basin) carbonate platforms on the northern Nicaraguan Rise reveal complex seismic intervals consisting of mounded, chaotic seismic facies interspersed with discontinuous, parallel/laminated seismic facies. We interpret that these intervals contain megabreccias (chaotic facies) and sandy turbidites (parallel/laminated facies). One megabreccia is exposed on the sea floor displaying an overall fan shape having individual blocks measuring nearly 300 m across and >110 m high. The source area consists of a scalloped embayment with a headwall scarp 180 m high. Reflections within the platform are sharply truncated by this escarpment. This single megabreccia is ∼120 m thick and extends ∼27 km along slope and ∼16 km out into the basin. Other megabreccias within the basin have individual blocks measuring >400 m across.
Rocks from dredge hauls are a mixture of shallow- and deep-water facies. Shallow-water facies consist of mixed, skeletal grain-stones and Halimeda packstones. Deep-water facies are massive chalks, chalks with shallow-water skeletal grains, and chalk-block breccias. This indicates that the megabreccias formed as a result of bank-margin collapse, during which the ensuing debris flow eroded into slope and basin facies, mixing rock types together. We speculate that bank-margin-collapse events, resulting in megabreccia formation, may have been seismically triggered, and we emphasize that these large-scale, mass-wasting events occurred along margins of low-relief carbonate platforms.
The geology of the St. Ann's Great River Inlier is revised. A new map of the inlier showing the faults is presented as a base to understand the succession. The lithostratigraphy is described and eight formations are recognised: Windsor Formation (Coniacian: 230+ m thick), Clamstead Formation (Santonian, divided into five members: Lower Clamstead Mudstones; Lower Clamstead Sandstones; Middle Clamstead Mudstones; Upper Clamstead Sandstones; Upper Clamstead Mudstones: 403 m thick), Liberty Hall Formation (Late Santonian and Middle Campanian separated by a major fault: 60+ m thick); Drax Hall Formation (Middle Campanian: 63 m thick); Cascade Formation (Middle-Late Campanian: 180 m thick); Lime Hall Formation (Late Campanian: 14 m thick); St. Ann's Great River Formation (Late Campanian: 14 m thick); and New Ground Formation (Early to Middle Eocene: 290 m thick). The age assignments of the various formations are discussed based on previous and new fossil records.
The Benbow Inlier in Jamaica contains the Devils Racecourse Formation, which is composed of a Hauterivian to Aptian island arc succession. The lavas can be split into a lower succession of basaltic andesites and dacites/rhyolites, which have an island arc tholeiite (IAT) composition and an upper basaltic and basaltic andesite sequence with a calc-alkaline (CA) chemistry. Trace element and Nd-Hf isotopic evidence reveals that the IAT and CA lavas are derived from two chemically similar mantle wedge source regions predominantly composed of normal midocean ridge-type spinel lherzolite. In addition, Th-light rare earth element/high field strength element-heavy rare earth element ratios, Nd-Hf isotope systematics, (Ce/Ce*) n-mn and Th/La ratios indicate that the IAT and CA mantle wedge source regions were enriched by chemically distinct slab fluxes, which were derived from both the altered basaltic portion of the slab and its accompanying pelagic and terrigenous sedimentary veneer respectively. The presence of IAT and CA island arc lavas before and after the Aptian-Albian demonstrates that the compositional change in the Great Arc of the Caribbean was the result of the subduction of chemically differing sedimentary material. There is therefore no evidence from the geochemistry of this lava succession to support arc-wide subduction polarity reversal in the Aptian-Albian.
The orbitoidal larger foraminifer Omphalocyclus maldonensis n. sp. is described from the Maldon Inlier of northwestern Jamaica, being the first record of this genus from the island. The limestone in which it occurs contains the Upper Cretaceous (Upper Maastrichtian) Titanosarcolites rudist fauna, together with larger foraminiferal specimens identified as Orbitoides megaloformis Papp & Küpper. The new species differs from Omphalocyclus macroporus, the only other widely recognized species, in possessing a much smaller nucleus. At least some of the earlier records of Omphalocyclus from the Upper Cretaceous of Venezuela and Cuba should probably be referred to O. maldonensis. J. Micropalaeontol 21(2): 149-153, December 2002.
Formal lithostratigraphic units are herein erected for the Upper Cretaceous succession of the Maldon Inlier, parish of St. James, Jamaica. The lithostratigraphic nomenclature of the Maldon Inlier is reviewed and clarified. New units have been recognized during a re-mapping exercise and these are described. The Woodlands, Maldon (inclusive of Shaw Castle Member), Popkin (inclusive of newly described Abingdon, Tangle River and Banana Ground members), Vaughansfield and Flamstead formations are herein recognised.
The rudist bivalve family Antillocaprinidae Mac Gillavry is revised following a study of nearly all available material in museum collections. Based on differences in their myocardinal arrangements, three subfamilies are recognized: the Titanosarcolitinae nov. subfam., the Antillocaprininae Mac Gillavry, and the Parasarcolitinae nov. subfam. Fifteen genera are described, of which ten are new: Eosarcolites nov. gen., Caenosarcolites nov. gen., Clinocaprina nov. gen., Rotacaprina nov. gen., Rudicaprina nov. gen., Stellacaprina nov. gen., Oligosarcolites nov. gen., Polysarcolites nov. gen., Alencasteria nov. gen., and Sawkinsonia nov. gen. Genera, which are placed in monophyletic radiations, are differentiated on minor differences in myocardinal arrangements, morphotype, and presence or absence of tubes. Six new species are described: Eosarcolites radiatus nov. gen., nov. sp., Caenosarcolites scholaris nov. gen., nov. sp., Rudicaprina planus nov. gen., nov. sp., Sawkinsonia maldonensis nov. gen., nov. sp., Alencasteria macrotubularis nov. gen., nov. sp., and Stellacaprina gunteri nov. gen., nov. sp. Cladistic analysis was performed on selected genera from the Caprinoidea, justifing the division of the Antillocaprinidae into three subfamilies, although extensive paraphyletic groupings exist in the lower part of the strict consensus tree. Weighting myocardinal characters produces a strict consensus tree largely consistent with current subfamily- and family-rank taxonomy, and is consistent with the order of appearance of taxa in the fossil record. The Antillocaprinidae show a major evolutionary radiation reaching a first peak in the middle Campanian, a decline in the late Campanian, and a second peak just before the rudist
extinction at the end of the Cretaceous.
The island of Jamaica forms the northern extent of the Nicaraguan Rise, an elongate linear tectonic feature stretching as far as Honduras and Nicaragua to the south. Uplift and subaerial exposure of Jamaica during the Neogene has made the island rare within the Caribbean region, as it is the only area where rocks of the Nicaraguan Rise are exposed on land. Biostratigraphic dating and palaeoenvironmental interpretations using larger benthic foraminifera, supplemented by planktonic foraminifera, nannopalaeontology and palynology of outcrop, well and corehole samples has enabled the creation of a regional relative sea-level curve through identification of several depositional sequences. This study recognises ten unconformity-bounded transgressive-regressive sequences which record a complete cycle of relative sea level rise and fall. Sequences are recognised in the Early to ‘Middle’ Cretaceous (EKTR1), Coniacian-Santonian (STR1), Campanian (CTR1), Maastrichtian (MTR1-2), Paleocene-Early Eocene (PETR1), Eocene (YTR1-3) and Late Eocene-Oligocene (WTR1). These transgressive-regressive cycles represent second to fourth order sequences, although most tie with globally recognised third order sequences. Comparisons of the Jamaican relative sea-level curve with other published global mean sea-level curves show that local tectonics exerts a strong control on the deposition of sedimentary sequences in Jamaica. Large unconformities (duration >1 Ma) are related to significant regional tectonic events, with minor overprint of a global eustatic signal, while smaller unconformities (duration <1 Ma) are produced by global eustatic trends. The relatively low rates of relative sea-level rise calculated from the regional relative sea-level curve indicate that carbonate production rates were able to keep pace with the rate of relative sea-level rise accounting for the thick successions of Maastrichtian carbonates and those of the Yellow and White Limestone Groups. Carbonate platform drowning within the White Limestone Group during the Oligocene to Miocene is attributed to environmental deterioration given the low rates of relative sea-level rise.
The 3.5 Ma Pliocene Bowden shell beds in southeast Jamaica constitute one of the best-known and well-studied paleontological sites in the Greater Antilles. More than 850 species of shelly fossils, dominated by molluscs, have been reported from the unit. Stratigraphic analysis of a newly cleared, continuous section revealed a submarine channel that contains two shelly conglomerates. Elsewhere in the section, newly discovered leaves show variation in modes of transport from mass flow to settling from suspension and are the first such specimens to be reported from Jamaica. The leaves are commonly fragmentary, making taxonomic determination difficult. However, a number of morphotypes are present, including representatives of Lauraceae, Fabaceae, the red mangrove Rhizophora mangle, and, more rarely, Euphorbiaceae, Clethraceae, and Burseraceae. Their occurrence indicates that most of the leaves were sourced from the coastal area, but some were probably derived from further inland. These new observations accentuate the unusual nature of this deposit, which consists of extrabasinal turbidites deposited from hyperpycnal flows.
The Benbow Inlier in Jamaica contains the Devils Racecourse Formation, which is composed of a Hauterivian to Aptian island arc succession. The lavas can be split into a lower succession of basaltic andesites and dacites/rhyolites, which have an island arc tholeiite (IAT) composition and an upper basaltic and basaltic andesite sequence with a calc-alkaline (CA) chemistry. Trace element and Nd–Hf isotopic evidence reveals that the IAT and CA lavas are derived from two chemically similar mantle wedge source regions predominantly composed of normal mid-ocean ridge-type spinel lherzolite. In addition, Th-light rare earth element/high field strength element–heavy rare earth element ratios, Nd–Hf isotope systematics, (Ce/Ce*)n-mn and Th/La ratios indicate that the IAT and CA mantle wedge source regions were enriched by chemically distinct slab fluxes, which were derived from both the altered basaltic portion of the slab and its accompanying pelagic and terrigenous sedimentary veneer respectively. The presence of IAT and CA island arc lavas before and after the Aptian–Albian demonstrates that the compositional change in the Great Arc of the Caribbean was the result of the subduction of chemically differing sedimentary material. There is therefore no evidence from the geochemistry of this lava succession to support arc-wide subduction polarity reversal in the Aptian–Albian.
Chapter 13 on the Cretaceous of a Concise Geologic TimeScale 2016 is an overview of the status of its global divisions and boundary placements (GSSPs), the main biological zonations, aspects of stable-isotope trends and climate excursions, geomagnetic polarity reversals, major sediment cycles and sea-level changes, and an age model for scaling these events and trends. The majority of the brief chapter consists of summary graphics.
Topographic features of submerged oceanic areas have received less attention from geographers than have inhabited islands or economically important fishing banks, with the result that geographic names are slow to become established and some areas may have several designations. This has been the case in the western Caribbean where the suboceanic ridge extending eastward from Central America to Jamaica and beyond—the Nicaragua Rise—is called by different names on recently published maps. Current practice seems to favor the direct use of a nearby land name for the oceanic feature without an adjective modification. Examples are Colombia Basin, Barbados Ridge, Grenada Trough, and Puerto Rico Trench. Where a name has not already become firmly established, this practice will be followed here.
Cretaceous orbitoid larger foraminifera of the families Pseudorbitoididae, Orbitoididae, and Orbitocyclinidae are known from the Green Island and Grange inliers (western Jamaica), from the Sunderland and Central inliers (west-central Jamaica), and from the Blue Mountain Inlier (eastern Jamaica). They occur in prominent limestone units that are regarded as ranging in age from Campanian to Early Maastrichtian on the basis of nannofossils and accompanying rudist assemblages. Cretaceous pseudorbitoid, orbitoid, and orbitocyclinid foraminifera are useful in interpreting fluctuations of the depositional environment and for time-stratigraphic correlation of Late Cretaceous limestones across Jamaica.
Thirty-four genera and fifty species and subspecies of Paleogene larger foraminifera from Jamaican localities are reviewed and illustrated. Three species, Athecocyclina stephensoni, Hexagonocyclirta inflata, and Rarukothalia catenula, are from Paleocene localities in eastern Jamaica, described for the first time. Ten species first appear in the early Eocene, sixteen in the early middle Eocene, and nine in the late middle Eocene. Four species are confined to the late Eocene. Six species first appear in the early Oligocene, including such characteristic forms as Lepidocyclina undosa and L. yurnagunensis. The first occurrence of Miogypsinoides spp. is used to define the base of the upper Oligocene, but in the back-reef and lagoonal carbonates of the White Limestone Group the boundary between the lower and upper Oligocene is still poorly defined. Here, peneroplid and related forms, such as Archaias asmaricus, not previously recorded from the Caribbean region, and Praerhapydionina delicata are of local biostratigraphic importance.
Calcareous nannofossil assemblages in Campanian rocks in the Sunderland Inlier, western Jamaica, are documented and assigned to Sissingh's (1977, emended 1978) zones 19, 21, and 22, his zone 20 being missing due either to a local fault or to an unconformity. Of the 107 calcareous nannofossil species identified, five new combinations are proposed: Chiastozygus dennisonii, n. comb., Cretarhabdus sinuosus, n. comb., Tranolithus bitraversus, n. comb., Uniplanarius sissinghii, n. comb., and Zygodiscus pontilithus, n. comb.
Recent sampling for larger foraminifers in the so-called Polylepidina gardnerae horizon in the middle Eocene Lisbon Formation of the Little Stave Creek section, southwest Alabama, did not produce any examples of the lepidocyclinid foraminifer Polylepidina gardnerae Cole, but several specimens of the stratigraphically younger species, Lepidocyclina ariana Cole and Ponton, were recovered. Although the P. gardnerae horizon is named on nearly all figures of this important Gulf Coast section published since 1944, preliminary research has also failed to turn up a published basis for the identification of P. gardnerae at this locality. As L. ariana and P. gardnerae are not normally found together, it is the writer's opinion that true P. gardnerae probably has not been collected from any part of the Lisbon Formation at Little Stave Creek. If it does occur, it should be found at a lower horizon than that indicated in the literature.
Dating by planktic microfossils is commonly difficult in very shallow marine paleoenvironments. On the other hand most groups of larger foraminifers thrived under such conditions. Although many larger foraminifers are regarded as being of limited use in studies involving high resolution biostratigraphy, exceptions should occur in cases where a new group is evolving. One such group, the Lepidocyclinidae, evolved in the early middle Eocene of the Americas from a coiled, Amphistegina-like ancestor via intermediate forms, such as Eulinderina and Polylepidina. Morphological modifications include shortening of the nepionic chamber spire and change in the position of the first chamber with a retrovert aperture. The precise nature and timing of these changes have remained obscure. Using samples from Alabama, Jamaica, and St. Bartholomew it is shown that progressive reduction in length of the nepionic spire of Eulinderina up-section occurred through planktic foraminiferal zones P11 and P12 (calcareous nannoplankton zones NP15 and NP16). Assemblages corresponding to Polylepidina appear at the NP16/CP14a level. A similar stage of development appears to be reached in populations of similar age from widely separated localities, based on available planktic microfossil dating. In shallow marine paleoenvironments, the biostratigraphic control provided by the evolutionary state of the Eulinderina-Polylepidina lineage is potentially superior to that providable by conventional planktic microfossils. A model correlating observed clustered values for two parameters of the nepionic spire with the TA 3.3 to TA 3.5 third order middle Eocene sequences of Haq and others is presented.
The Cretaceous Blue Mountain Inlier of eastern Jamaica contains the Bellevue lavas, which represent a Mid-to Late Campanian back-arc basin succession of tholeiitic volcanic rocks. The lavas are composed of basic/intermediate and intermediate/acidic subgroups that can be related by intraformation fractional crystallization. Trace element and Hf radiogenic isotope data reveal that the mantle component of the Bellevue magmas is consistent with derivation from a mantle plume (oceanic plateau) source region. Modeling indicates that the magmas formed by 10%-20% partial melting of an oceanic plateau mantle source comprising spinel peridotite that had previously undergone approximately 5%-7.5% prior melt extraction in the garnet stability field. Trace element and radiogenic isotope systematics suggest that the Bellevue mantle source region was contaminated with a slab-derived component from both the altered basaltic slab and its pelagic sedimentary veneer. The data from the Bellevue lavas support the plateau reversal model of Caribbean tectonic evolution, whereby subduction on the Great Arc of the Caribbean was to the northeast until the Caribbean oceanic plateau collided with the southern portion of the Great Arc in the Santonian (85.8-83.5 Ma), resulting in subduction polarity reversal and thus southwest-dipping subduction. This polarity reversal allowed oceanic plateau source regions to be melted beneath a new back-arc basin to the southwest of the Great Arc.
Based on data from some 40 samples, the first appearance of the Lepidocyclina ariana larger foraminiferal species group occurs at a horizon within the transgressive depositional system of Baum and Vail's TE3.1 sequence, as recently defined by Baum and others in the Bay Minette corehole, Alabama. The last occurrence of the genus Polylepidina Vaughan is observed in the same system in this core. These events also occur within the upper part of the Lisbon Formation as defined in the classical surface section at Little Stave Creek, Alabama, and at other localities in the Gulf Coast, corresponding to a biostratigraphic horizon near that of the boundary between the NP16 and NP17 calcareous nannofossil zones, of middle Eocene, Bartonian age. We illustrate the implication for dating and correlation at horizons near the middle Eocene - late Eocene boundary by the presentation of a correlation of part of the Bay Minette corehole with the section at Little Stave Creek, based on larger foraminiferal and calcareous nannofossil data. We discuss this correlation in relation to other selected localities in the Gulf Coast.
A study of the planktonic foraminifera that occur in the valley of St. Ann's Great River has yielded results that change previously assigned ages for some of the beds in this inlier. The Inoceramus beds range from late Coniacian to late Santonian. The base of the Campanian is at the base of the conglomerate below the Barrettia limestone. At least the upper part of the New Ground Conglomerate is Eocene in age.
The lithostratigraphy of the White Limestone Group (Eocene-Miocene) of Jamaica is revised based on geological mapping across
the northern part of the Clarendon block. Eight shallow-water formations are recognised which are from base to top: Healthy
Hill Formation (new name): predominantly white grainstones; Troy Formation: recrystallized and dolomitized limestones; Swanswick
Formation: white grainstones; Claremont Formation: pale micritic limestones (locally recrystallized and dolomitized); Somerset
Formation: pink grainstones and packstones with large white globular foraminifers; Walderston Formation: pink grainstones;
Browns Town Formation: white packstones and wackestones with abundant large lens shaped foraminifers and abundant corals;
and Newport Formation: pale wakestones and carbonate mudstones. The facies and their foraminifer assemblages are interpreted
in terms of sequence stratigraphy.
Strontium isotope ratios (87Sr/86Sr) in pristine
low-Mg calcite of shells of rudist bivalves from the Titanosarcolites
limestones exposed in the Central, Maldon, and Marchmont inliers of
Jamaica indicate that species-rich rudist-coral associations persisted
into the latest Maastrichtian (66 65 Ma). This finding contradicts the
currently accepted hypothesis of stepwise extinction of rudist bivalves
in the middle Maastrichtian and argues for a catastrophic,
impact-related demise of Caribbean Cretaceous reefal ecosystems at the
Cretaceous-Tertiary boundary.
Two domains of carbonate deposition characterized mid-Tertiary Jamaica. After latest Cretaceous to Paleocene orogeny, submergence of insular paleo-Jamaica accompanied the strike-slip or extensional faulting associated with the formation of the Cayman Trench to the north. Differential subsidence along a series of peripheral subsea escarpments (Duanvale-Wagwater escarpment) produced relief in excess of 2000 m by the Late Eocene. Shoalwater limestones covered the slowly subsiding Cornwall-Middlesex platform, thus ending the supply of clastics to deep-sea bottoms north and east of the escarpment where contemporaneous planktonic-foraminiferal pelagites accumulated. Middle Eocene to Middle Miocene carbonate rocks deposited in the deep-sea represent a distinctive lithogenetic unit termed the Montpelier Group.
Mapping a Cretaceous, island-arc, sedimentary basin revealed a northerly trending submarine canyon complex 4.5 km long and 2 km wide at its southern end. It widens to 4 km in the north, in a downslope direction. The canyon complex cuts across regional stratigraphy and is incised as much as 500 m into a shelf sequence of thinly bedded shale and reef-type limestone. The canyon fill consists of massive, unbedded, mafic, volcanic conglomerate (Tom Spring Formation) and an underlying sequence of volcaniclastic sandstone, calcarenite, shale, and minor conglomerate (Georgia Complex) that was penecontemporaneously deformed. Structures of the Georgia complex suggest a range of deformation mechanisms, including rigid body rotation of bedded blocks, folding, and mass flow. The variation in structural style is attributed to primary variability in rheological properties and to geometry of the basin floor. The deformation of the Georgia complex is attributed to the catastrophic emplacement of the overlying Tom Spring volcanic conglomerate and to gravity-driven processes within the submarine canyon.
The Yallahs Basin lying at a depth of 1,300 m is about 100 km2 in area and contains approximately 500 m of sediments. It is structurally controlled and probably fault bounded. It has been filled by resedimentation of noncarbonate material from two gravel fan deltas and, to a lesser extent, by carbonate from the Jamaican island shelf. After the basin was filled slides and turbidity currents from the more active of the two deltas cut the Yallahs canyon down some 200 m and back 16 km across the basin. Seismic profiling shows that two series of sediments occur in the basin, one laid down before the canyon was cut and one after. A short core from the upper series shows a well-graded sequence of sands and silts. Cable breaks indicate that the three main sediment sources are still active.
The ostracode fauna of the Montpelier Group (Upper Eocene-Middle Miocene) exposed in the western part of the North Coastal Belt of Jamaica contains representatives of three paleo-environments. Allochthonous shelf and littoral species, characterized by abraded carapaces and eye tubercles, and a diverse group of archibenthal (slope) forms are present throughout. Species restricted to the World Ocean Psychrosphere (> 1000 m), notably Bradleya dictyon, Australoecia tipica, Agrenocythere hazelae and Macrocypris spp., first occur in sediments of earliest Miocene age (planktonic foraminiferal zone N4). Their presence establishes a minimum age for the entry into the Cayman Trench of frigid (<8–10°C) water masses drawn from the Atlantic thermohaline stratification.
In the present paper, certain morphological features and the ontogenetical development of members of the subfamily Pseudorbitoidinae Rutten, 1935 are discussed. A study of the evolution of Pseudorbitoides Douvillé, 1922 resulted in testing the concept of nepionic reduction in populations of this genus from Jamaica (Green Island- and Sunderland Inlier) and Curaçao (Cas Abao Limestone lenses). Within the Pseudorbitoides-lineage, P. trechmanni pectinata subsp. nov. is distinguished from P. trechmanni trechmanni Douvillé on account of different post-juvenile features.
Tectonic models of the evolution of the inter-American region show that induced subduction initiation/polar-ity reversal is required in order to isolate the Caribbean as a separate plate. However, the timing and mech-anism of this subduction initiation/reversal are still controversial. In order to shed light on this issue we investigate the geochemistry of arc-derived, ~ 80 Ma, basic to acidic igneous rocks from the Main Ridge For-mation (MRF) in central Jamaica. The affinity of the mantle component in the MRF arc rocks can help increase our understanding of the initiation of any new subduction zone in the inter-American region. Trace element geochemistry demonstrates that the MRF mantle source component was N-MORB-like. Conversely, younger circum-Caribbean arc rocks (≤75 Ma) have a more enriched plume-like mantle component. Unfortunately, when considering the slab component, some of the most useful trace elements that can be used to identify the affinity of a slab flux in arc lavas (e.g., Ba) have been mobilised by subsolidus alteration processes in the MRF. Consequently, the immobile element Th/La–(Ce/Ce*) Nd discrimination diagram is proposed as a method of determining the affinity of slab components from altered igneous rocks. This diagram identifies sedimentary slab components that have potentially contaminated an arc source region, e.g., continental de-tritus, volcanic detritus, hydrogenous Fe–Mn oxides, fish debris-rich clay and hydrothermal sediments. In this study, the Th/La–(Ce/Ce*) Nd diagram suggests that the slab component in most of the MRF samples has a composition similar to continental detritus/GLOSS II. Additionally, several MRF samples are derived from a source region that has been fluxed with a subduction component, in part, composed of fish debris and hydrothermal sediments. These results help constrain the timing and mechanism of Cretaceous subduc-tion initiation in the inter-American region. The geochemical components recognised in the MRF rocks sup-port a Turonian–Campanian (93.5–70.6 Ma) model of intra-Caribbean induced subduction polarity reversal that resulted from the collision of the Caribbean oceanic plateau with an inter-American arc system (the Great Arc of the Caribbean).
We describe the regional fault pattern, geological setting and active fault kinematics of Jamaica, from published geological maps, earthquakes and GPS-based geodesy, to support a simple tectonic model for both the initial stage of restraining-bend formation and the subsequent stage of bend bypassing. Restraining-bend formation and widespread uplift in Jamaica began in the Late Miocene, and were probably controlled by the interaction of roughly east-west-trending strike-slip faults with two NNW-trending rifts oriented obliquely to the direction of ENE-trending, Late Neogene interplate shear. The interaction of the interplate strike-slip fault system (Enriquillo- Plantain Garden fault zone) and the oblique rifts has shifted the strike-slip fault trace c .5 0 km to the north and created the 150-km-long by 80-km-wide restraining bend that is now morphologi- cally expressed as the island of Jamaica. Recorded earthquakes and recent GPS results from Jamaica illustrate continued bend evolution during the most recent phase of strike-slip displace- ment, at a minimum GPS-measured rate of 8 + 1m m/a. GPS results show a gradient in left- lateral interplate strain from north to south, probably extending south of the island, and a likely gradient along a ENE-WSW cross-island profile. The observed GPS velocity field suggests that left-lateral shear continues to be transmitted across the Jamaican restraining bend by a series of intervening bend structures, including the Blue Mountain uplift of eastern Jamaica.
Calyx plates of the crinoid Uintacrinus anglicus are recorded from the top and bottom of a 5 m interval, 4 m above the disappearance of calyx plates of the crinoid Marsupites testudinarius within the Flamborough Chalk Formation at Danes Dyke in North Yorkshire, UK. The U. anglicus Zone, as used here, comprises the interval from the disappearance of M. testudinarius to the disappearance of U. anglicus calyx plates, and therefore includes, but does not comprise, the total range of the index species. Two subzones are recognized in the M. testudinarius Zone; a lower subzone characterized by smooth Marsupites calyx plates and an upper subzone characterized by variably ornamented Marsupites calyx plates. A provisional study of the belemnite indicates the Gonioteuthis granulataquadrata appears in the highest part of the M. testudinarius Zone. The 1983 Copenhagen symposium on Cretaceous stage boundaries proposed that the base of the Campanian Stage should be drawn at a level close to the appearance of G. granulataquadrata. Consequently, the extinction of M. testudinarius is used to define the base of the Campanian here and U. anglicus Zone is placed in the basal Lower Campanian.
Archean continental crust largely comprises the trondhjemite, tonalite, and granodiorite/dacite (TTG/D) suite of igneous rocks. Formation of the earliest Archean (>3.5 Ga) TTG/Ds is controversial, being attributed to either subduction zone processes with active plate tectonics or thermochemical mantle convection with no plate tectonic processes. A suite of Cenozoic adakite-like lavas in Jamaica has geochemical compositions comparable to early Archean TTG/D. The data indicate that the adakites were generated by underthrusting (or subducting) and partial melting of oceanic plateau crust beneath Jamaica. This setting is analogous to proposed plate tectonic processes in the early Archean where hot, thick, and more buoyant Archean oceanic crust underthrusts adjacent plates. The new adakite data imply that earliest Archean TTG/D continental crust could have formed above primitive subduction zones.
Rhyodacite lavas (Newcastle Volcanic Formation) from the Wagwater Basin in eastern Jamaica dated at 52.74 ± 0.34 Ma (2σ) have adakitic-like major element compositions, low Y and heavy rare Earth element (REE) concentrations and negative Nb and Ta anomalies on a normal mid-ocean ridge basalt normalised multi-element diagram. They also have lower Sr (< 400 ppm), MgO (≤ 2.0 wt.%), Ni (mostly ≤ 30 ppm) and Cr (mostly ≤ 40 ppm) concentrations compared to other modern adakites and middle-late Archaean (3.5–2.5 Ga) trondhjemite, tonalite and granodiorite/dacites (TTG/Ds). εNd(i) and εHf(i) values indicate that the Newcastle adakite-like lavas cannot be formed by assimilation and fractional crystallisation processes involving any other igneous rock in the area and so the composition of the lavas is largely the result of the residual mineralogy in the source region. Low Sr and Al2O3 contents indicate a fluid/vapour-absent source with residual plagioclase and REE systematics point to residual amphibole and garnet in the source region. Similarly, high silica values and constant Zr and P2O5 concentrations suggest residual quartz and accessory zircon and apatite. The plagioclase and garnet residue implies that the Newcastle magmas were derived from partially melting a metabasic protolith at 1.0–1.6 GPa, which would intersect the amphibole dehydration partial melt solidus at ~ 850–900 °C.