| 1. |
- Bazzi, Mohamad, et al.
(författare)
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Southern higher-latitude lamniform sharks track mid-Cretaceous environmental change
- 2022
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Ingår i: Gondwana Research. - : Elsevier. - 1342-937X .- 1878-0571. ; 103, s. 362-370
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Tidskriftsartikel (refereegranskat)abstract
- The mid-Cretaceous (Albian and Cenomanian, 113–93.9 Myr) marked a transformative interval of shark evolution during which lamniforms (mackerel sharks) diversified as dominant marine predators. Yet, their radiation dynamics relative to major biotic turnovers delimiting the Albian–Cenomanian and Cenomanian–Turonian boundaries are incompletely understood. Here, we use the high-resolution dental fossil record of lamniforms to track changing morphological disparity and tooth size through a succession of mid-Cretaceous shark assemblages from higher-palaeolatitude (up to ∼ 58°S) settings in Australia. Our geometric morphometric analyses and evolutionary model fitting reveal stable disparity throughout the late Albian–late Cenomanian. By contrast, lamniform disparity increased in the early Turonian, which might reflect local habitat differences and/or intraspecific variability through heterodonty. Nevertheless, clade-specific partial disparity increases are evident among small-bodied carchariids, and couple with a trend towards larger teeth as a proxy for body-size in coeval anacoracids. We correlate these signals with recovery after the Oceanic Anoxic Event 2, which severely disrupted latest Cenomanian marine ecosystems and apparently instigated disjunct responses in shark communities occupying epeiric versus outer neritic environments.
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| 2. |
- Betts, Marissa J., et al.
(författare)
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A new early Cambrian bradoriid (Arthropoda) assemblage from the northern Flinders Ranges, South Australia
- 2014
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Ingår i: Gondwana Research. - : Elsevier BV. - 1342-937X .- 1878-0571. ; 25, s. 420-437
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Tidskriftsartikel (refereegranskat)abstract
- A new assemblage of early Cambrian bivalved arthropods (Bradoriida) is described from the Arrowie Syncline in the northern Flinders Ranges, South Australia. The well preserved, largely endemic fauna comprises a total of six taxa (including five new species): Jiucunella phaseloa sp. nov., Jixinlingella daimonikoa sp. nov., Mongolitubulus anthelios sp. nov., Neokunmingella moroensis sp. nov., Phasoia cf. spicata ( Öpik, 1968), and Sinskolutella cuspidata sp. nov. This assemblage is derived from a carbonate sedimentary package representing a high energy, shallow water archaeocyath-Renalcis biohermal facies of Terreneuvian, Stage 2 age which transitions up-section to a more restricted, low energy, intra-shelf lagoonal environment that correlates with a Cambrian Series 2, Stage 3 age. The new taxon J. phaseloa sp. nov., has a first appearance datum (FAD) in shallow water biohermal facies of the Hideaway Well Member of the Wilkawillina Limestone at a level 47 m below the FAD of Pelagiella subangulata which is taken to approximate the base of Series 2, Stage 3 in South Australia. Along with Liangshanella circumbolina, this makes J. phaseloa sp. nov. amongst the oldest bivalved arthropods in South Australia and potentially greater Gondwana. The presence of 25 bradoriid taxa from the early Cambrian of South Australia suggests East Gondwana represents a major centre of origin for the Bradoriida.
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| 3. |
- Betts, Marissa, J., et al.
(författare)
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A new lower Cambrian shelly fossil biostratigraphy for South Australia
- 2016
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Ingår i: Gondwana Research. - : Elsevier BV. - 1342-937X .- 1878-0571. ; 36, s. 163-195
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Tidskriftsartikel (refereegranskat)abstract
- Definition of early Cambrian chronostratigraphic boundaries is problematic with many subdivisions stillawaiting ratification. Integrated multi-proxy data from well-resolved regional-scale schemes are ultimately the key to resolving broader issues of global correlationwithin the Cambrian. In Australia, early Cambrian biostratigraphy has been based predominantly on trilobites. Phosphatic shelly fauna have great potential as biostratigraphic tools, especially in pre-trilobitic strata because they are widespread and readily preserved, but they have remained underutilised. Here we demonstrate their value in a new biostratigraphic scheme for the early Cambrian of South Australia using a diverse shelly fauna including tommotiids, brachiopods, molluscs and bradoriids. Biostratigraphic data are derived from ten measured stratigraphic sections across the Arrowie Basin, targeting Hawker Group carbonates including the Wilkawillina, Wirrapowie and Ajax limestones and the Mernmerna Formation. The stratigraphic ranges of shelly fossils are predictable and repeatable across the Arrowie Basin, allowing three discrete shelly biozones to be identified, spanning Terreneuvian, Stage 2 to Series 2, Stages 3–4. The Kulparina rostrata Zone (new) and part of the overlyingMicrina etheridgei Zone (new) are pre-trilobitic (predominantly Terreneuvian). The Cambrian Series 2, Stage 3 Dailyatia odyssei Zone (new) features a very diverse shelly fauna and will be described in detail in a separate publication. These zones provide robust means to correlate Terreneuvian–Series 2 successions in neighbouring coeval basins in Australia, particularly the Stansbury Basin. Wider correlation is possible throughout East Gondwana, and especially with South China.
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| 4. |
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| 5. |
- Betts, Marissa, J., et al.
(författare)
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Global correlation of the early Cambrian of South Australia: Shelly faunaof the Dailyatia odyssei Zone
- 2017
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Ingår i: Gondwana Research. - Amsterdam : Elsevier BV. - 1342-937X .- 1878-0571. ; 46, s. 240-279
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Tidskriftsartikel (refereegranskat)abstract
- A lack of well resolved biostratigraphic data has prevented robust regional and global correlation of lower Cambriansuccessions from South Australia. A new early Cambrian biostratigraphy, based on data derived from 21measured stratigraphic sections and drill cores (11 described herein) reveals the abundance and diversity ofshelly fauna from the Arrowie Basin, and the value of early Cambrian “small shelly fossils” (SSF) for biostratigraphicstudies. Here we examine shelly fauna associated with the youngest of three recently establishedbiozones, the Dailyatia odyssei Taxon Range Zone (hereafter D. odyssei Zone), and their correlative potential.The D. odyssei Zone features a diverse suite of tommotiids, organophosphatic brachiopods, bradoriid arthropods,molluscs and phosphatic problematica. This fauna permits strong correlation (often at species-level) with othermajor early Cambrian terranes, particularly Antarctica, South China and Laurentia, and suggest a Cambrian Series2, Stages 3–4 age for the D. odyssei Zone. Bradoriids have proven to be useful biostratigraphic tools. Four newspeciesand three new genera are described herein: Acutobalteus sinuosus gen. et sp. nov., Eozhexiella adnyamathanha gen. etsp. nov., Manawarra jonesi gen. et sp. nov. and Mongolitubulus descensus sp. nov. The description of Eohadrotreta sp.cf. zhenbaensis represents the first occurrence of the acrotretoid brachiopod Eohadrotreta from Australia.
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| 6. |
- Burda, Jolanta, et al.
(författare)
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Tracing proto-Rheic - Qaidam Ocean vestiges into the Western Tatra Mountains and implications for the Palaeozoic palaeogeography of Central Europe
- 2021
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Ingår i: Gondwana Research. - : Elsevier. - 1342-937X .- 1878-0571. ; 91, s. 188-204
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Tidskriftsartikel (refereegranskat)abstract
- Zircon petrochronology from amphibolites and retrogressed eclogites from the basement of the Western Tatra Mountains (Central Western Carpathians) reveals a complex rock evolution. An island-arc related basaltic amphibolite from 2iarska Valley shows three distinct zircon forming events: igneous zircon growth at ca. 498 Ma (Middletlate Cambrian) and two phases of amphibolite-facies metamorphism at ca. 470 Ma (Early Ordovician) and at ca. 344 Ma (Early Carboniferous). A retrogressed eclogite from Baranec Mountain records two zircon forming events: metamorphic zircon growth under eclogite-facies conditions at ca. 367 Ma (Late Devonian) and amphibolite-facies metamorphism at ca. 349 Ma (Early Carboniferous). These data contribute towards understanding and correlating major tectonothermal events that shaped the eastern margin of Gondwana in the Early Palaeozoic and its subsequent Variscan evolution. The metabasites record vestiges of two completely independent oceanic domains preserved within the Central Western Carpathians: (1) An Ediacaran to Cambrian oceanic arc related to the proto-Rheic - Qaidam oceans and metamorphosed to amphibolite-facies in the Early Ordovician subduction of the proto-Rheic - Qaidam arc during the Cenerian orogeny (ca. 470 Ma) and (2) late Devonian oceanic crust related to a back-arc basin (Pernek-type), formed by the opening of the Paleotethys and metamorphosed to eclogite-facies during Devonian subduction (ca. 367 Ma). The common Variscan and later evolution of these oceanic remnants commenced with amphibolite-facies metamorphic overprinting in the Early Carboniferous (amphibolite: ca. 344 Ma; retrogressed eclogite: ca. 349 Ma) related to an Early Variscan consolidation and the formation of Pangea. None of the investigated rocks of the Central Western Carpathians show any evidence of being chronologically or palaeogeographically related to the Rheic Ocean, therefore any prolongation of the Rheic suture from the Sudetes into the Alpine-Carpathian realm is highly problematic. Instead, the Southern and Central Alpine Cenerian orogeny can be traced into the Central Western Carpathians.
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| 7. |
- Burton-Johnson, A., et al.
(författare)
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A Triassic to Jurassic arc in north Borneo : Geochronology, geochemistry, and genesis of the Segama Valley Felsic Intrusions and the Sabah ophiolite
- 2020
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Ingår i: Gondwana Research. - : Elsevier BV. - 1342-937X .- 1878-0571. ; 84, s. 229-244
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Tidskriftsartikel (refereegranskat)abstract
- New field, geochemical, and geochronological data from the Segama Valley Felsic Intrusions (SVFI) of Sabah, north Borneo, shows them to be arc-derived tonalites; not windows or partial melts of a crystalline basement beneath Sabah. U-Pb zircon ages date emplacement in the Triassic and Jurassic: 241.1 ± 2.0 Ma, 250.7 ± 1.9 Ma, 178.7 ± 2.4 Ma, and 178.6 ± 1.3 Ma; contemporaneous with peaks in magmatism and detrital zircons in Sarawak and west Kalimantan (west Borneo). Isotopic data for Sr, Nd, and Pb from whole rocks, and for Hf and O from zircon all show mantle and/or MORB affinities indicating a mantle-derived origin. Enrichment of fluid mobile trace elements and trace element ratios indicate that the most likely setting for this is in a continuation of the Sundaland continental arc. There is no evidence in the field, geochemical, or zircon U-Pb data for continental basement in the Segama Valley region. The intrusive nature of the Segama Valley tonalites constrains the emplacement age of their supra-subduction zone host rocks to at least the Triassic. This new data expands the Triassic and Jurassic extent of Borneo and the Sundaland arc, and challenges models of Borneo's development predominantly through allochthonous terrane accretion in the Cretaceous. Instead, we propose a model of protracted autochthonous growth through supra-subduction zone crustal extension and associated magmatism.
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| 8. |
- Cai, Pengjie, et al.
(författare)
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Two stages of crust-mantle interaction during oceanic subduction to continental collision : Insights from mafic-ultramafic complexes in the North Qaidam orogen
- 2021
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Ingår i: Gondwana Research. - : Elsevier. - 1342-937X .- 1878-0571. ; 89, s. 247-264
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Tidskriftsartikel (refereegranskat)abstract
- Subducted sedimentary rocks contribute to different reservoirs in the mantle, which results in crust-mantle interaction; however, the metasomatic processes involved in this sedimentary contribution to the mantle still remain poorly understood. Chromite is a robust mineral and together with its inclusions, occurring in orogenic peridotite, it is an important candidate for decoding both the petrogenetic and tectonic settings as well as crust-mantle interaction. This study presents an integrated petrological and geochemical study of the chromitite-bearing Luofengpo mafic-ultramafic complex (CLMC) in the North Qaidam orogen, China. The CLMC consists of amphibole pyroxenite, serpentinized peridotite, and serpentinized pyroxenite. Electron probe micro-analysis and laser ablation inductively coupled plasma mass spectrometry analysis demonstrated that the studied chromite grains display compositional zoning with the cores preserving primary igneous compositions. Chromitites with high Cr#(100*Cr/(Cr+Al)) signatures are enriched in IPGE (Os, Ir, and Ru) and depleted in PPGE (Rh, Pt, and Pd) indicating that they formed in the supra-subduction zone mantle wedge. Core compositions of chromite grains indicate that the parental melts of the chromitites were similar to typical boninitic melts, formed in a forearc setting related to subduction initiation. Petrographic, geochronological, and mineralogical analyses suggest that the CLMC underwent at least two stages of crust-mantle interaction. The first stage (metasomatic agent) occurred at 483.1 ± 3.5 Ma. The metasomatic agent was a hydrous melt derived from a mixed source of carbonates and sediments, subducted with the south Qilian oceanic slab. The second stage (metasomatic fluids) occurred at 434.2 ± 2.1 Ma and the metasomatic fluids originated from subduction and exhumation of the deeply subducted continental crust. These results suggest that the CLMC represents a supra-subduction zone mantle wedge slice, metasomatized by at least two stages of subduction crustal fluids during the transition from oceanic subduction to continental collision in the North Qaidam ultrahigh pressure metamorphic belt.
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| 9. |
- Chen, Feiyang, et al.
(författare)
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Cambrian ecological complexities: Perspectives from the earliest brachiopod – supported benthic communities in the early Cambrian Guanshan Lagerstätte
- 2022
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Ingår i: Gondwana Research. - Amsterdam : Elsevier. - 1342-937X .- 1878-0571. ; 107, s. 30-41
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Tidskriftsartikel (refereegranskat)abstract
- The Cambrian radiation is characterized by the emergence of diverse bilaterian animal phyla and theestablishment of complex marine ecosystems. The Guanshan Biota records an unusual ecological transition from trilobite- to brachiopod-dominated communities during Cambrian Stage 4. This community transition is accompanied by direct evidence of in situ biological interactions such as durophagous pre-dation and kleptoparasitism. Here we describe new material from the Guanshan biota, focusing on an association of palaeoscolecidomorphs and brachiopods with parasitic tube worms that occur on micro-bedding planes. The bedding plane assemblages are dominated by the organophosphatic brachiopod Neobolus wulongqingensis encrusted with kleptoparasitic tube-dwelling worms, along with infaunal palaeoscolecidans. Taphonomic and sedimentological evidence indicates that these specimens are com-monly preserved in life position, and thus the association between individuals represent potential biological interactions. This case study reveals that ecosystems during the early Cambrian exhibited a well-developed system of tiering and a complex trophic network, easily distinguished from the simple communities typical of precursor deposits in the Ediacaran. Brachiopods forming extremely dense concentrations on the sea floor are effectively acting as ecosystem engineers, not only to stabilize the soft-substrate seafloor, but also act as an alternative substrate for the oldest empirically demonstrated kleptoparasites.The in situ biological interactions preserved in the Guanshan Biota are critical for filling gaps in ourknowledge of ecosystem complexity in the Cambrian.
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| 10. |
- D'Agrella-Filho, Manoel S., et al.
(författare)
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The 1420 Ma Indiavaí Mafic Intrusion (SW Amazonian Craton): Paleomagnetic results and implications for the Columbia supercontinent
- 2012
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Ingår i: Gondwana Research. - : Elsevier BV. - 1342-937X .- 1878-0571. ; 22:3-4, s. 956-973
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Tidskriftsartikel (refereegranskat)abstract
- The configuration and the timing of assembly and break-up of Columbia are still matter of debate. In order to improve our knowledge about the Mesoproterozoic evolution of Columbia, a paleomagnetic study was carried out on the 1420 Ma Indiavaí mafic intrusive rocks that crosscut the polycyclic Proterozoic basement of the SW Amazonian Craton, in southwestern Mato Grosso State (Brazil). Alternating field and thermal demagnetization revealed south/southwest ChRM directions with downward inclinations for sixteen analyzed sites. These directions are probably carried by SD/PSD magnetite with high coercivities and high unblocking temperatures as indicated by additional rock magnetic tests, including thermomagnetic data, hysteresis data and the progressive acquisition of isothermal remanent magnetization. Different stable magnetization components isolated in host rocks from the basement 10 km NW away to the Indiavaí intrusion, further support the primary origin of the ChRM. A mean of the site mean directions was calculated at Dm = 209.8°, Im = 50.7° (α95 = 8.0°, K = 22.1), which yielded a paleomagnetic pole located at 249.7°E, -57.0°N (A95 = 8.6°). The similarity of this pole with the recently published 1420 Ma pole from the Nova Guarita dykes in northern Mato Grosso State suggests a similar tectonic framework for these two sites located 600 km apart, implying the bulk rigidity of the Rondonian-San Ignacio crust at that time. Furthermore these data provide new insights on the tectonic significance of the 1100-1000 Ma Nova Brasilândia belt –a major EW feature that cuts across the basement rocks of this province, which can now be interpreted as intracratonic, in contrast to previous interpretation. From a global perspective, a new Mesoproterozoic paleogeography of Columbia has been proposed based on comparison of these 1420 Ma poles and a 1780 Ma pole from Amazonia with other paleomagnetic poles of similar age from Baltica and Laurentia, a reconstruction in agreement with geological correlations.
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