Using the most up-to-the-date information available, we present a considerably revised plate tectonic and paleogeographic model for the Indian Ocean bordering continents, from Gondwana's Middle ...Jurassic break-up through to India's collision with Asia in the middle Cenozoic. The landmass framework is then used to explore the sometimes complex and occasionally counter-intuitive patterns that have been observed in the fossil and extant biological records of India, Madagascar, Africa and eastern Eurasia, as well those of the more distal continents.
Although the paleogeographic model confirms the traditional view that India became progressively more isolated from the major landmasses during the Cretaceous and Paleocene, it is likely that at various times minor physiographic features (principally ocean islands) provided causeways and/or stepping-stone trails along which land animals could have migrated to/from the sub-continent. Aside from a likely link (albeit broken by several marine gaps) to Africa for much of this time (it is notable, that the present-day/recent biota of Madagascar indicates that the ancestors of five land-mammal orders, plus bats, crossed the >
400-km-wide Mozambique Channel at different times in the Cenozoic), it is possible that the Kerguelen Plateau connected India and Australia–Antarctica in the mid-Cretaceous (approximately 115–90 Ma). Later, the Seychelles–Mascarene Plateau and nearby elevated sea-floor areas could have allowed faunas to pass between southern India and Madagascar in the Late Cretaceous, from around 85–65 Ma, with an early Cenozoic extension to this path forming as a result of the Reunion hot-spot trace islands growing on the ocean floor to the SSW of India. The modelling also suggests that India's northward passage towards Asia, with eventual collision at 35 Ma, involved the NE corner of the sub-continent making a glancing contact with Sumatra, followed by Burma from ~
57 Ma (late Paleocene) onwards, a scenario which is compatible with the fossil record indicating that India–Asia faunal exchanges began occurring at about this time. Finally, we contend that a number of biologically-based direct terrestrial migration routes that have been proposed for last 15 m.y. of the Cretaceous (Asia to India; Antarctica to Madagascar and/or India) can probably be dismissed because the marine barriers, likely varying from >
1000 up to 2500 km, were simply too wide.
When and where did India and Asia collide? Aitchison, Jonathan C.; Ali, Jason R.; Davis, Aileen M.
Journal of Geophysical Research - Solid Earth,
20/May , Letnik:
112, Številka:
B5
Journal Article
Recenzirano
Odprti dostop
Timing of the collision between India and Asia is the key boundary condition in all models for the evolution of the Himalaya‐Tibetan orogenic system. Thus it profoundly affects the interpretation of ...the rates of a multitude of associated geological processes ranging from Tibetan Plateau uplift through continental extrusion across eastern Asia, as well as our understanding of global climate change during the Cenozoic. Although an abrupt slowdown in the rate of convergence between India and Asia around 55 Ma is widely regarded as indicating the beginning of the collision, most of the effects attributed to this major tectonic episode do not occur until more than 20 Ma later. Refined estimates of the relative positions of India and Asia indicate that they were not close enough to one another to have collided at 55 Ma. On the basis of new field evidence from Tibet and a reassessment of published data we suggest that continent‐continent collision began around the Eocene/Oligocene boundary (∼34 Ma) and propose an alternative explanation for events at 55 Ma.
Tectonic interpretations of arc remnants in the Himalayan orogen remain uncertain, despite their important implications for the overall convergence history between India and Eurasia. Provenance ...results from deep‐water volcaniclastic rocks of the Indus Suture Zone in Ladakh provide new constraints on the Mesozoic tectonic evolution of the Dras and Kohistan‐Ladakh arcs. Detrital zircon (DZ) U‐Pb ages and whole‐rock geochemistry of the fault‐bounded Upper Cretaceous Nindam and Paleocene Jurutze formations present age patterns and compositions that are consistent with those of the Dras and Kohistan‐Ladakh arcs, respectively. The combination of DZs of the Nindam and Jurutze formations with the igneous zircons of the Dras and Kohistan‐Ladakh arcs shows similar age distributions that support a Late Jurassic to Paleocene tectonic connection between all these units. We argue that the secular trends in geochemical composition of DZs and volcaniclastic material are consistent with the magmatic evolution of one convergent margin, which shifted from a primitive to a mature stage during the Late Cretaceous. The recognition of a single Dras‐Kohistan‐Ladakh arc sets the stage for reevaluating competing scenarios of the Mesozoic evolution of the India–Eurasia convergent system. We find that the most likely scenario is that of a Jurassic arc formed above a south‐dipping intraoceanic subduction zone and accreted to Eurasia during the Early Cretaceous, after which it evolved above a north‐dipping subduction zone.
Plain Language Summary
The Himalayan orogen is the result of the collision between India and Eurasia and the closure of the intervening Neotethys Ocean. The suture zone between India and Eurasia hosts an incomplete and complex archive of the paleogeography that once existed between them prior to continent‐continent collision. Investigating suture zone rocks may therefore provide valuable information on the building blocks of the orogen and the overall history of the India‐Eurasia convergent system. Disparate remnants exposed in the Indus Suture Zone (Western Himalaya) suggest that volcanic arcs and sedimentary basins were formed above intraoceanic subduction zones, but there is no consensus on their original paleogeography. We discuss new and existing geological data from volcaniclastic rocks related to the Dras and Kohistan‐Ladakh arcs. Our data support the existence of a single Dras‐Kohistan‐Ladakh arc during the Mesozoic and provide additional insights into the complexity of the pre‐collisional convergence between India and Eurasia.
Key Points
Dissimilar ages and compositions of volcaniclastic units in the Indus Suture Zone reveal arc evolution from primitive to mature stages
Detrital zircon U‐Pb ages and geochemistry, and whole‐rock geochemistry support a common origin of the Dras and Kohistan‐Ladakh arcs
The recognition of a single Dras‐Kohistan‐Ladakh arc represents a key constraint in models of India‐Eurasia convergence
The Qilian Orogen in the northern margin of the Tibetan Plateau is the northernmost of the Tethyan domain. Abundant ophiolites record the closure of an early Tethyan ocean and amalgamations between ...micro-continents of North China, Qaidam, and Tarim. The Muli arc–ophiolite complex in the western segment of the South Qilian belt represents remnants of the Proto-Tethyan oceanic lithosphere. It comprises serpentinite, dunite, cumulate gabbro, basalt, plagiogranite, and chert, which are in tectonic contact with Upper Ordovician turbidites. Basalts have typical subduction-related calc-alkaline geochemical affinity, representing portions of an island arc. Geochemical results for plagiogranites and spinels from serpentinite indicate that the Muli arc–ophiolite complex represents a super-subduction zone (SSZ)-type ophiolite. U–Pb zircon data indicate formation associated with southward subduction of the Proto-Tethys Ocean during a short interval between 539 and 522 Ma. Results of petrology, geochemistry, and zircon U–Pb dating demonstrate that granitoids intruded into this complex are Middle to Late Ordovician (470–450 Ma) products of subduction-related arc magmatism. Voluminous Late Ordovician–Early Silurian rocks include deep-water marine siliciclastic and volcaniclastic turbidites and abundant volcanic arc rocks located to the south of the Muli arc–ophiolite complex, whereas fluvial coarse-grained sandstones and conglomerates unconformably overlie the Cambrian–Middle Ordovician ophiolite–arc systems in the eastern South Qilian belt. This indicates that closure of the Proto-Tethys Ocean was diachronous during the early Paleozoic.
AIM: We constructed a series of high‐resolution palaeogeographical models for the Galápagos archipelago for the last 700 kyr, accommodating thermal subsidence of the islands, eustatic sea‐level ...change, and associated sea‐floor loading. We assessed the possible impacts of these changes for the terrestrial fauna. LOCATION: The Galápagos Islands. METHODS: Palaeogeographical modelling and evaluation of biogeographical distributions. RESULTS: Since 700 ka, sea levels broadly similar to those today isolated the various Galápagos islands for intervals of c. 90 kyr. Intervening 5–10 kyr periods of extreme lowstands in sea level (−140 to −210 m) dramatically changed the central and western archipelago, with several large islands, plus their satellites, coalescing. During the several connection episodes the land‐locked vertebrates had significant or complete access to all of the newly exposed terrain. Analysis of the biological data suggests that these physical processes left detectable imprints on the biogeography of groups including racer snakes, lava lizards, land iguanas and leaf‐toed geckos. MAIN CONCLUSIONS: In the recent geological past, a sizeable region within the Galápagos chain must have experienced rapid, significant changes in its geography as a result of major shifts in local relative sea level periodically connecting and then isolating islands. This might explain striking patterns in the distribution and composition of the archipelago's land fauna. These insights provide a platform for future studies predicting the ages of subpopulation separations, which should correspond to the sea‐level rises that followed each of the lows. The oscillating geography mechanism described herein may provide a new lens to view biological evolution on a number of other island chains, including the Maldives, the Canaries and Cape Verde.
A diverse and well-preserved radiolarian assemblage from the Malongulli Formation, New South Wales, Australia, contains 13 species representing 10 genera and six families. One new genus, Wiradjuri, ...is introduced to accommodate pre-Devonian single-shelled entactiniid taxa, and one new species, Secuicollacta malongulliensis, is recorded together with some previously described forms. The microstructures of the “rotasphaerid structure/primary unit” and the “ectopic spicule” are investigated to validate their roles as fundamental units in the Secuicollactidae, together with comprehensive documentation of the previously enigmatic Pseudorotasphaera internal skeleton. The results of this investigation suggest that, among all radiolarian genera that survived the Late Ordovician Mass Extinction event (LOME) and transitioned into the Silurian, Secuicollacta, Haplotaeniatum, and Palaeoephippium maintained stable body plans during the transition and were more successfully established. The selective advantages these lineages had during the LOME were most likely spontaneous outcomes of the mode of structural development involving sequential skeletogenesis and a tendency to evolve toward simpler body plans. UUID: http://zoobank.org/264c026f-35af-4025-a4f7-de8f9a91f8b9
A diverse, well-preserved radiolarian assemblage is reported from the Sandbian age Climacograptus bicornis Graptolite Biozone. This new assemblage, recovered from the Pingliang Formation in the ...Guanzhuang section, China, includes six new species along with 13 other previously described taxa. Geminusphaera new genus incorporates G. grandis n. sp. and G. kongtongensis n. sp. and is proposed for inaniguttids constructed from two distinct porous spheres bearing seven or more primary spines. Protopylentonema new genus is introduced to incorporate pylomate entactinarians with five-rayed initial spicules. It includes P. ordosensis n. sp. as well as P. aperta, P. rimata, and P. insueta that were formerly assigned to Kalimnasphaera. Micro-computed tomography investigation of skeletal microstructure supports establishment of the new genera together with other new spumellarian species: Haplotaeniatum implexa n. sp., Inanigutta quadrispinosa n. sp., and Kalimnasphaera pingliangensis n. sp. It also indicates that family-level reassignment of Etymalbaillella from the Proventocitidae to the Ceratoikiscidae is appropriate. Global distribution of Late Ordovician radiolarian occurrences highlights a strong preference for areas with equatorial to tropical sea surface temperatures. This must have led to ecological stress among radiolarian communities in adapting to global cooling in the Hirnantian. UUID: http://zoobank.org/3d3f55b8-0e70-4f9f-9738-265750d8ec3a.
Knowledge of the detailed architecture of the earliest radiolarian microfossils is key to resolving the evolution and systematics of this important group of marine protozoans. Non-destructive methods ...for observing the complexity within the internal structures of their siliceous skeletons have long eluded paleontologists. By developing methodologies that overcome some limitations of existing micro-computed tomography (micro-CT) we demonstrate a technique with potential to provide new insight into their evolution. Using 3D micro-CT data to generate models for six well-preserved siliceous radiolarian skeletons from the Middle Cambrian Inca Formation in far north Queensland, Australia and the Middle Ordovician Piccadilly Formation, in western Newfoundland, Canada, we can reconstruct phylogenetic relationships amongst some of the earliest radiolarians. Better knowledge of early radiolarian morphologies clarifies the vital function of internal structures and hierarchical diagnosis across a range of taxonomic affiliations.
Thank You to Our 2022 Reviewers Schildgen, Taylor; Aitchison, Jonathan C.; Jolivet, Laurent ...
Tectonics,
April 2023, Letnik:
42, Številka:
4
Journal Article
Recenzirano
Odprti dostop
We the editors of Tectonics wish to express our sincere thanks to those of you who reviewed manuscripts for us in 2022. Science advances through open communication within the scientific community and ...trust in the integrity of scientific publications. Peer review is essential to scientific publication, helping to ensure that published work maintains the highest degree of rigor and integrity, is well communicated, accurately documented, appropriately placed in the context of prior work, and effectively archived for future usage. Considering our aim to ensure that all published work complies with FAIR data guidelines, we particularly appreciate the time reviewers have also spent on helping to improve data presentation and their suggestions for the best ways to ensure data reusability in the future. The 150 papers published in Tectonics in 2022 benefitted from the careful scrutiny and constructive criticism drawn from the expertise of 508 volunteer reviewers, who provided a total of 719 reviews. We thank you for helping Tectonics produce the high‐quality output that has helped us maintain a prominent position in scientific publishing for decades, and for the spirit of teamwork that makes the peer review process an asset in our community.
Plain Language Summary
Peer review is the key process through which every paper submitted to Tectonics is vetted, ensuring that each publication maintains the highest standards of scientific rigor and integrity. We depend on, and are grateful to, all of the volunteer peer reviewers who have devoted their time and considerable efforts toward this essential procedure. In 2022, the 150 papers published in Tectonics benefited from 719 reviews provided by 508 reviewers. On behalf of the entire editorial board of Tectonics, we want to express here our sincere gratitude to all of you. Thank you!
Key Points
The editors thank the 2022 peer reviewers
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