Showing papers on "Gondwana published in 2019"

The pre-orogenic detrital zircon record of the Peri-Gondwanan crust

Abstract: We present a statistical approach to data mining and quantitatively evaluating detrital age spectra for sedimentary provenance analyses and palaeogeographic reconstructions. Multidimensional scaling coupled with density-based clustering allows the objective identification of provenance end-member populations and sedimentary mixing processes for a composite crust. We compiled 58 601 detrital zircon U–Pb ages from 770 Precambrian to Lower Palaeozoic shelf sedimentary rocks from 160 publications and applied statistical provenance analysis for the Peri-Gondwanan crust north of Africa and the adjacent areas. We have filtered the dataset to reduce the age spectra to the provenance signal, and compared the signal with age patterns of potential source regions. In terms of provenance, our results reveal three distinct areas, namely the Avalonian, West African and East African–Arabian zircon provinces. Except for the Rheic Ocean separating the Avalonian Zircon Province from Gondwana, the statistical analysis provides no evidence for the existence of additional oceanic lithosphere. This implies a vast and contiguous Peri-Gondwanan shelf south of the Rheic Ocean that is supplied by two contrasting super-fan systems, reflected in the zircon provinces of West Africa and East Africa–Arabia.

Cyclical one-way continental rupture-drift in the Tethyan evolution: Subduction-driven plate tectonics

Abstract: Numerous continents have rifted and drifted away from Gondwana to repeatedly open ocean basins over the past ~500 million years. These Gondwana-derived continents drifted towards and collided with components of the Eurasian continent to successively close the preexisting oceans between the two. Plate tectonics satisfactorily describes the continental drift from Gondwana to Eurasia but does not define the geodynamic mechanism of continuously rifting to collisions of continents in the Tethyan Realm. After reappraisal of geological records of the rift, collision and subduction initiation from the surface and various geophysical observations from depth, we propose that Eurasia-directed subducting oceanic slabs would have driven Tethyan system in the Phanerozoic. The Eurasia-directed subduction would have dragged the passive Gondwana margin to rift and drift northwards, giving birth to new oceans since the Paleozoic. The closure of preexisting oceans between the Gondwana-derived continents and Eurasia led to continental collisions, which would have induced the initiation of oceanic subduction in the Tethyan Realm. Multiple episodic switches between collision-subduction-rift repeatedly led to the separation of continental fragments from Gondwana and dragged them to drift towards Eurasia. The final disappearance of Neo-Tethys would have induced collision of the Gondwana-derived continents with the Eurasian continent, giving rise to the Cenozoic Alpine-Zagros-Himalayan collisional system. Therefore, the Eurasia-directed oceanic subduction would have acted as a ‘one-way train’ that successively transferred the ruptured Gondwana continental fragments in the south, into the terminal in the north. In this regard, the engine of this “Tethyan one-way train” is the negative buoyancy of subducting oceanic slabs.

Tectonic evolution of the West Kunlun Orogenic Belt along the northern margin of the Tibetan Plateau: Implications for the assembly of the Tarim terrane to Gondwana

Abstract: The West Kunlun orogenic belt (WKOB) along the northern margin of the Tibetan Plateau is important for understanding the evolution of the Proto- and Paleo-Tethys oceans. Previous investigations have focused on the igneous rocks and ophiolites distributed mostly along the Xinjiang-Tibet road and the China-Pakistan road, and have constructed a preliminary tectonic model for this orogenic belt. However, few studies have focused on the so-called Precambrian basement in this area. As a result, the tectonic affinity of the individual terranes of the WKOB and their detailed evolution process are uncertain. Here we report new field observations, zircon and monazite U-Pb ages of the “Precambrian basement” of the South Kunlun terrane (SKT) and the Tianshuihai terrane (TSHT), two major terranes in the WKOB. Based on new zircon U-Pb age data, the amphibolite-facies metamorphosed volcano-sedimentary sequence within SKT was deposited during the late Neoproterozoic to Cambrian (600–500 Ma), and the flysch-affinity Tianshuihai Group, as the basement of the TSHT, was deposited during the late Neoproterozoic rather than Mesoproterozoic. The rock association of the volcano-sedimentary sequence within SKT suggests a large early Paleozoic accretionary wedge formed by the long-term low-angle southward subduction of the Proto-Tethys Ocean between Tarim and TSHT. The amphibolite-facies metamorphism in SKT occurred at ca. 440 Ma. This ca. 440 Ma metamorphism is genetically related to the closure of the Proto-Tethys Ocean between Tarim and the Tianshuihai terrane, which led to the assembly of Tarim to Eastern Gondwana and the final formation of the Gondwana. Since the late Paleozoic to early Mesozoic, the northward subduction of the Paleo-Tethys Ocean along the Hongshihu-Qiaoertianshan belt produced the voluminous early Mesozoic arc-signature granites along the southern part of NKT-TSHT. The Paleo-Tethys ocean between TSHT and Karakorum closed at ca. 200 Ma, as demonstrated by the monazite age of the paragneiss in the Kangxiwa Group. Our study does not favor the existence of a Precambrian basement in SKT.

Coupled stratigraphic and U-Pb zircon age constraints on the late Paleozoic icehouse-to-greenhouse turnover in south-central Gondwana

Abstract: The demise of the Late Paleozoic Ice Age has been hypothesized as diachronous, occurring first in western South America and progressing eastward across Africa and culminating in Australia over an ∼60 m.y. period, suggesting tectonic forcing mechanisms that operate on time scales of 106 yr or longer. We test this diachronous deglaciation hypothesis for southwestern and south-central Gondwana with new single crystal U-Pb zircon chemical abrasion thermal ionizing mass spectrometry (CA-TIMS) ages from volcaniclastic deposits in the Paraná (Brazil) and Karoo (South Africa) Basins that span the terminal deglaciation through the early postglacial period. Intrabasinal stratigraphic correlations permitted by the new high-resolution radioisotope ages indicate that deglaciation across the S to SE Paraná Basin was synchronous, with glaciation constrained to the Carboniferous. Cross-basin correlation reveals two additional glacial-deglacial cycles in the Karoo Basin after the terminal deglaciation in the Paraná Basin. South African glaciations were penecontemporaneous (within U-Pb age uncertainties) with third-order sequence boundaries (i.e., inferred base-level falls) in the Paraná Basin. Synchroneity between early Permian glacial-deglacial events in southwestern to south-central Gondwana and pCO2 fluctuations suggest a primary CO2 control on ice thresholds. The occurrence of renewed glaciation in the Karoo Basin, after terminal deglaciation in the Paraná Basin, reflects the secondary influences of regional paleogeography, topography, and moisture sources.

Tectonic Evolution of the Western Margin of the Burma Microplate Based on New Fossil and Radiometric Age Constraints

Abstract: Results of biostratigraphic and geochronological investigations in eastern Nagaland and Manipur, NE India, provide new constraints on the tectonic evolution of the western margin of the Burma microplate. U/Pb zircon ages indicate that the Naga Hills ophiolite developed in a suprasubduction zone setting as part of an intraoceanic island arc developed during late Early Cretaceous (mid-Aptian) time and is younger than similar rocks exposed along the Indus-Yarlung Tsangpo suture zone. Radiolarian microfossils provide Jurassic and Cretaceous age constraints for Tethyan ocean floor sediments that were subducted beneath the forming ophiolite. Timing of the emplacement of these rocks onto the passive margin of eastern India is constrained by Paleocene/Eocene radiolarians in sediments over which the ophiolitic assemblage has been thrust. Previously undated schists and gneisses in the Naga Metamorphics are of Early Ordovician age, and their sedimentary protolith was most likely derived from sources in the south of Western Australian and East Antarctica. After Barrovian-style metamorphism, these rocks were uplifted and eroded becoming an important source of detritus shed into the Eocene Phokphur Formation. This unit also contains abundant clasts sourced from the disrupted basement of the Naga Hills ophiolite, which it overlies. It also contains Permo-Triassic-aged detritus eroded off an enigmatic source that was possibly a continental convergent margin arc system somewhere along the northern margin of Gondwana.

Tectonics of the Eastern Desert of Egypt: Key to Understanding the Neoproterozoic Evolution of the Arabian–Nubian Shield (East African Orogen)

Abstract: The tectonic evolution of the Arabian–Nubian Shield (ANS), the northern continuation of the East African Orogen (EAO), is enigmatic and a matter of controversy. The EAO is observed as a N–S trending major suture zone separating East and West Gondwanaland. It documents a prolonged tectonic history bracketed by the fragmentation of Rodinia Supercontinent and the amalgamation of Gondwana. The ANS is dominated by Neoproterozoic juvenile continental crust (i.e., crust formed directly from the mantle), formed by magmatic arc accretion and subsequent post-tectonic magmatism, and includes a mosaic of tectonic terranes juxtaposed along ophiolite-decorated megashears (suture zones). Among them is the Eastern Desert terrane (namely, Aswan or Gerf terrane in some literatures) which is regarded as the western extension of Midyan terrane in Western Arabian and shows most of the polydeformed history of the ANS. This chapter is devoted to discuss the Neoproterozoic crustal evolution of the Pan-African belt of the Eastern Desert terrane in an attempt to understand the tectonic setting of the ANS. Main points to be discussed in this chapter are: (1) infracrustal–supracrustal rocks, (2) thrusting, shearing, and folding relations; (3) gneiss domes versus metamorphic core complexes; (4) the conjugate pairs of Najd-related shears; (5) role of Najd Fault System in tectonic evolution of gneiss domes; (6) rates and transport directions of metaultramafic nappes; (7) the voluminous intrusives in northern Eastern Desert; (8) the post-amalgamation Hammamat sediments and their relation to Dokhan Volcanics; and (9) the northward decrease in intensity of deformation in the entire Eastern Desert.

Initial Rifting of the Lhasa Terrane from Gondwana: Insights From the Permian (~262 Ma) Amphibole-Rich Lithospheric Mantle-Derived Yawa Basanitic Intrusions in Southern Tibet

Abstract: National Key Research and Development Project of China [2016YFC0600304]; Major State Basic Research Program of the People's Republic of China [2015CB452602]; Natural Science Foundation of China [41730427, 41803030, 41873037]; US National Science Foundation [EAR 1725002]; Romanian Executive Agency for Higher Education, Research, Development and Innovation Funding projects [PN-III-P4-ID-PCE-2016-0127, PN-III-P4-ID-PCCF-2016-0014]

A 60-Myr record of continental back-arc differentiation through cyclic melting

Abstract: Continental crust forms and evolves above subduction zones as a result of heat and mass transfer from the mantle below. The nature and extent of this transfer remain debated. Although it has been recognized that arc magmatism at active continental margins can be cyclical at 50- to 1-Myr timescales, such cyclicity has not been recognized in the back-arc. Here we investigate the melting of sedimentary rocks in the continental back-arc of the western Gondwana margin during the Cambrian–Ordovician Famatinian orogeny of Northwest Argentina. We determine the U−Pb ages of zircons that formed during crustal melting and find that they range from 505 to 440 million years ago, concentrated into age groups spaced by 10–15 Myr. This suggests multiple and cyclical melting events in the continental back-arc, which matches the more than 60 Myr duration of the magmatic activity in the arc and demonstrates that thermal and magmatic cyclicity also extends to the continental hinterland. We conclude that back-arc melting reflects a long-lasting, pulsating, cyclical heat transfer from mantle to crust that leads to thorough crustal reworking, transforming sedimentary rocks into crystalline continental crust. Thus, while magma transfer from the mantle promotes crustal growth in convergent margins, cyclical melting promotes crustal maturation of the back-arc. Melting of sedimentary rocks in the continental back-arc is cyclical with peaks of magmatism every 10 to 15 million years, according to zircon ages from Paleozoic western Gondwana margin samples.

Synthesis of the Tectonic and Structural Elements of the Bengal Basin and Its Surroundings

Abstract: The Bengal Basin is a collisional foreland basin in South Asia located at the juncture of the Eurasian, Indian and Burmese Plates occupying Bangladesh and parts of the Indian States of West Bengal, Tripura and Assam. Based on basement configuration, sedimentation pattern and geodynamic development/deformation, three geotectonic provinces, e.g. (i) Stable Shelf or Geotectonic Province 1, (ii) Central Foredeep Basin or Geotectonic Province 2 and (iii) Folded Flank (Chittagong–Tripura Fold Belt: CTFB) or Geotectonic Province 3 have been recognised. The chapter briefly synthesises the tectonic history emphasizing the structural features and related important stratigraphic units only. During the Precambrian, only the Geotectonic Province 1 (Stable Shelf of the Bengal Basin) was a part of the Indian Plate, which was an integral part of the Gondwana Supercontinent. Throughout the Paleozoic and much of the Mesozoic, the Indian Plate was occupying a central location in the Gondwana Supercontinent. During the Late Paleozoic–Mid Mesozoic, the basin (Geotectonic Province 1) had experienced extensional tectonics and was developed as an intra-cratonic rift basin. Afterwards, the Kerguelen igneous activity had resulted the spreading of the SE Indian Ocean and thus Geotectonic Province 1 experienced widespread volcanism known as the Rajmahal Trap. During this time, the Geotectonic Province 2 influenced by marine environment and also affected by this volcanic activity. The floor/base of the Geotectonic Province 2 has been developed as a transitional zone between continent-ocean crust during the initial break-up of the Gondwana and the formation of the Indian Plate. Subsequently, the Geotectonic Province 2 continuously subsided and received a massive volume of sediments during the Late Mesozoic through the Tertiary to Recent. The Indian Plate collided with a Neotethyan intra-oceanic arc during the Late Cretaceous and the Paleocene (between 120–57 Ma). The continental part of the Indian Plate then collided with the Tibetan part of the Eurasian Plate around the Eocene-Oligocene boundary (~35 Ma). The collision resulted the subduction of the northern Indian Plate beneath the southern Tibet, which caused the first uplift of the Himalayan region. Further movement of the Indian Plate continued in the north-easterly direction, resulted collision of the Indian Plate with the Burmese Plate and gave rise to the initial uplift in the Indo-Burman Ranges (IBR) region during the Late Oligocene and the Early Miocene. As compression/uplift continued in both the Himalayan and the IBR fronts, the mountain ranges welded through a syntexial bend. The Geotectonic Province 2 or the central Foredeep Basin was separated from the Assam Basin at ~23 Ma as a ‘remnant ocean basin’. The Geotectonic Province 2 and 3 received huge sediment during the Miocene to the Recent age through the Ganges, the Brahmaputra, the Meghna Rivers and their paleochannels due to the regional uplift in the Himalaya and IBR. These massive sediment loads were accommodated by the Geotectonic Province 1 and 2 through lithospheric flexure, subsidence and isostatic adjustment. Whereas, the sediments were accommodated in the Geotectonic Province 3 through upliftment, crustal shortening and fold thrust belt propagation.

Deconvolving the pre-Himalayan Indian margin – tales of crustal growth and destruction

Abstract: The metamorphic core of the Himalaya is composed of Indian cratonic rocks with two distinct crustal affinities that are defined by radiogenic isotopic geochemistry and detrital zircon age spectra. One is derived predominantly from the Paleoproterozoic and Archean rocks of the Indian cratonic interior and is either represented as metamorphosed sedimentary rocks of the Lesser Himalayan Sequence (LHS) or as slices of the distal cratonic margin. The other is the Greater Himalayan Sequence (GHS) whose provenance is less clear and has an enigmatic affinity. Here we present new detrital zircon Hf analyses from LHS and GHS samples spanning over 1000 km along the orogen that respectively show a striking similarity in age spectra and Hf isotope ratios. Within the GHS, the zircon age populations at 2800–2500 Ma, 1800 Ma, 1000 Ma and 500 Ma can be ascribed to various Gondwanan source regions; however, a pervasive and dominant Tonianage population (∼860–800 Ma) with a variably enriched radiogenic Hf isotope signature (eHf = 10 to −20) has not been identified from Gondwana or peripheral accreted terranes. We suggest this detrital zircon age population was derived from a crustal province that was subsequently removed by tectonic erosion. Substantial geologic evidence exists from previous studies across the Himalaya supporting the Cambro-Ordovician Kurgiakh Orogeny. We propose the tectonic removal of Tonian lithosphere occurred prior to or during this Cambro-Ordovician episode of orogenesis in a similar scenario as is seen in the modern Andean and Indonesian orogenies, wherein tectonic processes have removed significant portions of the continental lithosphere in a relatively short amount of time. This model described herein of the pre-Himalayan northern margin of Greater India highlights the paucity of the geologic record associated with the growth of continental crust. Although the continental crust is the archive of Earth history, it is vital to recognize the ways in which preservation bias and destruction of continental crust informs geologic models.

A Multiproxy provenance approach to uncovering the assembly of East Gondwana in Antarctica

Abstract: East Gondwana is generally thought to have assembled through the amalgamation of Indo-Antarctica and Australo-Antarctica along the Ediacaran–Cambrian Kuunga orogen. The location of a boundary between Indo-Antarctica and Australo-Antarctica within this key Gondwana-forming orogen remains controversial because extensive ice cover in East Antarctica precludes traditional characterization of terranes. Here, we integrated Pb-isotope analysis of detrital feldspar grains with U-Pb dating of detrital monazite and zircon grains from offshore sediments to infer the location of the onshore boundary between Indo-Antarctica and Australo-Antarctica. New and compiled data from onshore basement exposures highlight the different age and Pb-isotope signatures of Indo-Antarctica and Australo-Antarctica. Holocene sediments offshore from Mirny Station (Queen Mary Land, East Antarctica) have detrital feldspar Pb-isotope signatures and detrital monazite and zircon U-Pb ages that reflect contributions from both Indo-Antarctica and Australo-Antarctica. The presence of both Indo-Antarctic and Australo-Antarctic crust beneath ice cover near Mirny Station implies proximity to a fundamental terrane boundary within the Kuunga orogen, which could coincide with a geophysical lineament at ∼94°E (Mirny fault). The geophysical expression of this boundary extends into the subglacial interior of East Antarctica, where, prior to more recent rifting, it may have connected with one or more previously inferred Gondwana-forming sutures. The revised geometry of the Kuunga orogen suggests that the assembly of East Gondwana involved dominantly strike-slip motion in the Mirny region coupled with high-angle convergence between Indo-Antarctica and Australo-Antarctica to the west.

The Cambrian-Early Ordovician Rift Stage in the Gondwanan Units of the Iberian Massif

Abstract: A rifting stage initiated the Variscan cycle in NW Gondwana, lasted from Terreneuvian to Early Ordovician times and culminated in opening of the Rheic Ocean. The result of lithospheric stretching was the development of a horst-and-graben structure in the upper crust and formation of basins with sharp variations in thickness and facies of the sedimentary infill. Emplacement of large volumes of igneous rocks, both plutonic and volcanic, accompanied this stage in three different intervals: (i) Early Igneous Event (Terreneuvian), exclusively composed of felsic peraluminous rocks associated with the formation of core complexes in the mid-upper crust; (ii) Main Igneous Event (Cambrian Series 2 to Furongian), displaying bimodal character; and iii) Late Event (Tremadocian-Floian), with mixed characteristics of the other two events and abundant peralkaline rocks. The rifting axis was initially located close to the Cadomian suture that fringed the Ossa Morena Zone. For about 60 m.y. the rifting processes initially propagated “zip-like” along the axis and then widened cratonward to affect inner parts of Gondwana, such as the Central Iberian Zone. The rift/drift transition was diachronous, starting in Iberia (Ossa Morena Zone) in the Furongian.

The Appalachian and Black Warrior Basins: Foreland Basins in the Eastern United States

Abstract: The Appalachian and Black Warrior basins represent only two of the more than 200 sedimentary basins that have developed across the North American landmass, but these basins have probably had more influence than many others in understanding the interplay between sedimentation, structure, and tectonics. This is especially true for the Appalachian Basin, which is a composite, retroarc/peripheral foreland basin that formed during five orogenies. In many ways, the Appalachian Basin is the “type” foreland basin and the “type area” for the Wilson cycle. Our understanding of the basin, and others like it worldwide, is largely the legacy of a single observation by James Hall in 1857, an observation that also effectively established the framework for the later plate-tectonic paradigm, not to mention major framework developments in structure, tectonics, isostasy, flexural modeling, stratigraphy, sedimentation, paleoclimate, and paleogeography. As preserved today, the basin is about 2050 km long with an area of nearly 536,000 km2, extending from southern Quebec in Canada to northern Alabama in the United States; it reflects the structural influence of earlier Grenvillian convergence and Rodinian dispersal, as well as the paleoclimatic, paleogeographic, eustatic, and tectonic history of eastern Laurentia/Laurussia from latest Precambrian to early Mesozoic time. The associated Black Warrior Basin, on the extreme southwest margin of the Appalachian Basin, is a peripheral foreland basin that developed during a single orogeny. It is a more local basin, and as preserved today, it is about 383 km long by 313 km wide and encompasses an area of nearly 63,900 km2. During latest Precambrian to Early Ordovician time, the recently formed, southern to southeastern Appalachian margin of Laurentia, which now includes both basins, experienced mainly synrift and postrift, passive-margin sedimentation, largely controlled by local structure, regional climate and eustasy. However, by Cambrian time, on some of the more distal outboard parts of the Laurentian margin, the initial tectonic reorganization that would ultimately produce these basins had already begun. Major development of the Appalachian foreland basin began with the advent of the Taconian orogeny at about 470 Ma near the Early-Middle Ordovician transition and continued for nearly 200 Ma during five nearly continuous orogenies that reflect closure of the Iapetus and Rheic oceans and growth of Pangea. Closure of the Iapetus and Rheic oceans reflects the transfer of several Gondwanan terranes to the eastern margin of Laurentia and eventual collision with Gondwana during Paleozoic time. Tectonic dynamics controlled the extent and shape of the basin during various orogenies, and the resulting deformational loading seems to have largely generated the accommodation space in which Appalachian sediments accumulated. Sediment thicknesses up to 13,700 m accumulated in 13 third-order (106–107 years), unconformity-bound cycles that are clearly related to Appalachian tectophases, distinct phases of tectonism controlled by sequential convergence with continental promontories during orogeny. The Black Warrior Basin, in contrast, contains two Late Paleozoic tectophase cycles generated during the Ouachita orogeny. Appalachian tectophase cycles during the Taconian and Salinic orogenies and during the succeeding Acadian, Neoacadian, and Alleghanian orogenies form the larger, second-order (107–108 years), Caledonian and Variscan-Hercynian orogenic supercycles, which generally reflect closure of the Iapetus and Rheic oceans, respectively. In most parts of the basin, the brief transitional Siluro-Devonian, Helderberg interval separates these supercycles and is represented by a thin, widespread, shallow-water, clastic, and carbonate succession with poorly developed tectophase cycles. In contrast to the relative tectonic quiescence apparent in the foreland basin during the Helderberg interval, evidence from more outboard parts of the orogen indicates that the Helderberg interval appears to represent a transitional period of uplift, magmatism, and successor-basin formation during Taconian-Salinic orogen collapse and change to collision-related, strike-slip and transpressional regimes in succeeding orogenies. The first 11 cycles in the Appalachian foreland basin mainly reflect subduction-type orogenies and typically consist of basal, dark, marine shales succeeded in ascending order by flysch-like and molasse-like units, all of which track the progress of orogeny in time and space. The last two Alleghanian cycles, in contrast, reflect collision-type orogeny and are largely composed of clastic-dominated, terrestrial or marginal-marine sediments with a strong eustatic overprint related to Gondwanan glaciation. Although Alleghanian tectonism probably continued through Late Permian time, no foreland-basin sediments younger than Early Permian age are preserved. By Late Triassic time, thermo-tectonic thickening and uplift in the Alleghanian orogen and/or delamination of the underlying Rheic slab and resulting mantle upwelling into old crustal zones of weakness caused orogen collapse and extension, ending the Iapetan or Appalachian Wilson cycle and initiating Pangean dispersal and the current Atlantic Wilson cycle. The importance of the Appalachian Basin lies not only in its “type” status as a basis for our understanding of geomorphological, structural, stratigraphic, and sedimentary parts of the plate-tectonic paradigm, but also in the fact that it contains the relatively well-preserved 545-Ma stratigraphic and sedimentary record of one complete Wilson cycle and parts of others. The larger foreland-basin/orogen area clearly shows the orogen-collapse and extension phase of the previous Laurentian or Grenvillian Wilson cycle during dispersal of the Rodinia supercontinent, as well as late-synrift, passive-margin, active-margin, and orogen-collapse phases of the Iapetan or Appalachian cycle during accretion and dispersal of the Pangean supercontinent. The foreland-basin area itself shows evidence for all the phases except orogen collapse. Nonetheless, what is particularly apparent throughout the basin’s entire history is the fact that the zigzag shape of the old Iapetan margin and the basement structural framework remaining from the previous Laurentian cycle, combined with a series of probably global tectonic events, essentially controlled development and infill of the Appalachian foreland basin. This is apparent in the timing and distribution of the 13 sedimentary cycles that largely comprise its sedimentary infill. Even so, every cycle in the basin differs, reflecting the indelible overprint of changing climatic, geographic, and eustatic regimes. The Black Warrior Basin, in contrast, is not as well understood as the Appalachian Basin. Its roughly 30-Ma history during Mississippian-Pennsylvanian time is relatively short, but that history is very instructive in that it demonstrates how flexural forces from multiple orogenies interact to generate a unique basin response within the standard tectophase model. Moreover, it shows that flexural forces generated during nearby coeval orogenies may influence the sedimentary responses in adjacent foreland basins.

New information on the Cretaceous sauropod dinosaurs of Zhejiang Province, China: impact on Laurasian titanosauriform phylogeny and biogeography

Abstract: Titanosaurs were a globally distributed clade of Cretaceous sauropods. Historically regarded as a primarily Gondwanan radiation, there is a growing number of Eurasian taxa, with several putative ti...

Sedimentary Evolution and Resultant Geological Landscapes

Abstract: Details of the subsurface geology are scarce but in Late Palaeozoic times, the Maltese Islands lay close to the Equator in the Tethys Ocean, that extended between the continents of Gondwana and Laurasia. The oldest subsurface rocks recorded offshore in southeast Sicily are Late Triassic intertidal dolomites (Gela Formation), overlain by Jurassic Black shales (Streppenosa Formation) and platform carbonate of the Siracusa Formation. The exposed geology of the Maltese Islands comprises a marine sedimentary rock sequence about 250 m in thickness, composed of limestones, marls and clays. Ages range from the Upper Oligocene to the Holocene. The stratigraphy consists of the five principal pre-Pliocene Formations: the Lower Coralline Limestone (Oligocene); the Globigerina Limestone (Miocene); the Blue Clay (Miocene); Greensand (Miocene) and the Upper Coralline Limestone (Miocene). The Quaternary is represented by a variety of marine and freshwater deposits (i.e. raised beaches and deposits from freshwater lakes and marine high stands), whereas continental sedimentation is evidenced by fluvial conglomerates; fanglomerates; slope talus; sand-dunes; cave and fissure fills; caliche and speleothems.