bluuebunny/crossref_metadata_2025_split huggingface dataset:
Brachiopods: Cambrian-Tremadoc precursors to Ordovician radiation events
Authors: Bassett Michael G. , Popov Leonid E. , Holmer Lars E. 
Published: April 2008

Abstract
Brachiopod-dominated palaeocommunities incorporating a structure typical of faunal groups within the Palaeozoic Evolutionary Fauna were already present in North and East Gondwana and associated terranes as early as the mid-Cambrian, confined exclusively to shallow marine, inshore environments. The late Cambrian and Tremadoc record of these faunas is incomplete, because of pronounced global sea-level lowstand and subsequent break-up and destruction of the Cambrian Gondwanan margin. It is likely, however, that those groups later forming the core of the Palaeozoic Evolutionary Fauna evolved originally in shallow-water environments of low-latitude peri-Gondwana, and dispersed widely when favourable ecological conditions developed. Conspicuous sea-level rise through the early to mid-Arenig provided newly available habitats in the expanding epeiric seas, where the new faunas evolved and diversified by the mid-Ordovician, when rapid drift separated the early Palaeozoic continents. Relatively short-lived precursor and transitional brachiopod assemblages can be identified on most of the main palaeocontinents prior to the Ordovician radiation of the Palaeozoic Evolutionary Fauna.
Early Ordovician rhynchonelliformean brachiopod biodiversity: comparing some platforms, margins and intra-oceanic sites around the Iapetus Ocean
Authors: Harper David A. T. , Niocaill Conall Mac 
Published: April 2008

AbstractDuring the Arenig-Llanvirn interval a series of radiations across all the major clades, established the Brachiopoda as a major component of the Palaeozoic benthos. Radiations on Baltica and Laurentia during the Arenig formed the basis for two distinct biogeographical provinces with contrasting articulated brachiopod faunas. These platform provinces were supplemented by the marginal Celtic and Toquima-Head provinces; the latter included both marginal and intra-ocean island sites. These marginal and intra-oceanic sites may have served as both ‘cradles and museums’ alternately providing sources for radiations on the platforms and refugia for otherwise relict taxa. Such terranes also partitioned oceanic circulation patterns within the Iapetus Ocean and provided mosaics of rapidly changing, nearshore unstable environments. In contrast to later Ordovician brachiopod faunas, many early Ordovician genera are reported from only one or two sites in the Iapetus region; narrow geographical ranges are characteristic of many taxa. The strong biogeographic differentiation at the generic level is less marked at the familial and higher levels suggesting a series of late Cambrian and early Ordovician migrations prior to the more regional development of the Arenig-Llanvirn brachiopod biofacies across the Iapetus terranes. However, the origination of many brachiopod taxa apparently occurred outside the Iapetus region suggesting that the initial stages of the Ordovician radiations here were first spiked by a series of immigrations.
The spatial and temporal diversification of Early Palaeozoic vertebrates
Authors: Smith M. Paul , Donoghue Philip C. J. , Sansom Ivan J. 
Published: April 2008

Abstract
Recent discoveries have dramatically altered traditional views of the stratigraphic distribution and phylogeny of Early Palaeozoic vertebrates and permit a reappraisal of biogeographic patterns and processes over the first 120 million years of vertebrate evolution. Stratigraphic calibration of the phylogenetic trees indicates that most of the pre-Silurian record can be inferred only through ghost ranges. Assessment of the available data suggests that this is due to a shift in ecological niches after the latest Ordovician extinction event and a broadening of geographical range following the amalgamation of Euramerica during the early Silurian. Two major patterns are apparent in the biogeographic data. Firstly, the majority of jawless fishes with dermoskeletal, plated ‘armour’ were highly endemic during Cambrian-Ordovician time, with arandaspids restricted to Gondwana, galeaspids to China, and anatolepids, astraspids and, possibly, heterostracans confined to Laurentia. These Laurentian groups began to disperse to other continental blocks as the ‘Old Red Sandstone continent’ amalgamated through a series of tectonic collisions. The second major pattern, in contrast, encompasses a number of microsquamous and naked, jawed and jawless primitive vertebrates such as conodonts, thelodonts, placoderms, chondrichthyans and acanthodians, which dispersed rapidly and crossed oceanic barriers to attain cosmopolitan distributions, although many have Laurentian origins. A clear difference in dispersal potential exists between these two types of fishes. Overall, the development of biogeographic patterns in Early Palaeozoic vertebrates involved a complex interaction of dispersal, vicariance and tectonic convergence.
Integrating the present and past records of climate, biodiversity and biogeography: implications for palaeoecology and palaeoclimatology
Authors: Markwick Paul J. 
Published: April 2008

Abstract
A geographic information system (GIS) based, integrated dataset of Recent North American, European, southern African and Australian non-avian tetrapod faunas is used to examine the macroscale relationship between climate, biogeography and terrestrial taxonomic and functional species diversity (richness). The results support a modified form of the species-energy hypothesis, with the pattern of terrestrial biodiversity reflecting the manner in which species procure energy, rather than only the absolute amount of ‘available energy’. Area and history are also found to be important. Ectotherms show the simplest relationship with environmental variables (and strongest latitudinal diversity gradients), and endotherms the most complex. A strong linear relationship is found between the proportion of each fauna represented by ectotherms and temperature (mean annual temperature and coldest month mean temperature). This relationship is used in an experiment to retrodict the palaeotemperature for the Middle Eocene lagerstätten fauna from Messel, Germany. Results compare well with interpretations based on other climate proxies.
Paleogene plate tectonic evolution of the Arabian and Eastern Somali basins
Authors: Royer Jean-Yves , Chaubey A. K. , Dyment Jérome , Bhattacharya G. C. , Srinivas K. , Yatheesh V. , Ramprasad T. 
Published: April 2008

AbstractWe review previous models for the Paleogene tectonic evolution of the Arabian and Eastern Somali basins and present a model based on a new compilation of magnetic and gravity data. Using plate reconstructions, we derive a self-consistent set of isochrons for Chron 27 to Chron 21 (61–46 Ma). The new isochrons account for the development of successive ridge propagation events along the Carlsberg Ridge, leading to an important spreading asymmetry between the conjugate basins. Our model predicts the growth of the outer and inner pseudofaults associated with the ridge propagation events. The location of outer pseudo-faults appears to remain very stable despite a drastic change in the direction of ridge propagation before Chron 24 (c.54 Ma). The motion of the Indian plate relative to the Somalian plate is stable in direction through Paleogene time; spreading velocities decrease from 6 to 3 cm a−1. Our reconstructions also confirm that the Arabia-India plate boundary was located west of the Owen Ridge along the Oman margin during Paleogene time; some compression is predicted at about Chron 21 (47 Ma) between the Indian and Arabian plates.
Paleogene magnetic isochrons and palaeo-propagators in the Arabian and Eastern Somali basins, NW Indian Ocean
Authors: Chaubey A. K. , Dyment Jérome , Bhattacharya G. C. , Royer Jean-Yves , Srinivas K. , Yatheesh V. 
Published: April 2008

Abstract

We present a revised magnetic isochron map of the conjugate Arabian a and Eastern Somali basins based on an up-to-date compilation of Indian, French, and other available seasurface magnetic data. We have used the magnetic anomaly and the modulus of the analytical signal computed from the magnetic anomaly to identify and precisely locate the young and old edges of magnetic chrons in both basins. In addition to the major, well-defined anomalies, we have also used correlatable second-order features of the magnetic anomalies, the ‘tiny wiggles’, to strengthen the interpretation. The resulting isochrons and tectonic elements have been validated using the stochastic method of palaeogeographical reconstruction. The magnetic anomaly pattern in both basins depicts clear oblique offsets, characteristics of pseudofaults associated with propagating ridge segments. Our tectonic interpretation of the area revealed: (1) a complex pattern of ridge propagation between Chrons 28n (
c.
63 Ma) and 25n (
c.
56 Ma), with dominant eastward propagation between Chrons 26n (
c.
58 Ma) and 25n; (2) numerous, systematic westward propagations between Chrons 24n (
c.
53 Ma) and 20n (
c.
43 Ma); (3) asymmetric crustal accretion (caused by ridge propagation and asymmetric sea-floor spreading) in the conjugate basins during the whole period; (4) a slowing of India-Somalia motion after
c.
52 Ma.
Basalt and peridotite recovered from Murray Ridge: are they of supra-subduction origin?
Authors: Burgath Klaus-Peter , Von Rad Ulrich , Van Der Linden Willem , Block Martin , Khan Athar Ali , Roeser Hans Albert , Weiss Wolfgang 
Published: April 2008

Abstract

Petrographic and geochemical data for new basalt and peridotite samples recovered from sampling sites at the Southern Murray Ridge help to constrain models for the evolution of the Owen-Murray Ridge system, which forms the northwestern boundary of the Indian plate. Trace elements immobile during alteration (Ti, Zr, Nb, Y and rare earth elements) suggest that the altered microphyric metabasalt has affinities to magmatism of active margins (island-arc tholeiite
sensu lato
). It is distinctly different from mid-ocean ridge basalt, back-arc-basin basalt, or intra-plate Deccan Trap basalt. The sampled serpentinized harzburgite or clinopyroxene-poor lherzolite was deformed under mantle conditions and is similar to the mantle section of nearby ophiolite sequences. This association of rocks suggests that an ophiolite mélange was sampled. However, results from sampling station 462 NIOP indicate that the Murray Ridge complex also contains igneous rocks with Deccan Trap affinity. For the emplacement of the island-arc tholeiite we assume an origin in a convergent supra-subduction setting, related to the closing of a Late Cretaceous Neo-Tethyan ocean basin between the Arabian and Indian plates to the south and the Eurasian plate to the north. Since Neogene time, the Murray Ridge-Dalrymple Trough has been underlain by attenuated (?)continental crust and characterized by extensional rift tectonics.
Seismic stratigraphy of the offshore Indus Basin
Authors: Daley Tim , Alam Zaheer 
Published: April 2008

Abstract
In 1997 Lasmo Oil Pakistan Ltd (Lasmo) gained a significant position in the offshore Indus Basin with the award of the Indus A and B Blocks. The main hydrocarbon play comprises Miocene shelf-delta sands interbedded with intraformational shale seals and sourced by gas-prone offshore equivalents. Approximately 12 000 km of seismic data have been interpreted in the detailed evaluation of these blocks. However, only four wells have tested the preferred play type and no core or rock data were available to provide further insights into facies or age dating. Log data from two key wells in the offshore Indus area record the initial infilling of the basin by shale-dominated basinal or outer shelf sediments, followed by stacked thin-bedded sandstone-shale sequences of a shelf-delta nature. A zone of progradational sequences marks the transition between the two, but no other workable stratigraphic divisions were apparent. Regional seismic correlation established the diachronous nature of the prograding shelf package and this was matched by distinct bands of seismic progrades. A series of simple palaeogeographies of the prograding shelf margin were developed showing initial sediment input from the north and rapid progradation towards the south and west. The Oligo-Miocene basin fill of the offshore Indus Basin appears to be a ‘one-step’ fill process of a significant depocentre created between the Karachi Platform and the Murray Ridge. Canyons are a very distinct feature on seismic profiles and two main phases of development are apparent. The earlier phase is interpreted to be of Early Miocene age. Downcutting at this time rarely exceeded 400 m. The second phase of canyon development occurred during Plio-Pleistocene time, and these younger canyons often dominate the shallow section, with multiple phases of downcutting sometimes exceeding 1000 m. Where drilled, canyons of both ages have been found to be shale prone. These drilled canyons are interpreted to be on the palaeo-slope where erosion and sediment by-pass occurred during the active phase, and were subsequently filled by fine-grained deposits after abandonment. The two phases of canyoning are considered to relate to phases of tectonic activity in the collision zone between the western margin of the Indo-Pakistan plate and the Eurasian plate.
Quaternary climatic changes over Southern Arabia and the Thar Desert, India
Authors: Glennie K. W. , Singhvi A. K. , Lancaster N. , Teller J. T. 
Published: April 2008

AbstractThe distribution of sand dunes over the southern half of Arabia conforms to the influence of two wind systems: the northern Shamal, which is a strong wind that blows to the SSE down the Persian (Arabian) Gulf and then swings to the SW across the hyperarid Rub al Khali towards North Yemen; and the strong winds of the SW Monsoon system, which were responsible for forming linear dunes that trend north-south in the Wahiba Sands of eastern Oman and SW—NE in the Thar Desert (NW India). In the Thar Desert, the SW Monsoon alternates with the weaker NE Monsoon. The dating of exposures of older dune systems by isotopic, radiometric and optically stimulated luminescence (OSL) analyses has shown that the Shamal was active throughout the latter part of the Quaternary period, and probably as long ago as Mid-Miocene time (c.15 Ma). At times of glacial maxima, when global sea level was some 100–120 m or more lower than now, siliciclastic and carbonate grains were deflated from the exposed surface of the Persian Gulf and transported into the NE Rub al Khali within the United Arab Emirates. It is suspected that occasionally the Shamal also transported some quartz sands from the NW onto the exposed narrow continental shelf of SE Arabia, with silt-size particles being carried into the Arabian Sea. The SW Monsoon, on the other hand, was re-established over the coast of SE Arabia several millennia after the last glacial maximum and was fully established near the coast of SE Arabia during the early Holocene interglacial after the atmospheric high-pressure system associated with the glacial period had become weaker. Early during the Holocene interglacial periods when the SW Monsoon dominated, a combination of quartz and carbonate sands was deflated from the exposed continental shelf and transported to the north into the Wahiba Sands. Aeolian activity in the Thar Desert also peaked during this period of transition from full glacial to interglacial conditions. The dune systems of SE Arabia overlie the distal edges of older alluvial fans that in Oman date back at least 350 ka. The sediments of some of these fluvial sequences in Oman reached the Arabian Sea via Wadi Batha, only to be removed by along-shore currents driven by the SW Monsoon. In the Thar Desert, the supply of aeolian sediment is mostly from fluvial sources. Marine sediments from the Arabian Sea between Arabia and Thar record the contrasting effects of the Shamal and the SW Monsoon: the former mostly as a source of wind-blown dust from Arabia and the latter by causing upwelling of nutrient-rich waters leading to organic blooms.
Paleocene initiation of Cenozoic uplift in Norway
Authors: Nielsen S. B. , Paulsen G. E. , Hansen D. L. , Gemmer L. , Clausen O. R. , Jacobsen B. H. , Balling N. , Huuse M. , Gallagher K. 
Published: April 2008

Abstract
The timing of Cenozoic surface uplift in NW Europe relies on the assumption that the sedimentary response in basins is synchronous with tectonic processes in the source areas. However, many of the phenomena commonly used to infer recent uplift may as well be a consequence of climate change and sea-level fall. The timing of surface uplift therefore remains unconstrained from the sedimentary record alone, and it becomes necessary to consider the constraints imposed by physically and geologically plausible tectonic mechanisms, which have a causal relation to an initiating agent. The gradual reversal of the regional stress field following the break-up produced minor perturbations to the thermal subsidence on the Norwegian Shelf and in the North Sea. Pulses of increased compression cannot be the cause of Cenozoic land surface uplift and accelerated Neogene basin subsidence. Virtually deformation-free regional vertical movements could have been caused by changes in the density column of the lithosphere and asthenosphere following the emplacement of the Iceland plume. A transient uplift component was produced as the plume displaced denser asthenosphere at the base of the lithosphere. This component decayed as the plume material cooled. Permanent uplift as a result of igneous underplating occurred in areas of a thin lithosphere (some Palaeozoic and Mesozoic basins) or for lithosphere under extension at the time of plume emplacement (the ocean-continent boundary). In areas of a thicker lithosphere (East Greenland, Scotland and Norway) plume emplacement may have triggered a Rayleigh-Taylor instability, causing partial lithospheric delamination and associated transient surface uplift at a decreasing rate throughout Cenozoic time. A possible uplift history for the adjacent land areas hence reads: initial transient surface uplift around the break-up time at 53 Ma caused by plume emplacement, and permanent tectonic uplift caused by lithospheric delamination and associated lithospheric heating. The permanent tectonic uplift increased through Cenozoic time at a decreasing rate. Denudation acted on this evolving topography and reduced the average surface elevation, but significantly increased the elevation of the summit envelope. The marked variations in the sedimentary response in the basins were caused by climatic variations and the generally falling eustatic level. This scenario bridges the gap between the ideas of Paleocene-Eocene uplift versus repeated Cenozoic tectonic activity: the tectonic uplift history was initiated by the emplacement of the Iceland plume, but continued throughout Cenozoic time as a consequence of early plume emplacement, with climatic and eustatic control on denudation. The mechanism is consistent with topography, heat flow, crustal structure, and the Bouguer gravity of Norway, and may be applicable also to East Greenland.
Landforms and uplift in Scandinavia
Authors: Lidmar-Bergström K. , Näslund J. O. 
Published: April 2008

Abstract
The relation between Scandinavian landforms and Cenozoic uplift events is examined by analysis of digital elevation data in a regional geological context as well as in a geomorphological process perspective. Re-exposed flat sub-Cambrian and sub-Mesozoic hilly relief aids in deciphering uplift and erosional events. The highly dissected mountains of the Northern Scandes (NS) rise maximally 1500 m above a slightly titled lowest level continuing in the Muddus plains eastwards at 300–550 m above sea level (a.s.l.). This level is correlated with the lowest, slightly warped level of the Palaeic relief at 1000–1300 m a.s.l. of the Southern Scandes (SS), over which mountains of similar height rise. This lowest surface is thought to be the end result of Paleogene erosion to the general base level. Northern Scandinavia with the NS and the Muddus plains acted as a block that was progressively tilted to the SE, whereas the Southern Scandes experienced continuous doming, with a major uplift event of about 1000 m in Neogene time causing deep valley incision in the uplifted plateau. The South Swedish Dome emerged from its Palaeozoic and Mesozoic cover in Neogene time and still retains well-preserved re-exposed palaeosurfaces.
Pattern and timing of the post-Caledonian denudation of northern Scandinavia constrained by apatite fission-track thermochronology
Authors: Hendriks Bart W. H. , Andriessen Paul A. M. 
Published: April 2008

AbstractApatite fission-track thermochronology has been used to study the post-Caledonian denudation history of northern Scandinavia. Post-orogenic denudation progressively shifted from the interior of the continent towards the North Atlantic margin. The present-day area of maximum elevation in the Northern Scandes mountain range has experienced continuous denudation at least since Jurassic time. In Jurassic-Cretaceous time, the area north and east of this region experienced either no denudation at all or some denudation followed by a transient thermal event with a peak temperature in late Cretaceous time. Final denudation of the area to the east of the Northern Scandes probably started in late Cretaceous-Paleogene time and possibly accelerated in Neogene time. The denudation history of northern Scandinavia can be explained by scarp retreat of an uplifted rift flank. The pattern and timing of denudation of the Northern Scandes is different from that of the Southern Scandes, which experienced domal-style, late-stage postrift uplift in Neogene time. Geomorphological observations, offshore data from the Atlantic and Barents Sea margins, and scarce stratigraphical information from the mainland are in general agreement with the new thermochronological data.