EARLY CRETACEOUS EXTENSION IN UPPER-MIDDLE CRUST OF NE ASIA: EVIDENCES FROM WIDESPREAD SYN-THINNING GRANITIC DOMES

Numerous Early Cretaceous syn-thinning granitic domes are widespread in Mongolia and China-Mongolia border area. We observed relationships between deformation and magmatic activity that occurred in Baoder, Naran, Hanwula, Erdene, Altanshiree, Nartyn dome[Daoudene et al., 2012; Cheng et al., 2014; Guo et al., 2015], which developed in eastern Mongolia and China-Mongolia border area during Early Cretaceous crust-scale NW–SE extension.Numerous Early Cretaceous syn-thinning granitic domes are widespread in Mongolia and China-Mongolia border area. We observed relationships between deformation and magmatic activity that occurred in Baoder, Naran, Hanwula, Erdene, Altanshiree, Nartyn dome[Daoudene et al., 2012; Cheng et al., 2014; Guo et al., 2015], which developed in eastern Mongolia and China-Mongolia border area during Early Cretaceous crust-scale NW–SE extension

Early Cretaceous absolute geomagnetic paleointensities from Córdoba province (Argentina)

We present here new paleointensity and geochronology results from Early Cretaceous volcanic rocks of Sierra Chica de Cordoba (Argentina). The new K-Ar isotopic ages of 5 samples range from 136 to 122 Ma. Twenty five samples from 7 individual flows yielded acceptable paleointensity estimates. The mean paleointensity values per flow are ranging from 53.0±1.9 to 25.4±2.6 μT and the corresponding Virtual Dipole Moments (VDMs) are ranging from 9.3±1.3 to 4.6±0.5 (1022 Am2). This corresponds to the mean value of 7.3±1.7x1022 Am2, which is compatible to the present geomagnetic axial dipole. Currently available selected paleointensity data from 80 to 130 Ma suggest that geomagnetic field strength frequently fluctuated before and during the Cretaceous Normal Superchron while the magnetic polarity maintained stable. The mean paleointensities derived from Cordoba lavas agree remarkably well with those obtained from the Parana Magmatic Province (133-132 Ma). This reinforces the hypothesis about the unreliability of ‘Mesozoic Dipole Low'.Fil: Cejudo Ruiz, Ruben. Universidad Nacional Autónoma de México; MéxicoFil: Goguitchaichvili, Avto. Universidad Nacional Autónoma de México; MéxicoFil: Geuna, Silvana Evangelina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Geociencias Básicas, Aplicadas y Ambientales de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Geociencias Básicas, Aplicadas y Ambientales de Buenos Aires; ArgentinaFil: Alva-Valdivia, Luis M.. Universidad Nacional Autónoma de México; MéxicoFil: Solé, Jesus. Universidad Nacional Autónoma de México; MéxicoFil: Morales, Juan. Universidad Nacional Autónoma de México; Méxic

Early Cretaceous angiosperms and beetle evolution

The Coleoptera (beetles) constitute almost one–fourth of all known life-forms on earth. They are also among the most important pollinators of flowering plants, especially basal angiosperms. Beetle fossils are abundant, almost spanning the entire Early Cretaceous, and thus provide important clues to explore the co-evolutionary processes between beetles and angiosperms. We review the fossil record of some Early Cretaceous polyphagan beetles including Tenebrionoidea, Scarabaeoidea, Curculionoidea, and Chrysomeloidea. Both the fossil record and molecular analyses reveal that these four groups had already diversified during or before the Early Cretaceous, clearly before the initial rise of angiosperms to widespread floristic dominance. These four beetle groups are important pollinators of basal angiosperms today, suggesting that their ecological association with angiosperms probably formed as early as in the Early Cretaceous. With the description of additional well-preserved fossils and improvements in phylogenetic analyses, our knowledge of Mesozoic beetle–angiosperm mutualisms will greatly increase during the near future

Analysis of the Importance of Extension in Accounting for the Post-Carboniferous Subsidence of the North Sea Basin

Post Carboniferous sedimentary deposition in the Central North Sea basins can be separated into three major periods: Permian, Triassic and mid-Jurassic through present. Most efforts to explain the basin within an extensional framework have concentrated on the post mid-Jurassic subsidence. These efforts have ignored the large amount of prior extension required to account for the observed crustal thinning and the substantial Permian and Triassic sediment fill. In addition the models predict a mid-Jurassic through early Cretaceous extension that significantly exceeds estimates of the horizontal displacement observed on high angle faults on multichannel seismic lines. We show in areas of minimal pre-Permian subsidence that adding two earlier phase extensions, one in the late Carboniferous through early Permian and the other in the Triassic produces a nearly horizontal late Carboniferous crustal thickness. The time-dependent extensional model required to account for the three periods of sediment deposition gives an excellent match to the observed subsidence history of the basement. We present an analysis of a recent seismic reflection line nm across the Central Graben in the vicinity of published refraction and well data. We show that the extension required in the third phase of the three phase model is compatible with the observed displacement on the high angle mid-Jurassic through early Cretaceous faults. However, we find no evidence for major extension either in the Triassic or late Carboniferous through early Permian.Institute for Geophysic

The evolution of large-bodied theropod dinosaurs during the Mesozoic in Asia

The fossil record of large-bodied, apex carnivorous theropod dinosaurs in Eastern Asia is now among the best understood in the world, thanks to new discoveries and reinterpretations of long-neglected fossils. Asia boasts the most complete record of Middle Jurassic theropods globally, as well as one of the best-studied Late Cretaceous theropod faunas, and new research is helping to fill what was previously a 60-million-year gap in the Early-mid Cretaceous fossil record of large Asian predators. In general, the bio-geographic affinities of large-bodied Asian theropods over time were intimately related to physical geography, and progressively more derived theropod clades evolved large body size and occupied the apex predator niche throughout the Jurassic and Cretaceous. During the Middle Jurassic, largely endemic clades of basal tetanurans were prevalent in Asia, whereas during the Late Jurassic mid Cretaceous more derived “intermediate” tetanuran theropods with cosmopolitan affinities occupied the large predator role, including sinraptorids, spinosauris, and carcharodontosaurians. Finalli, during the final 20 million years of the Cretaceous, more derived, bird-like coelurosaurs attained large body size. Foremost among these were the tyrannosaurids, a radiation of northern (Asian and North American) megapredators whose ascent into the apex predator niche was a delayed event restricted to the Campanian-Masastrichian. As Asia is the focus of intense ongoing dinosaur fieldwork, our undestarnding of large-bodied theropod evolution will continue to be refined with future discoveries.El registro fósil de los dinosaurios carnívoros terópodos de gran talla en el este de Asia es uno de los mejor conocidos del mundo, gracias a nuevos descubrimientos y reinterpretaciones de fósiles que han permanecido pobremente estudiados durante mucho tiempo. Globalmente, Asia comprende el registro fósil mas completo de terópodos del Jurasico Medio, así como una de las faunas finicretácicas mejor estudiadas. Asimismo, las nuevas investigaciones están contribuyendo a completar un hiato de 60 millones de años en el registro fósil de grandes depredadores asiáticos correspondientes al Cretácico inferior-medio. En general las afinidades biogeográficas de los grandes terópodos asiáticos a través del tiempo se hallan íntimamente ligadas a la geografía física. Progresivamente, varios clados derivados de terópodos evolucionaron grandes tallas corporales, ocupando la cima del nicho de depredador durante todo el Jurasico y el Cretácico. Durante el Jurasico Medio prevalecieron clados de tetanuros basales mayormente endémicos, mientras que durante el Jurásico Superior-Cretácico Medio clados más derivados de terópodos tetanuros “intermedios” de afinidades cosmopolitas ocuparon el papel de gran depredador, incluyendo sinraptoridos, espinosauridos y carcharodontosauridos. Finalmente, durante los ultimos 20 millones de anos del Cretacico, coelurosaurios mas derivados con aspecto reminiscente a las aves alcanzaron grandes tallas corporales. Pirmordialmente entre estas formas se hallaban los tiranosauridos, una radiación septentrional (asiáticos y norteamericanos) de megadepredadores cuyo ascenso a la cumbre del nicho de gran depredador se retraso hasta el Campaniense y Maastrichtiense. Mientras Asia continua constituyendo el foco de una intensa actividad paleontológica, nuestros conocientos sobre la evolución de los grandes terópodos continuará refinándose con el estudio de futuros hallazgos

The Stratigraphic Record of Pre-breakup Geodynamics: Evidence from the Barrow Delta, offshore Northwest Australia

The structural and stratigraphic evolution of rift basins and passive margins has been widely studied, with many analyses demonstrating that delta systems can provide important records of post-rift geodynamic processes. However, the apparent lack of ancient syn-breakup delta systems and the paucity of seismic imaging across continent-ocean boundaries means the transition from continental rifting to oceanic spreading remains poorly understood. The Early Cretaceous Barrow Group of the North Carnarvon Basin, offshore NW Australia was a major deltaic system that formed during the latter stages of continental rifting, and represents a rich sedimentary archive, documenting uplift, subsidence and erosion of the margin. We use a regional database of 2D and 3D seismic and well data to constrain the internal architecture of the Barrow Group. Our results highlight three major depocentres: the Exmouth and Barrow sub-basins, and southern Exmouth Plateau. Over-compaction of pre-Cretaceous sedimentary rocks in the South Carnarvon Basin, and pervasive reworking of Permian and Triassic palynomorphs in the offshore Barrow Group, suggests that the onshore South Carnarvon Basin originally contained a thicker sedimentary succession, which was uplifted and eroded prior to breakup. Backstripping of sedimentary successions encountered in wells in the Exmouth Plateau depocentre indicate anomalously rapid tectonic subsidence (≤0.24 mm yr-1) accommodated Barrow Group deposition, despite evidence for minimal, contemporaneous upper crustal extension. Our results suggest that classic models of uniform extension cannot account for the observations of uplift and subsidence in the North Carnarvon Basin, and may indicate a period of depth-dependent extension or dynamic topography preceding breakup

Early Cretaceous biogeographic and oceanographic synthesis of Leg 123 (off Northwestern Australia)

Biogeographic observations made by Leg 123 shipboard paleontologists for Lower Cretaceous nannofossils, foraminifers, radiolarians, belemnites, and inoceramids are combined in this chapter to evaluate the paleoceanographic history of the northwestern Australian margin and adjacent basins. Each fossil group is characterized at specific intervals of Cretaceous time and compared with data from Tethyan and Southern Hemisphere high-latitude localities. Special attention is given to the biogeographic observations made for the Falkland Plateau (DSDP Legs 36 and 71) and the Weddell Sea (ODP Leg 113). Both areas have yielded valuable Lower Cretaceous fossil records of the circumantarctic high latitudes. In general, the Neocomian fossil record from DSDP and ODP sites off northwestern Australia has important southern high-latitude affinities and weak Tethyan influence. The same is true for the pelagic lithofacies: radiolarian chert and/or nannofossil limestone, dominant in the Tethyan Lower Cretaceous, are minor lithologies in the Exmouth-Argo sites. These observations, together with the young age of the Argo crust and plate tectonic considerations, suggest that the Argo Basin was not part of the Tethys Realm. The biogeography of the Neocomian radiolarian and nannofossil assemblages suggests opening of a seaway during the Berriasian that connected the circumantarctic area with the Argo Basin, which resulted in the influx of southern high-latitude waters. This conclusion constrains the initial fit and break-up history of Gondwana. Our results favor the loose fit of the western Australian margin with southeast India by Ricou et al. (1990), which accounts for a deeper water connection with the Weddell-Mozambique basins via drowned marginal plateaus as early as the Berriasian. In fits of the du Toit-type (1937), India would remain attached to Antarctica, at least until the late Valanginian, making such a connection impossible. After the Barremian, increasing Tethyan influence is evident in all fossil groups, although southern high-latitude taxa are still present. Biogeographic domains, such as the southern extension of Nannoconus and Ticinella suggest paleolatitudes of about 50°S for the Exmouth-Argo area. Alternatively, if paleolatitudes of about 35° are accepted, these biogeographic limits were displaced northward at least 15° along Australia in comparison to the southern Atlantic. In this case, the proto-circumantarctic current was deflected northward into an eastern boundary current off Australia and carried circumantarctic cold water into the middle latitudes. Late Aptian/early Albian time is characterized by mixing of Tethyan and southern faunal elements and a significant gradient in Albian surface-water temperatures over 10° latitude along the Australian margin, as indicated by planktonic foraminifers. Both phenomena may be indicative of convergence of temperate and antarctic waters near the Australian margin. High fertility conditions, reflected by radiolarian cherts, are suggestive of coastal upwelling during that time

Burmese amber fossils bridge the gap in the Cretaceous record of polypod ferns

publisher: Elsevier articletitle: Burmese amber fossils bridge the gap in the Cretaceous record of polypod ferns journaltitle: Perspectives in Plant Ecology, Evolution and Systematics articlelink: http://dx.doi.org/10.1016/j.ppees.2016.01.003 content_type: article copyright: Copyright © 2016 Elsevier GmbH. All rights reserved.Copyright © 2016 Elsevier GmbH. All rights reserved. This document is the authors' final accepted version of the journal article. You are advised to consult the publisher's version if you wish to cite from it

Detrital events within pelagic deposits of the Umbria-Marche basin (Northern Apennines, Italy). Further evidence of Early Cretaceous tectonics

Re-sedimented deposits characterize different stratigraphical intervals in the pelagic successions of the Umbria-Marche-Sabina Domain (Central and Northern Apennines, Italy). Three stratigraphic sections of the Maiolica and Marne a Fucoidi Formations, characterized by breccias and calcarenites embedded in pelagic sediments, were sampled across the Mt. Primo area (Umbria- Marche Ridge, Northern Apennines). Facies analysis indicates a gravity-driven origin for the clastic levels, interpreted as debris-flows, or turbidity flows. The massive lensoid-to-tabular levels are composed of loose shallow-water benthic material, sourced from an unknown carbonate platform, associated with: i) lithoclasts made of Lower Jurassic and Lower Cretaceous shallow-water carbonates; ii) Jurassic mudstones and wackestones referable to the pelagic succession; iii) calpionellid/radiolarian-rich soft pebbles (Maiolica-type facies). The compositional features of the studied detrital deposits imply submarine exposure and dismantling of portions of the stratigraphic succession older than the Barremian/Aptian, which had to be buried in the late Early Cretaceous. Such evidence led us to refer the investigated clastic event to an extensional tectonic phase. Our interpretation well fits with data coming from different geological settings of Italy, strongly suggesting the occurrence of a widespread extensional phase in the late Early Cretaceous

The thermal history of the Western Irish onshore

We present here a low-temperature thermochronological study that combines the apatite fission-track and (U + Th)/He dating methods with a pseudo-vertical sampling approach to generate continuous and well-constrained temperature–time histories from the onshore Irish Atlantic margin. The apatite fission-track and (U + Th)/He ages range from the Late Jurassic to Early Cretaceous and the mean track lengths are relatively short. Thermal histories derived from inverse modelling show that following post-orogenic exhumation the sample profiles cooled to c. 75 °C. A rapid cooling event to surface temperatures occurred during the Late Jurassic to Early Cretaceous and was diachronous from north to south. It was most probably caused by c. 2.5 km of rift-shoulder related exhumation and can be temporally linked to the main stage of Mesozoic rifting in the offshore basins. A slow phase of reheating during the Late Cretaceous and Early Cenozoic is attributed to the deposition of a thick sedimentary sequence that resulted in c. 1.5 km of burial. Our data imply a final pulse of exhumation in Neogene times, probably related to compression of the margin. However, it is possible that an Early Cenozoic cooling event, compatible with our data but not seen in our inverse models, accounts for part of the Cenozoic exhumation