The Jurassic-Cretaceous (J/K) and Cretaceous-Paleogene (K/Pg) boundaries/transitions are found in Pakistan especially well exposed on the western continental margin of the Indo-Pakistan plate (part of Gondwana) like K...The Jurassic-Cretaceous (J/K) and Cretaceous-Paleogene (K/Pg) boundaries/transitions are found in Pakistan especially well exposed on the western continental margin of the Indo-Pakistan plate (part of Gondwana) like Kirthar, Sulaiman and Kohat and Potwar basins. Its lithology is variable both lateral and also vertical. The J/K and K/Pg transitions are represented by terrestrial and marine strata like laterite, bauxite, vary colored shale, sandstones and conglomerates and rare limestone beds. Mesozoic vertebrates found so far belong to archosaurs like poripuchian titanosaurs (sauropods), theropods, mesoeucrocodiles, pterosaurs, snake and bird are briefly overviewed here.展开更多
The late Maastrichtian witnessed substantial surges in Deccan volcanism,prompting the hypothesis that these voluminous pulses may have instigated repeated episodes of ocean acidification during this period.The Cretace...The late Maastrichtian witnessed substantial surges in Deccan volcanism,prompting the hypothesis that these voluminous pulses may have instigated repeated episodes of ocean acidification during this period.The Cretaceous-Palaeogene(K/Pg)boundary at Bidart(France)is preceded by a~0.5 m thick interval with geochemical and taphonomic vestiges of an ocean acidification event linked with Deccan volcanism.New planktic foraminifera census and morphometric data now confirm biotic stress conditions related to acidification in the Deccan benchmark interval.The absolute abundance data of larger(>150μm)heavily calcified planktic morphogroups show fluctuating populations throughout zone CF1(spanning the final~225 ky),lowest peaks within the Deccan benchmark,and a demographic collapse(>90%)at the K/Pg boundary.The analyzed species are generally reduced in size,with thinner test walls in this~0.5 m interval,indicating the likelihood of calcification stress as a contributor to the overall biotic stress.At the K/Pg boundary,maximum biotic stress is recorded in all the tested faunal proxies.A preliminary graphic correlation of zone CF1 at Bidart with the auxiliary GSSP at Elles(Tunisia)constrains the Deccan benchmark interval of high biotic stress to the final~58ky of the late Maastrichtian,culminating in the K/Pg mass extinction.The volcanogenic Hg peaks coincident with faunal and taphonomic evidence of ocean acidification strengthen the Deccan-related ocean acidification hypothesis.展开更多
1 Introduction The Cretaceous/Tertiary(Paleogene)extinction event was a mass extinction event occurring at about 65 million years ago between the Mesozoic Cretaceous and Cenozoic Tertiary,which is the one closest to t...1 Introduction The Cretaceous/Tertiary(Paleogene)extinction event was a mass extinction event occurring at about 65 million years ago between the Mesozoic Cretaceous and Cenozoic Tertiary,which is the one closest to today among the five major extinction events in the the geological history period(Renne et al.,2013).At the end of the Cretaceous,the proportion of species declined gradually.展开更多
文摘The Jurassic-Cretaceous (J/K) and Cretaceous-Paleogene (K/Pg) boundaries/transitions are found in Pakistan especially well exposed on the western continental margin of the Indo-Pakistan plate (part of Gondwana) like Kirthar, Sulaiman and Kohat and Potwar basins. Its lithology is variable both lateral and also vertical. The J/K and K/Pg transitions are represented by terrestrial and marine strata like laterite, bauxite, vary colored shale, sandstones and conglomerates and rare limestone beds. Mesozoic vertebrates found so far belong to archosaurs like poripuchian titanosaurs (sauropods), theropods, mesoeucrocodiles, pterosaurs, snake and bird are briefly overviewed here.
基金supported by Princeton University’s Scott and Tuttle FundsThe Department of Science and Technology(DST,India)INSPIRE Faculty Award DST/INSPIRE/04/2015/0003110。
文摘The late Maastrichtian witnessed substantial surges in Deccan volcanism,prompting the hypothesis that these voluminous pulses may have instigated repeated episodes of ocean acidification during this period.The Cretaceous-Palaeogene(K/Pg)boundary at Bidart(France)is preceded by a~0.5 m thick interval with geochemical and taphonomic vestiges of an ocean acidification event linked with Deccan volcanism.New planktic foraminifera census and morphometric data now confirm biotic stress conditions related to acidification in the Deccan benchmark interval.The absolute abundance data of larger(>150μm)heavily calcified planktic morphogroups show fluctuating populations throughout zone CF1(spanning the final~225 ky),lowest peaks within the Deccan benchmark,and a demographic collapse(>90%)at the K/Pg boundary.The analyzed species are generally reduced in size,with thinner test walls in this~0.5 m interval,indicating the likelihood of calcification stress as a contributor to the overall biotic stress.At the K/Pg boundary,maximum biotic stress is recorded in all the tested faunal proxies.A preliminary graphic correlation of zone CF1 at Bidart with the auxiliary GSSP at Elles(Tunisia)constrains the Deccan benchmark interval of high biotic stress to the final~58ky of the late Maastrichtian,culminating in the K/Pg mass extinction.The volcanogenic Hg peaks coincident with faunal and taphonomic evidence of ocean acidification strengthen the Deccan-related ocean acidification hypothesis.
基金granted by the National Natural Science Foundation of China(Grant No.41272030)the IGCP608the National Basic Research Program of China(Grant No.2012CB822001).
文摘1 Introduction The Cretaceous/Tertiary(Paleogene)extinction event was a mass extinction event occurring at about 65 million years ago between the Mesozoic Cretaceous and Cenozoic Tertiary,which is the one closest to today among the five major extinction events in the the geological history period(Renne et al.,2013).At the end of the Cretaceous,the proportion of species declined gradually.
