The Triassic-Jurassic （Tr-J） boundary marks a major extinction event, which （～200 Ma）resulted in global extinctions of fauna and flora both in the marine and terrestrial realms. There prevail great challenges in ...The Triassic-Jurassic （Tr-J） boundary marks a major extinction event, which （～200 Ma）resulted in global extinctions of fauna and flora both in the marine and terrestrial realms. There prevail great challenges in determining the exact location of the terrestrial Tr-J boundary, because of endemism of taxa and the scarcity of fossils in terrestrial settings leading to difficulties in linking marine and terrestrial sedimentary successions. Investigation based on palynology and bivalves has been carried out over a 1113 m thick section, which is subdivided into 132 beds, along the Haojiagou valley on the southern margin of the Junggar Basin of the northern Xinjiang, northwestern China. The terrestrial Lower Jurassic is conformably resting on the Upper Triassic strata. The Upper Triassic covers the Huangshanjie Formation overlaid by the Haojiagou Formation, while the Lower Jurassic comprises the Badaowan Formation followed by the Sangonghe Formation. Fifty six pollen and spore taxa and one algal taxon were identified from the sediments. Based on the key-species and abundance of spores and pollen, three zones were erected： the Late Triassic （Rhaetian） Aratrisporites-Alisporites Assemblage, the Early Jurassic （Hettangian） Perinopollenites-Pinuspollenites Assemblage, and the Sinemurian Perinopollenites-Cycadopites Assemblage. The Tr-J boundary is placed between bed 44and 45 coincident with the boundary between the Haojiagou and Badaowan formations. Beds with Ferganoconcha （？）, Unio-Ferganoconcha and Waagenoperna-Yananoconcha bivalve assemblages are recognized. The Ferganoconcha （？） bed is limited to the upper Haojiagou Formation,Unio- Ferganoconcha and Waagenoperna- Yananoconcha assemblages are present in the middle and upper members of the Badaowan Formation. The sedimentary succession is interpreted as terrestrial with two mainly lake deposit intervals within Haojiagou and Badaowan formations, yielding fresh water algae and bivalves. However, the presence of brackish water algae Tasmanites展开更多
Triassic-Jurassic carbonates widely distributed in Eastern Indonesia are believed as oils source rock. The Mesozoic Tokala Formation exhibit source rock potential, as evidenced by high contents of organic matter. Rece...Triassic-Jurassic carbonates widely distributed in Eastern Indonesia are believed as oils source rock. The Mesozoic Tokala Formation exhibit source rock potential, as evidenced by high contents of organic matter. Recent exploration has been conducted in southeastern Sulawesi, targeting the Mesozoic intervals. Therefore, in this study, we attempted to determine source rock potential of Tokala Formation outcropped in southeastern Sulawesi area and its capability to generate hydrocarbon. Five distinct lithofacies were delineated, emphasizing lithological and mineralogical features: foraminifera wackestone (FW), lime mudstone (LM), massive bioturbated calcareous-argillaceous shale (MBCAS), weakly laminated argillaceous-calcareous shale (WLACS), and strongly laminated calcareous-argillaceous shale (SLCAS). Subsequent analyses showed that carbonate-rich samples (FW and LM facies, >50% CaO) had poor source rock potential. Conversely, shale facies with moderate carbonate content (WLACS, MBCAS, and SLCAS, 15% - 50% CaO) had good to excellent source rock characteristics, qualifying them as preferable source rock. In addition, levels of SiO2 and Al2O3 should not be neglected, as these constituents play important roles in clay mineral adsorption. Laminated shale facies with moderate CaO content tended to be more promising as source rock than bioturbated facies. The shale facies of Tokala Formation indicate prospective source rock horizon.展开更多
There are two factors,source composition and magmatic differentiation,potentially controlling W-Sn mineralization.Which one is more important is widely debated and may need to be determined for each individual deposit...There are two factors,source composition and magmatic differentiation,potentially controlling W-Sn mineralization.Which one is more important is widely debated and may need to be determined for each individual deposit.The Xitian granite batholith located in South China is a natural laboratory for investigating the above problem.It consists essentially of two separate components,formed in the Triassic at ca.226 Ma and Jurassic at ca.152 Ma,respectively.The Triassic and Jurassic rocks are both composed of porphyritic and fine-grained phases.The latter resulted from highlydifferentiated porphyritic ones but they have similar textural characteristics and mineral assemblages,indicating that they reached a similar degree of crystal fractionation.Although both fine-grained phases are highly differentiated with elevated rare metal contents,economic W–Sn mineralization is rare in the Triassic granitoids and this can be attributed to less fertile source materials than their Jurassic counterparts,with a slightly more enriched isotopic signature and whole-rockεNd(226 Ma)of−10.4 to−9.2(2σ=0.2)compared withεNd(152 Ma)of−9.2 to−8.2(2σ=0.2)for the Jurassic rocks.The initial W-Sn enrichment was derived from the metasedimentary rocks and strongly enhanced by reworking of the continental crust,culminating in the Jurassic.展开更多
The Late Triassic was a prolonged interval of elevated extinction rates and low origination rates that manifested themselves in a series of extinctions during Carnian, Norian and Rhaetian time. Most of these extinctio...The Late Triassic was a prolonged interval of elevated extinction rates and low origination rates that manifested themselves in a series of extinctions during Carnian, Norian and Rhaetian time. Most of these extinctions took place in the marine realm, particularly affecting radiolarians, conodonts, bivalves, ammonoids and reef-building organisms. On land, the case for a Late Triassic mass extinction is much more tenuous and has largely focused on tetrapod vertebrates（amphibians and reptiles）, though some workers advocate a sudden endTriassic（TJB） extinction of land plants. Nevertheless, an extensive literature does not identify a major extinction of land plants at the TJB, and a comprehensive review of palynological records concluded that TJB vegetation changes were non-uniform（different changes in different places）, not synchronous and not indicative of a mass extinction of land plants. Claims of a substantial perturbation of plant ecology and diversity at the TJB in East Greenland are indicative of a local change in the paleoflora largely driven by lithofacies changes resulting in changing taphonomic filters. Plant extinctions at the TJB were palaeogeographically localized events, not global in extent. With new and more detailed stratigraphic data, the perceived TJB tetrapod extinction is mostly an artifact of coarse temporal resolution, the compiled correlation effect. The amphibian, archosaur and synapsid extinctions of the Late Triassic are not concentrated at the TJB, but instead occur stepwise, beginning in the Norian and extending into the Hettangian. There was a disruption of the terrestrial ecosystem across the TJB, but it was more modest than generally claimed. The ecological severity of the end-Triassic nonmarine biotic events are relatively low on the global scale. Biotic turnover at the end of the Triassic was likely driven by the CAMP（Central Atlantic Magmatic Province） eruptions, which caused significant environmental perturbations（cooling, warming, acidification） through outga展开更多
A stratigraphic and depositional filling modal of Triassic—Jurassic North Tarim foreland basin system is erected, through synthetic analysis of geological setting, depositional provenance, sequence stratigraphy, and ...A stratigraphic and depositional filling modal of Triassic—Jurassic North Tarim foreland basin system is erected, through synthetic analysis of geological setting, depositional provenance, sequence stratigraphy, and quantitative tectonic stratigraphy. The result suggests that the major factors controlling formation and evolution of the system are oblique collision and convergence of different plates, and favorite hydrocarbon plays is predicted.The geological setting analysis emphasizes the historical succession of the foreland basin system formation and evolution. The tectonic setting analysis sketchy outlines formation of the system and tectonic setting of its successive evolution. The sedimentary geology analysis reveals the uplift and subsidence of the basin basement a seesaw style movement.展开更多
The end-Triassic mass extinction event is extensively known, however, the terrestrial response of this event is still poorly understood. Here we briefly report our preliminary results on the variation of floral divers...The end-Triassic mass extinction event is extensively known, however, the terrestrial response of this event is still poorly understood. Here we briefly report our preliminary results on the variation of floral diversity through the Triassic/Jurassic boundary deposits in the Tanha section of Hechuan region, Chongqing, southern China. It is recognized that the floral hiodiversity of the Hechuan region shows a distinct change through the Triassic and Jurassic transition; and the floral diversity loss reaches up to 92. 5% at species level. Meanwhile, in northeastern region of the Sichuan Basin, the floral diversity declines by about 50% across the T/J boundary at species level with a remarkable turnover of genera and species. The potential reasons and mechanisms that cause the floral diversity differentiation of the T/J boundary in the Sichuan Basin are briefly discussed in this note.展开更多
This paper presents organic geochemical evidence pointing to the occurrence of wildfire events at the Triassic-Jurassic boundary in Central Iran.The studied outcrop section(the Kamarmacheh Kuh section)is comprised of ...This paper presents organic geochemical evidence pointing to the occurrence of wildfire events at the Triassic-Jurassic boundary in Central Iran.The studied outcrop section(the Kamarmacheh Kuh section)is comprised of the Upper Triassic Nayband Formation which passes conformably into the Lower Jurassic Ab-e-Haji Formation with no sharp boundary.Organic petrographical studies reveal a higher concentration of semi-fusinite macerals and microscopic charcoal at the boundary between studied formations.This observation can be an evidence for widespread wildfire events at the Triassic-Jurassic boundary of the studied area.Following these fires,vast areas of land were exposed for erosion and large volumes of clastic sediments were provided due to increased run-off.This agrees well with previous sedimentological and stratigraphical studies suggesting a major change in the depositional conditions from marine to non-marine at the Triassic-Jurassic boundary of the Tabas Basin.These findings can have important implications about paleo-depositional settings of the studied formations and the nature of the associated organic matter.展开更多
基金supported by Special Basic Research Program of Ministry of Science and Technology of China (Grant No. 2006FY120300)National Committee of Stratigraphy of China. V. Vajda acknowledges the financial support provided by Swedish Research Council (VR, Grant No. 2007-4509)+1 种基金V. Vajda is a Swedish Royal Academy of Sciences Research Fellow founded through the Knut and Alice Wallenbergs Foundationa contribution to UNESCO-IUGS IGCP Project 506
文摘The Triassic-Jurassic （Tr-J） boundary marks a major extinction event, which （～200 Ma）resulted in global extinctions of fauna and flora both in the marine and terrestrial realms. There prevail great challenges in determining the exact location of the terrestrial Tr-J boundary, because of endemism of taxa and the scarcity of fossils in terrestrial settings leading to difficulties in linking marine and terrestrial sedimentary successions. Investigation based on palynology and bivalves has been carried out over a 1113 m thick section, which is subdivided into 132 beds, along the Haojiagou valley on the southern margin of the Junggar Basin of the northern Xinjiang, northwestern China. The terrestrial Lower Jurassic is conformably resting on the Upper Triassic strata. The Upper Triassic covers the Huangshanjie Formation overlaid by the Haojiagou Formation, while the Lower Jurassic comprises the Badaowan Formation followed by the Sangonghe Formation. Fifty six pollen and spore taxa and one algal taxon were identified from the sediments. Based on the key-species and abundance of spores and pollen, three zones were erected： the Late Triassic （Rhaetian） Aratrisporites-Alisporites Assemblage, the Early Jurassic （Hettangian） Perinopollenites-Pinuspollenites Assemblage, and the Sinemurian Perinopollenites-Cycadopites Assemblage. The Tr-J boundary is placed between bed 44and 45 coincident with the boundary between the Haojiagou and Badaowan formations. Beds with Ferganoconcha （？）, Unio-Ferganoconcha and Waagenoperna-Yananoconcha bivalve assemblages are recognized. The Ferganoconcha （？） bed is limited to the upper Haojiagou Formation,Unio- Ferganoconcha and Waagenoperna- Yananoconcha assemblages are present in the middle and upper members of the Badaowan Formation. The sedimentary succession is interpreted as terrestrial with two mainly lake deposit intervals within Haojiagou and Badaowan formations, yielding fresh water algae and bivalves. However, the presence of brackish water algae Tasmanites
文摘Triassic-Jurassic carbonates widely distributed in Eastern Indonesia are believed as oils source rock. The Mesozoic Tokala Formation exhibit source rock potential, as evidenced by high contents of organic matter. Recent exploration has been conducted in southeastern Sulawesi, targeting the Mesozoic intervals. Therefore, in this study, we attempted to determine source rock potential of Tokala Formation outcropped in southeastern Sulawesi area and its capability to generate hydrocarbon. Five distinct lithofacies were delineated, emphasizing lithological and mineralogical features: foraminifera wackestone (FW), lime mudstone (LM), massive bioturbated calcareous-argillaceous shale (MBCAS), weakly laminated argillaceous-calcareous shale (WLACS), and strongly laminated calcareous-argillaceous shale (SLCAS). Subsequent analyses showed that carbonate-rich samples (FW and LM facies, >50% CaO) had poor source rock potential. Conversely, shale facies with moderate carbonate content (WLACS, MBCAS, and SLCAS, 15% - 50% CaO) had good to excellent source rock characteristics, qualifying them as preferable source rock. In addition, levels of SiO2 and Al2O3 should not be neglected, as these constituents play important roles in clay mineral adsorption. Laminated shale facies with moderate CaO content tended to be more promising as source rock than bioturbated facies. The shale facies of Tokala Formation indicate prospective source rock horizon.
基金financially supported by the National Natural Science Foundation of China(Grant Nos.92162210,42172096 and 41773028).
文摘There are two factors,source composition and magmatic differentiation,potentially controlling W-Sn mineralization.Which one is more important is widely debated and may need to be determined for each individual deposit.The Xitian granite batholith located in South China is a natural laboratory for investigating the above problem.It consists essentially of two separate components,formed in the Triassic at ca.226 Ma and Jurassic at ca.152 Ma,respectively.The Triassic and Jurassic rocks are both composed of porphyritic and fine-grained phases.The latter resulted from highlydifferentiated porphyritic ones but they have similar textural characteristics and mineral assemblages,indicating that they reached a similar degree of crystal fractionation.Although both fine-grained phases are highly differentiated with elevated rare metal contents,economic W–Sn mineralization is rare in the Triassic granitoids and this can be attributed to less fertile source materials than their Jurassic counterparts,with a slightly more enriched isotopic signature and whole-rockεNd(226 Ma)of−10.4 to−9.2(2σ=0.2)compared withεNd(152 Ma)of−9.2 to−8.2(2σ=0.2)for the Jurassic rocks.The initial W-Sn enrichment was derived from the metasedimentary rocks and strongly enhanced by reworking of the continental crust,culminating in the Jurassic.
文摘The Late Triassic was a prolonged interval of elevated extinction rates and low origination rates that manifested themselves in a series of extinctions during Carnian, Norian and Rhaetian time. Most of these extinctions took place in the marine realm, particularly affecting radiolarians, conodonts, bivalves, ammonoids and reef-building organisms. On land, the case for a Late Triassic mass extinction is much more tenuous and has largely focused on tetrapod vertebrates（amphibians and reptiles）, though some workers advocate a sudden endTriassic（TJB） extinction of land plants. Nevertheless, an extensive literature does not identify a major extinction of land plants at the TJB, and a comprehensive review of palynological records concluded that TJB vegetation changes were non-uniform（different changes in different places）, not synchronous and not indicative of a mass extinction of land plants. Claims of a substantial perturbation of plant ecology and diversity at the TJB in East Greenland are indicative of a local change in the paleoflora largely driven by lithofacies changes resulting in changing taphonomic filters. Plant extinctions at the TJB were palaeogeographically localized events, not global in extent. With new and more detailed stratigraphic data, the perceived TJB tetrapod extinction is mostly an artifact of coarse temporal resolution, the compiled correlation effect. The amphibian, archosaur and synapsid extinctions of the Late Triassic are not concentrated at the TJB, but instead occur stepwise, beginning in the Norian and extending into the Hettangian. There was a disruption of the terrestrial ecosystem across the TJB, but it was more modest than generally claimed. The ecological severity of the end-Triassic nonmarine biotic events are relatively low on the global scale. Biotic turnover at the end of the Triassic was likely driven by the CAMP（Central Atlantic Magmatic Province） eruptions, which caused significant environmental perturbations（cooling, warming, acidification） through outga
文摘A stratigraphic and depositional filling modal of Triassic—Jurassic North Tarim foreland basin system is erected, through synthetic analysis of geological setting, depositional provenance, sequence stratigraphy, and quantitative tectonic stratigraphy. The result suggests that the major factors controlling formation and evolution of the system are oblique collision and convergence of different plates, and favorite hydrocarbon plays is predicted.The geological setting analysis emphasizes the historical succession of the foreland basin system formation and evolution. The tectonic setting analysis sketchy outlines formation of the system and tectonic setting of its successive evolution. The sedimentary geology analysis reveals the uplift and subsidence of the basin basement a seesaw style movement.
基金National Natural Sciences Foundation of China (No. 40472004)
文摘The end-Triassic mass extinction event is extensively known, however, the terrestrial response of this event is still poorly understood. Here we briefly report our preliminary results on the variation of floral diversity through the Triassic/Jurassic boundary deposits in the Tanha section of Hechuan region, Chongqing, southern China. It is recognized that the floral hiodiversity of the Hechuan region shows a distinct change through the Triassic and Jurassic transition; and the floral diversity loss reaches up to 92. 5% at species level. Meanwhile, in northeastern region of the Sichuan Basin, the floral diversity declines by about 50% across the T/J boundary at species level with a remarkable turnover of genera and species. The potential reasons and mechanisms that cause the floral diversity differentiation of the T/J boundary in the Sichuan Basin are briefly discussed in this note.
基金The exploration directorate of NIOC provided the data.The Petroleum Geology and Geochemistry Research Center(PGGRC)at Shahid Chamran University of Ahvaz provided laboratory services for conducting organic petrographic studies.
文摘This paper presents organic geochemical evidence pointing to the occurrence of wildfire events at the Triassic-Jurassic boundary in Central Iran.The studied outcrop section(the Kamarmacheh Kuh section)is comprised of the Upper Triassic Nayband Formation which passes conformably into the Lower Jurassic Ab-e-Haji Formation with no sharp boundary.Organic petrographical studies reveal a higher concentration of semi-fusinite macerals and microscopic charcoal at the boundary between studied formations.This observation can be an evidence for widespread wildfire events at the Triassic-Jurassic boundary of the studied area.Following these fires,vast areas of land were exposed for erosion and large volumes of clastic sediments were provided due to increased run-off.This agrees well with previous sedimentological and stratigraphical studies suggesting a major change in the depositional conditions from marine to non-marine at the Triassic-Jurassic boundary of the Tabas Basin.These findings can have important implications about paleo-depositional settings of the studied formations and the nature of the associated organic matter.
