This paper studies the Late Cretaceous dinosaur eggshell fossils from the Xixia Basin, Henan Province, by microscopy and carbon isotope method. Careful observation under microscope revealed that all dinosaur eggshell ...This paper studies the Late Cretaceous dinosaur eggshell fossils from the Xixia Basin, Henan Province, by microscopy and carbon isotope method. Careful observation under microscope revealed that all dinosaur eggshell fossils consist of primary calcite and secondary calcite. The content of the former is about 60.5% and the latter 39.5% according to image analysis. The δ\{\}\+\{13\}C values of secondary carbonate mineral filling within the dinosaur eggs in the strata range from -5.63‰ to -5.68‰, with an average value of -5.65‰. The δ\{\}\+\{13\}C values of sixteen dinosaur eggshell fossils are in the range from -5.88‰ to -7.79‰. Then we calculated the δ\{\}\+\{13\}C values of primary carbonate minerals, ranging from -6.03‰ to -9.19‰. Based on the δ\{\}\+\{13\}C values of the primary carbonate, the ancient food type and food proportion of dinosaurs were deduced. The dinosaur’s food proportions of C\-3 plant and C\-4 plant are 61% and 39%, respectively. Finally, it is inferred that the palaeoclimate in the Xixia Basin should be a warm—sub\|humid—sub\|arid climate in the subtropical zone of the Xixia Basin.展开更多
Weinan section consists of Holocene soil SO, last glacial loess L1, and last interglacial soil S1, furtherly L1 can be subdivided into three layers of loess (L1-1, L1-3, and L1-5), and two layerS of weakly developed s...Weinan section consists of Holocene soil SO, last glacial loess L1, and last interglacial soil S1, furtherly L1 can be subdivided into three layers of loess (L1-1, L1-3, and L1-5), and two layerS of weakly developed soil (L1-2 and L1-4). Based on studying the content variations of Carbonate, free Fe2O3, and the total organic content in Weinan section, the environmental evolution of this region has been discussed over the last glacial-interglacial cycle. Our results indicate that the chemical parameters can be ed as climatic proxy data, and the variations of these indexes reflect the cyclic nature of the Quaternary climatic change. In addition, the climatic records of Weinan section can also be correlated with that of the marine oxygen isotope records, so the environmental evolution of the Loess Plateau is also consistent with the global climatic changes. The unexpected finding is that the climatic curve of L1-5, which can be correlated with stage 4 of marine oxygen isotope records, consists of three troughs and two sandwiched peaks, and may suggest the existence of the second-order warmcold oscillations of this period.展开更多
The Kamenushka Formation, exposed in the northern part of South Primorye （Kamennshka-1 and Kamenushka-2 sections）, is one of the few localities in the world with richly fossiliferous Lower-Upper Olenekian sedimentar...The Kamenushka Formation, exposed in the northern part of South Primorye （Kamennshka-1 and Kamenushka-2 sections）, is one of the few localities in the world with richly fossiliferous Lower-Upper Olenekian sedimentary successions. Lower to Middle Triassic ammonoid-, brachiopod- and conodont-bearing silty-clayey deposits of the Kamenushka-1 and Kamenushka-2 sections have been isotope-geochemically investigated in detail. As a result, these sections, together with the previously investigated Abrek Section, exposed in the southern part of South Primorye, provide almost complete ^15Non- and ^13Corg- records for the Lower Triassic of this region. Nine N- isotope intervals and the five negative C-isotope excursions, reflecting, apparently, unstable climatic and hydrological conditions, have been distinguished in the Lower Triassic of South Primorye. On the basis of the new C-isotope data the Mesohedenstroemia bosphorensis Zone （upper part）, Shimanskyites shimanskyi and Neocolumbites insignis zones of South Primorye are correlated now with the Lower Smithian part of the Yinkeng Formation, the Upper Smithian part of the Helongshan Formation and the Middle Spathian part of the Nanlinghu Formation in South China, respectively, as has been observed in the Abrek, Kamenushka-2, West Pingdingshan and Majiashan sections.展开更多
In the Cordillera of western North America, the influence of the Pacific Interdecadal Oscillation only affects coastal areas west of the Coast Range and the lowlands of western and southern Alaska. The rest of the are...In the Cordillera of western North America, the influence of the Pacific Interdecadal Oscillation only affects coastal areas west of the Coast Range and the lowlands of western and southern Alaska. The rest of the area is subject to a climate controlled by the relative strengths of three distinct air masses, viz., the cold cA/cP air that is dominant in winter, the mP air bringing cool moist air over the mountains throughout the year, and the dry hot cT air from the deserts of the southwestern United States. The Arctic Front marks the boundary between the cA/cP air mass and the other two. Changes in the relative strengths of these air masses appear to explain the climatic changes documented throughout the region. Thus, in the last 30 years, the average position of the Arctic Front has moved north from about 53°N to 58°N, causing the warming in northern British Columbia and cooling south of Calgary, Alberta. This concept of changing positions of the air masses also appears to explain the mechanism behind the past climatic changes in this region. During the last Neoglacial event （c.1400-1900 A.D.）, it appears that the cA/cP air mass had strengthened enough to push the Arctic Front south of the 49th parallel. Incursions of mP air increased with localized areas of short-term heavy snowfalls resulting in small-scale advances of glaciers in these regions. This accounts for the variability in timing and extent of these glacial advances, while the resulting increased Chinook activity produced the development of a sand sea between Medicine Hat and Regina on the southern Prairies. The cT air mass was relatively weak, permitting these changes. During the maximum of the Altithermal/Hysithermal warm event （6,000 years B.P.）, the Arctic Front had retreated into the southern Yukon Territory as the cT air mass became stronger. The mP air could not move inland as easily, resulting in drier climates across the region. Prairie plants mi- grated into the southern Yukon Territory, and land snails from the eastern United Stat展开更多
文摘This paper studies the Late Cretaceous dinosaur eggshell fossils from the Xixia Basin, Henan Province, by microscopy and carbon isotope method. Careful observation under microscope revealed that all dinosaur eggshell fossils consist of primary calcite and secondary calcite. The content of the former is about 60.5% and the latter 39.5% according to image analysis. The δ\{\}\+\{13\}C values of secondary carbonate mineral filling within the dinosaur eggs in the strata range from -5.63‰ to -5.68‰, with an average value of -5.65‰. The δ\{\}\+\{13\}C values of sixteen dinosaur eggshell fossils are in the range from -5.88‰ to -7.79‰. Then we calculated the δ\{\}\+\{13\}C values of primary carbonate minerals, ranging from -6.03‰ to -9.19‰. Based on the δ\{\}\+\{13\}C values of the primary carbonate, the ancient food type and food proportion of dinosaurs were deduced. The dinosaur’s food proportions of C\-3 plant and C\-4 plant are 61% and 39%, respectively. Finally, it is inferred that the palaeoclimate in the Xixia Basin should be a warm—sub\|humid—sub\|arid climate in the subtropical zone of the Xixia Basin.
文摘Weinan section consists of Holocene soil SO, last glacial loess L1, and last interglacial soil S1, furtherly L1 can be subdivided into three layers of loess (L1-1, L1-3, and L1-5), and two layerS of weakly developed soil (L1-2 and L1-4). Based on studying the content variations of Carbonate, free Fe2O3, and the total organic content in Weinan section, the environmental evolution of this region has been discussed over the last glacial-interglacial cycle. Our results indicate that the chemical parameters can be ed as climatic proxy data, and the variations of these indexes reflect the cyclic nature of the Quaternary climatic change. In addition, the climatic records of Weinan section can also be correlated with that of the marine oxygen isotope records, so the environmental evolution of the Loess Plateau is also consistent with the global climatic changes. The unexpected finding is that the climatic curve of L1-5, which can be correlated with stage 4 of marine oxygen isotope records, consists of three troughs and two sandwiched peaks, and may suggest the existence of the second-order warmcold oscillations of this period.
文摘The Kamenushka Formation, exposed in the northern part of South Primorye （Kamennshka-1 and Kamenushka-2 sections）, is one of the few localities in the world with richly fossiliferous Lower-Upper Olenekian sedimentary successions. Lower to Middle Triassic ammonoid-, brachiopod- and conodont-bearing silty-clayey deposits of the Kamenushka-1 and Kamenushka-2 sections have been isotope-geochemically investigated in detail. As a result, these sections, together with the previously investigated Abrek Section, exposed in the southern part of South Primorye, provide almost complete ^15Non- and ^13Corg- records for the Lower Triassic of this region. Nine N- isotope intervals and the five negative C-isotope excursions, reflecting, apparently, unstable climatic and hydrological conditions, have been distinguished in the Lower Triassic of South Primorye. On the basis of the new C-isotope data the Mesohedenstroemia bosphorensis Zone （upper part）, Shimanskyites shimanskyi and Neocolumbites insignis zones of South Primorye are correlated now with the Lower Smithian part of the Yinkeng Formation, the Upper Smithian part of the Helongshan Formation and the Middle Spathian part of the Nanlinghu Formation in South China, respectively, as has been observed in the Abrek, Kamenushka-2, West Pingdingshan and Majiashan sections.
文摘In the Cordillera of western North America, the influence of the Pacific Interdecadal Oscillation only affects coastal areas west of the Coast Range and the lowlands of western and southern Alaska. The rest of the area is subject to a climate controlled by the relative strengths of three distinct air masses, viz., the cold cA/cP air that is dominant in winter, the mP air bringing cool moist air over the mountains throughout the year, and the dry hot cT air from the deserts of the southwestern United States. The Arctic Front marks the boundary between the cA/cP air mass and the other two. Changes in the relative strengths of these air masses appear to explain the climatic changes documented throughout the region. Thus, in the last 30 years, the average position of the Arctic Front has moved north from about 53°N to 58°N, causing the warming in northern British Columbia and cooling south of Calgary, Alberta. This concept of changing positions of the air masses also appears to explain the mechanism behind the past climatic changes in this region. During the last Neoglacial event （c.1400-1900 A.D.）, it appears that the cA/cP air mass had strengthened enough to push the Arctic Front south of the 49th parallel. Incursions of mP air increased with localized areas of short-term heavy snowfalls resulting in small-scale advances of glaciers in these regions. This accounts for the variability in timing and extent of these glacial advances, while the resulting increased Chinook activity produced the development of a sand sea between Medicine Hat and Regina on the southern Prairies. The cT air mass was relatively weak, permitting these changes. During the maximum of the Altithermal/Hysithermal warm event （6,000 years B.P.）, the Arctic Front had retreated into the southern Yukon Territory as the cT air mass became stronger. The mP air could not move inland as easily, resulting in drier climates across the region. Prairie plants mi- grated into the southern Yukon Territory, and land snails from the eastern United Stat
