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John S. Armstrong-Altrin J. Madhavaraju Alcides N. Sial Juan J. Kasper-Zubillaga R. Nagarajan K. Flores-Castro Janet Luna Rodríguez 《Journal of the Geological Society of India》2011,77(4):349-359
Petrography and stable isotopes (carbon and oxygen) geochemistry of limestones from the El Abra Formation, Actopan, were studied
to identify their digenetic environments. The major petrographic types identified are mudstone, wackestone, grainstone, and
boundstone. Most of the studied samples show positive δ13C values, except two samples (2 and 28), which are slightly negative values (−0.27‰ and −0.02‰). The organic remains identified
in foraminiferal wackestone type can be responsible for the negative δ13C values. The δ18O values range from −12.41‰ to −4.02‰ and indicate meteoric diagenesis. 相似文献
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Carlos Alberto Galaz-Samaniego M. Cristina Peñalba Francisco Abraham Paz-Moreno Iván Rosario Espinoza-Encinas Kinardo Flores-Castro Rogelio Monreal Carlos Lizárraga-Celaya 《第四纪科学杂志》2023,38(1):76-91
During the last glacial termination, the climate system experienced intense global variations whose causes and impacts are not fully defined, particularly for low latitudes. The northwestern Mexico Sky Islands present a climate-sensitive ideal setting to record palaeoecological and palaeoclimatic changes due to their physiographic complexity and location in the ecotone between temperate and tropical ecosystems. High-resolution pollen analysis and a detailed sedimentological study were conducted at the Ciénega Tonibabi tropical thorn scrub site. The 15 540–0 cal a bp nearly continuous record shows that the North Atlantic Ocean did have a cold and humid climatic influence during the glacial stages of the end of the Pleistocene, including a sharp pulse during the Younger Dryas. However, a shift to the Pacific Ocean influence occurred during the Holocene, which led to the development of the El Niño conditions prevailing today. Colder and warmer phases follow one another with higher or lower winter precipitation, including a sharp Bølling–Allerød and development and intensification of the North American monsoon. They are reflected in hydrological changes as well as in the advances, retreats and intermingling of coniferous forests and tropical thorn scrub. 相似文献
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