نتایج جستجو برای: stratotype
تعداد نتایج: 195 فیلتر نتایج به سال:
Cryogenic weathering is a key driver of periglacial sediment composition and properties. Selective mineral-grain caused by freeze-thaw cycles in permafrost environments has the ability to dominate this process, leading silt-rich grain-size distributions. The cryogenic index (CWI) promising tool quantify freezing conditions. It considers low resistance quartz compared feldspars. Using approach, ...
The current Triassic chronostratigraphic scale is a hierarchy of three series divided into seven stages, divided further into 15 substages. Ammonoid and conodont biostratigraphies provide the primary basis for chronostratigraphic definition based on global stratotype sections and points (GSSP). I propose that Triassic chronostratigraphic definition should rely entirely on ammonoid biochronologi...
This study is based on zircon U-Pb ages of 12 volcanic ash layers and volcanogenic sandstones from two deep water sections with conformable and continuous formational Permian–Triassic boundaries (PTBs) in the Nanpanjiang Basin (South China). Our dates of single, thermally annealed and chemically abraded zircons bracket the PTB in Dongpan and Penglaitan and provide the basis for a first proof-of...
The Greenland ice core from NorthGRIP (NGRIP) contains a proxy climate record across the Pleistocene–Holocene boundary of unprecedented clarity and resolution. Analysis of an array of physical and chemical parameters within the ice enables the base of the Holocene, as reflected in the first signs of climatic warming at the end of the Younger Dryas/Greenland Stadial 1 cold phase, to be locatedwi...
Human impacts on Earth are now so great that they have led to the concept of a new geological epoch defined by this global human influence: the Anthropocene. While not universally accepted, the term is increasingly popular and widely used. However, even among proponents, there is considerable debate regarding when the epoch may have started, from coeval with the Holocene, through the Industrial...
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