Stratigraphic section

Abstract: The term Anthropocene, proposed and increasingly employed to denote the current interval of anthropogenic global environmental change, may be discussed on stratigraphic grounds. A case can be made for its consideration as a formal epoch in that, since the start of the Industrial Revolution, Earth has endured changes sufficient to leave a global stratigraphic signature distinct from that of the Holocene or of previous Pleistocene interglacial phases, encompassing novel biotic, sedimentary, and geochemical change. These changes, although likely only in their initial phases, are sufficiently distinct and robustly established for suggestions of a Holocene–Anthropocene boundary in the recent historical past to be geologically reasonable. The boundary may be defined either via Global Stratigraphic Section and Point (“golden spike”) locations or by adopting a numerical date. Formal adoption of this term in the near future will largely depend on its utility, particularly to earth scientists working on late Holocene successions. This datum, from the perspective of the far future, will most probably approximate a distinctive stratigraphic boundary.

Abstract: The characteristics of a depositional agent are reflected in the texture of the sediment. This relationship is particularly evident if the texture is represented by two parameters of the grain size distribution: C the one percentile and M the median diameter. CM patterns formed by sample points of a deposit are characteristic of the agent of deposition. Since the first discussion of CM patterns (Passega 1957) more than ten thousand analyses of sediments ranging in age from Paleozoic to Recent, sampled in basins of all types and sizes, including the Rhine graben, mobile basins of the Apennines and southeast Iran, and Cratonic Sahara basins, confirmed the conclusions of the earlier paper. They also disclosed new relationships between CM patterns and sedimentation, valid under greatly different conditions. The most notable progress of recent research was the construction of paleobathymetric maps and logs showing the depth of ancient seas and the variations of this depth in a stratigraphic section. Paleobathymetry is geologically important as it seems related to such characteristics of the sediments as facies, permeability and possibly also petroleum productivity. CM patterns are a means for analyzing transportation mechanisms and determining the mechanisms that form peculiar deposits, such as stratigraphic traps. Turbidites and certain tractive current deposits have several common characteristics. Their texture shows that they may have a common origin as wave suspensions. The many applications of grain size analyses indicate that they are a versatile means of investigation that discloses the orderly arrangement of a number of geological factors. This order is a fertile field for geological research.