Geochronology/Chemostratigraphy

"Global changes in marine geochemistry, on scales between one thousand and one million years permit the detailed correlation of sedimentary sequences in different ocean basins. The condition is that the geochemical signals are at least approximately dated by biostratigraphy (and magnetostratigraphy, where applicable). Through mutual reenforcement of chemostratigraphy and biostratigraphy unusually high stratigraphic resolution can be obtained. The integration of chemostratigraphy and biostratigraphy opens new avenues for analyzing the record-producing system within the framework of systemic stratigraphy. This type of stratigraphy focuses on global change in sea level, climate, and general geologic setting. It attempts to identify the underlying causes of global stratigraphic signals by considering 1) changes in input of matter and energy ; 2) changes in spatial distribution of sediments ; and 3) temporary changes in the partitioning of materials between active geochemical reservoirs."

"Correlation based on fossils (biostratigraphy) generally is superior to correlation based on lithologic properties (lithostratigraphy) when the goal is chronologic equivalence of rock sequences."

"There is one type of chemical record which has a minimum of regional interference, namely that of the deep sea. It is here, therefore, that global geochemical signals are most easily detected."

"Carbonate dissolution cycles in the Indo-Pacific, Swedish Deep-Sea Expedition. Cores 45 (7°40'N, 106°21'W) and 59 (3°05'N. 133°06'W); stratigraphic record and numbering system from Arrhenius (1952). Core 153 (2°18'S, 55°33'E): record from Olausson (1960); numbers added by us. Note the striking similarities in these records, but also the difficulty in correlating older cycles without additional information."

The "the approach to stratigraphy [...] now provide the framework for Pleistocene history. It is to these chemostratigraphic (i.e. lithostratigraphic) sequences that the traditional subdivisions (Günz, Mindel, Riss, Würm; Nebraskan, Kansan, Illinoian, Wisconsin) must be correlated to have more than regional meaning."

"Chemostratigraphic signaIs such as carbonate cycles and isotope cycles appear closely linked to sea level changes, at least in the Neogene."

Def. the "study and dating of sedimentary strata by the analysis of trace elements and isotopic ratios" is called chemostratigraphy.

See also

• Dye 3
• Ice cores
• Black ice
• Brittle ice
• Clear ice
• Firns
• Sea ice
• Marker horizons
• Tephrochronology

External links

{{Archaeology resources}}