Cyclostratigraphy concepts, definitions, and applications

Abstract

Abstract. Cyclostratigraphy is the subdiscipline of stratigraphy that deals with the identification, characterization, correlation, and interpretation of cyclic variations in the stratigraphic record and, in particular, with their application in geochronology by improving the accuracy and resolution of time-stratigraphic frameworks. As such it uses astronomical cycles of known periodicities to date and interpret the sedimentary record. The most important of these cycles are the Earth's orbital cycles of precession, obliquity, and eccentricity (Milankovitch cycles), which result from perturbations of the Earth's orbit and its rotational axis. They have periods ranging from 20 to 400 kyr, and even up to millions of years. These cycles translate (via orbital-induced changes in insolation) into climatic, oceanographic, sedimentary, and biological changes that are potentially recorded in the sedimentary archives through geologic time. Many case studies have demonstrated that detailed analysis of the sedimentary record (stacking patterns of beds, disconformities, facies changes, fluctuations in biological composition, and/or changes in geochemical composition) enables identification of these cycles with high confidence. Once the relationship between the sedimentary record and the orbital forcing is established, an unprecedented high time resolution becomes available, providing a precise and accurate framework for the timing of Earth system processes. For the younger part of the geologic past, astronomical time scales have been constructed by tuning cyclic palaeoclimatic records to orbital and insolation target curves; these time scales are directly tied to the Present. In addition, the astronomical tuning has been used to calibrate the 40 Ar/ 39 Ar dating method. In the older geologic past, "floating" astronomical time scales provide a high time resolution for stratigraphic intervals, even if their radiometric age is subject to the error margins of the dating techniques.Because the term "sedimentary cycle" is used in many different ways by the geologic community and does not always imply time significance, we propose using "astrocycle" once the cycle periodicity has been demonstrated by a thorough cyclostratigraphic analysis.

Towards the standardization of sequence stratigraphy

“…Both correlative conformities are downlapped by overlying regressive deposits, and may merge basinward with the main downlap surface (i.e., the maximum flooding surface) where the underlying highstand systems tract thins into a condensed section. Strasser et al (2006) illustrated how carbonate sedimentary cycles record repetitive changes (e.g., in stacking pattern, facies, biological and geochemical composition), often driven by periodic changes in accommodation. These are commonly attributed to changes in the Earth's orbital parameters that vary with pe-riods of 20 to 100 kyr.…”

Sequence Stratigraphy: Methodology and Nomenclature

“…However, Milankovitch-band cycles may give discrete modes in the frequency distribution of sequence durations, albeit with slight change over geologic time, if they are not overprinted by other sequence-forming mechanisms that may operate within similar temporal scales. If it can be demonstrated that the hierarchy in the stacking of sequences was induced by orbital cycles, then the potential for the creation of a high-resolution time scale is presented (e. g., D'Argenio et al 1997;Strasser et al 2006).…”

“…It uses astronomical cycles of known periodicities (Berger et al 1989) to interpret repetitive patterns in the sedimentary record (e. g., Strasser et al 2006) and to establish astro chrono logical time scales (e. g., Hinnov and Ogg 2007). Astronomical cycles cause insolation changes at the top of the atmosphere, which then translate into climate changes and eventually into eustatic sea-level changes, mainly through glacioeustasy and thermal expansion and retraction of the uppermost layer of ocean water.…”

Chronostratigraphy and geochronology: A proposed realignment

“…These are typically of the last half billion years (the Phanerozoic Eon), where there are good fossil assemblages (i.e., biostratigraphy) that remain key to their definition, recognition, and correlation. Wherever feasible, additional tools, such as magnetostratigraphy, chemostratigraphy, sequence stratigraphy, cyclostratigraphy, and radiometric dating are employed (e.g., Strasser et al, 2006;Weissert et al, 2008;Langereis et al, 2010;Catuneanu et al, 2011;Gradstein et al, 2012). Most of the Precambrian units of the GTS, which largely lack useful fossil assemblages, remain defined by Global Standard Stratigraphic…”