Obtaining Timescales for Cyclostratigraphic Studies
Published:January 01, 2004
Walther Schwarzacher, 2004. "Obtaining Timescales for Cyclostratigraphic Studies", Cyclostratigraphy: Approaches and Case Histories, Bruno D’Argenio, Alfred G. Fischer, Isabella Premoli Silva, Helmut Weissert, Vittoria Ferreri
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Time in stratigraphy is derived from measuring the thickness of accumulated sediment. The quality of a time scale depends on the uniformity of the sedimentation. By subdividing a section using markers such as beds or cycles the uniformity of a section can be evaluated. By assuming that similar beds represent similar time intervals accumulation rates can be estimated. A cumulative plot of bed thickness against number tends towards a straight line if the sedimentation is uniform. Deviations from the straight line are due to both changes in accumulation rates and changes in the length of the time “unit”. Examples from Pliocene varves and Cenomanian limestones are used to demonstrate the use of beds and cycles as markers. The inaccuracies of timescales should be remembered when interpreting cyclic records.
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Cyclostratigraphy: Approaches and Case Histories
This volume is derived from an SEPM international workshop entitled Multidisciplinary Approach to Cyclostratigraphy, organized by the editors in May 2001 and held in Sorrento (Naples, Italy). In the Introduction we offer a brief history of how concepts of orbital cyclicity and its effects on the Earth evolved, an appraisal of the present state of research, and an overview of the papers in this volume. The main body of the volume consists of the contributed studies. These include a paper on conceptual and pragmatic approaches to stratification cycles by one of the pioneers of cyclostratigraphy, Walther Schwarzacher, who, in the 1940s, discovered the hierarchical expression of orbital cycles in rocks. The other contributions are specific studies of cyclic sequences, extending from the Quaternary back to the Triassic, covering the range from continental deposits to the deep sea, and employing a wide variety of techniques for extracting and processing the information.