Reaching for a Cyclostratigraphy

Alfred G. Fischer

In 1895, G. K. Gilbert suggested that cyclic patterns in certain sediments reflect climatic response to the Earth's scheduled orbital variations, endowing sensitive facies with high correlatability and built-in chronometers. In the following 90 years, varying lines of supporting evidence came to light. Three recent developments are: (1) the revelation of the complete precession-eccentricity syndrome (the ~ 20 ka, ~ 100 ka, and ~ 400 ka cycles) by instrumental scanning of an Albian core, (2) the synoptic expression of the curves in mirror-plots, yielding a distinctive fingerprint, and (3) the recognition of this fingerprint in borehole logs of chalks and lacustrine sediments, opening a large body of existing data to new interpretation. A "cyclostratigraphy" may be within r ach, and the Cretaceous chalks, climatically sensitive and amenable to global biostratigraphy, are a particularly promising target. A first step to test this prospect would be the mapping of Cretaceous cycle patterns in paleogeography, in time, and in relation to facies. The challenge calls for international cooperation in biostratigraphers and lithostratigraphers in industry, government, and academia.

AAPG Search and Discovery Article #91030©1988 AAPG Annual Convention, Houston, Texas, 20-23 March 1988.