In Search of Biostratigraphic Resolution
The Deep Sea Drilling Project has contributed greatly to the improvement and expansion of marine biostratigraphy. However, if stratigraphic resolution is described in terms of the number of zonal boundaries per million years, it appears that the resolution of zonal stratigraphies varies with time and is related to the degree of variability of the ocean environment. Several problems which contribute to the present limitations of stratigraphic resolution have to be dealt with: a) taxonomic inadequacies and disagreements in taxonomic applications; b) incompleteness of the preserved record; c) incompleteness and disturbed nature of DSDP recovery; d) correct interpretation and correlation of stratigraphically useful signals.
One approach to improving stratigraphic resolution is the development of broad, regional holistic stratigraphies which combine lithostratigraphy, isotopic stratigraphy, paleomagnetic stratigraphy and species assemblage stratigraphy with the use of first and last appearances for species from several fossil groups. Detailed stratigraphic and time-slice studies of the Quaternary serve as guides to both the possibilities and pitfalls of expanding and improving the resolution of Cenozoic stratigraphy. Using composite stratigraphies, the average limit of Quaternary stratigraphic resolution is near 20,000 years as opposed to the present limit of 100,000 years in the Cenozoic.
An improved coring technique recently developed by DSDP, the hydraulic piston corer, should diminish manyof the problems with section recovery and disturbance. It offers an opportunity to develop a holistic approach to Cenozoic stratigraphy and ultimately accomplish the goals of high stratigraphic resolution and global chronostratigraphy.
Figures & Tables
At the present the Glomar Challenger has drilled over 500 holes over the world ocean, involving hundreds of scientists from dozens of countries. This volume is intended as a review of some of theimportant results from the most comprehensive, ambitious and successful earth-bound geologic project ever undertaken. The symposium upon which this volume originated was held April 4, 1979 at the SEPM/AAPG Annual Meeting in Houston. No comprehensive synthesis of all aspects of the DSDP has appeared, and the topic coverage in this volume is biased towards the sediments and fossils, and their significance for certain aspects of earth history – paleogeography, bathymetry, climatology, oceanography, ecology, environments – all in keeping with the audience of sedimentary geologists.