A Paleozoic Eustatic Model: An Indispensable Tool for Exploration in Paleozoic Petroleum Systems

Bilal U. Haq
National Science Foundation

There has been substantial progress in recent years in integrating the record of Mesozoic and Cenozoic sea-level histories, but relatively little attention has been paid to re-evaluating or synthesizing the global Paleozoic eustatic data. In spite of the fact that the Paleozoic encompasses a large fraction of Phanerozoic petroleum systems, much of it remains unexplored. As we look for previously ignored targets, the Paleozoic basins are bound to become the subject of renewed attention worldwide. A re-evaluation of sea-level history of this Era would therefore not only serve as an invaluable tool for exploration geology, but could also revive interest in the Paleozoic Earth science as a whole.

In recent years the accumulation of worldwide sequence-stratigraphic data has shed new light on the second- and third-order base-level variations from various regions. These can be clearly distinguished as those caused by tectonic processes and those that cannot be ascribed to local tectonics (and were therefore most likely eustatic). Stacked data from various worldwide basins when periods of tectonic quiescence prevailed, forms the basis of the Paleozoic record of global mean sea-level change. This presentation will briefly enumerate the problems associated with various types of data in terms of base-level change interpretations and the extent of errors in determining the magnitude of such fluctuations. The concept of designated Reference Districts for eustatic events (that most closely represent the “global mean”) and the resultant Paleozoic model of sea level are introduced, together with estimates of magnitude of change. The included on-lap curve tracks facies (reservoir rock) migration, and the incorporation of known condensed sections (source rock-rich intervals) as well as Megabreccias (in carbonate systems) enhances the usefulness of this eustatic model as an exploration tool.

Presentation GEO India Expo XXI, Noida, New Delhi, India 2008©AAPG Search and Discovery