Ancient Shelf Sandstones
This paper is designed to review the geological evidence for storm deposits, and will only peripherally discuss modern processes. The papers in this volume by Swift give excellent coverage of the day-by-day and year-by-year processes which operate on modern shelves. However, the rarer events have a low probability of being observed or measured, yet the deposits of such events are probably abundant in the geological record. Thus, the record adds to, as well as compliments the body of knowledge acquired by oceanographers and marine geologists. It will be suggested, for example, that turbidites occur in ancient shallow marine situations, commonly with a periodicity of about 1000–10,000 years. There are no well established examples of modern turbidity currents that have deposited preservable beds in a shelf or shallow marine situation. It must be emphasized, therefore, that the geologist will inevitably have a different perspective on shelf storm deposits from that of a geological oceanographer.
This part of the notes is chronologically subdivided as follows:
1899, Silurian storm deposits in New York State; discussion of G. K. Gilbert's deduction of 20 m storm waves in the Medina ocean.
1967, Hurricanes Carla and Cindy. The work of Hayes can be taken as the beginning of “modern” geological studies of storm deposits.
1971-1975, Miscellaneous storm deposits. In this section, several storm interpretations are introduced, emphasizing both the nature of the deposit and the emplacing mechanism.
1975, Hummocky cross stratification. This sedimentary structure, present in both siliciclastic and carbonate rocks, is
Figures & Tables
Shelf sandstone reservoirs are becoming a more and more common exploration target. What they are, how they may be characterized, and how they differ from shoreline and deep-water deposits in the subject of this publication. Shelf sands and sandstone reservoirs are among the more poorly understood types of sandstones. Continental, shoreline and deep water sandstones have all been studied in much more depth than have shelf sands and sandstones. However, during the last fifteen years significant progress has been made in understanding shelf sands and sandstones. Studies of modern sediments have allowed us to understand many of the depositional processes active on the shelf. This book is intended to be an up-to-date summary of shelf processes and products. The papers are intended for those new to shelf sands and sandstones as well as the shelf specialist.