Published:January 01, 1989
Facies relations determined from outcrop studies have been used in conjunction with subsurface data to better understand the geologic evolution, depositional facies, and diagenesis of the Capitan shelf margin. These studies have centered on a 2400 ft (731 m) portion of a 4800 ft (1463 m) continuous core from the Gulf PDB-04 research well that is located in Eddy County, New Mexico, at the northern end of the Delaware Basin.
The evolution of the Capitan shelf and margin was examined after (a) the establishment of time lines for shelf-to-basin correlations in the Late Guadalupian and (b) the confirmation of the stratigraphic units penetrated in the PDB-04 well. Subsurface and outcrop data revealed that the evolution of the 2.5 m.y. duration Capitan shelf margin occurred in two major growth phases: a 1.5 m.y. duration phase during Seven Rivers time when over 80% of the total progradation, over half of the total aggradation, deposition of thick carbonate debris units on the slope and basin margin, and influx of over 60% of the total siliciclastics of the Bell Canyon Formation occurred. A subsequent, 1.0 m.y. growth phase during Yates and Tansill time is dominated by aggradation, steepening of the margin, and corresponds with abundant clastic deposition on the shelf. Maximum progradation of up to 12 miles (19 km) occurred along the northern rim of the basin, where progradation rates in excess of 7500 µm/year are measured.
Detailed shelf-to-basin correlations have revealed that three major processes were responsible for the profound progradation and differentiation of Capitan growth into two major phases: (a) fluctuations of sea level, (b) maximum emplacement of allochthonous carbonate debris along the basin margin during Seven Rivers time, and (c) that abundant siliciclastics bypassed the actively prograding shelf margin and were an important foundation for the progradation. Because the Capitan was a deeply submerged reef during most of its growth, progradation occurred during both
Figures & Tables
Subsurface and Outcrop Examination of the Capitan Shelf Margin, Northern Delaware Basin
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.