Provenance and diagenesis of the Lower Cetaceous to Middle Jurassic sandstones in the slope well Newburn H-23, Scotian Slope

Abstract

Newburn H-23 is one of seven deep wells drilled on the Scotian Slope. These wells are new and thus in the early stages of research. As such it is important to determine the history of the detrital and diagenetic minerals found in this well and to draw comparisons between them and their shallower age equivalents on the shelf. Sandy intervals from the Early Cretaceous have been analyzed dominantly using various methods to observe chemical and textural relationships between diagenetic and detrital minerals. The detrital mineralogy of these sandstone intervals is similar to other wells in the Sable Sub-basin, suggesting that they are sourced by the Sable River with minor input from Meguma Group metasediments and an increased supply of sodic volcanic clasts, probably from Scatarie Bank. The diagenetic history of this well, however, contains several mineralogical occurrences which are have not yet been identified elsewhere in the Scotian basin, including probable diagenetic zircon and fluorine rich ferroan-calcite. These minerals, along with diagenetic titania minerals suggest: a) low pH, a high organic content, and a high fluoride content in circulating basinal fluids during mesodiagenesis; and b) a supply of zirconium, increased salinity in basinal fluids, and higher than expected temperatures during mesodiagenesis. These findings are consistent with evidence from other wells for high salinities and temperatures late in the history of the Scotian Basin. Porosity values in these sandstones are similar to those of the Alma and Glenelg fields in the Scotian basin, contain gas shows, and are above the cut off permeability for gas reservoirs. These sandstones are therefore potentially economic reservoirs in the Scotian basin. However, they may not be of high quality since the sandy intervals in which potential sources are located in are thin with late diagenetic minerals filling some of the secondary porosity.