Abstract

Transgressive shoal-water calcarenites are characterized by pervasive overpacking of grains, neomorphism of originally aragonite grains and ferroan calcite and dolomite cement, which indicate movement from the marine-phreatic environment of deposition and diagenesis into the low-oxygen deeper-burial connate zone, with substantial compaction before any cementation. Offshore invertebrate calcarenites associated with offshore ("core") shales also are characterized by pervasive overpacking of grains and ferroan carbonate cements, which indicate a similar diagenetic history; their lack of discernible neomorphism relates to original absence of shallow-water aragonite grains. Regressive shoal-water calcarenites show a much greater variety of diagenetic features, including early marine cement rims and large-scale leaching of originally aragonite grains, often with subsequent collapse of micrite envelopes, grain fragments and overlying material in samples insufficiently stabilized by early cement rims. This was followed by pervasive cementation by block calcite before much further compaction, then by ferroan calcite and finally ferroan dolomite in remaining voids. This pattern indicates replacement of depositional marine-phreatic water by meteoric water.--Modified journal abstract.

First Page Preview

First page PDF preview
You do not currently have access to this article.