Intergranular pressure dissolution in a Plio-Pleistocene grainstone buried no more than 30 meters: Shoofly oolite, Southwestern Idaho

Abstract

Intergranular pressure dissolution has occurred in the shallowly buried Plio-Pleistocene Shoofly oolite of the Glenns Ferry Formation in southwestem Idaho. The Shoofly lies at the margin of a lake basin and was buried to depths of 30 m or less beneath lake sediments and gravels derived from nearby volcanic rocks. Flattened, concavo-convex, and sutured contacts between ooids are common and make up over half of all intergranular contacts in the uncemented Shoofly grainstones, whereas such contants are much rarer in uncompacted oolitic grainstones. Sutured contacts make up about 7% of all intergranular contacts in the Shoofly oolite and provide clear evidence of intergranular pressure dissolution.

This pressure dissolution took place in 1/8 the time and at about 1/4 the burial depth of the youngest and most shallowly buried example of pressure dissolution previously reported. Pressure dissolution is commonly considered a burial diagenetic process, but sutured contacts in the Shoofly demonstrate that intergranular pressure dissolution in uncemented grainstones requires neither the depths, temperatures, nor time typically ascribed to burial diagenesis. Instead, fluid circulation, rather than burial, may have been important in driving Shoofly pressure dissolution.