Three-Dimensional Stylolites and Migratory Routes of Oil and Gas: ABSTRACT

Abstract Stylolite seams are mutually interpenetrating sutures, illustrated in the literature as cross sections resembling a stylus. Typical two-dimensional views are those of sutures shown on polished marble and limestone. Three-dimensional views of stylolites are provided by many limestones in the Virgin Member, Moenkopi Formation (Lower Triassic), of southern Nevada. They are well developed in outcrops at Blue Diamond Hill and southwest of Las Vegas. Essentially all seams display a columnar stylus fluted with striations resembling slickensides. In cross section, stylolites range in size from a few millimeters to as much as 15 cm. In plan view, they are polygonal, ranging from pentagonal to octagonal, to some with more sides. Many Virgin Limestone stylolites parallel the stratification, but others are oriented at various angles. Seams bifurcate, braid, regroup, and display diverse patterns of solution channels. Some stylolites parallel cross-stratification. As interpreted, stylolites are solution-compaction phenomena, and the amplitude of sutures or length of fluted columns is a measurement of the amount of compaction resulting from removal of carbonate sediment. If interlocking columns are 15 cm high, this represents the thickness of bedding unit removed during solution-compaction. Stylolites, being postdepositional, early compaction features are avenues along which oil and gas migrate. Hydrocarbons migrate early during depositional history in depocenters. Stylolites studied in carbonates of the Virgin Member show migratory routes of hydrocarbons, including some which carried oil to fill bioherms.