About This Item
- Full TextFull Text(subscription required)
- Pay-Per-View PurchasePay-Per-View
Purchase Options Explain
Share This Item
The AAPG/Datapages Combined Publications Database
Journal of Sedimentary Research (SEPM)
Abstract
Quartz Geodes: Early Diagenetic Silicified Anhydrite Nodules Related to Dolomitization
Robert G. Maliva
ABSTRACT
Quartz geodes, interpreted to be silicified anhydrite nodules, are common in the Mississippian Ramp Creek Formation and Harrodsburg Limestone (Sanders Group) of southern Indiana. The abundance of a stenohaline fauna in the Sanders Group and the absence of sedimentologic features indicative of supratidal or hypersaline conditions, such as stromatolites, desiccation crocks, and "birdseye" vugs, suggest a subtidal, normal marine depositional environment. Geodes in the Ramp Creek and Harrodsburg Formations, as well as other geode-bearing strata, are almost invariably associated with dolomite. Seepage reflux of magnesium-rich brines produced during the deposition of the lower St. Louis Limestone is a likely mechanism for dolomitization of the Sanders Group. Replacement of calcite an aragonite by dolomite in hypersaline pore water may have increased the activity of calcium so that supersaturation with respect to anhydrite, or possibly gypsum, was reached and nodules formed in the still unlithified sediments.
Pay-Per-View Purchase Options
The article is available through a document delivery service. Explain these Purchase Options.
Watermarked PDF Document: $14 | |
Open PDF Document: $24 |