Kansas Geological Survey
Open-file Report 2003-82
The bioclastic-packstone-to-grainstone limestone lithofacies is light to medium gray. Diagnostic features of the lithofacies include medium bedding (10-30 cm), and well-preserved sparse marine bioclastic fragments (Figure 2.09). Stylolites are distributed throughout the facies, while caliche and rhizoliths are observed approaching the top of the facies. The dominant texture is packstone, although a peloidal, non-fossiliferous grainstone may also present in the facies. Identified fossils include disarticulated bryozoans, brachiopods, crinoids and fusulinids. Trace fossils are sparse, however the facies appears to be heavily bioturbated. Thickness of the bioclastic-packstone-to-grainstone facies ranges from 5 to 30 feet thick (1.5 to 9 m). Contacts with the overlying and underlying facies are gradational.
Peloidal grains, the lack of abundant trace fossils, and disarticulation of body fossils are evidence that the bioclastic-packstone-to-grainstone facies was deposited in a high to moderate energy environment, probably above fair weather wave base. Fragmentation of bioclasts is due to reworking by wave or tidal processes in a relatively shallow-water environment and from extensive bioturbation. Bryozoans, brachiopods, and crinoids indicate a normal salinity marine environment (Heckel, 1972). Presence of caliche and rhizoliths in the upper portion of the facies suggests post depositional alteration by pedogenic processes. The combination of texture, peloidal grains, and fauna present suggests that the bioclastic-packstone-to-grainstone was deposited in a relatively normal marine, higher energy, and shallow environment. Historically, the bioclastic-packstone-to-grainstone facies would be interpreted as part of the “upper limestone” in the cyclothem model (Heckel, 1977).
|Figure 2.09 - Polished core section of bioclastic packstone to grainstone facies comprised of marine fossil fragments (A). Sample 1 from 623' and sample 2 from 625' in the Hinthorn CW#1 well, 14-T32S-R16E, Montgomery County, Kansas|
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Last updated December 2003