107-4 Not Your Typical Tropics: Sedimentology and Stratigraphy of Mississippian (Osagean–Meramecian) Shallow-Water Carbonates in Kansas

Session: Sedimentary Geology Division/SEPM Student Research Poster Competition: Dynamics of Stratigraphy and Sedimentation

Presenting Author:

Authors:

Abstract:

Throughout the Mississippian, Kansas was covered by a shallow sea in the tropics at about 20° south. Shallow-marine carbonates composed predominantly of heterozoans and biosiliceous components, with minor siliciclastics, were deposited. Photozoans typically expected in tropical seas are largely absent, which previous work has attributed to northward upwelling of cold, nutrient-rich waters. This project utilized 22 cores from Ness and Hodgeman counties in Kansas to determine lithofacies, depositional environments, and stratigraphic correlations.

Preliminary results indicate facies are primarily composed of bioclastic packstones/grainstones and wackestones dominated by bryozoans, siliceous sponge spicules, and echinoderms with accessory brachiopods and bivalves. Siliciclastics (silt–clay) occur locally. Silica (chert) is abundant and occurs as nodular replacement of carbonate facies and pseudomorphic replacement of original evaporites. The dominant source of silica is thought to be from dissolved sponge spicules. Normal marine, inner- to mid-ramp environments are evidenced by grainy textures composed of diverse fauna, evidence of burrowing, and little to no evaporites. Restricted, intertidal to supratidal environments are evidenced by abundant silica-replaced evaporites, wackestones, wavy mud laminations (algal structures?), and local fenestral fabrics. Several horizons have red and green siliciclastic clays (some with pedogenic slickensides), Fe-oxides, rhizoliths(?), and autoclastic breccia indicating periods of subaerial exposure. The ramp that developed in Kansas shows a general N-S inner to outer ramp profile, with the ramp margin located near the Oklahoma border. Our study provides additional details to this general picture. The easternmost cores, which are closest to the Central Kansas Uplift (CKU), contain more siliciclastics and restricted facies, which are consistent with an inner-ramp setting and the adjacent CKU being a topographic high. Cores further west of the CKU are characterized by less siliciclastics and more abundant open marine facies consistent with inner- to mid-ramp environments. In addition, two subaerial exposure surfaces (sequence boundaries) can be traced throughout the area, which likely reflect relative sea-level fluctuations that influenced facies distribution and paleoenvironmental changes.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-7320

© Copyright 2025 The Geological Society of America (GSA), all rights reserved.