78-4 Phantom Sequences and the Elusive Role of Sequence Stratigraphy in Karstification of the Ozarks Region, USA

Session: New Frontiers in Cave and Karst Science

Presenting Author:

Authors:

Abstract:

The Ozarks plateau has been etched deeply by karstification for millions to hundreds of millions of years. Karstification is a quasi-continuous process that has involved a carbonate target succession, exposure to freshwater infiltration with uplift, and pathways for percolation of fluids, provided by folds, fractures, and faults, and to a lesser extent stratification. While the process seemingly is straightforward, the timing for episodes of susceptibility for karstification have proven elusive. Integrating sequence stratigraphy into a conceptual model for this timing provides a frameshift in our understanding.

Absence of evidence does not constitute evidence of absence. That said, while the Ozarks have a well-known stratigraphic succession, there likely were units that had a profound influence on karstification, but erosion has removed these units. Specifically, the upper Devonian Chattanooga Shale likely blanketed much of the Ozarks, and the succeeding sub-Mississippian unconformity likely removed much of the Chattanooga. A few “Easter egg” examples are noted. Deposition of the overlying Mississippian sequence likely blanketed the Ozarks immediately following the late Devonian sequence. There is scattered but ample evidence of its former more continuous presence. The well-known sub-Pennsylvanian unconformity likely removed the remains and denuded the Ozarks during late stages of the Ozarks uplift. Pennsylvanian strata surround the Ozarks, resulting in development of the foreland interior plateaus (FIPs) of other investigators.

We refer to the missing packages of strata with introduction of a new term, phantom sequences. These are rock successions that were bounded by unconformities, but no longer are present having been removed by erosion, nevertheless, they had an influence on subsequent sedimentation and karstification. The sub-late Devonian and sub-Mississippian unconformities were effective agents of erosion. Chattanooga was a major confining layer that likely inhibited deeper karstification, and the Mississippian likely was influential in nucleating karst in lower Paleozoic successions. A sequence stratigraphic framework provides an effective tool for revealing the history of karstification in the Ozarks region.

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

doi: 10.1130/abs/2025AM-8915

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