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Depositional environments, diagenesis and stratigraphy of the Upper Pennsylvanian Lansing-Kansas City Group in Nebraska
Abstract
The Upper Pennsylvanian (Missourian) Lansing-Kansas City Group of eastern, southcentral and western Nebraska consists of cyclic sequences of carbonates and fine-grained siliciclastic sediments. Glacial-eustatic fluctuations of sea level along with variations of clastic influx over a broad epicontinental shelf were the dominant mechanisms for the formation of these cyclic sequences. Cycles of different scales including sixth order transgressive-regressive (T-R) units were recognized. Significant variations in the stratigraphic, depositional and diagenetic characteristics of these sediments were observed among these three regions of Nebraska. Deeper water lithofacies including black fissile shale are common in eastern Nebraska cycles but are absent from cycles in western Nebraska. Subaerial-exposure-features including caliche profiles and vadose and phreatic meteoric diagenetic features show an increase in intensity and abundance from eastern to western Nebraska. The absence of deeper water lithofacies and well-developed subaerial exposure surfaces indicate a topographically higher shelf position for western Nebraska. Extensive developments of caliche and the presence of evaporites and red beds indicate a semiarid climate for western Nebraska. The presence of deeper water lithofacies, lack of well-developed subaerial exposure surfaces and the presence of meteoric diagenetic features in the upper regressive part of the cycles indicate a lower shelf position for eastern Nebraska. Presence of coal and plant fragments representing swamp environments, the lack of caliche features in most of the cycles, and the absence of evaporites indicate a subhumid climate for eastern Nebraska during the Late Pennsylvanian.
Subject Area
Geology
Recommended Citation
Salahuddin, Qazi, "Depositional environments, diagenesis and stratigraphy of the Upper Pennsylvanian Lansing-Kansas City Group in Nebraska" (1993). ETD collection for University of Nebraska-Lincoln. AAI9333982.
https://digitalcommons.unl.edu/dissertations/AAI9333982