Doctor of Philosophy (PhD)
Geology and Geophysics
The Global boundary Stratotype Section and Point (GSSP) of the base of the Cambrian Drumian Stage was defined at 62 m above the base of the Wheeler formation, at the First Appearance Datum (FAD) of Ptychagnostus atavus (P. atavus), and at 10 meter below the DrumIan Carbon isotope Excursion (DICE) on the Stratotype Ridge in the Drum Mountains western Utah, (Babcock at al., 2004; 2007). Tracing the base of the the Drumian stage to other Middle Cambrian sequences in the House Range Embayment (HRE), a fault-controlled deep-water intrusion into an extensive carbonate platform along the passive margin of western Laurentia, was tentative and uncertain. The complex lithological variations, the absence of lithostratigraphic and other reliable biostratigraphic markers, and the widely-spaced sampling and coarse correlation among HRE sections, have contributed to such uncertainty. This study focuses on regional high-resolution correlation among the Drumian GSSP section, the Marjum Pass section, and the Packrat section. The objective of this research is to account for such complex facies variations, and constrain not only the base of the Drumian Stage but also the Lowest Occurrence Observed Point (LOOP)/FAD of P. atavus, and the DICE within the HRE. The HRE lithological variations follow broad facies patterns. Carbonates dominate at the edges of the HRE and decrease inward, while detrital materials dominate along the HRE trough and decrease outward. Three storm layers helped in tracing important surfaces including the base of the Drumian Stage from one section into the other. Unfortunately, the GSSP was defined based on reworked P. atavus specimens at the base of the first storm layer that has an erosional base and is composed of reworked sediments. Therefore, the FAD/LOOP of P. atavus is diachronous and its acme is synchronous within the three studied sections. It is concluded also that the DICE is a chronostratigraphic marker that constrain the base of the Drumian Stage in the embayment and the nearby southern platform sections unless suppressed by the incoming heavy-isotopic platform carbonates. The DICE maximum negative 13C excursion is synchronous while the onset and the end of the DICE are diachronous.
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Elfar, Emad I., "High-Resolution Correlation Using Geophysical and Geochemical Methods on Three Cambrian Drumian Marine Sedimentary Successions in The House Range Embayment, Western Laurentia" (2016). LSU Doctoral Dissertations. 620.