Browsing by Author "Totten, Rebecca L."

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    The Cretaceous-Paleogene Boundary in West Alabama: Geologic Mapping and Foraminiferal Biostratigraphy of the Coatopa – 7.5- Minute Quadrangle
    (University of Alabama Libraries, 2023) Wood, Tyler James; Totten, Rebecca L.
    There is critical need for high-resolution geological maps in the Gulf Coastal Plain of the Southeastern U.S., especially in Alabama, specifically to support efforts to map and model groundwater resources. The Coatopa 7.5-Minute Quadrangle in Sumter County, West Central Alabama, was selected for high-resolution mapping, due to several existing outcrop studies along the Tombigbee River. The Coatopa Quadrangle includes a unique exposure of the Cretaceous – Paleogene (K/Pg) boundary at Moscow Landing (previously the site of Rooster Bridge on US Hwy 80, now County Road 25, Sumter County). The geology exposed at Moscow Landing has been the source of much debate, owing to unique sedimentary features of the Late Cretaceous Prairie Bluff Chalk (Maastrichtian) and the overlying Paleogene Clayton Formation sandstone (Danian). Key objectives addressed with this mapping are to improve local and regional stratigraphy with the aid of foraminiferal biostratigraphy and LiDAR imagery, and to prospect for additional K/Pg outcrops. While beyond the scope of this thesis, details from the map produced as part of this study may help inform discussion of depositional history in the Eastern Gulf Coastal Plain Region during the Late Cretaceous and early Paleogene. The map of the Coatopa 7.5-Minute Quadrangle, presented here, updates the formational contacts from the Geological Survey of Alabama State Geologic Map (Szabo et al., 1988), most notably extending the upper boundary of the Prairie Bluff Chalk formation one mile to the southwest. The detailed map and cross sections should be useful for groundwater-surface water models and water budgets that are currently being produced for Alabama.
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    Holocene melting of the West Antarctic Ice Sheet driven by tropical Pacific warming
    (Nature Portfolio, 2022) Sproson, Adam D.; Yokoyama, Yusuke; Miyairi, Yosuke; Aze, Takahiro; Totten, Rebecca L.; University of Tokyo; Japan Agency for Marine-Earth Science & Technology (JAMSTEC); Australian National University; University of Alabama Tuscaloosa
    Ice loss from the Amundsen Sea sector of West Antarctica is rapidly accelerating. Here, the authors reveal that this region also underwent thinning and retreat from 9 to 6 thousand years ago, due to atmospheric connections with a warming tropical Pacific. The primary Antarctic contribution to modern sea-level rise is glacial discharge from the Amundsen Sea sector of the West Antarctic Ice Sheet. The main processes responsible for ice mass loss include: (1) ocean-driven melting of ice shelves by upwelling of warm water onto the continental shelf; and (2) atmospheric-driven surface melting of glaciers along the Antarctic coast. Understanding the relative influence of these processes on glacial stability is imperative to predicting sea-level rise. Employing a beryllium isotope-based reconstruction of ice-shelf history, we demonstrate that glaciers flowing into the Amundsen Sea Embayment underwent melting and retreat between 9 and 6 thousand years ago. Despite warm ocean water influence, this melting event was mainly forced by atmospheric circulation changes over continental West Antarctica, linked via a Rossby wave train to tropical Pacific Ocean warming. This millennial-scale glacial history may be used to validate contemporary ice-sheet models and improve sea-level projections.