11 Sedimentology (Posters)

Sunday, 14 March 2010
8:00 AM - 12:05 PM
International ABCDF

FLUVIAL SEDIMENTOLOGY OF THE PENNSYLVANIAN JOGGINS, SPRINGHILL MINES, AND RAGGED REEF FORMATIONS: EXPLORING THE RELATIONSHIP BETWEEN PALEOGEOMORPHOLOGY, WALTHER'S LAW, TECTONISM, AND CLIMATE CHANGE

Paper number: 11-6
Program: Technical Sessions
Time: 8:00 AM – 12:05 PM

Authors

Abstract

The Pennsylvanian Joggins, Springhill Mines, and Ragged Reef Formations form a 2,500 m thick section that was deposited over ~ 2.5 million year period during the early Pennsylvanian (Langsettian-Duckmantian). These units were deposited in shallow marine embayments, peat-forming wetlands, clastic wetlands, dryland floodplains, and distal alluvial fans. The basal part of the section (Joggins Formation) consists of relatively well-developed cyclic alternations between shallow marine and terrestrial strata. Fixed and meandering channel bodies are common; scattered multistorey channel bodies may record phases of low accommodation, local geomorphic variability, or changes in sediment supply or hydrology. The overlying Springhill Mines Formation consists of poorly-developed, cyclic alternations between wetland and dryland facies. Wetland deposits decrease in thickness and abundance near the top of the formation, probably as a result of the progradation of clastic sediments from the Caledonia Highlands and resulting aggradation of the alluvial surface. Much like the underlying Joggins Formation, fixed and meandering channel bodies are common, although large meandering channel bodies become more abundant upsection. The presence of a single, broad, sheet-like channel within a particularly thick redbed interval may record a period of increased aridity. The overlying Ragged Reef Formation consists of alternations between thick, multistorey meandering channel bodies and dryland floodplain deposits. Alluvial fan deposits, conglomeratic channel bodies, and localized wetlands are present in the basin margin facies of the Ragged Reef Formation. These strata record continued progradation of a clastic wedge and aggradation of the alluvial surface.

The preservation of nearly complete stories within channel bodies and thick overbank successions was facilitated by rapid subsidence during deposition of these units. Although the overwhelming influence of tectonism and sediment supply mute the influence of climate, it does provide for a relatively complete snapshot of Pennsylvanian floodplains in a variety of paleogeomorphic settings and allows for an improved understanding of updip-downdip changes in depositional environments and fluvial systems.