Late Miocene fluvial sediment transport from the southern Appalachian Mountains to southern Florida: An example of an old mountain belt sediment production surge

• Published in: Sedimentology 2017-12, Vol.64 (7), p.1846-1870
• Main Authors: Missimer, Thomas M., Maliva, Robert G., Plink‐Björklund, Piret
• Format: Article
• Language: English
• Subjects: Carbonates; Climatic conditions; Erosion; Feldspars; Florida Platform geology; fluvial sedimentation; Fluvial sediments; Fluvial transport; Geomorphology; Hydraulic gradient; Miocene; Mountains; neogene tectonics; Platforms (geology); Pleistocene; Potassium; Quartzite; Rivers; Sea level; Sediment; Sediment transport; Sediments; southern Appalachian Mountains; Transport; Unloading; Uplift; Wet climates
• ISSN: 0037-0746; 1365-3091
• DOI: 10.1111/sed.12377

Past geomorphological models assume that erosion of sediments from old mountain belts occurred at a relatively constant rate, based on comparatively uniform isostatic adjustment caused by unloading. Late Miocene strata of the south‐eastern United States provide an example of pulsed tectonism resulting in a surge in siliciclastic sediment production and transport. Regional tectonism (uplift of the southern Appalachian Mountains) and climatic conditions during the Late Miocene resulted in the long‐distance (up to 1000 km) fluvial transport of coarse siliciclastic sediments onto a stable carbonate platform in southern Florida. The sediments are unusual in that they are significantly coarser than marine‐transported sands in southern Florida, with discoidal quartz and quartzite clasts up to 40 mm in diameter locally present, and have relatively high potassium feldspar contents (up to 16% in some sample fractions), whereas feldspar is rare in modern Florida beach sands. It is suggested that previously documented rejuvenation of the southern Appalachian Mountains during the Middle to Late Miocene time, coupled with the Messenian sea‐level low, generated the increased rate of sediment production and necessary hydraulic gradient to allow rapid transport of coarse sediments. Tectonic influence on the river pathway in Florida, as well as in the southern Appalachian Mountains, may have maintained the river on the narrow carbonate platform. The Florida Platform during the Late Miocene must also have had a sufficiently wet climate to cause episodic transport of the coarse sediments. Siliciclastic sediment transport on the Florida Platform during the Late Miocene greatly differed from Pleistocene to modern conditions, which are dominated by the transport of fine‐grained sands by longshore marine processes.