Lithofacies and Transport of Clastic Sediments in Kartsic Aquifers

open_access
Open Access
Author:
Bosch, Rachel Frances
Graduate Program:
Geosciences
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
March 27, 2015
Committee Members:
William Blaine White, Thesis Advisor/Co-Advisor
Keywords:
karst
cave
sediment
clastic sediment transport
channel facies
slackwater facies
backswamp facies
thalweg
diamicton
Abstract:
Karst aquifers require transport of clastic sediments for the conduit system to remain open and thus to continue to be an eligible route for ongoing speleogenesis. Sediments are injected into the aquifer by sinking surface streams and through sinkholes, vertical shafts, open fractures, and other pathways from the land surface. Transport of clastic sediments tends to be episodic with sediment loads held in storage until moved by infrequent flood events. Although the overall mix of clastics depends on material available in the source area, distinctly different facies are universally recognizable depending on the flow dynamics within the conduit system. The facies are most clearly recognized when the source areas provide a wide variety of particle sizes from clays to boulders. In order of decreasing prevalence, one can distinguish (i) channel facies: usually well-sorted and often well-stratified silt through gravel carried as bedload at intermediate flow levels, (ii) slackwater facies: mostly clay and silt, carried as suspended load and deposited from floodwaters backfilled into the conduit system, (iii) thalweg facies: coarse gravel- to cobble-sized material, well-winnowed, forming armoring on underground streams that moves only during flood flow, (iv) backswamp facies: fine-grained sediments derived from the insoluble residue of the limestone, deposited under phreatic conditions with little lateral transport, and (v) diamicton facies: masses of unsorted, unstratified clays through boulders carried as a slurry during flood events.