PDF of contents and abstracts - SEPM

is considered to be related to a downdip increase in precipitation and decreasing depth to water table. In
the Himalayan system, this is considered to be due to a combination of decreasing depth to water table
and increased surface flooding due to direct, monsoon-driven precipitation on the DFS surface. An
increase in poorly drained soil development occurs near the toe of the DFS in Botswana, despite high
transmission losses across the system.
A key implication from these modern systems is that a change from well-drained to poorly drained soils is
controlled by hydrology. This change occurs along a single isochronous surface that may extend for
hundreds of kilometers and could be preserved in the rock record. Rock record examples that describe a
downdip change from well-drained to poorly drained soils have been documented previously and are
attributed to tectonic, climatic, autocyclic, and hydromorphic controls. Our studies from modern DFSs
would suggest that a hydromorphic control is likely to be the most important factor.
Criteria derived from modern DFSs for distinguishing between changes in soil type that record climate
change include the observation that paleosols developed in the proximal well-drained area are likely to be
associated with a sandy parent material and sand-dominated channel facies. In contrast, in the distal
DFSs, more poorly drained soils are likely to be developed on a silt- or clay-rich parent material
interbedded with a mixture of sandy and muddy meandering channel-fill deposits, crevasse splays, and
floodplain sands and muds. Paleosols that record climate change should show no discernible relationship
between parent material and soil type. While similar relationships between soil type and parent material
have been described previously, their distribution within the context of a DFS has not been widely
documented.