7048

• UCREFRP Catalog Number: 7048
• Author: Desert Fishes Council ‎(Edwin Pister, e.
• Title: Proceedings of the Desert Fishes Council
• USFW Year: 1991.
• USFW - Doc Type: Volumes XX and XXI
• Copyright Material: NO

TIME OF ISOLATION OF CYPRINODON DIABOLIS IN DEVILS HOLE:
GEOLOGIC EVIDENCE
by Isaac J. Winograd and Barney J. Szabo
ABSTRACT
The modern water table in Devils Hole is about 16 m below
land surface. It is commonly believed that Cvprinodon diabolis
became isolated in this cavern at the close of the Pleistocene
Epoch, 12,000 to 15,000 years ago, as a direct result of
increasing aridity accompanied by a cessation of spring discharge
from Devils Hole. Uranium-series dating of speleothems from
Brown's Room in Devils Hole indicates, however, that the water
table stood only about 9 m above the modern level between 44,000 ±
1,000 and 27,000 ± 1,000 years ago, and declined thereafter.
Thus, if we assume that C. diabolis became isolated due to a
decline of water table then this species has been isolated a
minimum of 44,000 years.
What might be the maximum time of isolation of C. diabolis?
The distribution of vein calcite, tufa, and other evidence
indicative of paleo-ground water discharge, indicates that during
the early-to-middle Pleistocene (1.6 million to 700,000 years ago)
the water table in the central Amargosa Desert, Nevada was tens of
meters higher than the modern water table, and that ground-water
discharge occurred as far as 14 km upstream from modern discharge
areas. The apparent water-table decline in this part of the Great
Basin since the early-to-middle Pleistocene probably reflects a
combination of: a) tectonic uplift of vein calcite and tufa,
unaccompanied by a change in water-table altitude; b) lowering of
ground water base-level in response to tectonism or erosion; and;
c) decline in water-table altitude in response to increasing
aridity caused by major uplift of the Sierra Nevada and Transverse
Ranges during the Pleistocene. Uranium-series dating of the
calcitic veins permits calculation of rates of apparent water-
tab13 decline in the past million years; rates of 0.02 to 0.09
m/10 yr are indicated.
A synthesis of hydrogeologic, neotectonic, and paleo-
climatologic information with the vein-calcite data permits the
inference that the water table in the central Amargosa Desert,
progressively lowered throughout the Pleistocene. If we assume
that C. diabolis was isolated due to this progressive lowering of
the water table at a proto-Devils Hole, then -- using the water-
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