Sedimentation, faulting, and erosion in the Carlin basin, northeastern Nevada, and implications for mineral exploration and ground water resources

New mapping in the Carlin basin in northeastern Nevada near Carlin shows that
the present sediment-filled topographic basin is a product of both Miocene sedimentation
and faulting and Pliocene and younger erosion. Early south-directed alluvialfan
sedimentation began at or shortly before 15.2 Ma, depositing debris flows,
conglomerates, and sand derived from the southern Tuscarora Mountains and Swales
Mountain areas and finer-grained alluvial sediments from smaller streams sourced in
the Adobe Range, northern Piñon Range, and Marys Mountain areas. These sediments
interfingered with lacustrine sediments that were deposited in a shallow lake
centered in the southern part of the basin. The lake extended beyond the southern
ends of the modern Adobe Range and Marys Mountain, indicating low relief in those
areas. Eruption of the 15.2 Ma Palisade Canyon rhyolite in the southwestern corner
of the basin may have dammed through-going streams and caused the synchronous
formation of the lake and, by raising the base level, retention of clastic sediments in
the basin. Hot-spring activity produced sinters that are interbedded with the lacustrine
sediments, indicating periods of subaerial exposure. The lake eventually drained
or dried up, and subsequent sedimentation took place for an unknown period of time
in alluvial fans sourced in the surrounding highlands.
Faulting took place largely after sedimentation and produced offset in both the
paleohighlands and the basin sediments. Offset along some basin-flanking faults modestly
downdropped the basin-filling sediments, but many of the faults with the greatest
offset are well within the basin itself and created intra-basin tilted fault blocks,
including the east-tilted Schroeder Mountain horst. Thus, faulting was not responsible
for most of the present basin configuration. Today, the complex combination of
highly variable sedimentary facies and abundant high-angle faults strongly compartmentalizes
the ground water in the basin, likely affecting ground water flow and
dewatering related to the Gold Quarry mine.