Research about Little Lake, California

USGS2013

Chronology of tectonic, geomorphic, and volcanic interactions and the tempo of fault slip near Little Lake, California

New geochronologic and geomorphic constraints on the Little Lake fault in the Eastern California shear zone reveal steady, modest rates of dextral slip during and since the mid-to-late Pleistocene. We focus on a suite of offset fluvial landforms in the Pleistocene Owens River channel that formed in response to periodic interaction with nearby basalt flows, thereby recording displacement over multiple time intervals. Overlap between 40 Ar/ 39 Ar ages for the youngest intracanyon basalt flow and 10 Be surface exposure dating of downstream terrace surfaces suggests widespread channel incision during a prominent outburst flood through the Little Lake channel at ca. 64 ka. Older basalt flows flanking the upper and lower canyon margins indicate localization of the Owens River in its current position between 212 ± 14 and 197 ± 11 ka. Coupled with terrestrial light detection and ranging (lidar) and digital topographic measurements of dextral offset, the revised Little Lake chronology indicates average dextral slip rates of at least ∼0.6–0.7 mm/yr and <1.3 mm/yr over intervals ranging from ∼10 4 to 10 5 yr. Despite previous geodetic observations of relatively rapid interseismic strain along the Little Lake fault, we find no evidence for sustained temporal fluctuations in slip rates over multiple earthquake cycles. Instead, our results indicate that accelerated fault loading may be transient over much shorter periods (∼10 1 yr) and perhaps indicative of time-dependent seismic hazard associated with Eastern California shear zone faults.

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USGS1978

Pleistocene history of volcanism and the Owens River near Little Lake, California

During pluvial periods of the Pleistocene and Holocene, a large river flowed south from Owens Lake to China Lake between the Sierra Nevada and the Coso Range. The most recent channel, dry during historic time, is clearly marked by cliffs and falls. An older, now-abandoned part of the channel beneath Pleistocene lavas east of the present course is inferred from a meander-shaped ridge in Mesozoic basement rocks and a strong positive magnetic anomaly, presumably produced by a wedge of canyon-filling basalt. Three cycles of eruption and stream erosion have occurred along the present course. The first resulted when water impounded by damming of the now-abandoned eastern course found its way along the west margin of a basalt flow at the base of the Sierra Nevada escarpment, eventually carving a canyon at least 150 meters deep. Subsequently, two cycles, each consisting of an intracanyon basalt flow followed by major stream erosion, modified this canyon to its present configuration. A potassium-argon age of about 440000 years before present for the oldest of the three eroded lavas indicates that the river was not diverted from its easterly course until after that time. The age and character of lacustrine deposits in Searles Lake, a downstream part of the same drainage system, indicate that the greatest discharge of the river, and therefore, erosion of the two younger lavas since 440000 years B.P., probably occurred between 130000 and 10000 years B.P. An estimate of the rate of erosion during this period of time together with loosely constrained potassium-argon ages for the basalt of intermediate age suggests that the youngest lava is probably a few tens of thousands of years old and the intermediate lava somewhat less than 100000 years old. The youthfulness of the youngest basalt suggests that a fourth cycle of an intracanyon lava flow followed by stream erosion is a likely event for the near geologic future.

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