Neogene sediments in a structural and geomorphic high in the southwestern Honey Lake basin represent lacustrine deposition from 3.7 to 2.9 Ma, interrupted once by a significant lowstand. Tephras in the upper section are 3.26 Ma and 3.06 Ma. A thick debris-flow bed, truncated by an erosional surface and overlain concordantly by a thin interval of subaerial sediments, is evidence for lake-level fall at ca. 3.4 Ma. The dominant structure is a broad east-southeast–plunging anticline cut by several sets of faults. These include northwest-striking dextral and northeast-striking sinistral strike-slip faults and a conjugate set of west-northwest–striking thrust faults; all are consistent with north-south shortening. Mutually crosscutting relationships between faults, and tilt fanning of the dextral faults, indicate that tightening of the anticline was synchronous with faulting. A Quaternary strand of the dextral Honey Lake fault crops out near the northern end of the exposure, suggesting that the cause of the local shortening and uplift was a contractional stepover between two strands of the Honey Lake fault. The Neogene section limits this faulting to some time after 2.9 Ma. The Honey Lake basin lies at the intersection of the Walker Lane with the Sierran frontal fault system. Although the timing of tectonic disruption was roughly consistent with passage of the triple junction to the west and with uplift and exhumation of several nearby basins, the described deformation seems to be directly related to dextral faulting, dating the propagation of a strand of the Honey Lake fault through the southwestern Honey Lake basin.

Abstract Neogene sedimentary rocks, largely lacustrine and fluvial, were deposited in many areas of western Nevada and easternmost California, more or less continuously from ~12 Ma-3 Ma. These sediments were deposited on a surface of moderate primary relief developed on underlying Miocene volcanic rocks, and depositional facies are laterally variable, with sedimentation beginning and ending at different times in different areas. About 3 Ma, the basin system began to break up structurally, with strike-slip, oblique-slip and normal faulting, and local uplift. Modern topography inverts many original highs and lows. Stratigraphy and structure of Neogene strata document the progressive shut-down of the Neogene Cascade arc, the evolution of transtensional tectonics in the Walker Lane, and the encroachment of extensional faulting into the eastern Sierra Nevada .