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.

In this paper, we present results of new investigations and structural analyses on the geometries, strain patterns, and kinematics of folds in the Alpi Apuane, northwest Tuscany, Italy. The analyzed structures were formed in mid-upper crustal conditions (temperature and pressure range between 450 and 300°C and 0.6 and 0.4 GPa) during under-thrusting and early exhumation of a slice of Adria-derived continental crust involved in the continental subduction process. In particular, we focused our attention on the relationships between folds, localized zones of deformation, and superimposed strain patterns. Kilometer-scale fold-nappes with strongly noncylindric 3D geometries developed during the early regional scale deformation event D1, whereas later large-scale noncylindric folds associated with a subhorizontal crenulation axial planar foliation refold previous structures during D2. Although the early deformation D1 can be related to an important component of noncoaxial deformation, the following D2 was instead associated with a vertical shortening and a bulk coaxial strain. The above described D1 and D2 structures developed during crustal underplating and syn-contraction exhumation record strain regime partitioned through time with an overall decrease in the noncoaxiality of deformation. This possibly reflects the movement of the unit across the deeper part of the Late Oligocene-Miocene Apenninic wedge, with a progressive increase of gravity-induced sagging in the rear part of the orogen.