Quaternary stratigraphy and geomorphology of Northern Death Valley: Implications for tectonic activity on the Northern Death Valley fault.

摘要

The Quaternary stratigraphy and geomorphology along the Northern Death Valley fault provides important evidence regarding the recent tectonic development of northern Death Valley. Interbedded alluvial fan and lacustrine deposits along the fault record the interaction between the Northern Death Valley fault and related faults and folds, which provide physical constraints on the extent, timing, and style of tectonic deformation during the past 3 m.y. Tephra beds of known age recognized in new localities provide chronological control for the rate of alluvial fan and lacustrine sedimentation, soil development, and fault activity.; A soil chronosequence on a sequence of gravelly alluvial fan deposits along the Northern Death Valley fault was also examined in order to delineate and better estimate the age of the late Quaternary alluvial deposits. Development of certain soil characteristics on the sequence of alluvial fans increased with age. The extent of vesicular A horizon development, presence of translocated clays, and accumulation of soluble salts were most useful in discriminating soils of different ages. Differences in soil characteristics were most pronounced between the late Pleistocene and Holocene soils and appear to be related to changes in climatic conditions and the presence of lakes and marshes in Death Valley. Stratigraphic relationships between the alluvium, the tephra beds, and the late Pleistocene lacustrine and marsh deposits place constraints on the rate of soil development.; The relationships established between the Quaternary stratigraphy and the geomorphology enable evaluation of the latest Quaternary tectonic activity along the Northern Death Valley fault. The hyperarid environment of Death Valley and associated geomorphic processes have contributed to the preservation of prominent tectonic features associated with recent fault activity. These preserved features indicate that the interaction between the Northern Death Valley fault and other secondary structures, particularly the Texas Spring syncline and the northeast-striking Tin Mountain and Towne Pass faults, have played an important role in the late Quaternary landscape development of northern Death Valley. Combined with the stratigraphic constraints, these tectonic landforms help establish a geologically constrained slip rate between 3 and 9 mm/yr for the Northern Death Valley fault during the late Quaternary.