Late Tertiary tectonic evolution of the central Walker Lane, west-central Nevada and California
Keller, Richard Paul
Bally, Albert W.
Doctor of Philosophy
An integrated model is derived for the sequential development of tectonic events in time among different evolving component structural domains comprising the central Walker Lane, west-central Nevada, based on constraints from data compiled from multiple disciplines. Evidence indicates four major tectonic episodes: (1) between 27 and 22 Ma; (2) 22 to 17, 15 Ma; (3) 17, 15 to 11, 10 Ma, and; (4) post-11, 10 Ma. These can be consistently tied to a temporal clockwise reorientation of the regional extension (from northerly to NW-SE) within the central Walker Lane, and also correspond in time with the occurrence of four distinctive litho-compositional assemblages that are confined within major chrono-stratigraphic boundaries defined by regional unconformities within the Tertiary volcano-sedimentary section representing the last 30 m.y. Incorporation of the many isolated Tertiary sections into a regional chrono-stratigraphic framework based on abundant isotopic age data, provides the universal reference frame in time with which to correlate tectonic events among the component structural domains. In this model, the tectonic evolution of the component structural domains results from decomposition of the regional crustal relative displacement field into normal and trace-parallel components along major faults, within the upper brittle crustal layer. Conservation of net relative displacement fields is provided by the mechanical lamination along one or more mid-crustal low-angle to near-horizontal dislocation surfaces (detachment zones) above which decomposition of the changing displacement field is resolved along structures within adjacent developing structural domains. These changing displacement field decompositions and related extension occur E of a major coherent crustal boundary structure, the Sierra Nevada block, and are considered in terms of its motion relative to stable North America, for the evolution of the Walker Lane as a boundary region between it and the expanding Basin and Range to the east.