The Interplay of Tectonic and Climatic Forcing Factors in the Deposition of a Hydrologically-Closed Basin Fill Sequence: Copper Canyon “Formation”, Death Valley National Park

Nyborg, Torrey¹, Paul Buchheim¹ (1) Loma Linda University, Loma Linda, CA

The evolution of the Copper Canyon “formation” (CCF) basin fill sequence represents an excellent example of a hydrologically-closed basin controlled by tectonic (uplift rate, duration and spatial distribution) and climatic (precipitation/ evaporation ratios-P/E) factors. The CCF is a transtensional fault-bounded Tertiary basin associated with right steps within a low angle normal fault system that extended Death Valley and uplifted the Black Mountains and portions of the Funeral Mountains. Three basalt flows occur within the CCF constraining the age between ~5 and 3Ma. The CCF is divided into the fanglomerate, fluvial-lacustrine, and basalt “units”. Initial CCF deposits represent active uplift recorded by numerous fanglomerates deposited as debris flows fining upward into mud-drapes. The fanglomerate provenance suggests a local source and rapid episodic deposition. Fanglomerates become less dominant up section and interfinger with trangressive-regressive playa-lake deposits. Cyclicity of lacustrine sequences is interpreted as humid-wet and arid-dry climate cycles consisting of: evaporite facies (reflecting a hypersaline lake); alternating beds of calcimicrite and dolomicrite (representing alternating fresh and saline conditions); and bioclastic carbonate and limestone beds containing tufa mounds (reflecting active spring deposition). The CCF deposits end abruptly ~3Ma reflecting basin in-filling (loss of accommodation space), probably due to a decline in tectonic activity in Death Valley. The CCF is an excellent example of the interplay between tectonic and climate driven deposition within a hydrologically-closed basin.