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.