QUANTITATIVE-ANALYSIS OF A CYCLIC PERITIDAL CARBONATE SEQUENCE, THE MIDDLE AND UPPER DEVONIAN LOST-BURRO FORMATION, DEATH-VALLEY, CALIFORNIA - A POSSIBLE RECORD OF MILANKOVITCH CLIMATIC CYCLES

The middle and upper part of the type section of the Lost Burro Format ion is composed of 186 m of peritidal limestone, dolomite, and quartz arenite, Meter-scale analysis of lithology, sedimentary structures, fo ssil assemblages, and microfacies delineated 54 primary depositional c ycles of subtidal, intertidal, and supratidal facies and a larger-scal e trend of apparent sea-level change, Gamma analysis of Kominz and Bon d (1990) tests the assumptions that cycles have equal durations and th at each facies has a unique time-thickness relation, In the primary ga mma and spectral analyses, signals of Milankovitch climatic cycles are indicated on the spectrum of the spatial facies curve, but gamma tuni ng failed to improve the spectrum, In subsequent analysis, the 54 cycl es are subdivided into five subgroups of different mean durations base d on cycle period distributions, Gammas of three subgroups are strikin gly constant, indicating that they least violate the gamma assumptions , The grouping of cycles suggests that the primary cycles do not have the same duration, Gammas are used to convert the measured section int o two time series: one is gamma uncorrected (uniformly stretched), ano ther gamma corrected (nonuniformly stretched), After calibrating the g amma time unit as 18.4 ky, eight statistically significant spectral pe aks on the gamma-corrected spectrum match the predicted 377 Ma Milanko vitch eccentricity (2035, 413, 131, and 95 ky), obliquity (32 ky), and precession index (20, 17, and 9 ky (the constructive tone)) peaks, Th e match suggests that Milankovitch climatic forcing was an important c ontrol on the Lost Burro carbonate deposition, The effective accumulat ion rates of the subtidal (280 mm/ky), intertidal (160-190 mm/ky), and supratidal (60-70 mm/ky) facies are used to establish the cyclostrati graphy of the measured section.