Detrital Carbonates in a Sequence Stratigraphic Framework: An example from the Furongian Slope Environment in the Hot Creek Range of Central Nevada

摘要

An integrated sedimentological study of detrital carbonates of the late Cambrian (Furongian) Hales Limestone in central Nevada was conducted in order to model facies distribution and controlling mechanisms of carbonate gravity-flow deposits. Seven closely-spaced sections and numerous traceable short sections were measured to investigate temporal and spatial changes of detrital carbonates within a high-resolution stratigraphic framework supported by biostratigraphic and carbon isotope chemostratigraphic constraints and by key physical surfaces. Polished slabs and thin section petrographic analysis were used to identify micro- and macro-scale textures and diagenesis.Ten lithofacies are identified from the Hales Limestone. Lateral tracing of these facies reveals considerable facies variations within a distance of ~1 kilometer. Such lateral facies variations suggest their deposition in submarine fan systems where localized distributary channels were well developed. Progradation-retrogradation of the carbonate platform is recorded by the abundance of carbonate debris-flow deposits and by thickening- and coarsening-upward trend in background carbonate beds.Thick intervals of debris-flow deposits contain both platform- and slope-derived carbonate clasts. They were most likely deposited during progradation and exposure of the shelf margin. Sequence and biostratigraphic correlation across the platform-to-basin transect indicates that the major debris-flow breccia units of the Hales Limestone matches well with the relative sea-level fall events recorded in shelf successions. This suggests that the detrital carbonate deposits in slope-basinal environments of the Furongian-early Ordovician platform were mainly controlled by relative sea-level changes. This interpretation is consistent with a global sea-level curve constrained by bio- and chemostratigraphic data.