DETRITAL CARBONATES IN A SEQUENCE STRATIGRAPHIC FRAMEWORK: EXAMPLE FROM FURONGIAN SLOPE ENVIRONMENT IN THE HOT CREEK RANGE OF CENTRAL NEVADA

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 existing biostratigraphic constrains and examined key physical surfaces. Polished slabs and thin section petrographic analysis are used to identify micro- and macro-scale textures and diagenesis.

Eleven lithofacies were identified, which are clustered into six main facies associations, including (1) basin plain, (2) lower slope–basin plain, (3) lower slope, (4) middle–lower slope, (5) middle slope, and (6) upper–middle slope facies associations. Stratigraphic correlation reveals that packages of debris-flow and mud-flow deposits in the study area are laterally correlatable within a distance of ~1 kilometer. However, individual detrital carbonate units are laterally variable, and disappear within tens to hundreds of meters. These facies variations were demonstrably reworked density-flow deposits in subaqueous channels of submarine fans. The overall progradation of the carbonate platform recorded in the Hales Limestone is expressed by increases in redeposited carbonate breccia units and by the thickening- and coarsening-upward trend in background carbonate beds.

The internal facies architecture of the Hales Limestone shows repetitive allochthonous sequences in almost identical frequences, reflecting control of sea-level changes that may have triggered slope instability during Furongian time. Thick intervals of the gravity-flow deposits, composed of both platform- and slope-derived carbonate clasts, are interpreted to have been deposited during sea-level fall, whereas intervals of background and turbidite deposits were likely deposited during transgression or early sea-level highstand when the carbonate factory retrograded towards the interior of the carbonate platform. The sea-level controlled detrital carbonate sequences is consistent with global sea-level events constrained by bio- and chemostratigraphic data.