Sea level and climatic-induced facies variations in the Middle Cambrian House Range Embayment, western Laurentia
Abstract The Middle Cambrian House Range Embayment (HRE) represents a deep-water incursion into an extensive carbonate platform along the passive margin of western Laurentia. The distribution and source of HRE mixed siliciclastic-carbonate sediments are poorly understood because many key elements were missed during past field observations or coarse correlation. This study describes the HRE complex lithological variations, and improves current understanding concerning the global climatic and sea level fluctuations that drove these variations. Magnetic susceptibility (χ), gamma radiation (GR) and carbonate content (CaCO3%) are used to construct high-resolution correlation among three overlapping Middle Cambrian marine sedimentary sections: 1) the Drumian Global boundary Stratotype Section and Point (GSSP) in the Drum Mountains, western Utah, 2) the Marjum Pass section in the House Range, western Utah, and 3) the Packrat section Great Basin National Park in the Snake Range, eastern Nevada. Middle Cambrian HRE lithological variations followed broad facies patterns. Carbonate sediments dominated the HRE edges and decreased inward, while shale, dominated the HRE trough and decreased outward. The carbonate/detrital ratio varied along the area between the HRE Edge and trough due to; 1) sea level fluctuations, (2) the depositional setting at each section, and 3) the allocyclic, climatic variations that acted on the carbonate platform of western Laurentia. Sea level and climatic fluctuations drove temporal facies variations that are well correlated among the three sections, while the depositional setting for each section drove spatial facies variations that account for carbonate and detrital sediment sources and their trajectories into the HRE. The GSSP is a shallow trough section; Marjum Pass is a lower slope section of the northern HRE ramp; and the Packrat is a lower slope section situated along the southern HRE ramp. Sea level and climatic cycles during the Middle Cambrian Drumian Stage, induced long-term and short-term facies variations, respectively, that were superimposed on each other.