Deep‐water stratigraphic cyclicity and carbonate mud mound development in the Middle Cambrian Marjum Formation, House Range, Utah, USA

Abstract

In mid‐Middle Cambrian time, shallow‐water sedimentation along the Cordilleran passive margin was abruptly interrupted by the development of the deep‐water House Range embayment across Nevada and Utah. The Marjum Formation (330 m) in the central House Range represents deposition in the deepest part of the embayment and is composed of five deep‐water facies: limestone–argillaceous limestone rhythmites; shale; thin carbonate mud mounds; bioturbated limestone; and cross‐bedded limestone. These facies are cyclically arranged into 1·5 to 30 m thick parasequences that include rhythmite–mound, rhythmite–shale, rhythmite–bioturbated limestone and rhythmite–cross‐bedded limestone parasequences. Using biostratigraphically constrained sediment accumulation rates, the parasequences range in duration from ≈14 to 270 kyr. The mud mounds are thin (<2 m), closely spaced, laterally linked, symmetrical domes composed of massive, fenestral, peloidal to clotted microspar with sparse unoriented, poorly sorted skeletal material, calcitized bacterial(?) filaments/tubes and abundant fenestrae and stroma‐ tactoid structures. These petrographic and sedimentological features suggest that the microspar, peloids/clots and syndepositional micritic cement were precipitated in situ from the activity of benthic microbial communities. Concentrated growth of the microbial communities occurred during periods of decreased input of fine detrital carbonate transported offshore from the adjacent shallow‐water carbonate platform. In the neighbouring Wah Wah Range and throughout the southern Great Basin, coeval mid‐Middle Cambrian shallow‐water carbonates are composed of abundant metre‐scale, upward‐shallowing parasequences that record high‐frequency (104−105 years) eustatic sea‐level changes. Given this regional stratigraphic relationship, the Marjum Formation parasequences probably formed in response to high‐frequency sea‐level fluctuations that controlled the amount of detrital carbonate input into the deeper water embayment. During high‐frequency sea‐level rise and early highstand, detrital carbonate input into the embayment decreased as a result of carbonate factory retrogradation, resulting in the deposition of shale (base of rhythmite–shale parasequences) or thin nodular rhythmites, followed by in situ precipitated mud mounds (lower portion of rhythmite–mound parasequences). During the ensuing high‐frequency sea‐level fall/lowstand, detrital carbonate influx into the embayment increased on account of carbonate factory pro‐ gradation towards the embayment, resulting in deposition of rhythmites (upper part of rhythmite–mound parasequences), reworking of rhythmites by a lowered storm wave base (cross‐bedded limestone deposition) or bioturbation of rhythmites by a weakened/lowered O2‐minimum zone (bioturbated lime‐ stone deposition). This interpreted sea‐level control on offshore carbonate sedimentation patterns is unique to Palaeozoic and earliest Mesozoic deep‐water sediments. After the evolution of calcareous plankton in the Jurassic, the ...

Reefal and mud mound facies development in the Lower Devonian La Vid Group at the Colle outcrops (León province, Cantabrian Zone, NW Spain)

“…8D and E). This situation, which can clearly be deduced from the sequential arrangement of the succession, notably coincides with that inferred by Elrick and Snider (2002) for the deep-water Cambrian mud mounds of House Range (Utah, USA). Nevertheless, as said above, mud mounds do not occur in the same 5th-order sequences as the Synaptophyllum biostromes, suggesting that tuning between 4th-and 5th-order cyclicity played a role in determining mud mound development (Fig.…”

“…The overlying poorly exposed interval of the Valporquero Formation precludes drawing further conclusions about this topic. Nevertheless, this shaly interval could represent at least a part of the highstand system tract of the 4th-order sequence, since a higher clay input has been suggested to take place in the deeper basinal areas during rising sea-level periods (Pasquier and Strasser 1997;Elrick and Snider 2002).…”

High-resolution geochemical evidence for oxic bottom waters in three Cambrian Burgess Shale-type deposits

“…The development of the House Range embayment created two broad depositional settings: a relatively shallow carbonate shelf to the east and a deepwater trough to the west (Rees, 1986;Elrick and Snider, 2002). The Wheeler Shale is preserved both in the trough and on the platform.…”

Arthropod appendages from the Weeks Formation Konservat-Lagerstätte: new occurrences of anomalocaridids in the Cambrian of Utah, USA

“…This led to the local deposition of shales and argillaceous carbonates typical of the ODB, instead of the shallow-water carbonates of the MCB. In the central House Range, such deposits are represented by a continuous sequence encompassing the Wheeler and Marjum Formations and the lower part of the Weeks Formation (Elrick & Snider 2002, Miller et al 2012). In contrast, the Orr Formation, which conformably overlies the Weeks Formation, is composed of shallow-water carbonates typical of the MCB lithofacies (Miller et al 2012).…”