Sedimentology of a Late Mesoproterozoic Muddy Carbonate Ramp, Northern Baffin Island, Arctic Canada
Anne G. Sherman, Noel P. James, Guy M. Narbonne, 2000. "Sedimentology of a Late Mesoproterozoic Muddy Carbonate Ramp, Northern Baffin Island, Arctic Canada", Carbonate Sedimentation and Diagenesis in the Evolving Precambrian World, John P. Grotzinger, Noel P. James
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The ~1200 Ga Victor Bay Formation is a muddy, predominantly subtidaJ carbonate ramp succession that crops out in the Borden Basin of northern Baffin Island. The ~ 400-m-thick upper member is dominated by a variety of lime mudstone facies representing supratidal to deep subtidal environments. The lateral transition between shallow-water and deep-water environments is bes; exposed in cliff sections along the northeast margin of the Milne Inlet Trough, the major graben in the Borden Basin.
The upper Victor Bay Formation is interpreted as a ramp with well-defined inner-ramp facies (red shale facies, dololaminite facies, molar-tooth calcarenite fades), mid-ramp fades (molar-tooth mudstone fades), and outer-ramp fades (nodular limestone fades, ribbon and parted limestone facies, carbonaceous rhythmite fades). Episodic storms are considered to have been the main depositional influence on an otherwise low-energy ramp.
The principal controls on the style of deposition on the Victor Bay ramp are (1) production of lime mud, interpreted to have taken place in the water column, and (2) redistribution of the mud and mudstone-derived grains during storms. Grainstones in the shallow subtidal and nearshore environments are composed of subtidal molar-tooth crack-fill grains and intraclasts of peritidal dololaminite fades, with only minor amounts of ooids. Microbialites form large stromatolitic buildups that accreted during times of rapid increase in accommodation space and/or times of decreased lime mud production.
Comparison with other Proterozoic carbonate platforms indicates that the Victor Bay ramp represents an end member where production of clastic lime mud far exceeded seafloor cementation by inorganic precipitates or growth of microbialites. It is therefore more similar to mud- and grain-dominated Phanerozoic ramps than to cement- and stromatolite-dominated Paleoproterozoic carbonate systems. The close temporal association of the muddy Victor Bay ramp with the underlying Society Cliffs Formation, which has attributes more typical of early Paleoproterozoic carbonates, attests to the wide spectrum of carbonate depositional systems that had evolved by the late Mesoproterozoic.
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Carbonate Sedimentation and Diagenesis in the Evolving Precambrian World - Precambrian carbonates are usually regarded at the simple cousins of the sedimentary realm, composed of stromatolites and dolostones, texturally not challenging and commonly altered beyond recognition by the vagaries of time, diagenesis and metamorphism. However, these carbonates that formed deep in time are commonly exquisitely preserved and contain within them a record of the evolving young earth. SEPM Special Publication 67 explores these aspects. Resulting from a 1997 SEPM/CSPG symposium entitled? Precambrian Carbonates,? these 18 papers demonstrate the importance of understanding these rocks, since within them is contained a record of the early ocean, atmosphere, and biosphere.