02133nas a2200145   4500008004100000245014100041210006900182300001200251490000700263520157300270653002501843100001801868700001601886856008501902       1992                        eng d00aMixed Siliciclastic-carbonate Deposition in a Lower Cambrian Oxygen-stratified Basin, Chapel Island Formation, Southeastern Newfoundland0 aMixed Siliciclasticcarbonate Deposition in a Lower Cambrian Oxyg  a455-4730 v623 a<p>The upper portion of member 3 and member 4 of the uppermost Precambrian (Vendian)-Lower Cambrian Chapel Island Formation represents a large-scale shoaling-up deposit dominated by shelf siliciclastic mudstone. Medium-scale, higher-order shoaling-up cycles at the top of member 3 and in member 4 are capped by peritidal limestones that contain a wide variety of stromatolitic buildups and algal mud mounds. Sedimentation took place in an oxygen-stratified basin with accumulation of gray dysaerobic mudstone offshore and green and red mudstone in shallower, more oxygenated waters. Biofacies models for dysaerobic basins can be applied to this sequence and help in understanding the distribution of trace fossils, skeletal fossils (shells and pyritic steinkerns), and diagenetic features. These da a are important for the understanding of the stratigraphic distribution of shelly fossils within this lowest Cambrian unit.</p>

<p>A mixed carbonate-siliciclastic facies model is presented in which carbonate sediments formed in intertidal areas along the shoreline of a siliciclastic muddy shelf. The carbonate shoreline prograded during periods of increasing rate of relative sea-level fall or decreasing rate of relative sea-level rise. Restriction of carbonate sediments to the peritidal environment may have been due to a combination of higher rates of carbonate sediment production and accumulation in the peritidal zone, seaward dilution by siliciclastic mud, and a paleogeographic position near the latitudinal climatic extreme for carbonate production.</p>
10ageology paleontology1 aMyrow, P., M.1 aLanding, E.  uhttp://archives.datapages.com/data/sepm/journals/v59-62/data/062/062003/0455.htm