Taphonomy and depositional dynamics of Devonian shell-rich mudstones

Subsurface Correlation and Paleogeography of a Mixed Siliciclastic-Carbonate Unit Using Distinctive Faunal Horizons: Toward a New Methodology

“…Moreover, these sorts of phenomena are by no means unique to the Kope Formation or to the Ordovician. Very similar patterns of widely persistent limestone marker beds, epiboles, and obrution beds have been previously documented in similar mudrock successions of the Upper Ordovician Waynesville Formation (Frey, 1997;Schumacher and Shrake, 1997), the mid-Silurian Rochester shale (Taylor and Brett, 1996;Brett and Taylor, 1997), the Middle Devonian Hamilton Group Miller et al, 1988;Parsons et al, 1988), and the Cretaceous Greenhorn cyclothem of the Western Interior (Hattin, 1985;Kauffman, 1988, Kauffman et al, 1991. These comparable observations suggest that a very detailed form of layer-cake stratigraphy can and does exist in these offshore muddy facies; indeed, we suspect that this pattern typifies many muddy offshore successions, at least during greenhouse supercycles.…”

Microfacies development, sea-level change, and conodont stratigraphy of Famennian mid- to deep platform deposits of the Beringhauser Tunnel section (Rheinisches Schiefergebirge, Germany)

“…Bioturbation can also be responsible for shell fragmentation. Speyer and Brett (1991) and Parsons et al (1988) have proposed a different interpretation where the shell beds reflect complex background conditions and the sparsely fossiliferous layers represent muddy distal turbidites or storm-generated currents. The above scenarios-or a combination of all-are possible (e.g., Kidwell 1991) and point to a discontinuous sedimentation at least partly influenced by bottom currents that is typical to deep platform or ramp sediments deposited below storm wave base.…”

Middle to Upper Devonian Skeletal Concentrations From Carbonate-Dominated Settings of North America: Investigating the Effects of Bioclast Input and Burial Rates Across Multiple Temporal and Spatial Scales

“…Droser (1997, 1999) also described variation in the state of preservation and bioclastic fabric of skeletal concentrations across depositional environments that resulted from differences in storm and wave reworking. Studies of Paleozoic deposits in other regions have also documented facies-level variation in the characteristics of skeletal concentrations such that distinct taphofacies can be assigned based on the unique taphonomic attributes of bioclasts found in different depositional environments (Norris 1986;Speyer and Brett 1986;Parsons et al 1988;Speyer and Brett 1988;Cozar 2003;McLaughlin and Brett 2007).…”

“…Determining the role of these rates in the formation of skeletal concentrations can allow us to infer spatial and temporal changes in the production of carbonate producers and their subsequent breakdown (Kidwell and Brenchley 1996) Much of the Paleozoic fossil record comes from tropical, shallow marine, carbonate-dominated settings, whose preserved areal extent has declined relative to siliciclastic shelf deposits through the Phanerozoic (Walker et al 2002;Peters 2006;Miller and Foote 2009). Several studies have documented the characteristics of Paleozoic skeletal concentrations and their variation across time and space from siliciclastic or mixed siliciclastic-carbonate depositional settings, but relatively little is known about Paleozoic skeletal concentrations from carbonate-dominated settings (Kreisa 1981;Brett and Baird 1986;Parsons et al 1988; Speyer and Brett consistent with a previously documented Phanerozoic increase in shell bed thickness in siliciclastic settings attributed to the evolution of bioclast producers (Kidwell and Aigner 1985;Brenchley 1994, 1996). Droser (1997, 1999) also described variation in the state of preservation and bioclastic fabric of skeletal concentrations across depositional environments that resulted from differences in storm and wave reworking.…”