Sedimentation patterns during the Precambrian: A unique record?

Abstract

Although the similarities between depositional processes and products as well as the analogous controls on basinfilling and evolution appear to have enjoyed great uniformity throughout the sedimentary rock record, a noticeable distinction exists in the rates and intensities of a broad range of geological processes in the Precambrian epoch. This paper searches for distinctiveness in the Precambrian sedimentary record, both siliciclastic and carbonate, through an extensive, though not exhaustive, review of the relevant literature augmented by new observations. While differences in Precambrian deltaic, aeolian, glacial and possibly also lacustrine deposits and settings appear to have been small, their large-scale development was controlled largely by a combination of temporal and geodynamic influences, essentially of global compass. In this regard the onset of the supercontinent cycle and major perturbations in palaeo-atmospheric composition appear to have been significant. Marine environments provide a 2 poor platform for Precambrian -Phanerozoic comparisons of sedimentation patterns, as those from the former period are preserved almost exclusively in epeiric settings, an environment essentially lacking on modern Earth. For the shallow marine carbonates, biological mediation of chemical sediment deposition changed radically from dominance by microbial biota in the Precambrian to a combination of metazons, protozoans and algae for the skeletal carbonates of the Phanerozoic. Despite it being widely recognized that Precambrian channel systems were braided in all environments (deltaic, tidal, alluvial, fluvial) as a consequence of the lack of vegetation and poor development of soils, the fluvial setting has some enigmatic aspects. Amongst these is evidence for ponding of muddy detritus in apparently sandstone bed-load dominated braided systems, with effects on local palaeoslopes which have resulted in unusual palaeohydraulic parameters for Precambrian fluvial systems. This is perhaps a field of research which holds greater promise when investigating sedimentation patterns prior to the Phanerozoic.

Chapter 13 Geology of Mesoproterozoic Chhattisgarh Basin, central India: current status and future goals

“…Proterozoic sedimentary basins of India, traditionally referred to as the 'Purana' basins in Indian stratigraphy, represent classical examples of basins belonging to this category and have attracted sedimentologists and palaeobiologists seeking to understand Proterozoic near-surface processes including sediment -biota interaction. This is, indeed, tempting as these basin fills represent a phase in the Earth's history when the Sun was of lower luminosity, albedo was low, the land was without vegetation, the atmosphere was dominated by greenhouse gases and the climate was warm and humid, promoting high rate of mass wasting (Mueller & Corcoran 1998;Donaldson et al 2002;Bose et al 2012). Also, there were periodic rises in global sea-level, triggered by high rate of mid-ocean ridge activity and enhanced continental crustal growth, which inundated vast continental areas, forming large-scale epicontinental seas and embayments (Arndt 1999;Eriksson et al 2002).…”

Forced regressive wedge in the Mesoproterozoic Koldaha Shale, Vindhyan basin, Son valley, central India

“…Thus the two erosion surfaces, i.e., at the top and the base of the forced regressive wedge, are coeval and they eventually merge together towards the landward side. A rise in relative sea level occurred following the unconformity that caused aggradation of the fluvial braidplain deposits (cf., Bose et al, 2012;Sarkar et al, 2012). Marine incursion again prevailed with continuing transgression and development of a shallow marine shelf environment (Chorhat Sandstone) accumulated sediments in the depositional site with a transgressive lag at the base (Sarkar et al, 2006).…”

“…In comparison, study of a fluvial deposit in terms of geomorphic elements, designated as architectural elements, provides a more invariable picture, and a better understanding of the past fluvial systems and their evolution through time and space (for detailed discussion, see Miall, 1985). The term architectural element which can be defined as the macroform units that are larger than bedforms and smaller than channels (cf., Miall, 1985Miall, , 2006Yu et al, 2002;Miall and Jones, 2003;Fielding, 2006;Bose et al, 2012;Sarkar et al, 2012), is essential to understand the fluvial channel pattern and its evolution through time (Miall, 1985;Sarkar et al, 2012). Hence, a combination of facies analysis and architectural element analysis offers a far better and fairly comprehensive understanding of an ancient fluvial system and its evolution through time (Miall, 1988;Miall and Jones, 2003;Bose et al, 2008; Interpreted as river channels and/or individual branches of a braided river (Miall, 1985, Miall, 1996and Long, 2006.…”

Sedimentary cycles in a Mesoproterozoic aeolian erg-margin succession: Mangabeira Formation, Espinhaço Supergroup, Brazil

“…Aeolian successions of Precambrian age are typically highly fragmentary such that they lack the lateral continuity of exposure required to demonstrate the relationships between sequences and their bounding supersurfaces. Furthermore, subtle lithofacies relationships are typically not well preserved in these ancient -and commonly deformed and metamorphosedsuccessions (Eriksson and Simpson, 1998;Bose et al, 2012).…”