Tuesday, May 17, 2016

Highlights—Sediment on the Slippery Slope

Unlike fish, carbonate platforms commonly drown.  After they do, pre-existing margins can impart large-scale inflections in bathymetry below the subsequent shelf break that influence sediment dispersal on the slope.  Here, Hurd etal. explore the relation between a pre-existing, relict break in slope and subsequent accumulations in Permian strata of West Texas. The data reveal that increased slopes favor bypass and channels, which in turn favor accumulation of downdip, onlapping organic-rich shale and carbonate mud-dominated mass transport complexes. These results are interpreted to have general applicability to drowned carbonate platforms. And, no fish were harmed during this study either.     

Highlights—Mixing it Up in the Neuquén Basin

High-resolution sequence stratigraphy can be challenging, but mixed carbonate-siliciclastic systems offer unique challenges, but at times unique insights as well.  In this paper, Schwartz et al. document outcrop and subsurface data from a Cretaceous proximal to distal transect of the Neuquén Basin of western Argentina, exploring controls on high-resolution stratal patterns. The results suggest transgressive carbonate hemicycles, overlain by storm- and wave-influenced siliciclastic shoreface deposits during regressions. The data suggest that autogenic or eustatic controls did not control facies patterns; rather changes in sediment supply related to more arid–more humid shifts are interpreted to control the patterns in these strata.  These results emphasize the potentially important role of climate shifts on stratigraphy, and highlights its potential use for correlation.