%0 Journal Article
%T Multiscale Erosion Surfaces of the Organic-Rich Barnett Shale, Fort Worth Basin, USA
%A Mohamed O. Abouelresh
%J Journal of Geological Research
%D 2013
%I Hindawi Publishing Corporation
%R 10.1155/2013/759395
%X The high frequency and diversity of erosion surfaces throughout the Barnett Shale give a unique view into the short-duration stratigraphic intervals that were previously much more difficult to detect in such fine-grained rocks. The erosion surfaces in Barnett Shale exhibit variable relief (5.08¨C61£¿mm) which commonly consists of shelly laminae, shale rip-up clasts, reworked mud intraclasts, phosphatic pellets, and/or diagenetic minerals (dolomite and pyrite) mostly with clay-rich mudstone groundmass. Several factors control this lithological variation, including the energy conditions, rate of relative sea-level fluctuation, rate of sedimentation, sediment influx, and the lithofacies type of the underlying as well as the overlying beds. The erosional features and their associated surfaces make them serve at least in part as boundaries between different genetic types of deposits but with different scales according to their dependence on base level and/or sediment supply. Accordingly, the studied erosion surfaces of the Barnett Shale can be grouped into three different scales of sequence stratigraphic surfaces: sequence-scale surfaces, parasequence-scale surfaces, and within trend-scale surfaces. 1. Introduction The classic interpretation of organic-rich shale (¡İ0.5%£¿£¿total organic carbon) deposition emphasized continuous hemipelagic deposition in deep, quiet, low energy and stagnant basins, often with a stratified water column. However, Schieber [1] identified laterally continuous erosion surfaces in the Chattanooga Shale and he interpreted them as being the result of wave reworking and erosion of the sea floor. These surfaces are direct indications of major environmental events that may include nondeposition and/or erosion events. The multiple erosion events, resultant surfaces, and erosion features are common within the coarser clastic rocks and are pivotal in classifying depositional sequences based upon relative sea-level fluctuations. On the other hand, in fine-grained sediments, these events are subtle [2], although the identification is important in elucidating and development of the sequence stratigraphic framework for such rocks. Mud floored erosion in the geologic record is often associated with zones of intensely burrowed sediment; hiatus-concretions and prefossilized organic remains reveal complex cycles of exhumation and reburial associated with erosion (see [3¨C6]). Of particular significance are intervals of vertically mixed sediment, shells, and nodules associated with this erosion and/or reworking surfaces. Such sediment intervals yield a
%U http://www.hindawi.com/journals/jgr/2013/759395/