High-resolution correlations of strata within a sand-rich clinothem using grain fabric data, offshore New Jersey, USA

Abstract

Trajectories of successive clinoform rollovers are widely applied to predict patterns of spatio-temporal sand distribution. However, the detailed internal architecture of individual clinothems is rarely documented. Understanding the textural complexities of complete topset-foreset-bottomset clinothem sequences is a key factor in understanding how and when sediment is transferred basinward. This study used high-resolution, core-based analyses of 267 samples from three research boreholes from quasi-coeval topset, foreset, and bottomset deposits of a single Miocene intrashelf clinothem recovered during Integrated Ocean Drilling Program (IODP) Expedition 313, offshore New Jersey, USA. Topset deposits were subdivided into three sedimentary packages based on grain character and facies analysis, consisting of upper and lower river-dominated topset process-regime packages separated by a middle wave- and storm-dominated process-regime package. Temporal variability in topset process regime exerts a quantifiable effect on grain character across the complete depositional profile, which was used here to correlate topset deposits with time-equivalent sedimentary packages in foreset and bottomset positions. River-dominated sedimentary packages have higher sand-to-mud ratios; however, the grain character of river-dominated sedimentary packages is texturally less mature than that of wave- and storm-dominated deposits. Differences in grain character between packages dominated by different process regimes increase basinward. The novel use of quantitative grain-character data allows intraclinothem time lines to be established at a higher resolution than is possible using chronostratigraphic techniques. Additionally, stratigraphic changes in grain character were used to refine the placement of the basal sequence boundary. These results challenge the idea that clinoform trajectories and stacking patterns are sufficient to describe spatio-temporal sand-body evolution across successive clinothems.