Filter Or Conveyor? Establishing Relationships Between Clinoform Rollover Trajectory, Sedimentary Process Regime, and Grain Character Within Intrashelf Clinothems, Offshore New Jersey, U.S.A.

Abstract

Clinoform geometries and trajectories are widely used to predict the spatial and temporal evolution of sand distribution, but most analytical approaches underplay the significance of topset/shelf processregime in determining how and when sediment is conveyed downdip, or stored on the continental shelf. We present an integrated study of clinoform rollover trajectory and detailed grain-character analysis to assess the role of topset process-regime in determining sand distribution and sediment character across clinothems. This study targets the topset, foreset, and bottomset deposits of four successive Miocene intrashelf clinothem sequences, which represent deposition under either riverdominated or wave-dominated conditions. Seismic reflection data was combined with core analysis and grain-character data derived from 664 samples collected from 3 cored research boreholes. Within river-dominated clinothems, the transfer of coarse-grained sediment occurs under both rising and flatto-falling clinoform rollover trajectories, suggesting that process-regime is more important in determining sediment delivery than clinoform trajectory; river-dominated systems are effective conveyors of sediment into deeper water. Wave-dominated clinothems deposited exclusively under rising clinoform rollover trajectories largely retain sand within topset and foreset deposits; wavedominated systems are effective sediment filters. Notably, deposition under either river-or wavedominated topset/shelf process-regimes results in quantifiable differences in grain-character attributes along clinoform profiles. Sediments in river-dominated systems are coarser, less well-rounded and more poorly sorted, and show greater inter-and intra-sequence variability than those in wavedominated systems; prediction of sediment character is more challenging in river-dominated systems.This study highlights the need for caution when attempting to predict downdip sand distribution from clinoform trajectory alone, and provides a novel perspective into downdip grain-character profiles under end-member topset/shelf process-regime conditions. The results of this study can be used to better-constrain sediment grain-size and grain-shape distributions in process-based forward models, and have widespread applications in prediction of reservoir quality in both frontier and mature hydrocarbon basins. has been largely placed on the balance of accommodation and sediment supply. However, the dominant shelf process-regime also plays a key, but under-acknowledged, role in determining when coarse-grained sediment (i.e., fine sand and coarser) is stored on the continental shelf and when it is conveyed downdip Dixon et al 2012a;Covault and Fildani 2014;Gong et al., 2016;Peng et al., 2017).Recent studies have highlighted that shelf process-regime (resulting from the cumulative effects of fluvial, wave, tidal and oceanographic currents) is an important parameter to consider when predicting the presence or absence of coarse-grained sediment in downdip locations. For example, Dixon et al.(...

Ephemeral rollover points and clinothem evolution in the modern Po Delta based on repeated bathymetric surveys

“…Further advances in understanding the development of clinothems rely on the analysis of the rollover-point trajectory (Helland-Hansen & Martinsen, 1996), defined as the study of horizontal and vertical migration of geomorphological features and associated sedimentary environments, with emphasis on the migration paths of the shoreline and shelf-edge inflection points (Henriksen, Hampson, Helland-Hansen, Johannessen, & Steel, 2009). This approach can be used to reconstruct changes in accommodation and paleo environmental conditions recorded by stratigraphic successions and to predict the spatial distribution of lithological anisotropies associated with variations in shoreline position (Cosgrove, Hodgson, Poyatos-Moré, Mountney, & McCaffrey, 2018;Helland-Hansen & Martinsen, 1996;Poyatos-Moré et al, 2016;Steckler, Mountain, Miller, & Christie-Blick, 1999;Zhang, Steel, & Ambrose, 2016). Recognizing the nature of rollover points in the study of progradational systems has also led to the definition of compound clinothems, composed of a coastal clinothem (delta, beach) that is genetically linked to a subaqueous clinothem (Cattaneo et al, 2003;Pellegrini et al, 2015;Swenson, Paola, Pratson, Voller, & Murray, 2005).…”

Compound and hybrid clinothems of the last lowstand Mid‐Adriatic Deep: Processes, depositional environments, controls and implications for stratigraphic analysis of prograding systems

“…The partitioning of sediment between the shoreline area, the continental shelf and the continental slope is a function of relative sea‐level changes, the rate and calibre of river sediment supply and the strength of basin processes (Helland‐Hansen & Hampson, ; Patruno et al, ; Patruno & Helland‐Hansen, ; Pratson et al, ; Swenson, Paola, Pratson, Voller, & Brad Murray, ). The formation of compound clinoforms is evidence that oceanographic processes have relatively high energy (Cosgrove et al, ; Patruno & Helland‐Hansen, ; Pratson et al, ; Swenson et al, ). Compound clinoforms were the main components of the PRLW progradational architecture during the studied clinothems, suggesting that basinal processes of transport, erosion and deposition, dominated by waves and both long‐ and across‐shore currents, were very efficient during the last sea‐level lowstand.…”

“…Shelf process‐regime is a key factor in determining sediment distribution in time and in space along prograding continental margins, such as best illustrated by the development of compound clinoforms. Its fundamental role in determining the timing and locus of sandy sediment deposition is increasingly recognized (Cosgrove, Hodgson, Mountney, & McCaffrey, ; Cosgrove, Hodgson, Poyatos‐More, McCaffrey, & Mountney, ; Dixon, Steel, & Olariu, ; Hodgson et al, ; Jones, Hodgson, & Flint, ), but is, however, not adequately considered in trajectory analysis models.…”

Clinoform architecture and along‐strike facies variability through an exhumed erosional to accretionary basin margin transition

“…The Miocene clinothems of the New Jersey margin (Miller et al., ; Mountain, Proust, McInroy, & Cotterill, ; Proust et al., ) also display similar trajectory and gradient evolution, including flat progradational (like Unit G to WfC2), rising aggradational (like WfC 3‐5), and flat‐to‐falling progradational trajectory (like WfC 6‐8) (Figure a). However, in the New Jersey example, the dominant process regime had a stronger control than clinoform rollover trajectory on the character and quality of sand onto the foreset and bottomsets segments (Cosgrove et al., ). A similar architecture to the Laingsburg depocentre, with an upward‐shallowing clinoform geometry and the progressive reduction of sand‐rich deep‐water systems over time, is observed in cases like the Po River wedge in the Adriatic Sea (Pellegrini et al., ), the southern margin of the Neuquén Basin (Loss, Brinkworth, Vocaturo, Olariu, & Steel, ), and in the Pannonian Basin fill (Leever, Matenco, Garcia‐Castellanos, & Cloetingh, ; Matenco & Andriessen, ) (Figure ).…”

“…Two‐dimensional dip‐parallel sections have been widely used in clinoform trajectory analysis (Helland‐Hansen & Hampson, ; Henriksen, Hampson, Helland‐Hansen, Johannessen, & Steel, ; Steel & Olsen, ), to infer changes in relative sea‐level and to predict the timing of coarse‐grained sediment delivery to deep water. Clinoform trajectory analysis, however, tends to underplay the role of dominant process regime and along‐strike variability in basin margin physiography (Dixon et al., ; Jones, Hodgson, & Flint, ), which limits predictability in sediment character and partitioning between the shelf, slope and basin floor segments (Cosgrove, Hodgson, Poyatos‐Moré, Mountney, & McCaffrey, ; Prather et al., ). Modern and subsurface studies demonstrate that along‐strike variability in coastal process regime and shelf morphology commonly results in a laterally variable stratigraphic record (Ainsworth, Vakarelov, & Nanson, ; Jones et al., ; Laugier & Plink‐Björklund, ; Madof, Harris, & Connell, ; Olariu, Carvajal, Olariu, & Steel, ; Sanchez, Fulthorpe, & Steel, ), which can also be a key control on the nature of the SERZ (Pyles & Slatt, ; Olariu & Steel, ; Dixon et al., ; Gomis‐Cartesio et al., ).…”