Evolution of drainage, sediment‐flux and fluvio‐deltaic sedimentary systems response in hanging wall depocentres in evolving non‐marine rift basins: Paleogene of Raoyang Sag, Bohai Bay Basin, China

Abstract

The dynamics of sediment feeding into rift basins and the geomorphologic nature of source areas are critical elements in understanding the evolution of rifted basins. This study integrates seismic, well and geochronologic data on the western dipslope of the Raoyang Sag, a rift associated sub-basin to the larger Bohai Bay Basin of China to define the history of drainage development for the basin and to assess the sedimentologic response to drainage evolution events. In the Paleogene-age Lixian Slope, as indicated by paleo-drainage configuration, progradational seismic geometries, compositional maturity and zircon-tourmaline-rutile maturity index trends, three drainages; the paleo-Daqing River, paleo-Tang River and paleo-Dasha River drainages were feeding three closely spaced hanging wall deltaic depositional systems; Delta A fed from the northwest, Delta B fed from the west and Delta C fed from the southwest, respectively. From the late Eocene to early Oligocene, a decrease in sedimentflux into the hanging wall is documented and petrographic analysis is used to link these changes to stream-capture in the upstream catchment of the Daqing River. This change is coupled with morphologic changes in the geometries of Deltas A and C, both of which show decreasing deltaic areas, changes in lobe geometry and changes in distributary channel sizes. In addition, the progradational direction of Delta C changes from perpendicular-to-the-rift axis to prograding oblique-to-the-rift axis. It is apparent that the progradation and retrogradational changes in rift margin deltas do not happen in isolation, but such changes can affect growth and progradation direction in adjacent deltas. This work shows that the decrease in sediment-flux, caused by a drainage capture, will result in a decrease in distributary channel size and delta size and may result in upstream deltas taking advantage of such decreasing confinement to prograde more obliquely to the rift axis. K E Y W O R D SBohai Bay Basin, morphology, rift basin, sediment-flux, transverse delta, zircon | 117 EAGE CHEN Et al. Highlights • Headward incision, stream capture or drainage diversion are drivers of sediment flux change to the Lixian slope, Raoyang Sag. • Temporal changes in channel morphometrics and energy can be coupled with petrographic observations to map a basin's sediment flux history. • Transverse deltas entering a rift interact, influencing each other's size and progradation directions. 118 | EAGE CHEN Et al. | 119 EAGE CHEN Et al. 120 | EAGE CHEN Et al. F I G U R E 3A generalized stratigraphic column that shows the lithostratigraphic series and the rift stages, along with seismic-well ties and sedimentary facies for the G28 well. The column of lithology and depositional facies in the left side are modified after Zhang and Yin (2005) and Chen et al. (2017), and the geological time is after Ryder et al. (2012). The study interval includes the Paleogene Es2 and Es1 which are expanded on the right side of the diagram, showing detailed lithology, facies, sub-facies and g...

Sediment dispersal and redistributive processes in axial and transverse deep‐time source‐to‐sink systems of marine rift basins: Dampier Sub‐basin, Northwest Shelf, Australia

“…These terminus lines were used to calculate the width, length and area of hanging wall fans. We considered these seismic amplitudes‐based measurements a minimum because of seismic resolution limitations, and the fact that the increasing finer‐grained nature of fan margins decreases their reflection contrast with the fine‐grained background sediments, limiting imaging of this lithologically transitional fan fringe (e.g., Chen et al., 2019; Wood, 2007). Due to the large areal extent of some submarine fans, and their often overlapping nature, it is difficult to map the full extent of the fans sourced from each drainage catchment, thus we grouped submarine fans into fan complexes that correspond to each drainage domain.…”

“…Rift basins have long been the topic of many S2S studies, in part driven by their narrow floodplains and shelves which results in the development of shorter, less buffered S2S systems (e.g., Sømme et al., 2009). Topics of such studies include the landscape evolution of individual footwall blocks (e.g., Densmore, Dawers, Gupta, Allen, & Gilpin, 2003; Densmore, Dawers, Gupta, & Guidon, 2005; Dibiase, Whipple, Heimsath, & Ouimet, 2010; Duffy, Brocklehurst, Gawthorpe, Leeder, & Finch, 2015), the influence of sediment budget on hanging wall depositional systems (e.g., Chen, Zhu, Wood, & Shi, 2019; Liu et al, 2019) and rifts as a whole (e.g., Pechlivanidou et al., 2019; Watkins et al., 2018). Although most of such S2S studies focus on the single catchment‐fan system developed in the footwall or hanging wall of rift basins, such studies seldom incorporate the influences of axial sediment routing on these transverse depositional systems (e.g., Chen et al., 2019; Connell, Kim, Paola, & Smith, 2012; Gawthorpe & Leeder, 2000; Leeder, 2011).…”

Regional Exhumation and Tectonic History of the Shanxi Rift and Taihangshan, North China

“…The unconformity bounding the top of the syn‐rift section is late Oligocene in age and has been attributed to a brief period of shortening and basin inversion between the main phase of rifting in the Bohai Basin and subsequent Neogene thermal subsidence (Allen et al., 1997). The synextensional basin fill is dominated by nonmarine alluvial, braided fluvial, and deltaic‐lacustrine clastic rocks, sourced by paleo‐river systems from the Taihangshan in the western margin of the basin (e.g., H. Chen et al., 2020). One such example is the paleo‐Hutuo River.…”

The Influence of Complex Palaeobathymetry on Development of Deep-Lacustrine Fan Systems

“…In terraced settings, sand often becomes trapped within lows along terraced margins, which preserves the relict conduits of sedimentary channel systems that feed the basinally-located lobe-dominated areas (Stow and Johansson, 2000;Carvajal and Steel (2009); Jobe et al (2017). The basin geometries and overall structural configurations within deep-lacustrine settings display multiple types and scales of confinement (Gawthorpe and Leeder, 2000;Zhang and Scholz, 2015;Chen et al, 2020). Furthermore, deep-lacustrine settings have a range of internal and external controls on sedimentation and accommodation space.…”