Deep water geomorphology of the mixed siliciclastic‐carbonate system, Gulf of Papua

Abstract

International audienceThe Gulf of Papua (GoP) has become a focal point for understanding the deposition and accumulation of siliciclastic and carbonate material along and across a low-latitude continental margin. Although studies have addressed submarine geomorphological features on the inner and middle shelves, as well as processes that may have led to their formation, the seafloor of adjacent slope regions remains poorly documented. This study presents and interprets results from approximately 13,000 line-km of multibeam bathymetry, 9500 line-km of 3.5 kHz seismic, and 122 sediment cores that were collected from the GoP shelf edge and slope, primarily on two cruises (PANASH and PECTEN). Bathymetric maps, in conjunction with the seismic profiles and cores, were used to make extensive observations, descriptions, and interpretations of seafloor geomorphology and begin to address several key issues regarding the delivery and accumulation of sediment. This study divided the GoP slope region into physiographic regions including intraslope basins: Ashmore Trough, southern Pandora Trough, northern Pandora Trough, Moresby Trough and intraslope plateaus/platforms: carbonate platforms and atolls and Eastern Plateau. Ashmore Trough contains a very linear northern margin capped by a drowned barrier reef system. This shelf edge is also defined by a broad promontory with channels extending from its apex, interpreted as a relict shelf-edge delta. Southern Pandora Trough is characterized by pervasive slope channels and slump scars extending down slope to a thick depocenter and an extensive mass-transport complex. In contrast, northern Pandora Trough has few visible slope channels. Seismic observations reveal a wedge of sediment extending down slope from northern Pandora Trough shelf edge and filling preexisting bathymetry. Large fold-and-thrust-belt ridges are also present on the seafloor in this region and may act to divert and/or catch sediment, depending on sediment transport direction. Moresby Trough contains a large axial submarine channel that extends almost the entire length of the intraslope basin. In addition, an extensive system of canyons lines the NE margin of Moresby Trough. Mass-transport deposits have been fed from the canyons and in one case deposited a large (similar to 2000 km(2)) mass-transport complex. Fold-and-thrust-belt ridges also extend into Moresby Trough. Here they trend perpendicular to slope and catch gravity flow deposits on their updip side. GoP carbonate platforms/atolls all display very pronounced scalloped-margin morphology, which may indicate pervasive mass-wasting processes on carbonate margins. Northwest Eastern Plateau is dominantly carbonate and displays the characteristic scalloped margin morphology; however, most of the plateau is characterized by parallel seismic reflectors. These seismic observations in conjunction with core data indicate that accumulation on Eastern Plateau is primarily mixed pelagic and hemipelagic sediment. Observations and interpretations of the bathymetry have rev...

Siliciclastic influx and burial of the Cenozoic carbonate system in the Gulf of Papua

“…4; B) Gravity map of the study area with superimposed structural features, black dots are industrial wells; C) Main structural features in the GoP. Tcherepanov et al, 2008a;Francis et al, 2008;Jorry et al, 2008;Carson et al, 2008;Febo et al, 2008;Muhammad et al, 2008).…”

“…8). This can be interpreted as a large submarine fan, similar to the fan present in the modern Moresby Trough (Tcherepanov et al, 2008a;Francis et al, 2008), composed of a number of smaller fans (Figs. 8 and 9).…”

Assessing palaeobathymetry and sedimentation rates using palynomaceral analysis: a study of modern sediments from the Gulf of Papua, offshore Papua New Guinea

“…Carbonate deposition occurs in the southwest portion of the gulf at the northernmost extension of the Great Barrier Reef (Tcherepanov et al 2008). A synthesis of the major depositional environments in the Gulf of Papua (Walsh et al 2004;Carson et al 2008;Crockett et al 2008;Francis et al 2008;Martin et al 2008;Howell et al 2014), as well as ages of exposed geologic formations in Papua New Guinea and northern Australia (Steinshouer et al 1999), is shown in Figure 2. The sampling locations for this project span many depositional settings, which are described below.…”

“…Synthesis of major Gulf of Papua depositional environments(Walsh et al 2004;Carson et al 2008;Crockett et al 2008;Francis et al 2008;Martin et al 2008;Howell et al 2014). AT D Ashmore Trough, AR D Ashmore Reef, EFR D Eastern Fields Reef, cf D clinoform.…”

Quartz arenites of the Cambro-Ordovician Kamouraska Formation, Quebec Appalachians, Canada: I. Deep-water depositional processes in a continental-slope environment

“…The orientation of the latter is in part structurally controlled by the stack of thrust sheets in the imbricated wedge that affects basin development. Moresby Trough in the Gulf of PapuaCoral Sea contains an axial submarine channel, Moresby Canyon that stretches for several 100 km, in part obliquely to the slope, but parallel to the Papuan Plateau in water depth exceeding 2500 m (Francis et al 2008). Ancient slope-parallel fan-valley -submarine channel systems have been documented from foreland basins (e.g., Winn and Dott 1979) and forearc basins (e.g., Ingersoll 1979;Morris and Busby-Spera 1988), but the slope canyons that feed these systems are generally oriented more or less perpendicular to strike of the slope.…”