Miocene reversal of bottom water flow along the Pacific Margin of the Antarctic Peninsula: Stratigraphic evidence from a contourite sedimentary tail
Introduction
Bottom contour currents in modern ocean basins often generate large sedimentary bodies (contourite deposits or drifts), comparable in size to turbidite fans (Stow et al., 1986, Stow et al., 2002, Rebesco, 2005). Several drift classification systems have recently been proposed, based mainly on morphologic, sedimentologic and seismic characteristics (McCave and Tucholke, 1986, Faugères and Stow, 1993, Faugères et al., 1999, Rebesco and Stow, 2001, Stow et al., 2002, Rebesco, 2005). All drifts are related to the regional oceanographic conditions and the physiographic domains where they developed. Thus, it is possible to decode, from their morphologic, stratigraphic and sedimentary characteristics, the pathway and approximate flow velocity of the water mass that was responsible for their development. This is particularly relevant when buried contourite drifts and erosional discontinuities are found in the sedimentary record of a basin, because it is then possible to reconstruct it palaeoceanographic conditions.
We have recently completed a morphologic and stratigraphic interpretation of the region between 68° and 74°W and 65°–67°30′S (Fig. 1A), using multichannel seismic profiles and multibeam echo sounder data collected by several projects and research groups. In this area, on the central continental rise off Adelaide Island, we found a large Fossil Mounded Sedimentary Body (MB) (Hernández-Molina et al., 2004). In this paper we give a more complete description of the development of the MB, present new multibeam echo sounder data that reveals additional seamounts within the MB area, and discuss the palaeoceanographic implications of these observations.
Section snippets
Geological and oceanographic setting
There was continuous subduction at the Pacific margin of the Antarctic Peninsula at least from early Cretaceous time until the early Tertiary (Storey et al., 1996). During the Tertiary period, subduction stopped along most of the margin, as ridge-crest segments of the Antarctic–Phoenix spreading centre migrated into the trench (Barker, 1982, Larter and Barker, 1991a). Ridge-crest segments arrived first at the southwestern part of the margin during the Palaeocene or Eocene, then progressively
Methodology
The present study is based on the analysis of multichannel seismic reflection (MCS) profiles collected by the British Antarctic Survey (BAS) and the Istituto Nazionale di Oceanografía e di Geofisica Sperimentale (OGS). However, this work is part of a more extensive regional work (Hernández-Molina et al., in preparation) which also utilises seismic reflection data from the Brazilian Antarctic Program, Rice University of Texas, and Spain (Project ANT99-0817), as well as multibeam echo sounding
The fossil mounded sedimentary body (MB): morphosedimentary features and seismic stratigraphic analysis
We have identified a MB on the central continental rise offshore from Adelaide Island between 65°S and 65°30′S and 71°45′W–72°45′W (Fig. 1B). The MB (Seismic Units 8 to 6 in Fig. 3, Fig. 4) is buried 300 to 150 m below the sea floor, which is at a water depth of 3600 m, and at which it has no morphological expression. It has a mounded, elongated shape, overlapping and continuing to the NE of an extensive cluster of seamounts. Buried seamounts are identified on line IT110 and line BAS20,
Chronostratigraphic constraints
The age of the seismic units can be assessed by correlation with DSDP Site 325 (Hollister et al., 1976), through which lines BAS19 and IT110 both pass approximately 60 km NW of the MB (Fig. 1, Fig. 4A). Reflections on line 48 can also be traced to Site 325, via intersecting line IT89049 (Fig. 1B). In addition, a regional stratigraphic study of the continental margin off Adelaide Island has been carried out (Hernández-Molina et al., in preparation), taking into consideration chronostratigraphic
Effect of seamounts on an impinging flow
Knowledge of how seamounts and seamount chains interact with ocean circulation is important from a geological point of view. Akin to island mass effects (Heywood et al., 1990), seamounts generate seamount effects, with important effects on oceanographic processes (Roden, 1987), marine biota (Rogers, 1994), sedimentation and erosion rates (Davies and Laughton, 1972, Roberts et al., 1974), and hence palaeoceanographic interpretations (Roden, 1987). The streamline distortion around obstacles is
Conclusions
The analysis and interpretation of three parallel MCS profiles and multibeam echo sounding data collected over the continental rise on the Pacific margin of the Antarctic Peninsula can be summarised with the following conclusions:
- a)
A Fossil Mounded Sedimentary Body (MB) has been identified in the Early Miocene sedimentary record over the oceanic crust on the central continental rise offshore from Adelaide Island.
- b)
The MB has an elongated NE trend, overlapping and continuing to the NE of an
Acknowledgements
This research has been partially supported by Spain's Inter-ministerial Science and Technology Committee (CYCIT), through Project ANT99-0817 We thank the officers, crew, technical support staff and scientists who sailed on RRS Discovery cruise 172 (1988) and R/V OGS-Explora cruises in 1989 and 1992. On the OGS-Explora cruises, seismic data were collected as part of Italy's PNRA (Programma Nazionale di Ricerche in Antartide). PNRA supported Michele Rebesco's contributions through the SEDANO
References (88)
- et al.
The deep waters from the Southern Ocean at the entry to the Argentine Basin
Deep-Sea Res. II
(1999) - et al.
The opening of Drake Passage
Mar. Geol.
(1977) Late Miocene through early Pliocene deep water circulation and climate change viewed from the sub-Antarctic South Atlantic
Palaeogeogr. Palaeoclimatol. Palaeoecol.
(2002)- et al.
Bottom current controlled sedimentation: a synthesis of the contourite problem
Sediment. Geol.
(1993) - et al.
Seismic features diagnostic of contourite drifts
Marine Geology
(1999) - et al.
Notes on Southern Ocean hydrography, sea-ice and bottom water formation
Palaeogeogr. Palaeoclimatol. Palaeoecol.
(1988) - et al.
Distribution of clay minerals and proxies for productivity in surface sediments of the Bellingshausen and Amundsen seas (West Antarctica)—relation to modern environmental conditions
Mar. Geol.
(2003) - et al.
Contour currents in the Weddell Sea
Dee-Sea Res.
(1969) - et al.
The depositional pattern and distribution of glacial-interglacial sequences on the Antarctic Peninsula Pacific margin
Mar. Geol.
(1993) - et al.
Glaciomarine sedimentary processes of a high-latitude. Deep-sea sediment drift (Antarctic Peninsula Pacific margin)
Mar. Geol.
(2002)
Bottom deposits in the Central Scotia Sea: the importance of the Antarctic Circumpolar Current and the Weddell Gyre flows
Palaeogeogr. Palaeoclimatol. Palaeoecol.
Miocene to recent contourite drifts development in the northern Weddell Sea (Antarctica)
The origin of deep-water, coral-topped mounds in the northern Rockall trough, Northeast Atlantic
Mar. Geol.
Recent sedimentation beneath the deep Western Boundary Current off northern New Zealand
Deep-Sea Res. I
Sedimentary processes across the continental rise of the southern Antarctic Peninsula
Mar. Geol.
Modification and pathways of Southern Ocean Deep Waters in the Scotia Sea
Deep-Sea Res. I
On the export of Antarctic Bottom Water from the Weddell Sea
Deep-Sea Res. II
Westward bottom currents along the margin of the South Shetland Island Arc
Deep-Sea Res.
On the circulation and stratification of the Weddell Gyre
Deep-Sea Res. I
On the meridional extent and fronts of the Antarctic Circumpolar Current
Deep-Sea Res. I
Circulation, mixing and production of Antarctic Bottom Water
Progr. Oceanogr.
Sedimentation on the continental rise west of the Antarctic Peninsula over the last three glacial cycles
Mar. Geol.
Quaternary history of the Antarctic Circumpolar Current: evidence from the Scotia Sea
Mar. Geol.
Contourites
Sediment distribution around moated seamounts in the Rockall Trough
Deep-Sea Res.
Facies distribution and textural variations in Faro drifts contourites: velocity fluctuation and drift growth
Mar. Geol.
Sedimentation processes and acoustic stratigraphy in the Bellingshausen basin
Mar. Geol.
Weddell sea shelf water in the Bransfield Strait and Weddell–Scotia Confluence
Deep-Sea Res. I
In situ modification of modern submarine hyaloclastic/pyroclastic deposits by oceanic currents: an example from the Southern Kermadec arc (SW Pacific)
Mar. Geol.
Sedimentary structures, their character and physical basis
Fundamental properties of fluids and their relation to sediment transport processes
Current flow in the north-west Weddell Sea
Antarct. Sci.
Seismic record of glacial events affecting the Pacific Margin of the Northwestern Antarctic Peninsula
The Cenozoic subduction history of the Pacific margin of the Antarctic Peninsula: ridge crest–trench collisions
J. Geol. Soc. Lond.
Glacial history of the Antarctic Peninsula from Pacific margin sediments
Observations of seamount-attached eddies in the North Pacific
J. Geophys. Res.
Ten-month observation of the bottom current regime across a sediment drift of the Pacific margin of the Antarctic Peninsula
Antarct. Sci.
Revised calibration of the geomagnetic polarity timescale for the late Cretaceous and Cenozoic
J. Geophys. Res.
Sedimentary processes in the North Atlantic
Intrusion of circumpolar deep water along the Bellinshausen Sea continental shelf
Ocean Sci.
Observations of amplified flows atop a large seamount
J. Geophys. Res.
Formation and discharge of deep and bottom water in the northwestern Weddell Sea
J. Mar. Res.
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2022, Earth-Science ReviewsCitation Excerpt :In some cases, sub-circular to oval scours are attributed to vertical spouts of water and dynamic bottom current flows (Stoker et al., 2003), or from their interaction with seafloor irregularities (Lobo et al., 2011). Some examples have been identified offshore Antarctica in the Weddell Sea (Maldonado et al., 2005), as well as in the Scan Basin (Lobo et al., 2011) and PMAP (Hernández-Molina et al., 2006a, 2017). Contourite terraces have been identified mostly along the mounded drifts of the Argentinian mixed systems (Fig. 4B; Rodrigues et al., 2021).