Post-Eocene seismic stratigraphy of the deep ocean basin adjacent to the southeast African continental margin: a record of geostrophic bottom current systems

2000 ◽  
Vol 162 (2-4) ◽  
pp. 237-258 ◽  
Author(s):  
Tina M Niemi ◽  
Zvi Ben-Avraham ◽  
Chris J.H Hartnady ◽  
Margaret Reznikov
Keyword(s):  
Continental Margin ◽  
Deep Ocean ◽  
Seismic Stratigraphy ◽  
Ocean Basin ◽  
Bottom Current ◽  
Current Systems

DEPOSITIONAL ENVIRONMENTS AND GEOTECTONIC FRAMEWORK: SOUTHERN AUSTRALIAN CONTINENTAL MARGIN

1976 ◽  
Vol 16 (1) ◽  
pp. 25 ◽  
Author(s):  
I. Deighton ◽  
D.A. Falvey ◽  
D.J. Taylor
Keyword(s):  
Continental Margin ◽  
Rift Valley ◽  
Upper Cretaceous ◽  
Deep Ocean ◽  
Ocean Basin ◽  
Depositional Environments ◽  
Ocean Current ◽  
Spreading Ridge ◽  
Marine Influence ◽  
Sea Floor Spreading

Three principal phases occurred in the development of the basins of the southern Australian continental margin: epi-continental, marginal continental and oceanic. These correspond generally to the phases of margin development proposed by Falvey (1974): pre-rift, rift valley, and post-breakup; but tectonic and depositional transitions are not necessarily contemporaneous.Prior to the Upper Cretaceous, the region of the present day southern Australian margin lay well within the Eastern Gondwanaland continent, essentially barred from deep ocean basins. During the Upper Cretaceous the series of epicontinental basins was increasingly subjected to marine breakthroughs. Thus marine ingressive horizons were deposited along an incipient rift valley between the primitive Indian Ocean and Tasman Sea. Rift valley subsidence, possibly related to deep crustal metamorphism, was most significant on the flanks of the rift zone. Further marine influence during the Paleocene ('infra-breakup') and early Eocene corresponded to the onset of seafloor spreading between Australia and Antarctica. The neo-breakup phase is dominated by shelf and plateau subsidence and spreading ridge development, with topography influencing ocean current. The changing palaeogeography can be accurately illustrated by computer-derived reconstructions based on quantitative sea-floor spreading data. Quantitative thermal uplift/subsidence models can be used to estimate post-breakup water depth of the subsiding ocean basin and the continental margin. A complex pattern of transgressive continental deposition and submarine erosion diminished with the gradual widening of the Southern Ocean and the establishment of circumpolar ocean current paths. Oceanic basins dominated the margin through the Neogene.

Ferruginous bioforms accumulations in deep marine environments: an approach to their origin and formation mechanisms in the Transitional Zone province of the Galician Continental Margin (NW Iberian Peninsula)

2020 ◽  
Author(s):  
Ángel Enrique López-Pérez ◽  
Belén Rubio ◽  
Daniel Rey ◽  
Luís Pinheiro
Keyword(s):  
Steady State ◽  
Continental Margin ◽  
Deep Ocean ◽  
Direct Consequence ◽  
Transitional Zone ◽  
Ocean Floor ◽  
Bottom Current ◽  
Formation Mechanisms ◽  
Bottom Currents ◽  
Sea Bottom

<p>Ferruginous tubular structures concretions are widely distributed over the seafloor surrounding the <em>Gran Burato</em> depression in the Transitional Zone (TZ) province of the Galician Continental Margin (NW Iberian Margin). These bioforms-like structures are created by iron oxides precipitations into the tube-dwelling macrozoobenthos as a result of Fe<sup>2+</sup> upward diffusion and O<sub>2</sub> ventilation and diffusion acting in the water-sediment interphase in a non-steady state early diagenesis. X-ray diffraction analyses display that goethite is the main mineralogical component of these bioforms-like structures. Furthermore, non-steady state diagenesis has been identified by several oxidations fronts recognised in three piston cores, reflecting that the redoxcline has not achieved the deeper equilibrium in the study area. Afterwards, these ferruginous tubes were eroded, remobilised and redistributed over the seabed by bottom currents. Ocean-floor observations show erosion and sea-bottom current structures as ripples, grooves, erratic blocks, accumulations of pteropods and carbonate crusts associated with hardgrounds. Sedimentation rates calculated in a piston core display very low values for the last 30 cal ka BP (mean of 1.57 cm ky<sup>−1</sup>) with a marked hiatus between 17.80 to 10.45 cal ka BP, meanwhile abraded surfaces have been identified by high-resolution seismic data confirming erosional processes in this area of the TZ province. We conclude that the ferruginous bioforms accumulation over the deep-ocean floor is indicative of a present-day vigorous seafloor current acting and eroding the sediments of the TZ province. This bottom current is a direct consequence of the general seafloor elevation of the TZ province that causes constriction of the water masses (MOW and LSW) that induces a general intensification of the bottom currents and greater erosional capacity. This erosional process causes the continuous oxygenation of the upper sediments, and it prevents to reach the steady-state diagenesis, playing this fact an essential role in the ferruginous formations and accumulations in the study area.<br><br></p>

scholarly journals Organic geochemistry of continental margin and deep ocean sediments. Progress report, 1 March 1991--28 February 1993

1992 ◽  
Author(s):  
J.K. Whelan ◽  
J.M. Hunt ◽  
J.M. Seewald ◽  
L.B. Eglinton ◽  
M. Zawoysky ◽  
...  
Keyword(s):  
Continental Margin ◽  
Organic Geochemistry ◽  
Deep Ocean ◽  
Progress Report

scholarly journals Seismic stratigraphy of Cretaceous eastern Central Atlantic Ocean: Basin evolution and palaeoceanographic implications

2018 ◽  
Vol 499 ◽  
pp. 107-121 ◽  
Author(s):  
Yannick Mourlot ◽  
Gérôme Calvès ◽  
Peter D. Clift ◽  
Guillaume Baby ◽  
Anne-Claire Chaboureau ◽  
...  
Keyword(s):  
Atlantic Ocean ◽  
Seismic Stratigraphy ◽  
Ocean Basin ◽  
Basin Evolution ◽  
Central Atlantic

Continental Margin, Slope and Ocean Basin

1980 ◽  
pp. 457-501
Author(s):  
Hans-Erich Reineck ◽  
Indra Bir Singh
Keyword(s):  
Continental Margin ◽  
Ocean Basin

scholarly journals Neoproterozoic Nafun Group Sediments from Oman Affected by an Active Continental Margin

Minerals ◽  
2020 ◽  
Vol 10 (6) ◽  
pp. 511
Author(s):  
Liang Yue ◽  
Veerle Vandeginste
Keyword(s):  
Continental Margin ◽  
Water Oxidation ◽  
Tectonic Setting ◽  
Active Continental Margin ◽  
Trace Element Analysis ◽  
Deep Ocean ◽  
Geochemical Data ◽  
Ocean Water ◽  
Element Analysis ◽  
Deep Ocean Water

The Neoproterozoic era is a time of major environmental change in Earth history. The Ediacaran period (635–541 Ma), the uppermost division of Precambrian time, is characterized by the remarkable Shuram excursion (largest C isotope negative excursion), a deep ocean water oxidation event, and Ediacaran biota. The Nafun Group of Oman provides a well-preserved and mostly continuous section of an Ediacaran succession. Based on geochemical data from the Nafun Group, the Shuram excursion (SE) and deep ocean oxidation hypotheses were proposed. Now, we sampled this section at high stratigraphic resolution, and present here the petrographical and geochemical analysis of the Khufai, Shuram and Buah Formations. The major and trace element analysis of shales from the Shuram Formation indicates that northern Oman was an active continental margin environment in Neoproterozoic times. The provenance of the Shuram Formation was primarily mafic and intermediate igneous rocks. With the unsteady tectonic setting, the development of the Nafun Group was influenced by hydrothermal supply and volcaniclastic input. Based on the V/Cr and U/Th ratio of the samples from the Nafun Group, our study reveals the transition of the ocean water redox environment, which is connected to the rise and fall of the Ediacaran biota. Our study constrains the tectonic setting of northern Oman and the petrography and geochemical data from the Nafun Group for the hydrothermal and volcaniclastic supply. Thus, our study acknowledges more factors for the explanation of the Ediacaran conundrums.

Late Quaternary sedimentation in Baffin Bay

1987 ◽  
Vol 24 (9) ◽  
pp. 1833-1846 ◽  
Author(s):  
A. E. Aksu ◽  
David J. W. Piper
Keyword(s):  
Debris Flow ◽  
Late Quaternary ◽  
Ocean Basin ◽  
The Arctic ◽  
Bottom Current ◽  
Eastern Canada ◽  
Baffin Bay ◽  
Quaternary Glaciation ◽  
Continental Slopes ◽  
Channel Systems

Baffin Bay is a small ocean basin that connects the Arctic and Atlantic oceans. The adjacent continental shelves have been extensively reworked during Quaternary glaciation. The shelf break generally lies between 200 and 500 m. The continental slope passes directly into the abyssal plain of Baffin Bay basin without any major submarine canyon – deep-sea fan system being present, except for a large smooth sediment apron in northern Baffin Bay.On the basis of over 50 piston cores, six Quaternary sediment facies are distinguished from detrital mineralogy (reflected in colour) and sediment texture. Facies A, B, and C are predominantly ice-rafted or are debris flow deposits, each with a distinct mineralogy. Facies D is turbidites and bottom-current sorted sands, silts, and muds. Facies E is hemipelagic sediment. Facies F consists of sediments ranging from slumps, through debris flow deposits, to fine-grained turbidites, with a distinctive provenance in northern Baffin Bay.These sediment facies appear to be partly controlled by glacial conditions. Hemipelagic facies E predominates during the present interglacial. During glacial stages, facies D turbidites were deposited. They resulted from slumping of proglacial sediments on the continental slopes off Greenland and Baffin Island. Facies C and F occurred on the continental slopes at these times. Ice-rafted facies A and B predominate at several horizons, reflecting a rapid breakup of ice shelves in northern Baffin Bay and increased rates of iceberg melting within the Bay. Overall sedimentation rates are relatively low, reflecting dry-base ice sheets in source areas.Deep-sea channel systems floored by sorted coarse sediments and bounded by muddy levees are absent in Baffin Bay, in contrast to mid-latitude glaciated continental margins off eastern Canada. These channel systems are the result of melting of wet-base glaciers, which provide a localized supply of sediment that is sorted by ice margin processes. In Baffin Bay, most glacial sediments are derived by calving of icebergs, probably from dry-base glaciers. Sediments are gradually released over large areas as the bergs melt, and are subsequently redistributed by debris flows.

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