Genetic sequence stratigraphy of cool water slope carbonates (Pleistocene Eucla Shelf, southern Australia)

Saxena, S.; Betzler, Christian

doi:10.1007/s00531-003-0338-7

Cited by 16 publications

(34 citation statements)

References 26 publications

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“…The presence of dolomite rhombs in the fine fraction on the modern shelf indicates that at least some of the dolomite within the Pleistocene succession may be detrital. The relatively high amount of aragonite (30%) suggests that cool-water carbonates should not be considered as mostly calcitic (Saxena and Betzler, 2003). This is further supported by the high-resolution mineralogy record presented by Swart et al (this volume).…”

Section: Da Feary Et Al Leg 182 Synthesis: Exposed Secrets Of the supporting

confidence: 60%

“…The cycles described by Simo and Slatter (this volume) are packstone-wackestone couplets, with the coarser material representing the lower sea level part of the cycle and the finer material representing the higher sea level component. These cycles are younger than the cycles described by Saxena and Betzler (2003) and are interpreted as reflecting a precessionforced (100 k.y.) signal.…”

Section: Da Feary Et Al Leg 182 Synthesis: Exposed Secrets Of the mentioning

confidence: 68%

“…orbital forcing (Saxena and Betzler, 2003). Finer-grained (wackestone) sediment at the base of each cycle grades upward to coarser-grained (packstone) sediment at the top.…”

Section: Da Feary Et Al Leg 182 Synthesis: Exposed Secrets Of the mentioning

confidence: 99%

“…This particle constituent partitioning produced pronounced mineralogic cyclicity. Highmagnesium calcite (HMC) and aragonite are a more abundant component of the succession during sea level rises and highstands (Saxena and Betzler, 2003; Andres and McKenzie, this volume; Swart et al, this volume). Siliciclastic input, in the form of clay minerals, is higher during sea level highstands, reflecting higher rainfall and runoff.…”

Section: Da Feary Et Al Leg 182 Synthesis: Exposed Secrets Of the mentioning

confidence: 99%

“…Siliciclastic input, in the form of clay minerals, is higher during sea level highstands, reflecting higher rainfall and runoff. Dolomite is also present in sediment deposited during sea level rises (Saxena and Betzler, 2003). The presence of dolomite rhombs in the fine fraction on the modern shelf indicates that at least some of the dolomite within the Pleistocene succession may be detrital.…”

Section: Da Feary Et Al Leg 182 Synthesis: Exposed Secrets Of the mentioning

confidence: 99%

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Leg 182 Synthesis: Exposed Secrets of the Great Australian Bight

Secrets¹,

Bight²,

Hine³

et al. 2004

Proceedings of the Ocean Drilling Program, 182 Scientific Results

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During Ocean Drilling Program (ODP) Leg 182, nine sites were drilled across the southern Australian margin in the Great Australian Bight, with the objective of obtaining a more detailed understanding of cool-water carbonate depositional processes and global environmental change in mid-latitude settings. Drilling results provide insights into the temporal and spatial aspects of cool-water carbonate deposition in shelf edge and slope environments. Drilling showed that the spectacular prograding clinoform sequence forming the upper slope and outermost shelf of the Great Australian Bight margin was rapidly deposited during the Pleistocene. Meter-scale lithologic cycles rapidly accumulated in response to orbitally forced sea level fluctuations. Skeletal elements within these wackestone to packstone, coarsening-upward cycles consist of tunicate spicules, brown bioclasts, bryozoan fragments, and red coralline algal debris-a heterozoan assemblage typical of coolwater carbonates. The high accumulation rates, comparable to rates in warm-water carbonate environments, reflect partitioning of sedimentation between the shelf and slope as high wave energy from the Southern Ocean interacted with sea level fluctuations to generate vigorous off-shelf transport.Mound features visible on seismic reflection data on and underlying the uppermost slope throughout the Pleistocene of the central and western Great Australian Bight are in situ bryozoan reef mounds. These mounds consist of diverse suites of bryozoans, together with coralline algae, echinoid spines, and benthic foraminifers, in a mudstone to D.A. FEARY ET AL. LEG 182 SYNTHESIS: EXPOSED SECRETS OF THE GAB 2packstone matrix. Seismic and isotopic data indicate that mounds developed cyclically in response to glacial-interglacial productivity cycles. Increased upwelling during sea level lowstands promoted active mound growth, in contrast to the thin mud accumulations that draped inactive mounds during highstands. Such mounds have not previously been described from the "modern" ocean and provide unlithified analogs for similar features that occur in the mid-to late Paleozoic rock record. The interaction of high-salinity (up to 106‰) interstitial brines with abundant organic matter within the upper parts of the sedimentary succession produced high concentrations of methane (up to 50%) and hydrogen sulfide (up to 15%). This unusual chemical environment lead to extensive carbonate recrystallization and dissolution of highmagnesium calcite and the precipitation of low-magnesium calcite and dolomite. In certain environments, therefore, cool-water carbonates may be at least as diagenetically active as their warm-water counterparts. The brines probably formed in shallow evaporative pools and lagoons on the shelf during sea level lowstands, seeped into the underlying sediments, and flowed toward the upper slope. Thermodynamic considerations suggest that H 2 S and CH 4 disseminated gas hydrates might be present within the Great Australian Bight succession.

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Section: Da Feary Et Al Leg 182 Synthesis: Exposed Secrets Of the supporting

confidence: 60%

Section: Da Feary Et Al Leg 182 Synthesis: Exposed Secrets Of the mentioning

confidence: 68%

“…orbital forcing (Saxena and Betzler, 2003). Finer-grained (wackestone) sediment at the base of each cycle grades upward to coarser-grained (packstone) sediment at the top.…”

Section: Da Feary Et Al Leg 182 Synthesis: Exposed Secrets Of the mentioning

confidence: 99%

Section: Da Feary Et Al Leg 182 Synthesis: Exposed Secrets Of the mentioning

confidence: 99%

Section: Da Feary Et Al Leg 182 Synthesis: Exposed Secrets Of the mentioning

confidence: 99%

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