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2021 | Buch

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Biogenic Sedimentary Rocks in a Cold, Cenozoic Ocean

Neritic Southern Australia

verfasst von: Dr. Noel P. James, Yvonne Bone

Verlag: Springer International Publishing

Enthalten in: Springer Professional "Wirtschaft+Technik" , Springer Professional "Technik"

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Über dieses Buch

This book documents and interprets the onshore Cenozoic temperate carbonate depositional system along the southern margin of Australia. These strata, deposited in four separate basins, together with the extensive modern marine system offshore, comprise the largest such cool-water carbonate system on the globe. The approach is classic and comparative but the information is a synthesis of recent research and new information. A brief section of introduction outlines the setting, modern comparative sedimentology offshore, and structure of the Cenozoic onshore. The core of the book is a detailed analysis and illustration of the four Eocene to Pleistocene successions. Deposits range from temperate carbonates, to biosiliceous spiculites, to marginal marine siliciclastics. Each unit is interpreted, as much as possible, based on our understanding of the modern offshore depositional system. A subsequent part concentrates on diagenesis both before and after the late Miocene uplift. It turns out that alteration in the two packages is entirely different. The preceding attributes of each succession are then interpreted on the basis of controlling factors such as tectonics, oceanography, climate, and glaciation of nearby Antarctica. This research has revealed new implications for the interpretation of specific attributes of cool-water carbonate sedimentology that could only be discovered from the rock record. Insights concerning cyclicity, reef mounds, biosiliceous deposition, and trophic resources are detailed in the next section. The concluding part focuses on global comparisons, especially the Mediterranean and New Zealand.

Inhaltsverzeichnis

Frontmatter

Preamble

Frontmatter

1. Introduction and Setting

Abstract

The scientific approach herein is largely comparative because the same type of sediments that made up the Cenozoic strata are accumulating offshore today. The record was, however, controlled largely by changing oceanography, climate, tectonics, and the geohistory of Antarctica. The book focuses on the Paleogene and Neogene carbonate sedimentary rocks across southern Australia. The narrative is a combination of our own studies and those of previous workers. The book is structured in 4 parts. The latitude-parallel paleocontinental margin stretches ~2700 km from west to east. This margin was relatively quiescent in the Eocene and Miocene but upset by late Miocene uplift and exposure resulting in an entirely different depositional style in the Pliocene and Pleistocene. Climate evolved during the Cenozoic from early warm and humid to late cool and semi-arid. There are four separate depositional basins each with its own setting and geohistory. Strata are partitioned into discrete 4 successions, each with different parts.

Noel P. James, Yvonne Bone

2. The Modern Carbonate Depositional Realm

Abstract

The sediments being deposited offshore today are heterozoan and a modern benchmark for the older Cenozoic deposits. Modern oceanography is characterized by cool waters, a series of complex currents, and seasonal upwelling. Neritic sediments are composed of extraclasts, mainly relict and stranded particles, together with biofragments mostly from living bryozoans, benthic foraminifers, mollusks, echinoderms, brachiopods, coralline algae, and siliceous sponges. Depositional environments range from large nearshore embayments to marginal marine systems to the wide neritic realm. Tidal sand shoals, seagrass meadows, macroalgal forests, coralline pavements, rippled sand barrens, and rocky reefs typify the inner neritic zone above fair weather wave base. The middle neritic seafloor between fairweather wave base and storm wave base is characterized by rippled sands, subaqueous dunes, and rocky reefs. The deeper outer neritic environment, only disturbed by occasional storms, is a zone of muddy locally reworked sediment. The upper slope is largely a burrowed mud barren.

Noel P. James, Yvonne Bone

Sedimentary Successions

Frontmatter

3. Succession SA2: Middle Eocene to Lower Oligocene—‘The Biogenic Shelf’ ~ 43-28 Ma

Abstract

The succession ranges in age from middle Eocene to early Oligocene and is divided into four parts. Carbonate deposition was at first confined to the west but by the early Oligocene extended into the Otway Basin. SA2.1—Middle Eocene strata, are largely marginal, inner, and mid neritic siliciclastics passing outboard into carbonates with deep water bryozoan mounds. SA2.2—Mid to Upper Eocene rocks are mostly similar with carbonaceous inboard terrestrial facies and mid-neritic bryozoan-rich limestones. SA2.3—Uppermost Eocene neritic deposits are quite different with not only biofragmental carbonates but also extensive biosiliceous, spiculitic sediments. SA2.4—Lower Oligocene deposits are dominantly carbonate but again with extensive spicules and chert. By this time carbonate deposition had also begun to take place in western parts of the Otway Basin.

Noel P. James, Yvonne Bone

4. Succession SA3: Late Oligocene—Middle Miocene—‘The Carbonate Shelf’ ~28–11 Ma

Abstract

This period, Late Oligocene to Middle Miocene, was one of carbonate depositional along the entire continental margin. Following a mid-Oligocene sea level fall, Upper Oligocene deposition was cool-water throughout with extensive heterozoan deposits in all neritic environments as well as the epicratonic Murray Basin. The middle Miocene was much different with comparatively warm ocean waters resulting in numerous large benthic foraminifers, abundant coralline algae, and even local reef-building corals in the deposits. The Murray Basin deposits accumulating in a centripetal ramp system also had local photozoan facies.

Noel P. James, Yvonne Bone

5. Succession SA4: Plio-Pleistocene—“The Shaved Shelf” ~10.4 Ma–5.2 Ka

Abstract

Prolonged, passive margin deposition was interrupted in the late Miocene by tectonic uplift. The early Pliocene was a short period of warmth and siliciclastic-carbonate marginal marine, lacustrine, and estuarine sedimentation, with deposits especially rich in mollusks. Tectonics, however, led to minor shelf accommodation such that any sediment that accumulated was either swept landward or seaward, resulting in little long-term accumulation on the shelf proper. The sedimentary record was instead one of spectacular Pleistocene marginal marine aeolianite complexes and a massive slope accretionary wedge.

Noel P. James, Yvonne Bone

6. Diagenesis

Abstract

As a result of late Miocene tectonics alteration occurred in two different settings, pre-uplift and post-uplift. Pre-uplift diagenesis during passive margin subsidence was largely characterized by seafloor carbonate dissolution, omission surface precipitation (hardgrounds) and burial alteration, there was no significant meteoric alteration. This latter aspect was largely due to the fact that there were few aragonitic components in the sediment and there was likely seafloor aragonite dissolution similar to that taking place today. Dolomite formation was present but only locally. By contrast, post-uplift diagenesis was typified by extensive meteoric alteration. Widespread karst, both surface and subsurface, formed in the uplifted and Pleistocene carbonates. The most impressive karst is that on and beneath the Nullarbor Plain. The semi-arid climate also led to extensive pedogenic carbonate in the form of calcrete. The exposed Pleistocene carbonates were rapidly cemented because of abundant aragonite particles that were quickly blown into aeolianites from the nearby offshore.

Noel P. James, Yvonne Bone

Analysis

Frontmatter

7. Integration and Interpretation

Abstract

The Cenozoic successions are integrated and analyzed here with respect to the dominant controlling factors present during deposition, namely tectonics, oceanography, climate, and influence of Antarctica. Middle Eocene–early Oligocene SA2 biogenic shelf sediments accumulated during a time of at first warm, but then gradually cooling ocean waters under a relative quiescent tectonic regimen. The climate was mostly humid subtropical with extensive temperate rainforests and fluvial activity that gradually waned in the post-Eocene. It is interpreted that the prolific nutrient elements delivered from land during the Eocene promoted extensive neritic biosiliceous deposition. The Oligocene -Miocene SA3 carbonate shelf was similar to that of today under a progressively warming climate and ocean waters such that in the mid-Miocene sedimentation was nearly photozoan. The comparatively quiet AAG had evolved into the Southern Ocean by the Oligocene resulting in a much more active hydrodynamic marine system. Antarctica had become ice covered and glacioeustacy promoted extensive m-scale carbonate cyclicity. The Plio-Pleistocene SA4 shaved shelf developed because of active tectonism that is continuing today and resulted in a different sedimentary system dominated by marginal marine and slope carbonate deposition.

Noel P. James, Yvonne Bone

Discussion

Frontmatter

8. Sedimentary Attributes

Abstract

Several aspects in the preceding narrative such as m-scale cyclicity, reef mounds, biosiliceous sedimentation, and trophic resources are scientifically contentious and so are discussed herein. M-scale cyclicity is clearly driven by glacioeustacy, principally via waxing and waning of Antarctic ice sheets. A series of five different cycle styles are recognized, largely dependent on specific neritic environments and each with a distinct motif. Deep-water bryozoan reef mounds are present in the Eocene and Pleistocene but are not good analogs for similar Paleozoic structures. Trophic resources were critical not only for biosiliceous deposition but also development of phosphatic hardgrounds related to interpreted upwelling. Reasons for biosiliceous sedimentation are controversial but seem to be related to terrestrially derived nutrient elements controlled by climate and again a modern equivalent is not a good geohistorical analog. Carbonate deposition in the epicratonic Murray Basin was closely tied to climate and trophic resources.

Noel P. James, Yvonne Bone

9. Global Comparisons

Abstract

Cenozoic cool-water, heterozoan carbonates are dispersed worldwide but, after southern Australia, the two most studied regions are New Zealand and the northern Mediterranean. The strata in nearby New Zealand are similar except that ongoing tectonics has resulted in a less complete record, with most carbonates in the Oligocene and Pliocene. Strata there contain more oyster and barnacle deposits but fewer biosiliceous components, bryozoan mounds, aeolianites, and dolomitization. Burial diagenesis is, however, much more important than in Southern Australia. Mediterranean temperate carbonates are numerous and largely more warm-temperate than Southern Australia with common zooxanthellate corals and other photozoan elements during highstands. Many high-energy deposits are similar to those in New Zealand tidal straits. By contrast, aeolianites are common and diagenesis is similar to southern Australian carbonates.

Noel P. James, Yvonne Bone

Backmatter

Titel: Biogenic Sedimentary Rocks in a Cold, Cenozoic Ocean
verfasst von: Dr. Noel P. James
Yvonne Bone
Verlag: Springer International Publishing
Electronic ISBN: 978-3-030-63982-2
Print ISBN: 978-3-030-63981-5
DOI: https://doi.org/10.1007/978-3-030-63982-2