ABSTRACT Potential reservoir facies represented by lacustrine shoreline grainstones and rudstones are typically relatively thin compared to those from marine basins because of limited fetch and reduced wave action producing a shallow wave base. This is especially the case in low-gradient endorheic lakes in which rapid lake-level oscillations preclude the development of a stable shoreline. However, the closed lake deposits of the Barra Velha Formation locally have thick (decameter-scale) continuous packages of grainstones and rudstones comprising fragments of crystal shrubs, spherulites, intraclasts, and, in some cases, peloids and volcanic fragments. Grainstones and rudstones of this type occur on the escarpment and dip slopes of tilted fault blocks along which a marked thinning of the Barra Velha Formation is evident. They mainly consist of sharp-based, decimeter-to-meter–scale, fining-upward packages with well-sorted and well-rounded grains, planar/low-angle lamination and, less commonly, cross-lamination and planar cross-bedding. Those that occur on dip slopes are generally finer than those associated with escarpment slopes, the latter also being texturally less mature. At the formation scale, grainstone-dominated successions show radial depositional dip azimuth patterns orientated normal to paleoslope. The grainstones are interpreted as wave-dominated fan-delta shoreline deposits. Although much effort has focused on the origin of the in situ components of the Barra Velha Formation, such as crystal shrub facies, detrital deposits of the type documented here constitute significant potential targets.

Abstract The Middle Devonian carbonates of the Slave Point Formation, Hamburg field, northwestern Alberta, are composed mainly of stromatoporoid and Amphipora floatstones and rudstones, with interbedded mudstone and grainstone facies characteristic of deposition in open to slightly restricted marine platform environments. These carbonates have undergone a complex diagenetic history, from shallow to deep burial, as represented by fracturing, calcite cementation, silicification, and dolomitization. Petrographically, four different types of dolomite have been identified (from early to late): (1) fine-crystalline matrix dolomite; (2) pseudomorphic dolomite; (3) medium-crystalline pervasive dolomite; and (4) saddle dolomite. Fine-crystalline dolomite (5–50 (μm) replaces the mud matrix and slightly penetrates the edges of allochems. It occurred in mud-supported facies and was precipitated by marine fluids. Oxygen isotope values range from −11.62 to −9.34‰ (Peedee belemnite), lower than postulated values for Devonian carbonates. The enriched 87 Sr/ 86 Sr isotope value from this phase (0.71002) suggests that later diagenetic fluids may have recrystallized this dolomite. Pseudomorphic dolomite (50–100 μm) replaces crinoids and occurs as single, large dolomite crystals. Its oxygen and carbon isotopic values range from −10.58 to −9.65 and +4.24 to +4.49‰, respectively. Medium-crystalline pervasive dolomite (10–100 μm) occurs along dissolution seams and obliterates all previous fabrics. It is proposed that this medium-crystalline dolomite formed during shallow to intermediate burial because of its association with dissolution seams and high iron content. The range of oxygen isotope values for this dolomite (−11.74 to −9.5‰) suggests precipitation from a warm fluid, possibly in a burial environment, and/or later recrystallization by hydrothermal fluids. The relatively wide range of carbon isotope values (+1.19 to +4.49‰) and enriched strontium isotope ratio (0.710020) suggests recrystallization. Saddle dolomite (250–2000 μm) partially to completely occludes void spaces (both fractures and vugs) and also occurs as a minor replacement mineral. The oxygen isotope values for saddle dolomite (−?13.95 to −?11.97‰), as well as the nonradiogenic to enriched strontium isotope ratios for saddle dolomite (0.70494 to 0.710351), and the fluid-inclusion data (homogenization temperature, T h , range between 125 and 161°C and estimated salinity, between 22.2 and 24.7 wt.% NaCl equivalent) indicate precipitation from hot, highly saline, hydrothermal fluids, which were probably expelled tectonically during the Late Devonian-Mississippian Antler thrust belt development.

Abstract The giant Wilmington oil field of Los Angeles County, California, on production since 1932, has produced more than 2.6 billion barrels of oil from basin turbidite sandstones of the Pliocene and Miocene. To better define the actual hydrologic units, the seven productive zones were subdivided into 52 subzones through detailed reservoir characterization. The asymmetrical anticline is highly faulted, and development proceeded from west to east through each of the 10 fault blocks. In the western fault blocks, water cuts exceed 96%, and the reservoirs are near their economic limit. Several new technologies have been applied to specific areas to improve the production efficiencies and thus prolong the field life. Tertiary and secondary recovery techniques utilizing steam have proved successful in the heavy oil reservoirs, but potential subsidence has limited their application. Case history 1 involves detailed reservoir characterization and optimization of a steamflood in the Tar zone of Fault Block II. Lessons learned were successfully applied in the Tar zone, of Fault Block V (4000 m to the east). Case history 2 focuses on 3-D reservoir property and geologic modeling to define and exploit bypassed oil. Case history 3 describes how this technology is brought deeper into the formation to capture bypassed oil with a tight-radius horizontal well.

Abstract The giant Wilmington oil field of Los Angeles County California, on production since 1932, has produced over 2.5 billion barrels of oil from Pliocene and Miocene age basin turbidite sands. The seven productive zones were subdivided into 52 subzones through detailed reservoir characterization to better define the actual hydrologic units. The asymmetrical anticline is highly faulted and development proceeded from west to east through each of the ten fault blocks. In the western fault blocks water cuts exceed 96% and the reservoirs are near the economic limit. Several new technologies have been applied to specific areas to improve the production efficiencies and thus prolong the field life. Tertiary and secondary recovery techniques utilizing steam have proven successful in the heavy oil reservoirs but potential subsidence has limited its application. Case history 1 involves detailed reservoir characterization and optimization of a steam flood in the Tar Zone, Fault Block II. Lessons learned were successfully applied in the Tar Zone, Fault Block V (4000 meters to the East). Case history 2 focuses on 3-D reservoir property and geological modeling to define and exploit bypassed oil. Case history 3 describes how this technology is brought deeper into the formation to capture bypassed oil with a tight radius horizontal well.

Abstract: Modern cool-water, temperate, platform carbonates accumulate in seawater that is generally colder than 20°C. They are part of the Heterozoan Association (new term) of particle types produced by coralline algae and benlhic invertebrates that feed through a variety of heterotrophic means. Such sediments occur worldwide in all platform environments. In warm-water, euphotic, oligotrophic settings, they are swamped by particles from rapidly growing green calcareous algae, invertebrates with photosymbionts (corals) and active abiotic precipitation (mud, ooids, cements), here called the Photozoan Association (new term). The Heterozoan Association, however, prevails, together with photoautotrophs such as green algae, in warm-water environments where high nutrient levels enhance primary productivity and suppress growth of invertebrates with photosymbionts. Heterozoan carbonates form unrimmed ramps and open-shelves with their style being determined by local terrigenous clastic sediment input, oceanography, nutrient supply and sea-level history. Cool-water, temperate platform carbonates are typically grainy with discrete bydrodynamically- controlled facies. Kelp forests are common inboard, while subaqueous dunes are typical outboard. Slope or outer ramp environments are muddy with abundant sponge spicules and local sponge/bryozoan/coral buildups. Contemporaneous sub-tropical platform carbonates are Heterozoan in composition but contain minor Photozoan elements. They are typically rich in coralline algae and have extensive inboard grass banks. Polar and subpolar shelf carbonates are Heterozoan, are prolific at ice-fronts and are associated with biogenic siliceous and glacigene sediments. Physical sedimentary processes on cool-water carbonate shelves and banks are dominated by traction currents, storm-, swell- and tide-induced suspension of fines, active shallow-water particle abrasion and patchy development of subtidal hardgrounds. The degree of mineral-specific carbonate dissolution and/or precipitation is as yet unclear. Biotic sedimentary processes are dominated by post-mortem skeletal disarticulation, bioerosion and maceration. Criteria for the definitive identification of ancient cool-water carbonates are, at present, equivocal. Nevertheless, many Ordovician, Permo- Carboniferous, ?Upper Jurassic-Lower Cretaceous and Cenozoic limestones are strikingly similar in biotic makeup (Heterozoan), original mineralogy (calcite-dominated), sedimentary packaging (meter- and decameter-scale cyclicity) and carbonate platform geometries to modern cool-water deposits. Thus, modern cool-water carbonates may provide excellent analogues for the interpretation of many ancient ramp and shelf successions.

Abstract: The continental shelf of southwest Australia is part of a passive continental margin which is open, wave-dominated and characterised by cool-water carbonate sedimentation. The Houtman Abrollios coral reefs comprise three shelf-edge carbonate platforms which together form the discontinuously rimmed AbroLhos Shelf at latitude 28-29.5°S. This shelf lies in a biotic transition zone between northern tropical and southern temperate environments. There is also a regional transition between warm-water sediments to the north and the cool-water carbonate shelves of southwestern and southern Australia. There is a marked contrast between Abrolhos platform facies and adjacent shelf sediments. Platform sediments are aragonite-dominated coral framestones and aragonite/Mg calcite sand sheet facies composed of coral and coralline algal debris, with lesser amounts of bryozoans, foraminifers and molluscs. Shelf sediments are dominated by bryozoans and coralline red algae, with lesser molluscs and foraminifers, and are Mg calcite and calcite-rich. There are no ooids, and Halimeda is present only in trace amounts on the shelf. The abundance of corals imparts a warm-water character to the platform deposits, whilst the shelf sediments are indistinguishable from other cool-water shelf deposits which extend from Australia’s southern margin to the western margin, at least to the latitude of the Abrolhos shelf. A poleward-flowing warm-water current (the Leeuwin Current) influences the biotic transition and the relatively high southerly latitude of the Abrolhos reef platforms, which are near the temperature limits for reef-building coral growth. During Tertiary to Quaternary time, there was a vertical transition from cool-water ramp sedimentation to reefal platform development near the shelf edge at the Abrolhos, as a result of Australia’s northward drift and establishment of the Leeuwin Current. Such facies transitions owe their existence to regional patterns of oceanographic circulation, driven in the long term by changes in paleolatitude, and have been an integral part of carbonate platform evolution during the Phanerozoic.

Abstract: Vibracores collected from the middle and outer continental shelf of New South Wales, Australia (32.5° to 34.8°S) contain a well- preserved record of cool-water carbonate sedimentation during the last three glacial lowstands. The cores show an increase in the proportion of carbonate with increasing water depth and distance offshore and mimic a pattern previously identified for surficial shelf sediments. Degraded biogenic sand and shell gravel on the winnowed surface of the outer shelf (water depths of 135 to 150 m) is underlain by thick sequences of well-preserved, shallow-marine bivalves (dominantly Pecten fumatus) in a carbonate sand matrix. These cool-water bivalves occur cyclically in at least 10 cores from the outer shelf, separated by intervening deposits of deeper water species in finer grained carbonate sand. Numerous radiocarbon dates confirm that the uppermost Peclen unit is of last glacial age (13,000 to 27,000 yr BP), while amino acid racemisation analyses of the lithologically analogous underlying Peclen units indicate that previous late Pleistocene lowstand events (isotopic stages 6 and 8) are also preserved. These lowstand, carbonate-rich sediments contrast sharply with the predominantly quartzose sand characteristic of the highstand inner shelf and indicate that little terrigenous sand was supplied to the shelf during lowstands. The sedimentary sequence identified in the outer shelf cores also indicates a marked change in environmental conditions from productive, shallow-marine carbonate sedimentation during the last glacial lowstand to non-deposition and bioerosion during the highstand, with intervening periods of intermediate water depth (isotope stages 3 and 4?) also characterized by carbonate sedimentation. This cycle was repeated during previous late Quaternary sea-level fluctuations, and the data indicate on-going accretion of the outer shelf sediment wedge at a rate of 1 to 4 m/100,000 years.

Abstract: The storm-dominated, high-energy, cool-water Lincoln Shelf occupies the central part of the southern Australian continental margin. Carbonate sediments on this modern distally-steepened ramp were produced by slow deposition during the Terminal Quaternary Sea-level Cycle (0 75 Ka), a high-amplitude, asymmetric cycle of sea-level change. The 50 to 150-mwd (meters water depth), 120-170 km-wide surface is a rocky substrate covered by a patchy, m-scale, palimpsest sediment veneer composed mostly of bryozoans, molluscs, foraminifers and coralline algae. Facies of the condensed Terminal Quaternary Sequence are interpreted to reflect accumulation during different parts of the Terminal Quaternary Sea-level Cycle that are now variably mixed. Accumulation during early stages of the Terminal Quaternary Regression, Isotope Stage-3/4 (IS-3/4), when sea level fluctuated between 30- and at least 60-mwd, took place in a series of shallow marine to paludal environments. Small-scale, 5th-order sea-level fluctuations resulted in recurring deposition, surf-zone reworking and exposure. Such conditions generating Relict Particles, brown- colored, abraded grains filled with carbonate precipitates, that are now concentrated on the middle to inner shelf (< 100-mwd). The Terminal Quaternary Lowstand (early IS-2) at 120-mwd resulted in deposition on the outermost shelf and exposure of the middle and inner shelf. This was a period of mesotrophic conditions and overall upwelling, leading to prolific bryozoan growth and the formation of a bryozoan biostrome at the shelf edge. These conditions continued during the early Terminal Quaternary Transgression (late IS-2) resulting in shelf facies rich in articulated coralline algal particles and rhodolites. Rapid sea-level rise, coupled with a change to more oligotrophic conditions during the late Terminal Quaternary Transgression (early IS-1), drowned these environments and resulted in belts of Stranded Particles on the middle to outer shelf. The modern setting, during the present Terminal Quaternary Highstand, reflects a complex oceanography. Waters are mildly oligotrophic, with yearly incursion of warm, oligotrophic waters from the west, seasonal upwelling of mesotrophic waters and annual outflow of cold, saline bottomwaters from the large shallow embayment of Spencer Gulf. Recent Particles are diverse: bivalves dominate inner-middle shelf sediments; bryozoans are most abundant on the outer shelf; shelf sediments opposite Spencer Gulf saline outflows are rich in benthic foraminifers; and corallines are most abundant inshore. The moribund biostrome is now populated by a rich and diverse suite of deeper water bryozoans and ahermatypic corals. Sediments on the western part of the shelf, with scattered large foraminifers, illustrate the sporadic influence of warmer waters.

Abstract: Many modern continental shelves are areas of calcareous faunal and floral growth and subsequent carbonate accumulation. These de- positional environments can be subdivided into three major zones: (1) tropica I/warm-water; (2) temperate/cool-water and (3) polar/cold-water. Our research focused on the temperate environment. We analysed 51 samples of corals, coralline algae and bryozoans and 9 calcitic cements from bottom sediment samples from the Lacepede Shelf, South Australia for their mineralogy, oxygen and carbon isotopes, and distribution of major, minor and trace elements. Azooxanthellate corals are depleted in 8 18 0 and 8 I3 C in comparison to equilibrium values but less so than their tropical counterparts. Coralline algae are enriched in 8 18 0 and 8 I3 C compared to tropical samples. Both azooxanthellate corals and coralline algae display a positive correlation between their isotopes. The bottom temperature versus S ls O curve for the aragonitic bryozoan Adeona sp. parallels the equilibrium aragonite curve. These B 1S 0 values are in equilibrium with the ambient water but differ from those for Adeona sp. from the Indian (tropical) Ocean. Its 8 13 C content is almost in equilibrium and higher than its tropical counterpart, despite lower 8 13 C values for dissolved inorganic carbon (DIC) in the study area. This study shows that carbon isotope disequilibrium of carbonate-rich biota is greater than that of oxygen isotopes. Furthermore, the isotopic ratios for similar organisms are different from one environment to another. Even more importantly, diverse organisms living in the same environment may have dissimilar isotope values. This can be attributed to either metabolic processes or kinetic effects. For the former, photosynthesis is the major cause of 8 I3 C enrichment in photosynthetic organisms, and respiration induces some depletion. Extrinsic factors (e.g., depth, salinity, temperature, turbidity, substrate, and oxygen levels, etc.) variably mediate differences. Organisms with aragonitic mineralogy, such as corals and some bryozoans, have higher Sr and lower Mg, Fe and Mn concentrations than calcitic ones (e.g., coraUine algae). These differences may be functions of various combinations of the following processes: (a) mineralogical discrimination against some trace elements, (b) skeletal formation process, (c) environmental variables and (d) physiology of the organism. Differences between temperate and tropical biotic geochemistry may be useful for differentiating between temperate and tropical environments in the rock record, providing diagenesis has not altered the primary signatures.

Abstract: The mineralogy of living bryozoans and recent bryozoan skeletal particles on the cool-water Lacepede Shelf between water depths of 38 and 180 m is variable, with growth forms composed of aragonite and/or calcite with low or intermediate amounts of magnesium. The MgC0 3 content of LMC (low-magnesium calcite) and 1MC (intermediate-magnesium calcite) bryozoans is not temperature dependent, so that the composition of the same species is constant to water depths of 180 m. Stable carbon and oxygen isotopes values from CaC0 3 in these same bryozoans indicate that most, but not all, probably precipitate their skeletons close to isotopic equilibrium with ambient seawater. All morphotypes, except fenestrate and flat robust branching aragonite morphotypes, are potentially useful for paleotemperature and paleoenvironmental interpretation purposes if the mineralogy of the skeletons has not been changed. The most geologically useful forms, if the sediments have been altered to low-Mg calcite (LMC), are delicate branching cyclostomes or, if the original mineralogy can be determined to have been intermediate-Mg calcite (IMC), articulated branching cheilostomes. Such results indicate that bryozoans may be useful throughout the geological record as additional proxies for the determination of paleoceanographic parameters.

Abstract: The Otway margin forms part of the cool-water carbonate province that extends along the entire southern margin of Australia. Open shelf and upper slope sediments are bryozoan rich. Sediments on the modern slope to depths of at least 2300 m are dominantly fine-grained mud flow deposits, reworked from the upper slope. Small-scale muddy bryozoan-rich debris flows occur locally. Lower slopes accumulate hemipelagic sediment. Analysis of cores from two slope transects provides insight into the effects of sea-level changes through the Pleistocene glacial/interglacial cycles of stable-isotope stages 1 to 6. During highstand and lowstand conditions, fine-grained mud flows dominate sedimentation on the upper and midslopes. In contrast, transgression is marked by a distinct event, traceable as an influx of sandy debris flow and sandy mud flow sediments. Canyon systems become active during lowstands and transgressions, resulting in deposition of turbidites on lower slopes and abyssal fans. Overspill turbidites found in lower slope cores are typically fine-grained and show a mixed terrigenous and biogenic carbonate composition. Turbidites, unlike mud flow deposits, are mainly derived from reworked lowstand dune sands and exposed Tertiary sediments. High rates of downslope sediment transport are due to a combination of factors, including the depth of production by the “carbonate factory”, the high-energy nature of the margin, high-bioclastic content of the sediments and localised oversteepening. The extent of sediment transport is much greater than has been implied in previous sediment studies. This is due, in part, to lack of recognition of fine-grained transported sediments. In terms of depositional models, this margin is more analogous in many ways to a clastic system than to tropical carbonate models. It differs from both clastic and tropical carbonate models in that sediment accumulation on the upper slope and downslope transport remain relatively unaffected by sea level fluctuations.

Abstract: Mixed siliciclastic-carbonate sediments are presently accumulating on the inner to mid Wanganui shelf (20 to 110-m water depth) off central western New Zealand (40°S). Cluster analysis identifies five surficial sediment facies across this sector of the shelf. A modern, high- carbonate (avg. >70%) skeletal sandy gravel (Facies 2) occupies an irregular lobe, up to 2000 km 2 and 1 m thick, over the inner to mid shelf (30- 90 m). At inner shelf depths (<50 m), Facies 2 passes relatively abruptly shorewards into a modern, very low carbonate (avg. <10%) siliciclastic sand (Facies la) or a relict, low carbonate (avg. 20%) bivalve-bearing gravelly sand (Facies lb). Offshore, the skeletal carbonates (Facies 2) pass more gradually via a moderate carbonate (avg. 30%) bivalve-bearing muddy sand (Facies 3; 75- 110 m) into a low carbonate (avg. <15%) siliciclastic mud (Facies 4; 85 110 m) and micaceous sand (Facies 5; 95-105 m), all predominantly modern. The high carbonate facies (Facies 2) occurs in a region of relatively reduced siliciclastic sediment input and is maintained by recurring colonization by epibiota upon the coarse shelly substrate. The nearshore siliciclastic facies are sourced mainly from southwestern North Island rivers and southeastwards longshore drift. The offshore siliciclastic facies include both North and South Island-derived sediments, the latter introduced by the prevailing oceanic currents. Analogues of the five facies defined for the surficial sediments are identified in short cores (<2.5 m) taken from Wanganui shelf. The ideal facies motif in these cores changes upwards from siliciclastic gravelly sands (Facies lb) to skeletal-rich carbonates (Facies 2 and 3) to siliciclastic sandy muds and muddy sands (Facies 4 and 5). This vertical succession formed in response to Holocene transgression associated with the last postglacial rise of sea level and the accompanying changes in hydraulic regime on Wanganui shelf. In a sequence stratigraphic context, Facies lb gravelly sands represent transgressive systems tract deposits. The overlying skeletal carbonates (Facies 2 and 3) form a condensed shellbed up to about 1 m thick. The locally capping fine siliciclastics (Facies la, 4 and 5) equate to highstand systems tract sediments, fed from opposite directions by dual North and South Island sources, which are slowly encroaching upon and covering the surficial carbonate deposits. The Holocene Wanganui shelf record affords a modern analogue of comparable glacio-eustatic cyclothemic facies widely developed in uplifted Plio-Pleistocene deposits on the North Island. In common with many other temperate-region carbonates, the Wanganui shelf carbonates are dominated by bivalve molluscan and bryozoan remains, comprise mixtures of fresh and moderately to highly degraded skeletal material, have low positive (c. +1 to 4-2%) 8 ls O and 8 I3 C values and are closely associated with siliciclastic sediments. The Wanganui carbonates also exhibit characteristics that contrast with the larger Australasian temperate carbonate platform deposits. These characteristics include: (1) moderately high total mud (up to 50%) and carbonate mud (avg. 27%) contents, (2) abundant living and diverse fauna in areas with otherwise moderately high terrigenous mud inputs, (3) a significant proportion (up to c. 50%) of aragonitic components, mainly infaunal bivalves, (4) relatively high accumulation rates (c. 5-10 cm/ky), and (5) bivalve molluscan shells, rather than rocky surfaces, as the main substrate for attachment and encrustation. These kinds of differences exemplify the substantial variations that can occur amongst temperate carbonate facies, and require consideration as models of temperate carbonate sedimentation continue to develop.

Abstract: A deep-water coral reef mound is located along the upper western slope of Stjernsund-Sill in the Norwegian West Firaimark District at 70°N. It grows between a muddy basinal Qord and an erosive sill-crest sedimentary environment in 260- to 235-m water depth, thriving in water temperatures between 5° and 6°C. Maximum framework thickness of Lopheliapertusa is 10 m. Despite its deep position far below storm-wave base, the reef is strongly zoned and two stages of reef development can be distinguished, a growing stage and a dying stage. Each stage is characterized by distinct colony growth habits representing ecotypes. Active reef mound growth dominates along the upcurrent, deeper section of the mound, whereas framework destruction is confined to the shallower, downcurrent area of the mound complex. If the unlithified deep-water coral reef mound is not buried by sediments, the preservational style will be a detrital collapse structure rather than an intact framework. Preliminary growth estimates yield unexpectedly high growth rates of up to 2 cm/yr. On the basis of this value, the onset of mound formation was only 520 years ago. If this preliminary estimation is substantiated by more detailed analysis, L. pertusa has the potential of rapid accretion under suitable environmental conditions. Main environmental controls are nourishment and a homothermal water mass passing over the reef mound, availability of hard substrates and a current regime preventing sedimentation. At present, the Stjernsund reef mound is just below the thermocline. The upper, dying reef areas are already affected episodically by the properties of fluctuating water masses.

Abstract: Spitsbergen Bank is the largest open-shelf cold-water carbonate platform in the Arctic region. Carbonate production is centered around two main carbonate “factories.” The first one, kelp forests growing on the shallowest parts of the platform are the main source area for barnacle sands (i.e., Balanus crenatus). These mobile carbonate sands are transported within a huge clockwise gyre of polar water over the platform. This gives rise to a thin veneer of skeletal sand on the platform interior and carbonate mega-dunes at the margin. At these high latitudes, extreme seasonality is reflected in variation in sea ice cover over the bank and changes in sediment dynamics. Migration of marginal mega-dunes is related to heavy storm events in late autumn/early winter. Smoothing of the dune relief occurs by bottom traction currents through the rest of the year. The second carbonate “factory” is situated on the flanks of the platform, where high productivity conditions are established along the Polar Front at the zone between Atlantic and Arctic water masses. Very efficient bentho-pelagic coupling (e.g., a rapid transfer of planktic food to the benthic communities), accounts for the development of a high biomass. The biota features dense colonies of infaunal bivalves as well as Balanus balanus- hydrozoan- soft coral-sponge-bryozoan buildups. The postglacial succession of cold-water settings on Spitsbergen Bank display a distinct evolutionary trend which highlights variable balances between the main driving forces on cyclically-glaciated carbonate platforms. There is a complete switch-over between the two end-member conditions: maximum drowning and eustatic sea-level lowstands during glacial periods versus maximum efficiency of glacio-isostatic uplift and eustatic sea- level highstand in the Holocene time. These changes in platform configuration are associated with a shift in sedimentary regimes from low-energy, proximal-glaciomarine settings during the glacial and early postglacial period to high-energy, distal-glaciomarine conditions in Holocene time. Evolutionary phases of this shift can be deduced from detailed analysis of facies belts on Spitsbergen Bank and are summarized in a hypothetical model for two successive glacial/interglacial cycles. This model may serve as a reference for the interpretation of fossil counterparts.

Abstract: The neritic stratigraphic record in southern Australia sorts into four cycles or sequences which resemble global second-order cycles based on sequence stratigraphy. The record is highly incomplete at the second order, due especially to a 9 my gap in the middle Eocene and poor and restricted records of the early Oligocene and the late Miocene series, and at the third order where hiatuses become more apparent as stratigraphy advances. Correlations and age determinations are based mostly on micropalaeontology and are limited by the neritic facies, the extratropical situation and the lack of a local or regional geomagnetic pattern. In this composite regional succession, we have had to proceed from regional stages based only loosely on fossils, to biostratigraphic ranges and formal zones (of planktonic foraminifera), to faunal associations based on transgressions and regressions, so that we are but a short step from a revision of the regional stages in terms of sequence biostratigraphy. This geochrono- logical scaffolding is important not only to the neritic realm itself, but to the neritic-oceanic link and ODP drilling in one direction and to the terrestrial environmental and paleobiological realm in the other. The Cenozoic record of global climatic deterioration has temporary reversals punctuated by four sharp coolings (“chills”) in the early middle Eocene, earliest Oligocene, middle Miocene and late Pliocene, and they too are chronologically consistent with the regional neritic record. In the oldest cycle, the sediments are marginal marine siliciclastics with several very brief transgressions with marine microfaunas and rare macrofossils but no limestones. Extratropical carbonates begin abruptly in the late middle Eocene series at the base of the second cycle and the Wilson Bluff transgression, which is the Khirthar Restoration of the Indo-Pacific region. At the same time there develops a distinction between warmer and cooler intermediate watermasses in the Indian Ocean, and the Leeuwin Current is born. These events are responses to accelerated Australia/Antarctica separation from 43- 42 Ma. The third-order components of this cycle are marked by marine transgressions; they are consistent in number and timing with the putative late Eocene global pattern. The third cycle is the Miocene oscillation which begins in late Oligocene time and peaks in sea level and warming at the Miocene climatic optimum in early middle Miocene time. As shown in a correlation chart, the extratropical “cool-water carbonates” are mostly in the second and third cycles, although there are carbonates in the extensive marine horizons of the Pliocene reversal. The Eocene-Miocene neritic carbonate record comprises third-order sequences, seen most clearly as marine transgressions. The transgressions can be related to third-order glaciations and eustatic cycles in plausible if not always compelling correlations. Horizons of warming, upwelling, and siliceous facies complete a framework of an outstanding extratropical, neritic carbonate record.

Abstract: Abstract: The onshore Tertiary Gippsland Basin records the transition from terrestrial sediments to platform cool-water carbonates. This paper is the first integrated study of the carbonate sediments to combine sequence stratigraphy, biostratigraphy and paleoenvironmental analyses and then quantify Oligo-Miocene eustatic sea-level and climatic fluctuations. Data for this study are derived from continuously cored wells tied to a regional network of seismic profiling. The 16,000 km 2 of the onshore Gippsland Basin contains up to 500 meters of carbonates which are assigned to the Seaspray Group and its constituent formations including the Lakes Entrance, Gippsland Limestone and Wuk Wuk Marl Formations. This group is now divided into nine new sequence stratigraphic intervals: i. Four comprising the Lake Entrance Formation (LEF) where Lower LEF = TB 4.5 (Early Oligocene), Middle B LEF = TB 1.2 and Middle A LEF = TB 1.3 (Late Oligocene). The Upper LEF = partTB 1.4 (Early Miocene). Based on microfossil evidence, eutrophic upwelling paleo- environments are suggested for the marly transgressive systems tracts (TST’s) of the LEF sequences, whereas their highstand system tracts (HST’s), mixed carbonates and clastics, are interpreted to have formed under warm water oligotrophic conditions. ii. Four comprising the Gippsland Limestone Formation (GLF) where Lower B GLF = part TB 1.4, Lower A GLF = TB 1.5, Middle GLF = TB 2.1 and Upper GLF = TB 2.2 (all Early Miocene). The Early Miocene GLF consists of interbedded marly limestones representing deposition in cold-water mid- to outer shelf depths. Near the end of the Early Miocene and the top of the GLF, warm shallow oligotrophic conditions appear in the HST ofTB 2.1. iii. One or two in the Wuk Wuk Marl Formation (WWM). The Middle Miocene WWM records the first two sequences of the Mid Miocene Climatic Optimum, with an influx of the Orbulina lineage and globorotaliids. They are tied to the sequence chronostratigraphic cycles TB 2.3 and TB 2.4(?). Relative depths of sea-level change, together with sedimentation rates, were determined from accommodation calculations on seismic lines, foraminiferal assemblages and durations of sequence chronostratigraphic cycles. The data suggest water depths varied between 0- 200 + m and the secular eustatic variation was similar. Sedimentation rate is highest in oligotrophic HST facies. The paleoenvironments vary from terrestrial lignites to outer shelf carbonates over a horizontal distance of 5 km. This suggest a carbonate ramp with an average slope of 3° existed in the onshore Gippsland Basin during Oligocene and Miocene times. A hinge point at the clastic/carbonate interface allowed Oligo-Miocene subsidence and marine transgression into the onshore part of the basin. The events can be tied to the separation of Australia, Lord Howe Rise and Antarctica and the development of early glacial/interglacial eustatic cycles.

Abstract: The Oligocene to Recent sediments of the Seaspray Group in offshore Gippsland Basin consist of about 20,000 km 3 of marls and limestones deposited in temperate latitudes between 58° and 38°S. The Seaspray Group can be subdivided into four lithological units, using cores and sidewall cores from wells in the Central Deep region. Unit I, of Oligocene to Early Miocene age, overlies the Latrobe Group and is characterized by hemipelagic mudstones in the Central Deep. These sediments accumulated under deep marine conditions at accumulation rates ranging from <10 m/my at the base of the unit to 80 m/my at the top. Unit II marks a change in depositional processes near the Early/Middle Miocene boundary. Through most of the Central Deep, the sediments are interpreted as fine-grained, carbonate-rich turbidites, comprising bioclastic wackestones and packstones deposited on the continental slope. Al- lochems were partly derived from the adjacent shelf, and accumulation rates significantly increased to a maximum of 220 m/my. At the western end of the Central Deep, outer shelf sediments accumulated. Unit III represents most of Middle Miocene time. The base of this unit coincides with major sea-level falls which initiated submarine canyon- cutting. Slope sediments infill most of these channels and are characteristically wackestones and packstones with very abundant bioclastic debris. Closer to shore the sediments become coarse-grained, porous, quartzose bioclastic packstones and grainstones, deposited probably on a high-energy shelf. Sedimentation rates were very rapid, peaking at 250 m/my. The Late Miocene to Recent Unit IV represents open shelf sedimentation and consists of coarse-grained highly fossiliferous wackestones and packstones. Sedimentation rates fall to under 100 m/my over most of the basin, although higher accumulation rates occur at the shelf edge. Initiation of carbonate deposition in the basin appears to be related to the establishment of deep ocean currents south of Australia. Maximum Middle Miocene accumulation rates may reflect the presence of the Subtropical Convergence at the same latitude as the Gippsland Basin, aided by a general increase in surface productivity in the Pacific Ocean at the time.