(Table 2) Aragonite, high and low magnesium calcite, major elements, bioclast and planktic foraminifera from ODP Hole 133-817A

Investigation of the Middle Miocene-Pleistocene succession in cores at ODP Site 817A (Leg 133), drilled on the slope south of the Queensland Plateau, identified the various material fluxes contributing to sedimentation and has determined thereby the paleogeographic events which occurred close to the studied area and influenced these fluxes. To determine proportions of platform origin and of plankton origin of carbonate mud, two reference sediments were collected: (1) back-reef carbonate mud from the Young Reef area (Great Barrier Reef); and (2) Late Miocene chalk from the Loyalty Basin, off New Caledonia. Through their biofacies and mineralogical and geochemical characters, these reference sediments were used to distinguish the proportions of platform and basin components in carbonate muds of 25 core samples from Hole 817A. Two "origin indexes" (i1 and i2) relate the proportion in platform and basin materials. The relative sedimentation rate is inferred from the high-frequency cycles determined by redox intervals in the cores. Bulk carbonate deposited in each core has been calculated in two ways with close results: (1) from calcimetric data available in the Leg 133 preliminary reports (Davies et al., 1991); and (2) from average magnetic susceptibility of cores, a value negatively correlated to the average carbonate content. Vertical changes in sedimentation rates, in carbonate content, in origin indexes and in "linear fluxes" document the evolution of sediment origins from platform carbonates, planktonic carbonates and insoluble material through time. These data are augmented with the variations in organic-matter content through the 817A succession. The observed changes and their interpretation are not modified by compaction, and are compatible with major paleogeographic events including drowning of the Queensland Plateau (Middle Miocene-Early Pliocene) and the renewal of shallow carbonate production, (1) during the Late Pliocene, and (2) from the Early Pleistocene. The birth and growth of the Great Barrier Reef is also recorded from 0.5 Ma by a strengthening of detrital carbonate deposition and possibly by a lack of clay minerals in the 4 upper cores, a response to trapping of terrigenous material behind this barrier. In addition, a maximum of biological silica production is displayed in the Middle Miocene. These changes constrain the time of events and the sequence-stratigraphy framework some components of which are transgression surface, maximum flooding surface and low-stand turbidites. Sedimentation rates and material fluxes show cycles lasting 1.75 Myr. Whatever their origin (climatic and/or eustatic) these cycles affected the planktonic production primarily. The changes also show that major carbonate variations in the deposits are due to a dilution effect by insoluble material (clay, biogenic silica and volcanic glasses) and that plankton productivity, controlling the major fraction of carbonate sedimentation, depends principally on terrigenous supplies, but also on deep-water upwelling. Accuracy of the method is reduced by redeposition, reworking, and probable occurrence of hiatuses.

(Table 1) Biostratigraphic datums of ODP Leg 133 sites

We use benthic foraminifers to reconstruct the Neogene paleobathymetric history of the Marion Plateau, Queensland Plateau, Townsville Trough, and Queensland Trough on the northeastern Australian margin (Ocean Drilling Program Leg 133). Western Queensland Plateau Site 811/825 (present depth, ~938 m) deepened from the neritic zone (0-200 m) to the upper bathyal zone (200-600 m) during the middle Miocene (~13-14 Ma), with further deepening into the middle bathyal zone (600-1000 m) occurring during the late Miocene (~7 Ma). A depth transect across the southern Queensland Plateau shows that deepening from the outer neritic zone (100-200 m) to the upper bathyal zone began during the latest Miocene (~6 Ma) at the deepest location (Site 813, present depth, 539.1 m), whereas the shallower Sites 812 and 814 (present depths, 461.6 and 520.4 m, respectively) deepened during the late Pliocene (~2.7 and ~2.9 Ma). At Marion Plateau Site 815 (present depth, 465.5 m), water depth increased during the late Miocene (~6.7 Ma) from the outer neritic to the upper bathyal zone. Nearby Site 816 (present water depth, 437.3 m) contains Pliocene upper bathyal assemblages that directly overlie middle Miocene shallow neritic deposits; the timing of the deepening is uncertain because of a late Miocene hiatus. On the northern slope of the Townsville Trough (Site 817, present depth, 1015.8 m), benthic foraminifers and sponge spicules indicate deepening from the lower upper bathyal (400-600 m) to the middle bathyal zone in the late Miocene (by ~6.8 Ma). Benthic foraminiferal faunas at nearby Site 818 (present water depth, 752.1 m) do not show evidence of paleobathymetric change; however, a late Pliocene (~2-3 Ma) increase in downslope transport may have been related to the drowning of the Queensland Plateau. Site 822 (present depth, 955.2 m), at the base of the Great Barrier Reef slope, deepened from the upper bathyal to the middle bathyal zone during the late Pliocene (by ~2.3 Ma). Queensland Trough Site 823 (present depth, 1638.4 m) deepened from the middle bathyal to the lower bathyal (1000-2000 m) zone during the late Miocene (~6.5 Ma). Benthic foraminiferal faunal changes at these Leg 133 sites indicate that rapid deepening occurred during the middle Miocene (~13-14 Ma), late Miocene (6-7 Ma), and late Pliocene (2-3 Ma) along the northeastern Australian margin.

Sea-surface paleotemperature reconstructions for the middle Miocene-Holocene of ODP Site 133-811 in the Coral Sea off northeast Australia

The derivation of a detailed sea-surface paleotemperature curve for the middle Miocene-Holocene (10-0 Ma) from ODP Site 811 on the Queensland Plateau, northeast Australia, has clarified the role of sea-surface temperature fluctuations as a control on the initiation and development of the extensive carbonate platforms of this region. This curve was derived from isotopic analyses of the planktonic foraminifer Globigerinoides ruber, and converted to temperature using the surface-water paleotemperature equation accounting for variations in global ice volume. The accuracy of these data were confirmed by derivation of paleotemperatures using the water column isotopic gradient (Delta delta18O), corrected for salinity and variations in seafloor water mass temperature. Results indicate that during this period surface-water temperatures were, on average, greater than the minimum required for tropical reef growth (20°C; Veron, 1986), with the exception of the late Miocene and earliest early Pliocene (10-4.9 Ma), when there were repeated intervals of temperatures between 18-20°C. Tropical reef growth on the Queensland Plateau was extensive from the early to early middle Miocene (~21-13 Ma), after which reef development began to decline. A lowstand near 11 Ma probably exposed shallower portions of the plateau; after re-immersion near 7 Ma, the areal extent of reef development was greatly reduced (~ 50%). Paleotemperature data from Site 811 indicate that decreased sea-surface temperatures were likely to have been instrumental in reducing the area of active reef growth on the Queensland Plateau. Reduced reefal growth rates continued until the late Pliocene or Quaternary, despite the increase of average sea-surface paleotemperatures to 22-23°C. Studies on modern corals show that when sea-surface temperatures are below ~24°C, as they were from the late Miocene to the Pleistocene off northeast Australia, corals are stressed and growth rates are greatly reduced. Consequently, when temperatures are in this range, corals have difficulty keeping pace with subsidence and changing environmental factors. In the late Pliocene, sedimentation rates increased due to increases in non-reefal carbonate production and falling sea levels. It was not until the mid-Quaternary (0.6-0.7 Ma) that sea-surface paleotemperatures increased above 24°C as a result of the formation of a western Coral Sea warm water pool. Because of age discrepancies, it is unclear exactly when an effective barrier developed on the central Great Barrier Reef; the formation of the warm water pool was likely to have either assisted the formation of this barrier and/or permitted increased coral growth rates. Fluctuations in sea-surface temperature can account for much of the observed spatial and temporal variations of reef growth and carbonate platform distribution off northeast Australia, and therefore we conclude that paleotemperature variations are a critical control on the development of carbonate platforms, and must be considered an important cause of ancient platform "drowning".

Cretaceous nannofossils of southeast France

The Aptian-lower Albian succession of the Vocontian Basin (SE France) consists of marine hemipelagic sediments including several black shale horizons. The latter are partly of regional and partly of global distribution. This sedimentary succession records the nannoplankton evolution of the Aptian-early Albian interval and thus provides an excellent opportunity to calibrate the calcareous nannofossil record with Tethyan ammonite and planktic foraminiferal biostratigraphy. The calcareous nannofossil biostratigraphy presented in this paper supports previous zonations, but it also provides a much higher resolution and thus improves the correlation of different black shale horizons on a supraregional scale. Up to 23 major (supraregionally significant) and minor (regionally significant) first and last occurrences of calcareous nannofossil taxa are recognized. Nannoconid abundances decrease rapidly in the upper Lower Aptian (nannoconid crisis I, NCI) and in the middle Upper Aptian (nannoconid crisis II, NCII). Both decreases correlate with carbonate-platform drowning events. The upper Lower Aptian interval above the NCI is characterized by high abundances of large specimens of Assipetra infracretacea and Rucinolithus terebrodentarius probably of supraregional significance. The uppermost Aptian-Lower Albian is characterized by high abundances of the calcareous nannoplankton taxon Repagulum parvidentatum, reflecting boreal influence on the Tethyan Realm. This suggests a temporary decrease in surface-water temperatures in the Vocontian Basin.

X-ray diffraction analysis, binocular component analysis and radiocarbon dating of sediment cores from the NW Iberian shelf system

Based on a well-established stratigraphic framework and 47 AMS-14C dated sediment cores, the distribution of facies types on the NW Iberian margin is analysed in response to the last deglacial sea-level rise, thus providing a case study on the sedimentary evolution of a high-energy, low-accumulation shelf system. Altogether, four main types of sedimentary facies are defined. (1) A gravel-dominated facies occurs mostly as time-transgressive ravinement beds, which initially developed as shoreface and storm deposits in shallow waters on the outer shelf during the last sea-level lowstand; (2) A widespread, time-transgressive mixed siliceous/biogenic-carbonaceous sand facies indicates areas of moderate hydrodynamic regimes, high contribution of reworked shelf material, and fluvial supply to the shelf; (3) A glaucony-containing sand facies in a stationary position on the outer shelf formed mostly during the last-glacial sea-level rise by reworking of older deposits as well as authigenic mineral formation; and (4) A mud facies is mostly restricted to confined Holocene fine-grained depocentres, which are located in mid-shelf position. The observed spatial and temporal distribution of these facies types on the high-energy, low-accumulation NW Iberian shelf was essentially controlled by the local interplay of sediment supply, shelf morphology, and strength of the hydrodynamic system. These patterns are in contrast to high-accumulation systems where extensive sediment supply is the dominant factor on the facies distribution. This study emphasises the importance of large-scale erosion and material recycling on the sedimentary buildup during the deglacial drowning of the shelf. The presence of a homogenous and up to 15-m thick transgressive cover above a lag horizon contradicts the common assumption of sparse and laterally confined sediment accumulation on high-energy shelf systems during deglacial sea-level rise. In contrast to this extensive sand cover, laterally very confined and maximal 4-m thin mud depocentres developed during the Holocene sea-level highstand. This restricted formation of fine-grained depocentres was related to the combination of: (1) frequently occurring high-energy hydrodynamic conditions; (2) low overall terrigenous input by the adjacent rivers; and (3) the large distance of the Galicia Mud Belt to its main sediment supplier.

Location and ages of terrestrial peatlands located on continental shelves and in coastal sediments

This synthesis dataset contains records of freshwater peat and lake sediments from continental shelves and coastal areas. Information included is site location (when available), thickness and description of terrestrial sediments as well as underlying and overlying sediments, dates (when available), and references.

Characterization of the defined MDC types and compilation of MDC initiation times (excel-file 19 kB)

Mud accumulates on continental shelves under a variety of environmental conditions and results in a diverse formation of mud depocenters (MDCs). Their three-dimensional architectures have been in the focus of several recent studies. Due to some terminological confusion concerning MDCs, the present study sets out to define eight individual MDC types in terms of surface sediment distribution and internal geometry. Under conditions of substantial sediment supply, prodeltas (distal zones off river deltas; triangular sheets), subaqueous deltas (disconnected from deltas by strong normal-to-shore currents; wedge-like clinoforms), and mud patches (scattered distribution) and mud blankets (widespread covers) are formed. Forced by hydrodynamic conditions, mud belts in the strict sense (detached from source; elongated bodies), and shallow-water contourite drifts (detached from source; growing normal to prevailing current direction; triangular clinoforms) develop. Controlled by local morphology, mud entrapments (in depressions, behind morphological steps) and mud wedges (triangular clinoforms growing in flow direction) are deposited. Shelf mud deposition took place (1) during early outer-shelf drowning (~14 ka), (2) after inner-shelf inundation to maximum flooding (9.5-6.5 ka), and (3) in sub-recent times (<2 ka). Subsequent expansion may be (1) concentric, in cases where the depocenter formed near the fluvial source, (2) uni-directional, extending along advective current transport paths, and (3) progradational, forming clinoforms that grow either parallel or normal to the bottom current direction. Classical mud belts may be initiated around defined nuclei, the remote sites of which are determined by seafloor morphology rather than the location of the source. From a stratigraphic perspective, mud depocenters coincide with sea-level highstand-related, shelf-wide condensed sections. They often show a conformable succession from transgressive to highstand systems tract stages.

Grain size distribution of the lagoonal deposits within the South Malé Atoll, Maldives, Indian Ocean

Seismic and multibeam data, as well as sediment samples were acquired in the South Malé Atoll in the Maldives archipelago in 2011 to unravel the stratigraphy and facies of the lagoonal deposits. Multichannel seismic lines show that the sedimentary succession locally reaches a maximum thickness of 15-20 m above an unconformity interpreted as the emersion surface which developed during the last glacial sea-level lowstand. Such depocenters are located in current-protected areas flanking the reef rim of the atoll or in infillings of karst dolinas. Much of the 50 m deep sea floor in the lagoon interior is current swept, and has no or very minor sediment cover. Erosive current moats line drowned patch reefs, whereas other areas are characterized by nondeposition. Karst sink holes, blue holes and karst valleys occur throughout the lagoon, from its rim to its center. Lagoonal sediments are mostly carbonate rubble and coarse-grained carbonate sands with frequent large benthic foraminifers, Halimeda flakes, red algal nodules, mollusks, bioclasts, and intraclasts, some of them glauconitic, as well as very minor ooids. Finer-grained deposits locally are deposited in current-protected areas behind elongated faros, i.e., small atolls which are part of the rim of South Malé Atoll. The South Malé Atoll is a current-flushed atoll, where water and sediment export with the open sea is facilitated by the multiple passes dissecting the atoll rim. With an elevated reef rim and tower-like reefs in the atoll interior it is an example of a leaky bucket atoll which shares characteristics of incipiently drowned carbonate banks or drowning sequences as known from the geological record.