(Table 1) CaCO3, terrigenous matter and Corg calculations from DSDP Hole 75-532B

Samples taken at 10 cm intervals from DSDP Core 532B-17 contain variations in carbonate, opal, organic carbon, and terrigenous components that correlate with light-dark cycles in sediment color. The core site, at 1300 m water depth, is well above the CCD, yet the color variations appear to result largely from cyclical fluctuations in carbonate dissolution, which was greater during glacial periods. Higher concentrations of organic carbon and of terrigenous sediment components correlate with enhanced carbonate dissolution, but opal concentrations inversely correlate and suggest that biological productivity at this site diminished during glacial periods. A complicated glacial-interglacial picture emerges from the data. In interglacial times, upwelling associated with the Benguela Current produced abundant opaline material, organic matter was fairly well preserved, and carbonate was only moderately dissolved. In glacial times, the upwelling core shifted as sea level fell and winds intensified. Productivity in the waters over Site 532 decreased, but lateral supply of oxidizable organic matter enhanced carbonate dissolution, giving rise to light-dark cycles in these sediments.

Jurassic sedimentation history at DSDP Hole 76-534A

Site 534 reflects a complex interplay of global, basinal, and local influences on sedimentation during the Callovian and Late Jurassic. Rifting and rapid subsidence of the continental margins of the North Atlantic-Tethys seaway occurred during the late Early Jurassic (Sinemurian-Pliensbachian), but rapid spreading between the North American margin (Blake Spur Ridge and magnetic lineation) and the northwest African margin did not commence until the Bathonian or earliest Callovian. Site 534, drilled on marine magnetic anomaly "M-28" of Bryan et al. (1980), was initially about 150 km from either continental margin. The ?middle Callovian basal sediments are dusky red silty marl. Callovian transgression led to active carbonate platforms on the margin, recorded at Site 534 as a rise in the CCD (carbonate compensation depth), then arrival of lime-rich turbidites from the Blake Plateau platform across the Blake Spur Ridge. The host pelagic sediment is greenish black, organic-rich, radiolarian-rich, silty claystone. Hydrothermal activity on the nearby spreading ridge enriched this lower unit in metals. In the Oxfordian, the input of terrestrial silt rapidly diminished; radiolarians or other bioclasts were not preserved. The dark variegated claystone has fine-grained marl and reddish claystone turbidite beds. The late Callovian-Oxfordian Western Tethys has radiolarian chert deposition, marine hiatuses, or organic-rich sediments. The Kimmeridgian and Tithonian had a stable or receding sea level. Near the end of the Jurassic many of the carbonate platforms of the margins were buried beneath prograding fan or alluvial deposits. Carbonate deposition shifted to the deep sea. Site 534 records the deepening of the CCD and ACD (aragonite compensation depth) during the Kimmeridgian and early Tithonian, then a rise of the ACD in the middle Tithonian. Similar trends occurred throughout the Western Tethys-Atlantic. High nannofossil productivity of the seaway led to deposition of very widespread white micritic limestone in the late Tithonian-Berriasian. The underlying sediment had a slower deposition rate of carbonate, therefore its higher clay and associated Fe content produced a red marl. A short sea-level incursion occurred on the Atlantic margins during the Kimmeridgian and is reflected in the Site 534 greenish gray marl unit by numerous turbidite beds of shallow-water carbonates.

Cretaceous calcareous nannofossils of ODP Leg 103 holes

Ocean Drilling Program Leg 103 recovered Lower Cretaceous sediments from the Galicia margin off the coast of Iberia. The high diversity and abundance of assemblages makes this excellent material for the study of Early Cretaceous calcareous nannofossils. With the exception of a hiatus between the upper Hauterivian and lower Barremian, nannofossil distributions form a continuous composite section from the lower Valanginian to lower Cenomanian sediments recovered at the four sites. The sedimentation history of this rifted continental margin is complex, and careful examination of the nannofossil content and lithology is necessary in order to obtain optimum biostratigraphic resolution. The Lower Cretaceous sequence consists of a lower Valanginian calpionellid marlstone overlain by terrigenous sandstone turbidites deposited in the Valanginian and Hauterivian during initial rifting of this part of the margin. Interbedded calcareous marl and claystone microturbidites overlie the sandstone turbidites. Rifting processes culminated in the late Aptian-early Albian, resulting in the deposition of a calcareous, clastic turbidite sequence. The subsequent deposition of dark carbonaceous claystones (black shales) represents the beginning of seafloor spreading, as the margin continued to subside to depths near or below the CCD. The diversity, abundance, and preservation of nannofossils within these varied lithologies differ, and an attempt to distinguish between near shore and open-marine assemblages is made. Genera used for this purpose include Nannoconus, Micrantholithus, Pickelhaube, and Lithraphidites. In this study, six new species and one new subspecies are described and documented. Ranges of other species are extended, and an attempt is made to clarify existing, yet poorly understood, taxonomic concepts. A technique in which a single specimen is viewed with both light and scanning electron microscopes was used extensively to aid in this task. In addition, further subdivisions of the Sissingh (1977) zonation are suggested in order to increase biostratigraphic resolution.

Carbon cycle change in the Eocene

The transition from the extreme global warmth of the early Eocene 'greenhouse' climate ~55 million years ago to the present glaciated state is one of the most prominent changes in Earth's climatic evolution. It is widely accepted that large ice sheets first appeared on Antarctica ~34 million years ago, coincident with decreasing atmospheric carbon dioxide concentrations and a deepening of the calcite compensation depth in the world's oceans, and that glaciation in the Northern Hemisphere began much later, between 10 and 6 million years ago. Here we present records of sediment and foraminiferal geochemistry covering the greenhouse-icehouse climate transition. We report evidence for synchronous deepening and subsequent oscillations in the calcite compensation depth in the tropical Pacific and South Atlantic oceans from ~42 million years ago, with a permanent deepening 34 million years ago. The most prominent variations in the calcite compensation depth coincide with changes in seawater oxygen isotope ratios of up to 1.5 per mil, suggesting a lowering of global sea level through significant storage of ice in both hemispheres by at least 100 to 125 metres. Variations in benthic carbon isotope ratios of up to ~1.4 per mil occurred at the same time, indicating large changes in carbon cycling. We suggest that the greenhouse-icehouse transition was closely coupled to the evolution of atmospheric carbon dioxide, and that negative carbon cycle feedbacks may have prevented the permanent establishment of large ice sheets earlier than 34 million years ago.

Documentation of sediment cores from the Great Meteor Seamount, North Atlantic

Sedimentological and biostratigraphic investigations of 15 cores (total length: 88 m) from the vicinity of Great Meteor seamount (about 30° N, 28° W) showed that the calcareous ooze are asymmetrically distributed around the seamount and vertically differentiated into two intervals. East and west of the seampunt, the upper "A"-interval is characterized by yellowish-brown sediment colors and bioturbation; ash layers and diatoms are restricted to the eastern cores. On both seamount flanks, the sediment of the lower "B"-interval are white and very rich in CaCO3 with a major fine silt (2-16 µ) mode (mainly coccoliths). Lamination, manganese micronodules, Tertiary foraminifera and discoasters, and small limestone and basalt fragments are typical of the "B"-interval of the eastern cores only. The sediments contain abundant displaced material which was reworked from the upper parts of the seamount. The sedimentation around the seamount is strongly influenced by the kind of displaced material and the intensity of its differentiated dispersal: the sedimentation rates are generally higher on the east than on the west flank /e.g. in "B": 0.9 cm/1000 y in the W; 3.1 cm/1000 y in the E), and lower for the "A" than for the "B"-interval. The lamination is explained by the combination of increased sedimentation rates with a strong input of material poor in organic carbon producing a hostile environment for benthic life. The CaCO3 content of the core is highly influenced by the proportion of displaced bigenous carbonate material (mainly coccoliths). The genuine in-situ conditions of the dissolution facies are only reflected by the minimum CaCO3 values of the cores (CCD = about 5,500 m; first bend in dissolution curve = 4,000 m; ACD = about 3,400 m). The preservation of the total foraminiferal association depends on the proportions of in-situ versus displaced specimens. In greater water depths (stronger dissolution), for example, the preservation can be improved by the admixture of relatively well preserved displaced foraminifera. Carbonate cementation and the formation of manganese micronodules are restricted to microenvironments with locally increased organic carbon contents (e.g. pellets; foraminifera). The ash layers consist of redeposited, silicic volcanic glass of trachytic composition and Mio-Pliocene age; possibly, they can be derived from the upper part of the seamount. Siliceous organisms, especially diatoms, are frequent close to the ash layers and probably also redeposited. Their preservation was favoured by the increase of the SiO2 content in the pore water caused by the silicic volcanic glass. The cores were biostraftsraphically subdivided with the aid of planktonic foraminifera and partly alsococcoliths. In most cases, the biostratigraphically determined cold- and warm sections could be correlated from core to core. Almost all cores do not penetrate the Late Pleistocene. All Tertiary fossils are reworked. In general, the warm/cold boundary W2/C2 corresponds with the lithostratigraphic A/B boundray. Benthonic foraminifera indicate the original site deposition of the displaced material (summit plateau or flanks of the seamount). The asymmetric distribution of the sediments around the seamount east and west of the NE-directed antarctic bottom current (AABW) is explained by the distortion of the streamlines by the Coriolis force; by this process the current velocity is increased west of the seamount and decreased east of it. The different proportion of displaced material within the "A" and "B" interval is explained by changes of the intensity of the oceanic circulation. At the time of "B" the flow of the AABW around the seamount was stronger than during "A"; this can be inferred from the presence of characteristic benthonic foraminifera. The increased oceanic circulation implies an enhanced differentiation of the current velocities, and by that, also of the sedimentation rates, and intensifies the winnowed sediment material was transported downslope by turbid layers into the deep-sea, incorporated into the current system of the AABW, and asymmetrically deposited around the seamount.

Miocene dissolution facies and microfacies at Northwest Atlantic Deep Sea Drilling Project Site 93-603

Depth fluctuations of the lysocline and calcite compensation depth (CCD) through time were investigated at Deep Sea Drilling Project Site 603, Leg 93. The CCD fell during the middle Miocene at the onset of the Western Boundary Undercurrent, correlated with seismic Horizon X. Subsequently deposited units show fluctuations of the dissolution curve. Major changes in dissolution facies correspond with lithologic boundaries.

Eocene to Quaternary planktonic foraminifers from the Northwest Pacific

Eocene through Quaternary planktonic foraminifers were identified in cores recovered during Leg 126. Turbidites and volcanic ash beds are intercalated with hemipelagic sediments. Preservation of foraminifers is variable, ranging from excellent to poor and appears to have been affected by fluctuations in the carbonate compensation depth (CCD), depth of burial, changes in bottom water temperature, current velocity, sediment accumulation rates and seafloor topography. Preservation of foraminifers in Quaternary sediments is generally good, however, species abundance varies by a factor of I05-106 and reflects dilution by volcanogenic as well as terrigenous constituents and cannot be used for paleoceanographic reconstructions. In pre-Quaternary deposits planktonic foraminiferal tests frequently exhibit dissolution effects; biostratigraphic zonation and placement of zonal boundaries is difficult owing to hiatuses, dissolution facies, extraneously deposited sediments, and discontinuous coring. The Eocene foraminiferal faunas include specimens of the Globorotalia cerroazulensis plexus, markers of Zone P16 as well as Globigerina senni and Globigerinatheka spp., which became extinct before the end of the Eocene. Six hiatuses and/or dissolution periods, probably reflecting global cooling events and/or changes in oceanic circulation patterns were recorded at Site 792. Recrystallized, poorly preserved, possibly reworked Eocene species (Globigerina senni and Globigerapsis sp.) were recorded in sediments at Site 793.

The Paleocene-Eocene boundary in ODP Leg 208 sites

The Paleocene-Eocene thermal maximum (PETM) has been attributed to the rapid release of ~2000 * 10**9 metric tons of carbon in the form of methane. In theory, oxidation and ocean absorption of this carbon should have lowerd deep-sea pH, thereby triggering a rapid (<10,000-year) shoaling of the calcite compensation depth (CCD), followed by gradual recovery. Here we present geochemical data from five new South Atlantic deep-sea sections that constrain the timing and extent of massive sea-floor carbonate dissolution coincident with the PETM. The sections, from between 2.7 and 4.8 kilometers water depth, are marked by a prominent clay layer, the character of which indicates that the CCD shoaled rapidly (<10,000 years) by more than 2 kilometers and recovered gradually (>100,000 years). These findings indicate that a large mass of carbon (>>2000 * 10**9 metric tons of carbon) dissolved in the ocean at the Paleocene-Eocene boundary and that permanent sequestration of this carbon occurred through silicate weathering feedback.

(Table 1) Sample levels of diatom and silicoflagellate datums at DSDP Holes 69-504 and 69-505

A standard biostratigraphic system, based upon diatom datum levels previously correlated to the paleomagnetic record, was applied to Deep Sea Drilling Project Sites 501/504 and 505. Sedimentation appears to have been constant at the three sites, averaging 50 m/m.y. at Sites 501/504 and 60 m/m.y. at Site 505. Calcium carbonate is rather poorly preserved at both sites, because of depth of water and, at Sites 501/504, alteration by diagenesis. Siliceous microfossils are common and moderately well preserved at the three sites; at Sites 501/504, diatoms disappear abruptly below the first occurrence of chert. The uppermost Miocene diatom assemblage occurs just above chert and is characterized by a strong dominance of Thalassionema and Thalassiothrix, which implies very high silica production during the latest Miocene; the chert probably is derived from a similar assemblage. In the earliest Pliocene, silica production appears to have decreased sharply; about 3 Ma, preservation of calcium carbonate also diminished, suggesting a shoaling of the CCD. At 2 Ma, there occurred a short interval of low production of both calcium carbonate and silica, which lasted into the earliest Pleistocene.

Plume-top altitude time-series during 2010 volcanic eruption of Eyjafjallajökull

The eruption of Eyjafjallajökull volcano in 2010 lasted for 39 days, 14 April-23 May. The eruption had two explosive phases separated by a phase with lava formation and reduced explosive activity. The height of the plume was monitored every 5 min with a C-band weather radar located in Keflavík International Airport, 155 km distance from the volcano. Furthermore, several web cameras were mounted with a view of the volcano, and their images saved every five seconds. Time series of the plume-top altitude were constructed from the radar observations and images from a web camera located in the village Hvolsvöllur at 34 km distance from the volcano. This paper presents the independent radar and web camera time series and performs cross validation.

Strontium isotope ratios of planktonic foraminifera from late Neogene sediment samples

A curve describing the variation of the strontium isotopic composition of seawater for the late Neogene (9 to 2 Ma) was constructed from 87Sr/86Sr analyses of marine carbonate in five Deep Sea Drilling Project (DSDP) sites: 502, 519, 588, 590, and 593. The strontium isotopic composition of the oceans increased between 9 and 2 Ma with several changes in slope. From 9 to 5.5 Ma, 87Sr/86Sr values were nearly constant at ~0.708925. Between 5.5 and 4.5 Ma, 87Sr/86Sr ratios increased monotonically at a rate of not, vert, similar 1 * 10**-4 per million years. The steep slope during this interval provides the potential for high resolution strontium isotope stratigraphy across the Miocene/Pliocene boundary. The rate of change of 87Sr/86Sr decreases to near zero again during the interval 4.5-2.5 Ma, and ratios average 0.709025. The relatively rapid increase of 87Sr/86Sr between 5.5 and 4.5 Ma must be related to changes in the flux or average 87Sr/86Sr ratios of the major inputs of Sr to the oceans. Quantitative modelling of these inputs suggests that the increase was most probably caused by an increase in the dissolved riverine flux of strontium to the oceans, an increase in the average 87Sr/86Sr composition of river water, or some combination of these parameters. Modelling of this period as a transient-state requires a pulse-like increase in the input of 87Sr to the oceans between 5.5 and 4.5 Ma. Alternatively, the 5.5-4.5 Ma period can be modelled as a simple transition from one steady-state to another if the oceanic residence time of strontium was eight times less than the currently accepted value of 4 Ma. During the time interval of steep 87Sr/86Sr increase, other geochemical and sedimentologic changes also occur including an increase in sediment accumulation rates, a drop in the calcite compensation depth (CCD), and a decrease in the delta13C of dissolved bicarbonate (i.e., "carbon shift"). The simplest mechanism to explain 87Sr/86Sr variation and these related geochemical changes is to invoke an increase in the dissolved chemical fluxes carried by rivers to the oceans. This, in turn, implies increased chemical denudation rates of the continents and shelves during the late Neogene. The increase in chemical weathering rates is attributed to increased exposure of the continents by eustatic regression, intensified glacial/interglacial cycles, and accelerated rates of global tectonism beginning at 5.5 Ma during the latest Miocene.

Eocene to Quaternary benthic foraminifers from the Izu-Bonin Arc

The benthic foraminifer fauna at Sumisu Rift Sites 790 and 791 indicates that a deep open-ocean (>2300 m) or a basin with open-ocean access existed between 1.1 and 0.7 Ma at the time of the initiation of rifting. The appearance of a low- to medium-oxygen fauna (1600-2300 m) between 0.7 and 0.5 Ma suggests that the open-ocean access may have been terminated at this time because of the development of volcanoes and rift flank uplifts around the basin. The occurrence of low-oxygen faunas at 0.03 Ma suggests a secondary closing of the basin. The lower bathyal benthic faunas from lower Pliocene sediments of rift margin Site 788 suggest about 0.6-1.6 km of total basement uplift. This uplift may have led to the formation of the major hiatus between 2.3 and <0.3 Ma. The faunal changes of benthic foraminifers at Sites 792 and 793 in the forearc basin document a shallowing water depth from below the carbonate compensation depth (CCD) (about 3.5 km) in the late early Oligocene to the present depths of 1800 and 2975 m, respectively. These data suggest about 1 km of total basement uplift in the inner part of the forearc basin (Site 792) and about 0.6 km total basement subsidence in the central part of the forearc basin (Site 793) since about 31 Ma. The former uplift led to a thinner sediment accumulation (800 m) and the latter subsidence to a thicker sediment accumulation (1400 m) at these sites. Faunal changes of benthic foraminifers observed in Sites 782 and 786 sequences drilled at the outer-arc high document a deepening water depth from 1.3 to 2.1 km in late Eocene to the present depth of about 3 km. These data suggest about 1.1-1.9 and 1.3-2.1 km of total basement subsidence at Sites 786 and 782, respectively. These results indicate total basement uplift in the inner part of the Bonin arc-trench system since late Oligocene and total basement subsidence in the outer part of the system since late Eocene. The last occurrence (LO) of Stilostomella spp. and Pleurostomella spp. and the first occurrence (F0) of Bulimina aculeata d'Orbigny occurred consistently at 0.7 Ma at all three arc proximal sites (790,791, and 792). This fact is taken to suggest a change of water mass, from one originating from the central part of the ocean to that originating from ocean-margin areas at that time.

Accumulation rates, carbon composition and Eocene carbonate compensation depths of ODP Sites 199-1218 and 199-1219

CaCO3, Corg, and biogenic SiO2 were measured in Eocene equatorial Pacific sediments from Sites 1218 and 1219, and bulk oxygen and carbon isotopes were measured on selected intervals from Site 1219. These data delineate a series of CaCO3 events that first appeared at ~48 Ma and continued to the Eocene/Oligocene boundary. Each event lasted 1-2 m.y. and is separated from the next by a low CaCO3 interval of a similar time span. The largest of these carbonate accumulation events (CAE-3) is in Magnetochron 18. It began at ~42.2 Ma, lasted until ~40.3 Ma, and was marked by higher than average productivity. The end of CAE-3 was abrupt and was associated with a large-scale carbon transfer to the oceans prior to warming of high-latitude regions. Changes in carbonate compensation depth associated with CAE excursions were small in the early part of the middle Eocene but increased to as much as 800 m by the late middle Eocene before decreasing into the late Eocene. Oxygen isotope data indicate that the carbonate events are associated with cooling conditions and may mark small glaciations in the Eocene.

Sedimentary and subsidence history of ODP Sites 135-840 and 135-841

Sedimentary sections recovered from the Tonga platform and forearc during Ocean Drilling Program Leg 135 provide a record of the sedimentary evolution of the active margin of the Indo-Australian Plate from late Eocene time to the Present. Facies analyses of the sediments, coupled with interpretations of downhole Formation MicroScanner logs, allow the complete sedimentary and subsidence history of each site to be reconstructed. After taking into account the water depths in which the sediments were deposited and their subsequent compaction, the forearc region of the Tofua Arc (Site 841) can be seen to have experienced an initial period of tectonic subsidence dating from 35.5 Ma. Subsidence has probably been gradual since that time, with possible phases of accelerated subsidence, starting at 16.2 and 10.0 Ma. The Tonga Platform (Site 840) records only the last 7.0 Ma of arc evolution. However, the increased accuracy of paleowater depth determinations possible with shallow-water platform sediments allows the resolution of a distinct increase in subsidence rates at 5.30 Ma. Thus, sedimentology and subsidence analyses show the existence of at least two, and possibly four, separate subsidence events in the forearc region. Subsidence dating from 35.5 Ma is linked to rifting of the South Fiji Basin. Any subsidence dating from 16.2 Ma at Site 841 does not correlate with another known tectonic event and is perhaps linked to localized extensional faulting related to slab roll back during steady-state subduction. Subsidence from 10.0 Ma coincides with the breakup of the early Tertiary Vitiaz Arc because of the subduction polarity reversal in the New Hebrides and the subsequent readjustment of the plate boundary geometry. More recently, rapid subsidence and deposition of a upward-fining cycle from 5.30 Ma to the Present at Site 840 is thought to relate to rifting of the Lau Basin. Sedimentation is principally controlled by tectonic activity, with variations in eustatic sea level playing a significant, but subordinate role. Subduction of the Louisville Seamount Chain seems to have disrupted the forearc region locally, although it had only a modest effect on the subsidence history and sedimentation of the Tonga Platform as a whole.

Composite of coastal seagrass meadows in Queensland, Australia - November 1984 to June 2010

Approximately 18,400 km**2 of seagrass habitat has been mapped within the coastal waters (<15 m) of Queensland (Australia) between November 1984 and June 2010. The total seagrass meadow distribution was calculated by merging maps from 115 separate mapping surveys (varying locations and dates). Due to tropical seagrass dynamism, meadow distribution can change seasonally and between years, and as a consequence, the composite represents the maximum area of seabed where seagrass has been observed/recorded. Mapping survey methodologies followed standardised global seagrass research methods (McKenzie et al. 2001) where the presence of seagrass was determined from in situ visual assessment of the seabed by either divers or drop cameras at GPS marked positions. Seagrass meadow boundaries were determined based on the positions of survey sites and the presence of seagrass, coupled with depth contours and remote sensing (e.g. aerial photography) where available. The merged meadow boundary accuracy was dependent on the original survey maps and varied from 10-100 m. The resulting composite seagrass distribution was saved as an ArcMap polygon shapefile, and projected to Geocentric Datum of Australia GDA94.