Deeper Cores Research Articles

Tiny Teeth Fairy Tale

Background: “Obsessed by a fairy tale, we spend our lives searching for a magic door and a lost kingdom of peace.”- Eugene O’Neill I believe we love fairy tales because they are surprisingly relevant to real life. And in our deepest core, we know it. Fairy tales are extremely important stories with lessons that we remember all our lives. They are loved by absolutely everyone, because of the hidden deep meaning and lesson that each new story gives us. My article “Tiny Teeth Fairy Tale” is not an exception, but an addition to this statement. A review article emphasising the importance of teeth in a fairy tale format is presented to your attention. I believe that you will like it.

Unraveling extreme events from deep water cores of the south Caspian Sea

South Caspian Sea sub-basin, as the deepest part of the Caspian Sea (CS) remained as land-locked basin even during extreme sea level fall that most part of the CS desiccated. Therefore, bottom sediments of the south CS continuously recorded many past intra-basinal and extra-basinal events. In the current research we have used four short cores (<2 m) from deep waters of the south CS (300–800 m) to unravel past extreme events based on the sedimentological and geochemical analysis. Presence of coarse grained sediment laminae in the deep basin represents frequent slope failure that transported materials from lower shelf. XRF core scanning along with Magnetic Susceptibility measurements showed multiple changes along the cores. Elements incorporating in biological activities (Ca, Sr) have sharp contrast with lithogenic elements (Zr, Ti) mainly during rapid environmental changes. The deepest core has significant changes in the basal part that covers certainly Younger Dryas or even older sediments. Material influx into the deep basin of the south CS demonstrate both basinal extreme events as turbidite and mass wasting as well as catchment basin events e.g. river avulsion that caused changes in sediment properties.

Scientific drilling of sediments at Darwin Crater, Tasmania

Abstract. A 70 m long continental sediment record was recovered at Darwin Crater in western Tasmania, Australia. The sediment succession includes a pre-lake silty sand deposit overlain by lacustrine silts that have accumulated in the ∼816 ka meteorite impact crater. A total of 160 m of overlapping sediment cores were drilled from three closely spaced holes. Here we report on the drilling operations at Darwin Crater and present the first results from petrophysical whole core logging, lithological core description, and multi-proxy pilot analysis of core end samples. The multi-proxy dataset includes spectrophotometry, grain size, natural gamma rays, paleo- and rock magnetism, loss on ignition, and pollen analyses. The results provide clear signatures of alternating, distinctly different lithologies likely representing glacial and interglacial sediment facies. Initial paleomagnetic analysis indicate normal magnetic polarity in the deepest core at Hole B. If acquired at the time of deposition, this result indicates that the sediment 1 m below commencement of lacustrine deposition post-date the Matuyama–Brunhes geomagnetic reversal ∼773 ka.

Is this America? Unfinished business with the U.S. national imaginary, religion and violence

AbstractThis article first proposes definitions and raises questions about what it means to be a nation. I then analyze the national imaginary of the United States, and suggest that at its deepest core we find “substitute ultimates” regarding America's sacrificial war‐culture. This cultural violence perpetuates destructive consequences, including the phenomena of “U.S. war‐culture,” and “moral injury” among military servicemembers and veterans. But widespread legitimation of the imaginary largely inhibits citizens from awareness about their own reality. Lastly, I inquire about the role of prophetic public theology to address nationalism, and engage in a thought experiment with an imagined community of diverse partners.

National Gas Hydrate Program Expedition 01 offshore India; gas hydrate systems as revealed by hydrocarbon gas geochemistry

Abstract The National Gas Hydrate Program Expedition 01 (NGHP-01) targeted gas hydrate accumulations offshore of the Indian Peninsula and along the Andaman convergent margin. The primary objectives of coring were to understand the geologic and geochemical controls on the accumulation of methane hydrate and their linkages to underlying petroleum systems. Four areas were investigated: 1) the Kerala-Konkan Basin in the eastern Arabian Sea, 2) the Mahanadi and 3) Krishna-Godavari Basins in the western Bay of Bengal, and 4) the Andaman forearc Basin in the Andaman Sea. Upward flux of methane at three of the four of the sites cored during NGHP-01 is apparent from the presence of seafloor mounds, seismic evidence for upward gas migration, shallow sub-seafloor geochemical evidence of methane oxidation, and near-seafloor gas composition that resembles gas from depth. The Kerala-Konkan Basin well contained only CO2 with no detectable hydrocarbons suggesting there is no gas hydrate system here. Gas and gas hydrate from the Krishna-Godavari Basin is mainly microbial methane with δ13C values ranging from −58.9 to −78.9‰, with small contributions from microbial ethane (−52.1‰) and CO2. Gas from the Mahanadi Basin was mainly methane with lower concentrations of C2-C5 hydrocarbons (C1/C2 ratios typically >1000) and CO2. Carbon isotopic compositions that ranged from −70.7 to −86.6‰ for methane and −62.9 to −63.7‰ for ethane are consistent with a microbial gas source; however deeper cores contained higher molecular weight hydrocarbon gases suggesting a small contribution from a thermogenic gas source. Gas composition in the Andaman Basin was mainly methane with lower concentrations of ethane to isopentane and CO2, C1/C2 ratios were mainly >1000 although deeper samples were

Pleistocene to Holocene benthic foraminiferal assemblages from the Peruvian continental margin

The benthic foraminiferal inventory and their assemblage composition was documented along five sediment cores from the Peruvian margin between 3°S and 18°S at water depths of 500 to 1250 m, covering the lower boundary of today’s Oxygen Minimum Zone (OMZ). Emphasis was given to certain time intervals during the last 22 thousand years when different climatic and oceanographic conditions prevailed than today. In total three agglutinated and 186 calcareous species were recognised. Bolivina costata, Bolivinita minuta, Cassidulina delicata and Epistominella exigua were most abundant. The foraminiferal distributions revealed a marked change in assemblage composition particularly at the deeper cores during and after the deglaciation. The diversity declined and Bolivina species became dominant. These changes took place gradually over several millennia, and high-frequency fluctuations were not recorded. This pattern provides evidence for rather stable ecological conditions and sluggish changes in bottom water circulation during the last deglaciation.

Paleomagnetic record determined in cores from deep research wells in the Quaternary Santa Clara basin, California

Paleomagnetic study of cores from six deep wells provides an independent temporal framework for much of the alluvial stratigraphy of the Quaternary basin beneath the Santa Clara Valley. This stratigraphy consists of 8 upward-fining cycles in the upper 300 m of section and an underlying 150 m or more of largely fine-grained sediment. The eight cycles have been correlated with the marine oxygen isotope record, thus providing one means of dating the section. The section has also proved to contain a rich paleomagnetic record despite the intermittent sedimentation characteristic of alluvial environments. Each well was designed to reach a depth of ∼300 m, although 2 were terminated at shallower depth where bedrock was encountered and one (GUAD) was deepened to bedrock at 407.2 m. Cores were taken at intermittent intervals in most of the wells, composing ∼20%–25% of their depths. In GUAD an attempt was made to core the entire upper 300 m, with core recovery of 201.8 m (67%). The paleomagnetic framework ranges from the 32 ka Mono Lake excursion near the top of the second sedimentary cycle to below the 780 ka Brunhes- Matuyama geomagnetic reversal beneath the eighth cycle. These ages nicely fit those assigned to the section based on correlation with the marine oxygen isotope record. Several episodes of anomalous magnetic inclinations were also found within the cyclic section in some of the wells. Some of the episodes of anomalous magnetic inclinations are only separated by short normal intervals in a pattern similar to that described for some well-documented excursions. We consider that a geomagnetic excursion was likely only if the anomalous inclinations were found at approximately the same stratigraphic position in more than one drill hole. A deeper time constraint is provided by the upper boundary (990 ka) of the Jaramillo Normal Polarity Subchron recognized at a depth of 302 m in one deeply penetrating well (GUAD). Approximately 100 m of normal Jaramillo section is evident below that in wells GUAD and EVGR. The reversal that we identify as the 780 ka Brunhes-Matuyama boundary, found at depths of 291–303 m in three wells, indicates an average rate of deposition in this upper section of ∼37 cm/k.y. In GUAD, the top of the underlying normally polarized section, which we assign to the upper part of the Jaramillo Normal Polarity Subchron, was found between 301.8 and 304.5 m. The resultant 10 m of reversed polarity section above the Jaramillo seems anomalously short for this 210 k.y. part of the Matuyama Chron, during which several times that thickness of section probably should have accumulated. This observation indicates that a significant unconformity should be present in that short section between the Jaramillo Subchron and the Brunhes-Matuyama boundary. Deeper cores in two wells (GUAD and EVGR) all have normal polarity and seem to represent much of the Jaramillo Subchron, although no base for that subchron was found. The resultant minimum rate of sedimentation for this lower section beneath the unconformity is 170 cm/k.y. The Mono Lake (ca. 32 ka), Pringle Falls (ca. 210 ka), and Big Lost (ca. 565 ka) geomagnetic excursions all seem to be represented in the Santa Clara Valley wells. Possible correlations to the Laschamp (ca. 40 ka) and Blake (ca. 110 ka) excursions are also noted. Three additional excursions that have apparently not been previously reported from western North America occur within cycle 6 (between 536 and 433 ka), near the base of cycle 5 (after 433 ka), and near the middle of cycle 2 (before ca. 75 ka).

Uranium isotopes and dissolved organic carbon in loess permafrost: Modeling the age of ancient ice

The residence time of ice in permafrost is an indicator of past climate history, and of the resilience and vulnerability of high-latitude ecosystems to global change. Development of geochemical indicators of ground-ice residence times in permafrost will advance understanding of the circumstances and evidence of permafrost formation, preservation, and thaw in response to climate warming and other disturbance. We used uranium isotopes to evaluate the residence time of segregated ground ice from ice-rich loess permafrost cores in central Alaska. Activity ratios of 234U vs. 238U (234U/238U) in water from thawed core sections ranged between 1.163 and 1.904 due to contact of ice and associated liquid water with mineral surfaces over time. Measured (234U/238U) values in ground ice showed an overall increase with depth in a series of five neighboring cores up to 21m deep. This is consistent with increasing residence time of ice with depth as a result of accumulation of loess over time, as well as characteristic ice morphologies, high segregated ice content, and wedge ice, all of which support an interpretation of syngenetic permafrost formation associated with loess deposition. At the same time, stratigraphic evidence indicates some past sediment redistribution and possibly shallow thaw among cores, with local mixing of aged thaw waters. Using measures of surface area and a leaching experiment to determine U distribution, a geometric model of (234U/238U) evolution suggests mean ages of up to ∼200kyBP in the deepest core, with estimated uncertainties of up to an order of magnitude. Evidence of secondary coatings on loess grains with elevated (234U/238U) values and U concentrations suggests that refinement of the geometric model to account for weathering processes is needed to reduce uncertainty. We suggest that in this area of deep ice-rich loess permafrost, ice bodies have been preserved from the last glacial period (10–100kyBP), despite subsequent fluctuations in climate, fire disturbance and vegetation. Radiocarbon (14C) analysis of dissolved organic carbon (DOC) in thaw waters supports ages greater than ∼40kyBP below 10m. DOC concentrations in thaw waters increased with depth to maxima of >1000ppm, despite little change in ice content or cryostructures. These relations suggest time-dependent production of old DOC that will be released upon permafrost thaw at a rate that is mediated by sediment transport, among other factors.

Observed water current and transport through Qiongzhou Strait during August 2010

The velocity structure of the residual current across an entire section of the Qiongzhou Strait (QS) in summer is presented for the first time. Shipboard Acoustic Doppler Current Profile measurements, from the mid-region of the QS (110.18°E), were collected on 1–4 August 2010. The diurnal tidal currents had their maximum amplitudes between 4.24 and 20.24 m. Their amplitude along the major axis ranged from approximately 0.55 m/s in the middle part of the strait (20.15°N) to 0.84 m/s in the north part of the strait (20.20°N). Both anticlockwise and clockwise tidal current rotations exist in the QS. During the observation period (neap tide), a significant westward residual current occupied almost the entire study section. Two velocity cores of westward current were observed at the northern part and near the deepest trough, although an eastward current appeared in the middle part of the transect. The deepest core was located near 62 m at 20.13°N, with a maximum velocity of −0.34 m/s. The shallower core was located at approximately 16 m at 20.20°N, with a maximum velocity of −0.33 m/s. The estimated total volume of water transported through the QS was −0.16 Sv. This value is an important boundary condition, applicable to numerical models studying coastal ocean circulation in the northwestern South China Sea.

Vertical oxygen minimum zone oscillations since 20 ka in Santa Barbara Basin: A benthic foraminiferal community perspective

[1] Here we present a history of deoxygenation of upper intermediate waters during the last deglaciation from Santa Barbara Basin (SBB), based on quantitative analyses of benthic foraminiferal assemblages, from a new shallow piston core above basin sill depth (MV0811-15JC, 418m), and previously described sequences in the deeper basin (MD02-2504, 481m and MD02-2503, 570m). We document a 152m depth transect of benthic foraminiferal assemblages to extract changing community structure (density, diversity, and evenness) and improve paleoenvironmental interpretation of late Quaternary vertical oscillations in the upper boundary of the oxygen minimum zone (OMZ). Close interaction between changes in open margin OMZ and that of the restricted SBB is documented using these quantitative techniques. MV0811-15JC, while being unlaminated, contains strongly hypoxic foraminiferal assemblages (including species Bolivina tumida and Nonionella stella), coeval with preserved sediment laminations in the deeper cores. Last Glacial Maximum (LGM) assemblages across this transect contained oxic fauna and high diversity. At 14.7ka, glacial termination IA, hypoxic benthic fauna appeared across the transect, recording hypoxic waters (<0.5mlL 1 ) <300m from the ocean surface. Bolling/Allerod (B/A) assemblages uniquely stand out in the record, exhibited by low density, diversity, and evenness, and taxonomic composition reflecting extreme and stressful hypoxia and methane-rich environments. Younger Dryas assemblages were diverse and composed of oxic fauna, similar to LGM assemblages. Termination IB initiated another deoxygenation shift, followed by OMZ-associated faunal and density patterns. This analysis strengthens the quantitative assessment of oxygen concentrations involved in deglacial OMZ change and reveals the unexpected, remarkable shallowness of OMZ influence during the B/A.

Anthropogenic and Authigenic Uranium in Marine Sediments of the Central Gulf of California Adjacent to the Santa Rosalía Mining Region

To investigate the causes of uranium (U) enrichment in marine sediments in the eastern sector of the Gulf of California, surface sediments and sediment cores were collected adjacent to the Santa Rosalía copper mining region in the Baja California peninsula. Three coastal sediment cores were found to display high concentrations of U (from 54.2 ± 7.3 mg kg(-1) to 110 ± 13 mg kg(-1)) exceeding those found in the deeper cores (1.36 ± 0.26 mg kg(-1) in the Guaymas Basin to 9.31 ± 3.03 mg kg(-1) in the SR63 core from the suboxic zone). The contribution of non-lithogenic U (estimated using scandium to normalize) to the total U content in sediments of three coastal cores varied from 97.2 ± 0.4 % to 98.82 % versus 49.8 ± 3 % (Guaymas Basin) to 84.2 ± 8.2 % (SR62 core) in the deeper cores. The U content record in a lead-210 ((210)Pb)-dated core had two peaks (in 1923 and 1967) corresponding to the history of ancient mining and smelting activities in Santa Rosalía.

Building on previous OSL dating techniques for gypsum: A case study from Salt Basin playa, New Mexico and Texas

The long term stability and reliability of the luminescence signal for gypsum has not been well documented or systematically measured until just recently. A review of the current literature for luminescence dating of gypsum is compiled here along with original efforts at dating an intact and in-situ bed of selenite gypsum at Salt Basin Playa, New Mexico and Texas. This effort differs from other documented luminescence dating efforts because the gypsum is not powdery or redistributed from its original growth patterns within the playa basin but is instead of a crystalline form. Sixteen ages from eight cores were ultimately produced with seven of the ages coming from rare detrital quartz encased in or with the gypsum crystals while the remaining ages are from the crystalline gypsum. As far as can be ascertained, the quartz was measured separately from the gypsum and no contaminants were noted in any of the aliquots. Some basic and preliminary tests of signal stability were measured and found to be mitigated by lessening of pre-heat protocols. Ages ranged from 8 ka to 10 ka in the shallow cores and 16 ka to 22 ka in the deeper cores. These ages will be useful in determining rates of gypsum growth within a sequence of evaporates which, in turn, will help to better document historic rates of evaporation and thus estimate, with more precision, the corresponding annual evaporation rates.

Spiritual Narratives on Equality

Personal therapy has not made the world a more equal place as many of us hoped it would in the 20th century. I argue here that we also need a spiritual narrative. Equality in many forms has been central to the aims of most radical progressive social movements. The intention is often also to be non-hierarchical in their organization, thinking and lifestyles. However, few have succeeded for long. Many psychotherapists such as Wilhelm Reich have studied this problem and suggested solutions such as dismantling psychological defences and living from the core of ourselves. But people often mistook the idea of ‘core’ as merely acting from our impulses, leading, for example, to the shadow sides of ‘60s ‘freedoms’. Perhaps the deepest core is actually where we attune to what Engels called the spirit in nature. Today the spiritual dimension is returning into the world of psychotherapy and politics from the surprising source of postmodernism. But exactly what kind of spirituality might be emerging to co-create with the new equality politics in shaping the 21st century? In this article inspired by the ideas of postmodernists such as Julia Kristeva and mystics such as Lao Tzu, I outline some ideas that may be important. One of these is the concept of ‘jouissance’, which is an embodied ecstatic joy. Fluidity, flow, rhythm, dance, nomadic wandering, alternation and eternal return may also be features of the new spirituality. Copyright © 2011 John Wiley & Sons, Ltd.

‘Who touched my clothes?’: The Healing of the Woman with the Haemorrhage (Mark 5: 24–34; Luke 8: 42–48 and Matthew 9: 19–22) in Early Medieval Visual Culture

within the biblical miraculous healings, the story of the Haemorrhoissa (the haemorrhaging woman) has a special place (Mark 5: 24–34; Luke 8: 42–48 and Matthew 9: 19–22). The healing takes place th...

Late Quaternary siliciclastic/carbonate sedimentation model for the Capricorn Channel, southern Great Barrier Reef province, Australia

A model is presented for hemipelagic siliciclastic and carbonate sedimentation during the last glacial–interglacial cycle in the Capricorn Channel, southern Great Barrier Reef (GBR). Stable isotope ratios, grainsize, carbonate content and mineralogy were analysed for seven cores in a depth transect from 166 to 2892 m below sea level (mbsl). Results show variations in the flux of terrigenous, neritic and pelagic sediments to the continental slope over the last sea level cycle. During the glacial lowstand terrigenous sediment influenced all the cores down to 2000 mbsl. The percentages of quartz and feldspar in the cores decreased with water depth, while the percentage of clay increased. X-ray diffraction analysis of the glacial lowstand clay mineralogy suggests that the siliciclastic sediment was primarily sourced from the Fitzroy River, which debouched directly into the northwest sector of the Capricorn Channel at this time. The cores also show a decrease in pelagic calcite and an increase in aragonite and high magnesium calcite (HMC) during the glacial. The influx of HMC and aragonite is most likely from reworking of coral reefs exposed on the continental shelf during the glacial, and also from HMC ooids precipitated at the head of the Capricorn Channel at this time. Mass accumulation rates (MARs) are high (13.5 g cm − 3 kyr − 1 ) during the glacial and peak at ~ 20 g cm − 3 kyr − 1 in the early transgression (16–14 ka BP). MARs then decline with further sea level rise as the Fitzroy River mouth retreats from the edge of the continental shelf after 13.5 ka BP. MARs remain low (4 cm − 3 kyr − 1 ) throughout the Holocene highstand. Data for the Holocene highstand indicate there is a reduction in siliciclastic influx to the Capricorn Channel with little quartz and feldspar below 350 mbsl. However, fine-grained fluvial sediments, presumably from the Fitzroy River, were still accumulating on the mid slope down to 2000 mbsl. The proportion of pelagic calcite in the core tops increases with water depth, while HMC decreases, and is present only in trace amounts in cores below 1500 mbsl. The difference in the percentage of HMC in the deeper cores between the glacial and Holocene may reflect differences in supply or deepening of the HMC lysocline during the glacial. Sediment accumulation rates also vary between cores in the Capricorn Channel and do not show the expected exponential decrease with depth. This may be due to intermediate or deep water currents reworking the sediments. It is also possible that present bathymetry data are too sparse to detect the potential role that submarine channels may play in the distribution and accumulation of sediments. Comparison of the Capricorn Channel MARs with those for other mixed carbonate/siliciclastic provinces from the northeast margin of Australia indicates that peak MARs in the early transgression in the Capricorn Channel precede those from the central GBR and south of Fraser Island. The difference in the timing of the carbonate and siliciclastic MAR peaks along the northeast margin is primarily related to differences in the physiography and climate of the provinces. The only common trend in the MARs from the northeast margin of Australia is the near synchronicity of the carbonate and siliciclastic MAR peaks in individual sediment cores, which supports a coeval sedimentation model.

Natural gas geochemistry of sediments drilled on the 2005 Gulf of Mexico JIP cruise

In April and May 2005, cores were acquired and sub-sampled for gases in lease blocks Atwater Valley 13 and 14 and Keathley Canyon 151 during deep subseafloor drilling conducted as part of the JIP study of gas hydrates in the northern Gulf of Mexico. Sample types included sediment headspace gas, free gas derived from sediment gas exsolution, and gas exsolution from controlled degassing of pressurized cores. The gases measured both onboard and in shore-based labs were nitrogen, oxygen, hydrogen sulfide, carbon dioxide, and the hydrocarbons methane through hexane. The presence of seafloor mounds, seismic anomalies, a shallow sulfate–methane interface, and similar gas compositions and isotopic compositions near the seafloor and at depth suggest an upward flux of methane at both sites. Sediment gases at the Atwater Valley sites, where seafloor mounds and adjacent sediments were cored, strongly suggest a microbial source of methane, with very little thermogenic gas input. Sediment gas from all cores contained from about 96 to 99.9% methane, with the balance composed primarily of carbon dioxide. Methane to ethane ratios were greater than 1000, and often over 10,000. Gases from cores at Keathley Canyon were similar to those at Atwater Valley, however, deeper cores from Keathley Canyon contained more ethane, propane, and butane suggesting mixing with minor concentrations thermogenic gas. The isotopic composition of methane, ethane, and carbon dioxide were measured, and δ 13C values range from −84.3 to −71.5‰, −65.2 to −46.8‰, and −23.5 to −3.0‰, respectively, all consistent with microbial gas sources, early diagenesis of organic matter and perhaps biodegradation of petroleum. The presence of deep microbial gas at these sites here and elsewhere highlights a potentially significant, predominantly microbial gas source in the northern Gulf of Mexico.

Glacial deep water carbonate chemistry inferred from foraminiferal Mg/Ca: A case study from the western tropical Atlantic

We explore using changes in planktonic foraminiferal Mg/Ca with water depth in a single region to infer relative changes in deep water carbonate chemistry. The Mg/Ca ratio in foraminiferal calcite is quantitatively lowered by dissolution. We exploit this dissolution effect to generate a profile of carbonate ion concentration (CO32−) for the deep waters of the tropical Atlantic during the Last Glacial Maximum. We generated Mg/Ca data for three species, G. ruber, G. sacculifer, and N. dutertrei, from three cores located along a depth transect (2.8 to 4.0 km) on the Ceara Rise in the western equatorial Atlantic. We attribute lower Mg/Ca in glacial intervals from the shallow core to changes in sea surface temperature (SST). The even lower glacial Mg/Ca values in the deeper cores are attributed to dissolution and are used to reconstruct a paleo‐CO32− profile. Our down core Mg/Ca data for G. ruber and G. sacculifer confirm that these species are more resistant to Mg loss due to dissolution than N. dutertrei. The greater susceptibility of N. dutertrei's Mg content to dissolution limits the utility of this species in thermocline temperature reconstructions to cores above the lysocline but, significant to this study, makes N. dutertrei useful in quantifying changes in deep water CO32−. Our paleo‐CO32− reconstruction based on N. dutertrei suggests the Last Glacial Maximum CO32− gradient in the Atlantic was much steeper than today, implying that the boundary between deepwater masses in the Atlantic was shallower during the Last Glacial Maximum. Our results suggest comparison of Mg/Ca from multiple cores from one region could similarly provide constraints on changes in carbonate chemistry in other basins and other time periods.

Fossil record of holococcoliths and selected hetero-holococcolith associations from the Mediterranean (Holocene–late Pleistocene): Evaluation of carbonate diagenesis and palaeoecological–palaeocenographic implications

The Holocene–late Pleistocene distribution of holococcoliths, is quantified by light microscopy from cores from the Western Mediterranean, the Aegean Sea and eight eastern Mediterranean cores recovering sapropel S1. The diversity of fossil holococcoliths is much lower than is seen in the plankton, indicating selective preservation. However the holococcolith phases of Syracosphaera pulchra and Helicosphaera carteri are abundantly preserved allowing a comparison of fossil records of heterococcolith and holococcolith phases of these species. In shallow cores a primary palaeocological signal appears to be preserved, suggesting that under suitable circumstances it is possible to use holococcoliths in palaeoceanography. The common occurrence of holococcoliths in the sapropels from these cores suggests low surface-water productivity, supporting previous inferences that productivity enhancement during sapropel deposition was confined to the deep-chlorophyll maximum. In deeper cores there is dramatic decrease in abundance of S. pulchra holococcoliths within sapropel sediments. From comparison of shallow and deep cores and from Emiliania huxleyi preservation data we conclude that this is a preservation signal. Evidently the calyptroliths produced by S. pulchra have a lower preservation potential than the syracoliths produced by H. carteri, we interpret this as a product of their more open structure.

Temporal shifts in reef lagoon sediment composition, Discovery Bay, Jamaica

Discovery Bay, north Jamaica, forms a large (1.5 km wide), deep (up to 56 m) embayment that acts as a sink for reef-derived and lagoonal carbonate sediments. Since the mid-1960s, the bay has also provided a sink for inputs of bauxite sediment that are spilled during loading at a boat terminal constructed within Discovery Bay. Bauxite has accumulated across much of the southern section of the bay with surficial sediments presently composed of up to 35 weight% non-carbonate. Cores recovered from sites on the western side of the bay provide a stratigraphic record of this history of bauxite contamination across water depths from 5 to 25 m. The bauxite-influenced upper sediment horizons are clearly visible in each core from the distinctive red–brown colouration of the sediment. These sediments are composed of approximately 10% non-carbonate (bauxite) and have Fe contents of around 2–3000 μg/g (up to 7000 μg/g). The thickness of this upper bauxite-contaminated sequence increases down transect (approximately 18 cm in the shallowest core, to around 47 cm in the deepest core), and in each core overlies a sequence of ‘clean’ lagoon carbonates. These typically are poorly sorted carbonate sands with variable amounts of coral rubble. Down-core data on CaCO 3 and Fe content provide a chemical record of decreasing sediment contamination with depth, with the lower ‘clean’ carbonates composed of only around 2% non-carbonate and <700 μg/g Fe. Down-core sediment-constituent data also indicate significant changes in sediment production at the shallowest sites. At depths of 5 and 10 m, sediment assemblages have shifted from diverse assemblages of coral, mollusc, Amphiroa and Halimeda in the clean lagoon sands, to assemblages dominated by Halimeda and Amphiroa within the surficial sediments. At the deeper sites, no major down-core shifts in sediment constituents occur. These sites thus record a rather complex history of changes in sediment composition and chemistry. Clear shifts in chemistry and stratigraphy occur in all the cores and reflect progressive bauxite contamination in the near-surface horizons. These inputs, however, do not appear to have directly affected carbonate production, since the major constituent changes appear to be a response to more regional declines in coral community and reef status.

Micropalaeontological evidence for the Holocene earthquake history of the eastern Bay of Plenty, New Zealand, and a new index for determining the land elevation record

Fossil foraminifera and diatoms are used to identify sudden, probably earthquake-related, elevational changes in three Holocene sedimentary sequences from the high-tidal fringes of Ohiwa Harbour, eastern Bay of Plenty, New Zealand. Modern analogue calibration sets of faunal and floral census data are used to estimate palaeosalinities and palaeotidal elevations that help quantify seismic-related, vertical displacements. Age models for the three vibracored sequences are built on a combination of tephrostratigraphy and radiocarbon dating. A new index, the land elevation record (LER), is introduced to graphically portray earthquake-related vertical land displacements on a time-depth diagram. Also plotted are elements used to calculate LER, such as the indicative depth estimated from microfossils, inferred sediment compaction, and the New Zealand Holocene palaeo-sea-level curve. All three Ohiwa cores, spread over 3 km of coast, contain both freshwater and intertidal sediments. A prominent erosional contact between freshwater peat or soil and overlying intertidal mud, records a major subsidence event in each core of c. 2 m, dated at ca 2600 cal years BP. The deepest core (7.4 m) indicates that this is the only substantial vertical displacement event to have occurred in the last 8 ka. A small subsidence event (ca 0.3–0.7 m) is indicated close to the top of one core, but is not present in the other two sites. This may be the result of a local land subsidence during the poorly known Taneatua Earthquake of 1866. There is no historic human record of earthquake displacements around Ohiwa, but mid-Pleistocene, interglacial, marine sediments have been uplifted 10–60 m in several identified fault blocks. Our study provides conclusive evidence of at least 2 m of earthquake-related, subsidence during the Holocene, with a recurrence time of major earthquakes of ca 5 ka.