Offshore Core Research Articles

Investigation of submarine groundwater discharge into the Baltic Sea through varved glacial clays

Submarine groundwater discharge (SGD) is an important process responsible for transporting terrestrial dissolved chemical substances into the coastal ocean, thereby impacting the marine ecosystem. Despites its significance, there are few studies addressing SGD in the northern Baltic Sea. Here we investigate the potential occurrence of SGD in an area characterized by seafloor terraces formed in varved glacial clay located around Fifång Island, Southern Stockholm Archipelago. We analyzed 222Rn activity and porewater geochemistry in both marine and terrestrial sediment cores retrieved from Fifång Island and its surrounding offshore areas. Results from 222Rn mass-balance calculations, water isotopes, salinity, chloride concentration, and dating (including 14C and helium-tritium dating) indicate that modern groundwater flows through varved glacial clay layers and fractured rocks on Fifång Island and discharges into Fifång Bay. Additionally, the offshore cores reveal a saline groundwater source that, dating of the dissolved inorganic carbon, appears systematically younger than the hosting clay varves dated using the Swedish clay varve chronology. Acoustic blanking in our acquired sub-bottom profiles may be related to this fluid migration. The occurrence of this saline groundwater seems to be independent from the distance to the submarine terraces. Collectively, our study confirms the occurrence of submarine groundwater in the varved glacial clay close to Fifång Island and further offshore. Our findings help establish the significance of submarine groundwater discharge in influencing the past and present coastal environment in the Baltic Sea region.

Study on the influence of steam state on seepage, production, migration and deposition of offshore heavy oilfields

In this paper, the influence of steam state on seepage, production, migration and deposition are refined, and the superiority of superheated steam is confirmed. Firstly, the relative permeability of oil-water and oil-steam in offshore cores was measured to analyze flowing characteristics. Then the cyclic steam stimulation of long core was conducted with supersaturated, saturated and superheated steam, and the recovery capacity was quantified, the difference in composition of produced oil was analyzed. Finally, the CT scanning and digital core 3D reconstruction were performed to visualize the influence of steam state on migration of heavy oil components. The results show that the temperature has a significantly higher effect on seepage capacity than permeability, which can effectively broaden the co-seepage range and reduce residual oil saturation. The total recovery of superheated steam is 12 % and 7 % higher than the other two steam respectively, and the main recovery cycle is the former four rounds, which accounts for over 85 % of total recovery. The retention of heavy components can reduce porosity by 4 %∼7 %, superheated steam can alleviate blockage and increase the porosity by over 2 %. This work is expected to provide valuable insights into the application of superheated steam in offshore heavy oilfields.

Connecting link between a sediment source and its deep-sea sink: Ilan Shelf offshore northeastern Taiwan

The northeast Taiwan margin provides an excellent example of the route of sediment flux from a small mountainous river, the Lanyang River, to a deep-sea basin, the Southern Okinawa Trough (SOT), via a very narrow（8–14 km in width）Ilan Shelf at different time scales. Based on seismic and sub-bottom chirp profiles and onshore borehole and offshore core data, we identify three echo types on the Ilan Shelf that delineate sheets of sediment, mass movement deposits, and echoes indicative of igneous activity. By recognizing lithofacies and seismic facies changes, the Last Glacial Maximum Unconformity and maximum flooding surface are correlated in onshore cores and offshore reflection seismic profiles. With the aids of sequence stratigraphic analysis, the postglacial sedimentation rates on the Ilan Shelf are estimated to range from 0.04 to 1.53 cm/yr. Considering its sediment budget in a source-to-sink system, the Ilan Shelf can be regarded primarily as a temporary trap for fluvial sediment discharged from the Lanyang River. Overall, it has trapped at least 50% of the discharged sediment during the Holocene, and the bulk of sediment was transported, primarily via mass movement to SOT. We deduce that earthquake-induced faulting, axial incision in the channel, and retrogressive failures appear to be triggers for mass wasting, which then combined with channel transport, can play leading roles in rapid downslope transportation to the trough. This inference is indicated by high deposition rates in the western end of SOT and widely distributed mass transport deposits observed in the shallow strata of SOT. We found that the deep strata of SOT are deformed by normal faults, indicating that the sediment accommodation space is structurally controlled by the active back-arc extension. This study documents that frequent typhoons and flooding events, together with strong tidal currents, are significant agents of sediment input over the short term. In contrast, earthquakes and volcanic events occasionally affect sediment dispersal from the Ilan Shelf to SOT.

Dynamic Field Retrieval and Analysis of Structural Evolution in Offshore Core Area of Typhoon Higos Based on Ground-Based Radar Observation

Three ground-based radars in the Pearl River Delta successfully observed Typhoon Higos (2020), which traveled over the offshore area in the South China Sea. During the observation period, the stratiform region of the outer rainband of HIGOS became active while swirling inward, merging into an unclosed eyewall and spreading outward, but its structure was asymmetric between upwind and downwind. To understand the dynamic mechanism of the asymmetry of the stratiform region in detail, the refined wind speed distributions in the inner core of Higos was retrieved by using the radar observation data and a three-dimensional, variational, direct, data assimilation, Dual-Doppler analysis (DDA). In addition, an Observing System Simulation Experiment (OSSE) was conducted with the numerical simulations by the Weather Research and Forecasting (WRF) model and numerical emulations by Cloud Resolving Model Radar SIMulator (CR-SIM) software to validate the retrieved data. From the OSSE, the emulated retrieved data were comparable with the WRF-out data. The analysis shows that the dynamic mechanisms are different between upwind and downwind in the stratiform rainband. In the former, the inflow sinks in the middle troposphere. In addition, there is an inflow in the lower troposphere, with an outflow aloft the inflow. In the latter, however, the stratiform rainband is primarily influenced by outflow from inside the rainband and inflow from outside the monsoon-related southwesterly winds. The vertical velocity characteristics in the stratiform rainband downwind also differ from those upwind. The upwind updraft was distinct in the middle troposphere, whereas the downwind updraft was caused by the convergence of the outflow from inside the stratiform rainband and the monsoon-related southwesterly inflow in the lower troposphere.

Multi-proxy evidence of Caribbean-sourced marine incursions in the Neogene of Western Amazonia, Brazil

The timing of continental-scale marine flooding events in Western Amazonia during the Neogene is still an unsolved question. Despite broad proxy-based evidence of such events, the pathways and duration of late Miocene marine incursions remain controversial. We provide coupled calcareous and organic microfossil and geochemical data from six onshore cores from Neogene sequences of the Solimões Basin, Brazil. Our records support minor marine influence in the early Miocene (23.0, 21.1, 18.6, and 16.3 Ma), middle Miocene (14.9, 13.7, and 12.9 Ma) and early Pliocene (4.7, 4.2–4.1, and 3.8 Ma), and conspicuous marine incursions in the late Miocene (11.1–8.8 Ma) suggested by the consistent presence of salinity-indicative microfossils and geochemical data. Our findings challenge the view of major marine incursions in the early and middle Miocene in the studied area. We propose for the first time a new late Miocene incursion (LMI) event as the main marine flooding event in Western Amazonia during the Neogene. These onshore records are compared with three offshore cores from the Atlantic and Pacific Oceans. The similarity between microfossil assemblages of the Solimões Basin and the Caribbean Sea, and evidence of increased runoff from the Orinoco river drainage system, strongly suggest the Caribbean Sea as the primary source area of the marine incursions, supporting a Venezuelan seaway. We further show for the first time the potential linkage between Neogene marine incursions (mainly the LMI) into the Solimões Basin and major disturbances in the global carbon cycle.

West Coast vegetation shifts as a response to climate change over the past 130,000 years: geographic patterns and process from pollen data

ABSTRACT We compiled pollen sequences from lake and offshore cores at least 6,000 years old (6 ka) for the Mediterranean and Marine ecoregions of the US West Coast. Principal Component Analysis highlighted vegetation differences in core-tops, the Holocene Thermal Maximum (6 ka) and Last Glacial Maximum (LGM, 19 ka). Core-top and HTM ordination produced clusters that reflected geographic clusters in the Sierra Nevada, and the Pacific Northwest coast. Little change in these clusters between 6-0 ka suggested that vegetation communities in coastal and alpine settings persisted, despite warmer global temperatures. PCA outliers reflect distinct pollen assemblages that often were isolated sites or bordered the Great Basin. During the LGM, greater shrub and herb presence in the Marine ecoregion interior indicated enhanced aridity, while conifer presence in coastal and Southern California indicated moist conditions. Qualitatively, tree taxa from the Last Interglacial (~130–120 ka) showed how vegetation shifted over 6–10 kyr from alder, to oak, then redwood, a successional pattern that began again at the Late Glacial (~15 ka). In future West Coast pollen studies, sampling and chronologic control at centennial resolution will enable further study of more time periods and rates of vegetation change in response to climate.

Molluscan aminostratigraphy of the US Mid-Atlantic Quaternary coastal system: Implications for onshore-offshore correlation, paleochannel and barrier island evolution, and local late Quaternary sea-level history

The Quaternary record of the US Mid-Atlantic coastal system includes onshore emergent late Pleistocene shoreline deposits, offshore inner shelf and barrier island units, and paleovalleys formed during multiple glacial stage sea-level lowstands. The geochronology of this coastal system is based on uranium series, radiocarbon, amino acid racemization (AAR), and optically stimulated luminescence (OSL) methods. We report over 600 mollusk AAR results from 93 sites between northeastern North Carolina and the central New Jersey shelf, representing samples from both onshore cores or outcrops, sub-barrier and offshore cores, and transported shells from barrier island beaches. AAR age estimates are constrained by paired 14C analyses on specific shells and associated U-series coral ages from onshore sites. AAR data from offshore cores are interpreted in the context of detailed seismic stratigraphy. The distribution of Pleistocene-age shells on the island beaches is linked to the distribution of inner shelf or sub-barrier source units. Age mixing over a range of time-scales (~1 ka to ~100 ka) is identified by AAR results from onshore, beach, and shelf collections, often contributing insights into the processes forming individual barrier islands. The regional aminostratigraphic framework identifies a widespread late Pleistocene (Marine Isotope Stage 5) aminozone, with isolated records of middle and early Pleistocene deposition. AAR results provide age estimates for the timing of formation of the three major paleochannels that underlie the Delmarva Peninsula: Persimmon Point paleochannel ≥800 ka; Exmore paleochannel ~400–500 ka (MIS 12); and Eastville paleochannel > 125 ka (MIS 6). The results demonstrate the value of synthesizing abundant AAR chronologic data across various coastal environments, integrating multiple distinct geologic studies. The ages and elevations of the Quaternary units are important for current hypotheses about relative sea-level history and crustal dynamics in the region, which was likely influenced by the Laurentide ice sheet, the margin just ~400 km to the north.

Late Quaternary vegetation and climate of SE Europe–NW Asia according to pollen records in three offshore cores from the Black and Marmara seas

High-resolution pollen analyses were performed on two cores from the western Black Sea and one core from the Marmara Sea, covering the Late Glacial-Holocene transition using 14C chronology. Particular effort was invested in the botanical identification of pollen grains thereby significantly improving our knowledge of regional flora. When interpreted with respect to modern vegetation, pollen records revealed all the major changes caused by climatic fluctuations over the last 20,000 years. The results of this study provide evidence for the occurrence of relict thermophilous-hygrophilous trees (papillate Cupressaceae, Carya, Liquidambar, Zelkova) in certain refugia up to the Holocene. Vegetation dynamics is specified for some taxa (e.g. Cupressus–Juniperus, Fagus, Cedrus) and some ecosystems (e.g. mesophilous forests, Mediterranean sclerophyllous populations, steppes). Pollen data enabled palaeoclimatic reconstructions which were compared with available estimates in the region. The use of a powerful pollen ratio between ‘thermophilous and steppe taxa’ led to fruitful climatostratigraphic relationships with the oxygen isotope curve from the NGRIP core. The Younger Dryas and cooling at 8.2 ka are among the most obvious climatic phases identified in the three cores studied here.

Integration of Formation Evaluation Data Overcomes Offshore Coring Challenges

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 195866, “Overcoming Coring Challenges in a New Unconventional Play Offshore by Integration of Formation Evaluation Data,” by Thomas Bradley, SPE, Baker Hughes, and Per Henrik Fjeld and Jonathan Scott, Aker BP, et al., prepared for the 2019 SPE Annual Technical Conference and Exhibition, Calgary, 30 September-2 October. The paper has not been peer reviewed. A well was drilled into a prospective unconventional mudstone play offshore Norway. Two of five coring runs were successful while the rest yielded little to no core recovery. Subsequent investigation of the core substantiated that the coring issues largely had natural causes. This understanding is being applied to two imminent coring operations and has driven selection of drilling, coring, and wireline technology and procedures and is informing casing design. Introduction The Valhall field is in Block 2/8 of the Norwegian North Sea. The primary reservoir is Cretaceous chalk, located at approximately 2400 m true vertical depth. Production of this reservoir began in 1982. Above this reservoir are other formations, including a shallower potential unconventional mudstone reservoir. A production well was drilled targeting the Cretaceous chalk reservoir. As part of the drilling program, logging-while-drilling (LWD) and wireline logs - including LWD density, neutron, gamma ray and acoustic, wireline spectral gamma ray, cross-dipole acoustic, nuclear-magnetic-resonance, and formation-testing and -sampling - were run across the potential mudstone reservoir to appraise the standard petrophysical properties. A conventional core was also attempted; however, recovery was poor, with repeated jams. Coring Challenges During coring operations, significant problems were encountered when coring the mudstone intervals. These challenges are illustrated in Fig. 1, which shows a section of the core from xx14 m, demonstrating the typical condition of the recovered core when still in the core barrel. At the time of operation, poor recovery was attributed to the coring practices used and no further coring was attempted. Formation Evaluation The mudstone interval was not a primary target for the well. Therefore, limited formation evaluation of these intervals was performed, mainly to estimate the petrophysical properties. However, at the time of initial logging, more-advanced formation evaluation data (e.g., images, full waveform acoustic, and nuclear-magnetic-resonance data) were not evaluated fully. A few years after initial operations, the log data were revisited - specifically, detailed interpretation was conducted for all recorded log measurements. On examination of the results over much of the interval, the integration of the conventional and advanced volumetric measurements gave considerable extra value in assessing the petrophysical properties of the mudstone. However, detailed discussion of these results is outside the scope of this paper. In addition to the extra information gleaned from the advanced volumetric interpretation, over certain intervals, some unusual log responses and interpretation results were seen that were deemed worthy of further investigation.

The potential of marginal coastal nursery habitats for the conservation of a culturally important Caribbean marine species

AbstractAimIdentifying the potential of marginal habitats for species conservation is of key importance when their core high‐quality habitats are under substantial disturbances and threats. However, there is currently a knowledge gap on how useful marine marginal habitats may be for conserving endangered marine species. Here, we investigate the potential of groundwater‐fed coastal areas for the conservation of the queen conch, an economically and culturally important marine gastropod.LocationThe inlet of Xel‐Há, typical of groundwater‐fed coastal areas widely distributed along the Yucatan Peninsula coast in Mexico and partially protected by a network of marine protected areas.MethodsWe tracked 66 queen conchs (Lobatus gigas) using acoustic telemetry over a period of 3.5 years. We investigated for ontogenetic niche shift using a network analysis and by modelling their growth.ResultsThe queen conchs exhibited the same ontogenetic niche shift required to complete their life cycle in this marginal habitat as they do in offshore core habitats. A total of 33 individuals departed the inlet and migrated from shallow groundwater‐affected nursery grounds to deeper marine habitats more suitable for breeding aggregation.Main conclusionsAs the broad‐scale movement behaviour of queen conch in this inlet is similar to that observed on the overfished core habitats, our findings suggest that groundwater‐fed coastal areas should be included in conservation planning for an effective management of this species within a network of marine protected areas.

Mercury in sediment cores from the southern Gulf of Mexico: Preindustrial levels and temporal enrichment trends.

Spatial and temporal variability of mercury concentrations in sediments was evaluated in 210Pb-dated sediment cores from offshore and intertidal areas in the southern Gulf of Mexico. In offshore cores, mercury concentrations were comparable (11.2-69.2 ng g-1), and intermediate between concentrations in intertidal cores from the eastern (6.0-34.4 ng g-1) and the western (34.9-137.7 ng g-1) inlets of Términos Lagoon. The enrichment factor (EF) indicated minimal contamination (EF < 2) in most offshore cores, whereas in some intertidal cores steadily increasing mercury enrichment and fluxes were observed along the past century. No evidence of oil industry related mercury contamination was found, as the minor but increasing enrichment in intertidal cores is most likely related to land-derived sources such as catchment eroded soils and waste water runoff. Results highlight the importance to control catchment erosion and untreated sewage releases to reduce mercury loadings to the coastal zone.

Mercury Inputs to Chinese Marginal Seas: Impact of Industrialization and Development of China

AbstractIn the past decades, China has experienced substantial economic growth and industrialization. However, the effects of vast development of China on Hg input to the nearby oceans are still unclear. In this study, the influx and isotopic compositions of Hg in four 210Pb‐dated sediment cores were examined to investigate changes in Hg deposition to the marginal seas off China over a century. Nearshore cores had higher Hg influxes than offshore cores. Increases of Hg influxes started since the 1950s, which coincides with China's economic development. Dramatic historical changes in Hg isotopic composition were observed in the cores (δ202Hg: −2.01‰ to −0.69‰; Δ199Hg: −0.16‰ to 0.31‰; n = 106). δ202Hg increased from the deep to the surface layers of the cores. The offshore cores mainly showed positive Δ199Hg values, but the pre‐1950 samples had more positive Δ199Hg values than the younger samples. The nearshore cores mainly showed negative Δ199Hg values in the pre‐1950s samples, but the younger samples showed Δ199Hg values close to zero. A triple‐mixing isotope model, used to quantify the contribution of potential Hg inputs (e.g., direct discharge of industrial Hg, soil Hg, and precipitation‐derived Hg), showed clear evidence of enhanced industrial Hg inputs to the ocean margin, but slightly decreased watershed soil Hg inputs in the last few decades. The variations of watershed‐derived Hg were likely caused by the construction of impoundments in major rivers of China. This study demonstrates that mercury inputs to Chinese marginal seas have been largely altered due to the industrialization and economic development of China.

Sediment routing and basin evolution in Proterozoic to Mesozoic east Gondwana: A case study from southern Australia

Sedimentary rocks along the southern margin of Australia host an important record of the break-up history of east Gondwana, as well as fragments of a deeper geological history, which collectively help inform the geological evolution of a vast and largely underexplored region. New drilling through Cenozoic cover has allowed examination of the Cretaceous rift-related Madura Shelf sequence (Bight Basin), and identification of two new stratigraphic units beneath the shelf; the possibly Proterozoic Shanes Dam Conglomerate and the interpreted Palaeozoic southern Officer Basin unit, the Decoration Sandstone. Recognition of these new units indicates an earlier basinal history than previously known.Lithostratigraphy of the new drillcore has been integrated with that published from onshore and offshore cores to present isopach maps of sedimentary cover on the Madura Shelf. New palynological data demonstrate progression from more localised freshwater-brackish fluvio-lacustrine clastics in the early Cretaceous (Foraminisporis wonthaggiensis – Valanginian to Barremian) to widespread topography-blanketing, fully marine, glauconitic mudrocks in the mid Cretaceous (Endoceratium ludbrookiae – Albian).Geochronology and Hf-isotope geochemistry show detrital zircon populations from the Madura Shelf are comparable to those from the southern Officer Basin, as well as Cenozoic shoreline and palaeovalley sediments in the region. The detrital zircon population from the Shanes Dam Conglomerate is defined by a unimodal ~1400Ma peak, which correlates with directly underlying crystalline basement of the Madura Province. Peak ages of ~1150Ma and ~1650Ma dominate the age spectra of all other samples, indicating a stable sediment reservoir through much of the Phanerozoic, with sediments largely sourced from the Albany-Fraser Orogen and Musgrave Province (directly and via multiple recycling events). The Madura Shelf detrital zircon population differs from published data for the Upper Cretaceous Ceduna Delta to the east, indicating significant differences in sediment provenance and routing between the Ceduna Sub-basin and central Bight Basin.

Warming and Cooling: The Medieval Climate Anomaly in Africa and Arabia

AbstractThe Medieval Climate Anomaly (MCA) is a well‐recognized climate perturbation in many parts of the world, with a core period of 1000–1200 Common Era. Here we present a palaeotemperature synthesis for the MCA in Africa and Arabia, based on 44 published localities. The data sets have been thoroughly correlated and the MCA trends palaeoclimatologically mapped. The vast majority of available Afro‐Arabian onshore sites suggest a warm MCA, with the exception of the southern Levant where the MCA appears to have been cold. MCA cooling has also been documented in many segments of the circum‐Africa‐Arabian upwelling systems, as a result of changes in the wind systems which were leading to an intensification of cold water upwelling. Offshore cores from outside upwelling systems mostly show warm MCA conditions. The most likely key drivers of the observed medieval climate change are solar forcing and ocean cycles. Conspicuous cold spikes during the earliest and latest MCA may help to discriminate between solar (Oort Minimum) and ocean cycle (Atlantic Multidecadal Oscillation, AMO) influence. Compared to its large share of nearly one quarter of the world's landmass, data from Africa and Arabia are significantly underrepresented in global temperature reconstructions of the past 2,000 years. Onshore data are still absent for most regions in Africa and Arabia, except for regional data clusters in Morocco, South Africa, the East African Rift, and the Levant coast. In order to reconstruct land palaeotemperatures more robustly over Africa and Arabia, a systematic research program is needed.

Transition from incised valley to barrier island systems during MIS 5e in the northern Chiba area, Kanto Plain, central Japan

Facies analysis, together with palynostratigraphic studies of the Kioroshi Formation, which lies beneath the northern Chiba area of the Kanto Plain of central Japan, reveal the sedimentary processes in the fluvial to coastal settings during marine isotope stage (MIS) 5e in this region. The depositional sequence of the Kioroshi Formation comprises a lower incised valley system and an upper barrier island system. The incised valley system consists of fluvial, estuary, and central basin facies with sandbar facies in the baymouth area. In the study area, the overlying barrier island system includes flood tidal delta, spit, and lagoon facies. These facies form part of the barrier island system known as Paleo-Tokyo Bay, which covered the present-day Kanto Plain. On the basis of palynostratigraphic correlation with the oxygen isotope curve in an offshore core (MD01-2421), the fluvial and estuary facies, together with the lower half of the central basin facies of the incised valley system are interpreted to have accumulated during a sea level rise in the early stage of MIS 5e. The baymouth sandbar also developed and retrograded with the rising sea level and was abruptly covered by the central basin facies during the middle stage of MIS 5e, probably due to the migration of the sandbar to the outer-bay area. The abrupt change corresponds with the initial stage of development of the barrier island system. The landward (westward) retreating bay ravinement erosion resulted in the transition to the barrier island system during middle MIS 5e. Maximum transgression also occurred during middle MIS 5e. The back-barrier lagoon was infilled during the late stage of MIS 5e. The sedimentary processes of the Kioroshi Formation are almost in accordance with the marine isotope curve.

Earthquake imprints on a lacustrine deltaic system: The Kürk Delta along the East Anatolian Fault (Turkey)

AbstractDeltas contain sedimentary records that are not only indicative of water‐level changes, but also particularly sensitive to earthquake shaking typically resulting in soft‐sediment‐deformation structures. The Kürk lacustrine delta lies at the south‐western extremity of Lake Hazar in eastern Turkey and is adjacent to the seismogenic East Anatolian Fault, which has generated earthquakes of magnitude 7. This study re‐evaluates water‐level changes and earthquake shaking that have affected the Kürk Delta, combining geophysical data (seismic‐reflection profiles and side‐scan sonar), remote sensing images, historical data, onland outcrops and offshore coring. The history of water‐level changes provides a temporal framework for the depositional record. In addition to the common soft‐sediment deformation documented previously, onland outcrops reveal a record of deformation (fracturing, tilt and clastic dykes) linked to large earthquake‐induced liquefactions and lateral spreading. The recurrent liquefaction structures can be used to obtain a palaeoseismological record. Five event horizons were identified that could be linked to historical earthquakes occurring in the last 1000 years along the East Anatolian Fault. Sedimentary cores sampling the most recent subaqueous sedimentation revealed the occurrence of another type of earthquake indicator. Based on radionuclide dating (137Cs and 210Pb), two major sedimentary events were attributed to the ad 1874 to 1875 East Anatolian Fault earthquake sequence. Their sedimentological characteristics were determined by X‐ray imagery, X‐ray diffraction, loss‐on‐ignition, grain‐size distribution and geophysical measurements. The events are interpreted to be hyperpycnal deposits linked to post‐seismic sediment reworking of earthquake‐triggered landslides.

The stratigraphic architecture and depositional environments of non-marine carbonates from barremian-aptian pre-salt strata of the Brazilian continental margin

The stratigraphic architecture and depositional environments of non-marine carbonates from barremian-aptian pre-salt strata of the Brazilian continental margin

Palaeoenvironments during a terminal Oligocene or early Miocene transgression in a fluvial system at the southwestern tip of Africa

A multi-proxy study of an offshore core in Saldanha Bay (South Africa) provides new insights into fluvial deposition, ecosystems, phytogeography and sea-level history during the late Paleogene-early Neogene. Offshore seismic data reveal bedrock topography, and provide evidence of relative sea levels as low as −100m during the Oligocene. 3D landscape reconstruction reveals hills, plains and an anastomosing river system. A Chattian or early Miocene age for the sediments is inferred from dinoflagellate taxa Distatodinium craterum, Chiropteridium lobospinosum, Homotryblium plectilum and Impagidinium paradoxum. The subtropical forest revealed by palynology includes lianas and vines, evergreen trees, palms and ferns, implying higher water availability than today, probably reduced seasonal drought and stronger summer rainfall. From topography, sedimentology and palynology we reconstruct Podocarpaceae-dominated forests, Proto-Fynbos, and swamp/riparian forests with palms and other angiosperms. Rhizophoraceae present the first South African evidence of Palaeogene/Neogene mangroves. Subtropical woodland-thicket with Combretaceae and Brachystegia (Peregrinipollis nigericus) probably developed on coastal plains. Some of the last remaining Gondwana elements on the sub-continent, e.g., Araucariaceae, are recorded. Charred particles signal fires prior to the onset of summer dry climate at the Cape. Marine and terrestrial palynomorphs, together with organic and inorganic geochemical proxy data, suggest a gradual glacio-eustatic transgression. The data shed light on Southern Hemisphere biogeography and regional climatic conditions at the Palaeogene-Neogene transition. The proliferation of the vegetation is partly ascribed to changes in South Atlantic oceanographic circulation, linked to the closure of the Central American Seaway and the onset of the Benguela Current ~14Ma.

A New Species of Trachyleberididae (Ostracoda, Crustacea) from the Early Miocene of the Pelotas Basin, Southernmost Brazil

Abstract. Actinocythereis imbeensis n. sp. is described from the early Miocene strata of the Pelotas Basin, the southernmost Brazilian marginal basin. The specimens were recovered from the base to the top of an offshore core composed of greenish-gray shale interpreted as part of a transgressive sequence. Morphological features and faunal composition indicate that the ostracods were autochthonous and lived in the photic zone.

Offshore Evidence for an Undocumented Tsunami Event in the 'Low Risk' Gulf of Aqaba-Eilat, Northern Red Sea.

Although the Gulf of Aqaba-Eilat is located in the tectonically active northern Red Sea, it has been described as low-risk with regard to tsunami activity because there are no modern records of damaging tsunami events and only one tsunami (1068 AD) referred to in historical records. However, this assessment may be poorly informed given that the area was formed by and is located along the seismically active Dead Sea Fault, its population is known to fluctuate in size and literacy in part due to its harsh hyper-arid climate, and there is a dearth of field studies addressing the presence or absence of tsunamigenic deposits. Here we show evidence from two offshore cores for a major paleotsunami that occurred ~2300 years ago with a sedimentological footprint that far exceeds the scarce markers of the historically mentioned 1068 AD event. The interpretation is based on the presence of a laterally continuous and synchronous, anomalous sedimentological deposit that includes allochtonous inclusions and unique structural characteristics. Based on sedimentological parameters, these deposits could not be accounted for by other transport events, or other known background sedimentological processes.