Calcareous Nannofossil Biostratigraphy and Ostracoda Paleoecology of Hartha Formation from Balad (1) well, Central Iraq

Seventeen samples of Hartha Formation in Balad (1) well, central Iraq, are studied on the basis of stratigraphic ranges of the recorded calcareous nannofossils for twenty species belonging to twelve genera. The studied section reveals three biozones arranged from oldest to youngest as follows; (1) Calculites ovalis Interval Biozone (CC19), (2) Ceratolithoides aculeus Interval Biozone (CC20), (3) Quadrum sissinghii Interval Biozone (CC21). These Biozones are correlated with other calcareous nannofossils biozones from both local and regional sections, leading to conclude the age of the Middle Campanian. Rerecorded eighteen ostracode species that belong to eleven genera are identified, all of which were previously recorded from Iraq and adjacent regions. The occurrence of these species leads to conclude a continental shelf environment, while they are typical of inner shelf-outer shelf depth.

The Depositional Environments in the Cilento Offshore (Southern Tyrrhenian Sea, Italy) Based on Marine Geological Data

The depositional environments offshore of the Cilento Promontory have been reconstructed based on the geological studies performed in the frame of the marine geological mapping of the geological sheet n. 502 “Agropoli”. The littoral environment (toe-of-coastal cliff deposits and submerged beach deposits), the inner continental shelf environment (inner shelf deposits and bioclastic deposits), the outer continental shelf environment (outer shelf deposits and bioclastic deposits), the lowstand system tract and the Pleistocene relict marine units have been singled out. The littoral, inner shelf and outer shelf environments have been interpreted as the highstand system tract of the Late Quaternary depositional sequence. This sequence overlies the Cenozoic substratum (ssi unit), composed of Cenozoic siliciclastic rocks, genetically related with the Cilento Flysch. On the inner shelf four main seismo-stratigraphic units, overlying the undifferentiated acoustic basement have been recognized based on the geological interpretation of seismic profiles. On the outer shelf, palimpsest deposits of emerged to submerged beach and forming elongated dunes have been recognized on sub-bottom profiles and calibrated with gravity core data collected in previous papers. The sedimentological analysis of sea bottom samples has shown the occurrence of several grain sizes occurring in this portion of the Cilento offshore.

Stratigraphic and Microfacies Study of Kometan Formation (Upper Turonian-Lower Campanian), in the Dokan area, Northern Iraq

The Kometan Formation is widely distributed in the northern (Kurdistan region) and central Iraq. The studied area is located near the Dokan Dam, about 58 km., to the Northwest of the Sulaymaniyah city, Northeastern Iraq. The Kometan Formation is exposed on the southwest flank of the Sarah anticline. The formation consists of limestone and dolomitic limestone, which have cherts nodules throughout the formation. The Gulneri Formation is recorded below the Kometan Formation with unconformable contact, while at the top is bounded by the Shiranish Formation unconformably too. Three microfacies are identified, these are lime mudstone, planktic foraminiferal lime wackestone-packstone, keeld planktonic foraminiferal lime wackestone-packstone microfacies. All the sedimentary and fossil evidence refer that the sedimentary environment of the formation is the outer shelf to upper bathyal at the lower and upper parts of formation and its extension to the middle bathyal in the middle part of the formation. Based on the stratigraphic ranges of the recorded Calcareous nannofossils biozones, the age of the Kometan Formation at Dokan area is Late Turonian-Early Campanian.

Glider observations of sediment resuspension during storm conditions

<p>Sediment resuspension and transport on continental shelves are primarily driven by episodic energetic events, such as storm. Unfortunately, resuspension processes remain poorly quantified using traditional sampling techniques due to the intermittency and the intensity of these events. The recent integration of Acoustic Doppler Current Profilers (ADCPs) onto underwater gliders changes the way current and sediment dynamics in the coastal zone can be monitored. Their endurance and ability to measure in all weather conditions increase the probability of capturing sporadic meteorological events. We used a Slocum glider equipped with a CTD (Conductivity, Temperature, Depth), an optical payload and a RDI 600 kHz phased array ADCP to examine storm-induced sediment resuspension in the Gulf of Lion’s shelf (NW Mediterranean). Observations show that early in the storm, when the waves are highest, resuspension is limited by stratification. During the storm, erosion of the pycnocline through thickening of the bottom and surface mixed layers lead to resuspension in the full water column. Coincident optical and acoustic backscatter measurements indicate that the resuspended particulate assemblage is homogeneous and composed of large particles. Glider-ADCP observations showed for the first time that waves may be the predominant forcing which drive the resuspension on the outer shelf (> 80 m) during the winter storm. While, in the Gulf of Lions, which is considered as a relatively low energy continental shelf, modeling studies consider that only current drive resuspension in the outer shelf. This study highlights the usefulness of glider-ADCP to describe episodic processes and to support validation and improvement of regional hydrodynamic models.</p>

The late Pleistocene and Holocene glaciation history of sub-Antarctic South Georgia

<p>The ice cap of the sub-Antarctic island South Georgia is influenced by the Antarctic Circumpolar Current and is hence more sensitive to changing climate than the significantly larger and more isolated Antarctic ice sheets. Furthermore, the sediment deposits in fjords and glacially eroded troughs around the island have superbly archived glacier behavior, environmental and climatic changes since the late Pleistocene. This makes South Georgia an attractive target to study past climate variability in the Southern Hemisphere. Nevertheless, the ice sheet’s extents and dynamics during the Last Glacial Maximum (LGM), the Antarctic Cold Reversal (ACR), and the Holocene deglaciation phase are still poorly understood. Although several studies on land and in marine near-shore areas of South Georgia have addressed this, only few studies are based on marine sediment cores from the continental shelf. In this study, we use ten gravity cores from three different troughs on the southern and northwestern shelf to further investigate the climatic and glaciological evolution of South Georgia during and since the LGM.</p><p>Multi-proxy sedimentological analyses carried out in this study include core logging, XRF geochemical profiling, XRD analyses on bulk sediment and clay fraction, measurements of physical properties, magnetic susceptibility, grain size distribution and shear strength. For the Drygalski Trough on the southern shelf, lithofacies description reveals the deposition of stratified, predominantly sandy diamicton and greenish-grey massive to laminated, sometimes bioturbated mud with variable amounts of clasts. First radiocarbon ages from benthic foraminifera constrain the deposition of the diamicton, interpreted as waterlain till, on the outer shelf to the LGM. Inferred linear sedimentation rates attest to low sediment input on the outer shelf during the LGM (34 cm/ka) and the Holocene (23-32 cm/ka). In contrast, a higher sedimentation rate (114 cm/ka) between 14.7 and 13.7 cal ka BP is likely associated with enhanced erosion due to a possible re-advance of South Georgia’s glaciers during the ACR’s colder and wetter climate. For island-proximal cores, sedimentation rates are generally higher than on the outer shelf with rates of 80-2300 cm/ka during the Mid- to Late Holocene. This stronger fluctuation of sedimentation rates is due to higher temporal resolution of the dated sediments compared to the outer shelf. Grain-size distribution on the outer shelf shows a gravel content of 1-28 wt% in the diamicton facies from the LGM and 1-5 wt% in a sediment interval dated to 16.8 cal ka BP. This sediment interval is also characterized by a high content of pebbles, likely reflecting an increased input of IRD. The overlying ACR and Holocene show a low gravel content of 0-0.7 wt%. The diamicton suggests that ice-proximal conditions prevailed on the outer shelf during the LGM and therefore supports the theory of a shelf-wide glaciation. The combination of a low-resolution sediment core from the outer shelf and island-proximal high-resolution sediment cores has the potential to give new insights into South Georgia’s climate history from the Late Pleistocene to the Late Holocene.</p>

The recovery of the biological pump across the K/Pg boundary in the GSSP of El Kef, Tunisia

<p>The study of Earth’s Big Five mass extinctions provides insight into the resilience of ecosystems to environmental perturbations. Earth’s most recent mass extinction at the Cretaceous/Paleogene boundary (K/Pg) was caused by the impact of an asteroid in the Yucatan peninsula rather than by intense volcanism. Mass extinctions among marine calcareous nannoplankton heavily disrupted the marine food web resulting in a severe weakening of the ocean’s biological pump. The timing and heterogeneous nature of the recovery of the biological pump remain poorly resolved in the neritic zone in the aftermath of the impact. Here, we address the evolution of the biological pump across the K/Pg at the Global Boundary Stratotype Section (GSSP) at El Kef, Tunisia using high-resolution compound-specific carbon isotope records (<em>δ</em><sup>13</sup>C<sub>biomarker</sub>) of non-calcareous marine phototrophs from an outer shelf to upper bathyal setting of the southwestern Tethys Ocean. We use <em>δ</em><sup>13</sup>C<sub>biomarker</sub> to reconstruct ε<sub>p</sub>, which is a function of the community structure of marine phototrophs, their rate of carbon fixation, and the concentration and isotopic composition of aqueous CO<sub>2</sub>. We then use our <em>ε</em><sub>p</sub> record to constrain the recovery of the biological pump in this region while considering the composition of marine phytoplankton, the assemblage and isotopic composition of benthic foraminifera, state-of-the-art physiological models for <em>ε</em><sub>p</sub>, and carbon cycle simulations using cGENIE. Our results indicate that the recovery of the biological pump in the outer shelf-upper bathyal zone likely outpaced the recovery in the open ocean. This is in agreement with the selective extinctions among phytoplankton at the K/Pg, with most survivors that would later repopulate open-ocean sites being adapted to neritic environments.</p>

IODP Exp. 374 provides clues into the Antarctic Ice Sheet contribution to sea level changes

<p>The five sites drilled during International Ocean Discovery Program (IODP) Expedition 374 recovered the distal geological component of a Neogene latitudinal and depth transect across the Ross Sea continental shelf, slope and rise, that can be combined with previous records of ANDRILL and the Deep Sea Drilling Project Leg 28. This transect provides clues into the ocean and atmospheric forcings on marine ice sheet instabilities and provides new direct constraints for reconstructing the Antarctic Ice Sheet contribution to global sea level change. Site U1521 recovered a middle Miocene record that allows identification of the different processes that lead to the expansion and retreat of ice streams emanating from the East and West Antarctic Ice Sheets across the Ross Sea continental shelf. This site also recovered a semi-continuous, expanded, high-resolution record of the Miocene Climatic Optimum in an ice-proximal location. Site U1522 recovered a Pleistocene to upper Miocene sequence from the outer shelf, dating the step-wise continental shelf–wide expansion and coalescing of marine-based ice streams from West Antarctica. Thin diatom-rich mudstone and diatomite beds were recovered in some intervals that provide snapshot records of a deglaciated outer shelf environment in the late Miocene. Site U1523 targeted a Miocene to Pleistocene sediment drift on the outermost continental shelf and informs about the changing vigor of the eastward flowing Antarctic Slope Current (ASC) through time. Changes in ASC vigor is a key control on regulating heat flux onto the continental shelf, making the ASC a key control on ice sheet mass balance. Sites U1524 and U1525 cored a continental rise levee system near the flank of the Hillary Canyon. The upper ~50 m at Site U1525 belong to a large trough-mouth fan deposited to the west of the site. The lower 100 m at Site U1525 and the entire 400 m succession of sediment at Site U1524 recovered near-continuous records of the downslope flow of Ross Sea Bottom Water and turbidity currents, but also of ASC vigor and iceberg discharge. Analyses of Exp. 374 sediments is ongoing, but following initial shipboard characterization, the intial results of sample analysis, the correlation between downhole synthetic logs and the associated seismic sections provide insight into the ages and the processes of erosion and deposition of glacial and marine strata. Exp. 374 sediments are providing key chronological constraints on the major Ross Sea seismic unconformities, enabling reconstruction of paleo-bathymetry and assessment of the geomorphological changes associated with Neogene ice sheet and ocean circulation changes. Exp. 374 results are fundamental for improving the boundary conditions of numerical ice sheet, ocean, and coupled climate models, which are critically required for understanding past ice sheet and global sea level response during warm climate intervals. Such data will enable more accurate predictions of ice sheet behavior and sea level rise anticipated with future warming. </p>

Cross shelf gradients of scleractinian corals in the Spermonde Islands, South Sulawesi, Indonesia

Yusuf S, Beger M, Tassakka ACMAR, Brauwer MD, Pricella A, Rahmi, Umar W, Limmon GV, Moore AM, Jompa J. 2021. Cross shelf gradients of scleractinian corals in the Spermonde Islands, South Sulawesi, Indonesia. Biodiversitas 22: 1415-1423. Coral reef ecosystems around the world have suffered extensive degradation, including the reefs of the Wallacea region within the Coral Triangle global biodiversity hotspot. Anthropogenic and natural threats can reduce the level of coral reef biodiversity differentially across environmental or impact gradients. The purpose of this study was to evaluate the changes in hard coral (Scleractinia) diversity and community structure across an inshore-offshore zonation gradient in the Spermonde Islands, South Sulawesi, Indonesia. Data on coral colony species and abundance as well as live coral cover were collected from 10 m2 belt transects at a depth of 6 to 8 m. A total of 72 transects were placed around the 12 island stations in three zones: the inner mid-shelf zone, outer mid-shelf zone and outer shelf zone. Data were analyzed to determine the species richness, and three ecological indices for the hard coral communities were calculated: the Shannon Diversity Index (H'), Similarity Index (E), and Dominance Index (C). A total of 310 hard coral species belonging to 62 genera were recorded. The coral communities were dominated by the genera Fungia, Montipora and Porites, and coral cover was in the 'moderate' category. The number of species was directly proportional to the number of colonies within each zone. Live coral cover was higher in the inner mid-shelf zone and outer shelf zone than the outer mid-shelf zone; conversely, the species richness and coral colony abundance were higher in the outer mid-shelf zone. However, the differences were not statistically significant. The indices H’, C, and E did not differ significantly between the zones. However, Tambakulu Island in Zone 4 had the lowest values of E and H’ and the highest value of C. Findings suggest that most-hard coral communities in the cross-shelf zones of the Spermonde Islands are stable communities characterized by relatively high diversity and low dominance indices.