Marine Geological Data Research Articles

An integrated geological characterization of the Mid‐Pleistocene to Holocene geology of the Sørlige Nordsjø II offshore wind site, southern North Sea

Subsurface deposits in recently glaciated marine areas are highly heterogeneous, representing a range of glacial and postglacial environments and processes including glacitectonism, overconsolidation, fluvial and lacustrine deposition, and transgression. These heterogeneities are often linked to variations in engineering properties, with important implications for the design and installation of offshore wind infrastructure. In this study we present an integrated geological characterization of the Sørlige Nordsjø II offshore wind site, located in waters of 50–70 m depth along the southern border of the Norwegian North Sea, focusing on the evolution of the area's depositional setting during the late Quaternary period and its implications for offshore wind development. We integrate interpretations from a marine geological data set acquired in 2022 with legacy 3D seismic data and a review of the current understanding of the southern North Sea's complex glacial history. A preliminary ground model and accompanying risk map for the site is presented with five main geological units: (i) homogeneous and layered marine sands covering most of the site, with patchy distribution and coarser‐grained deposits in the east; (ii) buried, layered channel deposits containing organic material and possible associated shallow gas; (iii) buried, stiff glacilacustrine clay deposits; (iv) a buried, layered, glacitectonized unit incised by tunnel valleys, with a sandy marine infill; and (v) mounded tills and glacitectonized deposits containing boulders, exposed to shallowly buried in the east. Salt diapirism and gas migration were also found to be important potential geohazards at the site. Three‐dimensional seismic attribute maps were found to be a powerful aid to understanding the distribution and genesis of seismic facies identified on 2D high‐resolution sub‐bottom profiles. This type of data integration is an under‐utilized methodology for generating detailed preliminary ground models, which can inform more cost‐effective site survey and early foundation concept planning at geologically complex offshore wind sites.

Underwater Sensing Technologies for Assessment of Marine Geological Hazards

In recent years, more and more countries are facing the threat of marine geological hazards. The huge losses caused by marine geological disasters have forced people to put on the agenda to develop technologies that can monitor marine geological hazards. There are currently multiple technologies available for monitoring marine geological hazards, the purpose of this article is to explore possibly the basic information of technologies used for marine geohazards assessment and their advantages for using various assessment technologies to monitor the occurrence of marine geological hazards. The technologies to be explored in this article include AUV, multibeam sonar mapping, and sub-bottom profiler. UAVs can take images of the seafloor, seamount, and sediments of the eruptions, and multiple sensors carried by the AUVs can collect related marine geological data including the temperature and salinity of the seawater. The data collected and the images produced can be used to assess the occurrence of marine geohazards. The multi-beam sonars with different working frequencies are used for different purposes, which means that sonars with different working frequencies are also attached to different platforms to fit their mission assigned. The sub-bottom profilers can be used for assessment of eruptions of mud volcanoes and the fluid mud produced during the eruptions.

A review of the CARG Project of the Campania Region (marine counterpart; southern Tyrrhenian Sea): New perspectives in marine geology and cartography

A review of the CARG Project of the Campania Region (marine counterpart) up to water depths of 200 m is herein proposed referring to the Gulf of Naples (southern Tyrrhenian Sea) aimed at focusing on the main scientific results obtained in the frame of this important project of marine geological cartography. The Gulf of Naples includes several geological sheets, namely n. 464 “Island of Ischia” both at the 1:25,000 and 1:10,000 scale, n. 465 “Island of Procida” at the 1:50,000 scale, n. 466–485 “Sorrento–Termini” at the 1:50,000 scale, n. 446–447 Naples at the 1:50,000 scale, and n. 484 “Island of Capri” at the 1:25,000 scale. The detailed revision of both the marine geological and geophysical data and of the literature data has allowed us to outline new perspectives in marine geology and cartography of Campania Region, including monitoring of coastal zone and individuation of coastal and volcano-tectonic and marine hazards.

Arctic Marine Geology and Geophysics cruise to the northern Svalbard Margin and the Yermak Plateau

From the evening of July 23rd to the morning of August 1st, the Department of Geosciences at UiT The Arctic University of Norway, arranged an educational cruise to the northern Svalbard Margin/Yermak Plateau (Figure 1) for the courses GEO-3144 and GEO-8144 (Marine geology and geophysics cruise). The main aim of the cruise was to introduce the students to work at sea, which included acquisition of marine geological data (acoustic data and sediment cores) and lab analyses of split gravity cores. The students worked 12-hour shifts during the cruise The cruise may be known as: IG19-3_AMGG

Identification and evolution of tectonic units in the Philippine Sea Plate

The Philippine Sea Plate is located at the convergence zone of the Eurasian Plate, the Pacific Plate, and the Indo-Australian Plate. This paper divides the Philippine Sea Plate into two second-order tectonic units and eight third-order tectonic units by summarizing the marine geological, geophysical, and submarine geomorphological data of the Philippine Sea Plate collected for years and referring to the seafloor spreading theory and the trench-arc-basin system. The two second-order tectonic units are the West Philippine Sea block and the Izu-Bonin-Mariana arc-basin system. The former includes the West Philippine Basin, the Huatung Basin, the Daito Basin, and the Palau Basin, while the latter consists of the Kyushu-Palau Ridge, the Shikoku-Parece Vela Basin, the Izu-Bonin Arc, and the Mariana Arc. Furthermore, this study concludes that the Philippine Sea Plate has undergone three stages of tectonic evolution, namely the early stage of the evolution of marginal basins with Cretaceous basement (Early Cretaceous), the middle stage of the spreading of the West Philippine Basin (Eocene), and the late stage of the subduction of the Izu-Bonin-Mariana arc-basin system (Oligocene-present). The Kyushu-Palau Ridge is a window to discover the tectonic evolution of the Philippine Sea Plate due to its unique geographical location.© 2022 China Geology Editorial Office.

Identification and evolution of tectonic units in the Philippine Sea Plate

The Philippine Sea Plate is located at the convergence zone of the Eurasian Plate, the Pacific Plate, and the Indo-Australian Plate. This paper divides the Philippine Sea Plate into two second-order tectonic units and eight third-order tectonic units by summarizing the marine geological, geophysical, and submarine geomorphological data of the Philippine Sea Plate collected for years and referring to the seafloor spreading theory and the trench-arc-basin system. The two second-order tectonic units are the West Philippine Sea block and the Izu-Bonin-Mariana arc-basin system. The former includes the West Philippine Basin, the Huatung Basin, the Daito Basin, and the Palau Basin, while the latter consists of the Kyushu-Palau Ridge, the Shikoku-Parece Vela Basin, the Izu-Bonin Arc, and the Mariana Arc. Furthermore, this study concludes that the Philippine Sea Plate has undergone three stages of tectonic evolution, namely the early stage of the evolution of marginal basins with Cretaceous basement (Early Cretaceous), the middle stage of the spreading of the West Philippine Basin (Eocene), and the late stage of the subduction of the Izu-Bonin-Mariana arc-basin system (Oligocene-present). The Kyushu-Palau Ridge is a window to discover the tectonic evolution of the Philippine Sea Plate due to its unique geographical location.© 2022 China Geology Editorial Office.

Georeferenced Gridded Data Handled by GMT: Cartographic Solutions for Geophysical Mapping

The functionality of Generic Mapping Tools (GMT) to process and visualize geospatial information is crucial to the development of the advanced cartographic method. This paper presents modelling and spatial analysis of the marine geological data using GMT shell scripting. GMT demonstrated effective cartographic solutions for visualization of the georeferenced data. The particular feature of GMT consists in its scripting modular approach that enables to use machine learning to explore reliable georeferenced data. Here, the study applies a sequential shell scripting to devise GMT modules for depicting marine geological data on the Mariana Trench. The data cover bathymetry, geophysics, tectonics and geology. The first method makes use of the 'nearneighbor' GMT module for grid contour modelling using Nearest Neighbor algorithm. This form of modelling classifies the geospatial data based on a similarity. The second method presents surface modelling from the initial XYZ-ASCII dataset by a combination of the 'blockmean' and 'surface' modules. The third method includes the use of the modules 'grdimage', 'psbasemap' and 'grdcontour' for plotting. Compared to GIS methods in which data are processed in a menu, GMT presents the console-based approach which automates cartographic data processing. The results present seven new maps and explanations of scripts.A combination of visual approaches applied using a color fill and various textures to represent data, which is effective in allowing readers to assess geophysical setting. The study demonstrated the effectiveness of GMT in geodata visualization.

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.

Exploring the impact of atmospheric forcing and basal drag on the Antarctic Ice Sheet under Last Glacial Maximum conditions

Abstract. Little is known about the distribution of ice in the Antarctic Ice Sheet (AIS) during the Last Glacial Maximum (LGM). Whereas marine and terrestrial geological data indicate that the grounded ice advanced to a position close to the continental-shelf break, the total ice volume is unclear. Glacial boundary conditions are potentially important sources of uncertainty, in particular basal friction and climatic boundary conditions. Basal friction exerts a strong control on the large-scale dynamics of the ice sheet and thus affects its size and is not well constrained. Glacial climatic boundary conditions determine the net accumulation and ice temperature and are also poorly known. Here we explore the effect of the uncertainty in both features on the total simulated ice storage of the AIS at the LGM. For this purpose we use a hybrid ice sheet shelf model that is forced with different basal drag choices and glacial background climatic conditions obtained from the LGM ensemble climate simulations of the third phase of the Paleoclimate Modelling Intercomparison Project (PMIP3). Overall, we find that the spread in the simulated ice volume for the tested basal drag parameterizations is about the same range as for the different general circulation model (GCM) forcings (4 to 6 m sea level equivalent). For a wide range of plausible basal friction configurations, the simulated ice dynamics vary widely but all simulations produce fully extended ice sheets towards the continental-shelf break. More dynamically active ice sheets correspond to lower ice volumes, while they remain consistent with the available constraints on ice extent. Thus, this work points to the possibility of an AIS with very active ice streams during the LGM. In addition, we find that the surface boundary temperature field plays a crucial role in determining the ice extent through its effect on viscosity. For ice sheets of a similar extent and comparable dynamics, we find that the precipitation field determines the total AIS volume. However, precipitation is highly uncertain. Climatic fields simulated by climate models show more precipitation in coastal regions than a spatially uniform anomaly, which can lead to larger ice volumes. Our results strongly support using these paleoclimatic fields to simulate and study the LGM and potentially other time periods like the last interglacial. However, their accuracy must be assessed as well, as differences between climate model forcing lead to a large spread in the simulated ice volume and extension.

Depositional and erosional signatures in sedimentary successions on the continental slope and rise off Prydz Bay, East Antarctica– implications for Pliocene paleoclimate

The Prydz Bay region of Antarctica is the immediate recipient of ice and sediments transported by the Lambert Glacier, the single largest outflow from the East Antarctic Ice Sheet. The continental slope and rise provide records covering multiple glacial cycles and containing paleoclimatic information. Marine geological and geophysical data collected from the continental shelf and adjacent slope of Prydz Bay, Antarctica, including seismic reflection data, bathymetry, and core records from ODP drilling sites, reveal the history of glacial sediment transport and deposition since the early Pliocene times. Seismic facies are interpreted in terms of episodes of slope progradation, contourite, turbidite, trough-mouth fan, and mass transport deposition. Two seismic units with estimated age of early to late Pliocene and late Pliocene to recent have been analyzed in detail for the area immediately offshore the Lambert Glacier and Prydz Bay and the adjacent Mac. Robertson margin. The upper slope is dominated by episodic mass transport deposits, many of which accumulated to form a trough mouth fan since Early Pliocene times. The trough mouth fan contrasts with the adjacent steep (4–6°) continental slope of the Mac. Robertson margin, where glacigenic sediments have been transported down slope as high-velocity turbidity currents via submarine channels. The distal region exhibits evidence for contrasting effects of high-energy, traction-dominated versus lower-energy, fallout-dominated suspension flows. The counter-clockwise Coriolis force modifies the erosion and deposition patterns of turbidity currents creating an asymmetric channel-levee architecture. Since the early Pliocene, turbidite sedimentation surpassed the amount of sediment reworked and transported by westward-flowing contour currents along the base of slope. On the continental rise, contourites and sediment waves were deposited in response to enhanced bottom-water formation, which is consistent with climatic cooling since late Pliocene times. This study, based on existing seismic reflection and ODP data, highlights the need for a future scientific ocean drilling proposal on the Prydz Bay continental slope and rise in order to more accurately determine the timing of the important events that have influenced the evolution of this margin.

Python libraries matplotlib, seaborn and pandas for visualization geospatial datasets generated by QGIS

This work aim is to perform modelling and spatial analysis of the marine geological data using combination of the QGIS and Python programming. Selecting proper cartographic software is important part of the geospatial research. QGIS provides organizing data in a GIS project for mapping and spatial visualization through vector and raster layers stored in GIS. Study area is Mariana Trench, west Pacific Ocean. A series of cross-section profiles were digitized in QGIS and used for further data processing in Python. Mariana Trench has complex geomorphic structure and unevenness in profiles stretching south-westwards. The geomorphology is subjected to various phenomena that affect its shape. These include bathymetry, geodesy, gravimetry, tectonics plates and geological settings, studied in this paper. To understand the structure of the trench, a data modelling using bathymetric analysis was performed by combination of QGIS mapping and statistical analysis in Python’s library Seaborn. Statistical data modelling aimed at the analysis of the spatial variation of the geomorphology of the trench using following methods: multiple facet grids, area charts for the data frames, regression analysis, letter- value plots, hexagonal and Kernel density estimation. The results of the geospatial data analysis show spatial unevenness of the geomorphic structure, gravimetric, geodetic and bathymetric settings of the Mariana Trench. The study demonstrated effectiveness of Python application in geographic data analysis with Python codes provided for repeatability.

VISUALIZATION OF THE GEOPHYSICAL SETTINGS IN THE PHILIPPINE SEA MARGINS BY MEANS OF GMT AND ISC DATA

The presented research aimed to perform geophysical modelling (gravity and geoid) and to evaluate the spatio-temporal variation of the marine geological data (distribution and depth of earthquakes) using combination of the Generic Mapping Tools (GMT) and available sources from the International Seismological Centre (ISC-EHB) that produce data on earthquakes as part of seismic survey and regional research projects. The target study area is a Philippine Sea basin (PSB) with two focused marginal areas: Philippine Trench and Mariana Trench, two hadal trenches located in the places of the tectonic plates subduction. Marine free-air gravity anomaly in the PSP shows higher values (>80 mGal) of the gravity fields structure at the volcanic areas and Philippine archipelago. Current study presented comparative geophysical analysis, and mapping free-air gravity and geoid in the Philippine Sea basin area. As a result of this study, the average level of earthquakes located in the Philippine Trench and Mariana Trench areas were compared, and those located in the Philippine archipelago are determined to be in the souther-western part (area of west Mindanao, south-west Visayas islands), while Luzon Islands shown shallower located earthquakes. The results on the Mariana Trench segment shown shallower located earthquakes compared of the other marginal regions of the Philippine Sea Basin. Current paper contributes to the studies on natural hazards through visualization and analysis of the earthquakes activities (occurrence and magnitude intensity), due to increasing interest to the problems of seismicity in the Pacific Ocean, which may have environmental effects causing harmful consequences and possible risks for coastal population of the Philippine islands through aftershocks and tsunami.

Digital mapping of geological events in European Seas

Geological mapping has been fundamental in understanding Earth history and in gathering information necessary to tackle land-use related problems. In recent decades, digital mapping and database criteria have provided additional contributions to traditional cartography management.The Geological Survey of Italy is involved in the EMODnet Geology Project, which promotes the collection and harmonization of marine geological data in European Seas, to be represented on digital maps at multiple scales, accessible online through a dedicated Portal. Data are subdivided into Work Packages (WP) dealing with different features. The Geological Survey of Italy has contributed constructively to the realization of geological datasets and leads the WP Geological Events and Probabilities with the aim to identify and map significant earthquakes, submarine landslides, volcanic centers, tectonics, tsunamis and fluid emissions occurring in European Seas.In order to provide harmonized European digital maps, the process of WP6 deliverable production was subdivided into several phases: Guidelines elaboration, data collection, harmonization, data processing and implementation.The activity resulted in the collection of a large amount of data which are displayed on the Portal. A few examples are provided to illustrate digital maps and how to browse through them and use data contained in the attached database.

New sedimentological and coastal and marine geological data on the Quaternary marine deposits of the Ischia Island (Gulf of Naples, Southern Tyrrhenian Sea, Italy)

Quaternary marine deposits of the Ischia Island have been analyzed based on marine geological survey and sedimentological data. The Ischia Island represents the emerged part of a large volcanic field, extending from the Procida island to the submerged volcanoes of the western Ischia offshore. The volcanic field develops over an area of about 42 km2, E-W trending, composed of calderas, such as the Ischia caldera, linked to the great explosive eruptions, plinian and ignimbritic (“Sintema del Rifugio di S. Nicola”). The grain-size analyses of sea bottom samples have shown that gravelly sands, sands, silty sands, muddy sands, sandy silts, and silts all occur. The comparison of the obtained results with previous sedimentological data collected in the Ischia offshore, coupled with the construction of marine geological maps at the 1:10,000 scale, has shown that sands seem to prevail in the eastern Ischia offshore, while gravelly sands, mainly bioclastic, are located at the top of relict volcanic edifices, such as the Forio Bank (western Ischia offshore) and the Ischia Bank (south-eastern Ischia offshore). Moreover, the obtained data show that rhodolith beds occur on the relict volcanic edifice of the Ischia Bank, on the related parasitic vent, and in the Ischia Channel, a morphological saddle located between the Ischia and Procida islands.

Insights on the Source of the 28 September 2018 Sulawesi Tsunami, Indonesia Based on Spectral Analyses and Numerical Simulations

The 28 September 2018 Sulawesi tsunami has been a puzzle because extreme deadly tsunami waves were generated following an Mw 7.5 strike-slip earthquake, while such earthquakes are not usually considered to produce large tsunamis. Here, we obtained, processed and analyzed two sea level records of the tsunami in the near-field (Pantoloan located inside the Palu Bay) and far-field (Mamuju located outside the Palu Bay) and conducted numerical simulations to shed light on the tsunami source. The two tide gauges recorded maximum tsunami trough-to-crest heights of 380 and 24 cm, respectively, with respective dominating wave periods of 3.6−4.4 and 10 min, and respective high-energy wave duration of 5.5 and >14 h. The two observed waveforms were significantly different with wave amplitude and period ratios of ~16 and ~3, respectively. We infer tsunamigenic source dimensions of 3.4–4.1 km and 32.5 km, for inside and outside of the Palu Bay, respectively. Our numerical simulations fairly well reproduced both tsunami observations in Pantoloan and Mamuju; except for the arrival time in Mamuju. However, it was incapable of reproducing the maximum reported coastal amplitudes of 6–11 m. It is possible that these two sources are different parts of the same tectonic source. A bay oscillation mode of ~85 min was revealed for the Palu Bay through numerical modeling. Actual sea surface disturbances and landslide-generated waves were captured by two video recordings from inside the Palu Bay shortly after the earthquake. It is possible that a large submarine landslide contributed to and intensified the Sulawesi tsunami. We identify the southern part of the Palu Bay, around the latitude of -0.82oS, as the most likely location of a potential landslide based on our backward tsunami ray tracing analysis. However, marine geological data from the Palu Bay are required to confirm such hypothesis.

Tectonics and geodynamics of the eastern Tethys and northern Gondwana since the Jurassic

Southeast Asia experienced a complex tectonic and geodynamic history related to the subduction of the eastern Tethyan ocean basins, resulting from the long-term convergence between the Indo-Australian, Eurasian, and Pacific plates since Pangea breakup. The complex collage of continental and island arc terranes can be reconstructed into an estimated ancient arrangement using plate tectonic reconstruction approaches based on a synthesis of continental and marine geological and geophysical data. We use the open-source and cross-platform software GPlates (www.gplates.org) to refine the evolution of the eastern Neo-Tethys since the latest Jurassic rifting episodes along northern Gondwana. We apply the resulting plate motions to drive numerical models of mantle flow in order to predict the evolving mantle structure. New Guinea’s northward motion over subducted slabs, related to the Sepik back-arc basin and the Maramuni subduction system, resulted in long-term flooding of the margin since ~20 Ma, despite falling long-term global sea levels. The Sundaland continental promontory experienced dynamic uplift in the latest Cretaceous to Eocene times due to the accretion of the Woyla Arc at ~80 Ma, leading to slab breakoff and a temporary interruption of subduction. However, renewed subduction along the Sunda margin resulted in renewed dynamic subsidence from ~30 Ma, which was amplified by regional basin rifting events. In addition, the sinking Sunda slab likely triggered a mantle slab avalanche, resulting in a counterintuitive combination of contemporaneous basin inversion and strong dynamic subsidence from ~15 Ma. The evolution of the eastern Tethyan oceanic gateway provides an important framework for understanding the role of plate tectonics in controlling long-term oceanic circulation and climate, as well as shedding light on the complex interplay between deep Earth and surface processes in driving basin formation and evolution. These results provide new avenues for reconciling stratigraphic and tectonic processes, as well as contributing new approaches for basin analysis and hydrocarbon exploration.

Evidence of active fluid seepage (AFS) in the southern region of the central Mediterranean Sea

Active fluid seepage (AFS) at the seafloor is a global phenomenon associated with seafloor morphologies in different geodynamic contexts. Advanced geophysical techniques have allowed geoscientists to characterise pockmarks, mounds and flares associated with AFS. We present a range of new marine geological data acquired in the southern region of the central Mediterranean Sea (northern Sicily continental margin, northwestern Sicily Channel and offshore of the Maltese Islands), which allow us to identify AFSs. AFSs are spatially distributed as clusters, aligned or isolated at different depths, ranging from few decametres offshore of the Maltese Islands; up to 400 m offshore of northern Sicily and in the northwestern Sicily Channel. Mounds have heights ranging from 2 to 15 m and form hummocky surfaces. Seafloor samples were collected at the top of the mounds and were analysed using a SEM with an EDX. Geochemical features reveal that seafloor samples are slightly enriched in O, S and Ba and seem to indicate the existence of an external source of fluids and the occurrence of sediment-fluids interaction processes. Pockmarks with sub-circular planform shapes and U/V-shaped cross-sections are found in sizes ranging from 5 to 530 m. Gas flares occur on both the continental shelf as well as the upper slope.

Initiation and long-term instability of the East Antarctic Ice Sheet

Antarctica's continental-scale ice sheets have evolved over the past 50 million years. However, the dearth of ice-proximal geological records limits our understanding of past East Antarctic Ice Sheet (EAIS) behaviour and thus our ability to evaluate its response to ongoing environmental change. The EAIS is marine-terminating and grounded below sea level within the Aurora subglacial basin, indicating that this catchment, which drains ice to the Sabrina Coast, may be sensitive to climate perturbations. Here we show, using marine geological and geophysical data from the continental shelf seaward of the Aurora subglacial basin, that marine-terminating glaciers existed at the Sabrina Coast by the early to middle Eocene epoch. This finding implies the existence of substantial ice volume in the Aurora subglacial basin before continental-scale ice sheets were established about 34 million years ago. Subsequently, ice advanced across and retreated from the Sabrina Coast continental shelf at least 11 times during the Oligocene and Miocene epochs. Tunnel valleys associated with half of these glaciations indicate that a surface-meltwater-rich sub-polar glacial system existed under climate conditions similar to those anticipated with continued anthropogenic warming. Cooling since the late Miocene resulted in an expanded polar EAIS and a limited glacial response to Pliocene warmth in the Aurora subglacial basin catchment. Geological records from the Sabrina Coast shelf indicate that, in addition to ocean temperature, atmospheric temperature and surface-derived meltwater influenced East Antarctic ice mass balance under warmer-than-present climate conditions. Our results imply a dynamic EAIS response with continued anthropogenic warming and suggest that the EAIS contribution to future global sea-level projections may be under-estimated.

Evidence for a dynamic grounding line in outer Filchner Trough, Antarctica, until the early Holocene

Previous reconstructions of ice-sheet changes in Antarctica’s Weddell Sea sector since the Last Glacial Maximum (LGM) at 19–23 cal. (calibrated) kyr B.P. suffered from large uncertainties and were partly contradictory. As a consequence, the contribution of this sector to the LGM sea-level lowstand and post-LGM sea-level rise was unclear. Furthermore, whether and how precursor water masses for Antarctic Bottom Water (AABW) were formed in the Weddell Sea Embayment under glacial conditions is unknown, as this today requires the existence of the floating Filchner-Ronne Ice Shelf. Here we present new marine geophysical and marine geological data from the outer shelf section of the Filchner paleo–ice stream trough documenting that grounded ice had advanced onto and retreated from the outer shelf prior to 27.5 cal. kyr B.P., i.e., >4500 yr before the LGM. The data reveal the presence of a stacked grounding-zone wedge (GZW) just south of 75°30′S. This GZW was formed during two episodes of grounding-line re-advance onto the outer shelf after 11.8 cal. kyr B.P., with data further inshore implying paleo–ice stream retreat from the GZW location prior to 8.7 cal. kyr B.P. Our findings show that (1) ice-sheet buildup in the Weddell Sea sector made only limited contributions to the LGM sea-level lowstand, (2) ice-ocean interaction below an ice shelf in outer Filchner Trough could have contributed to AABW production at the LGM, and (3) numerical models need to take into account a highly dynamic ice-sheet behavior in regions of the West Antarctic Ice Sheet and East Antarctic Ice Sheet confluence.

Depositional canyon heads at the edge of narrow and tectonically steepened continental shelves: Comparing geomorphic elements, processes and facies in modern and outcrop examples

Marine geology data show that canyon heads can be the site of depositional processes and furnish the details of the geometry of their geomorphic elements. Canyon heads are usually floored by sediment with a prevailing coarse-grained nature and their sampling is very difficult thus preventing the characterization of the facies of their infill. Lithological and facies information is however available through outcrop studies. In this paper, we integrate modern seafloor and outcrop data to characterize the architecture of depositional canyon heads in tectonically active continental margins with a narrow shelf. The modern examples are located along the northeastern Sicilian margin (Milazzo and Niceto canyon-head systems), whereas the ancient one, Pliocene in age, is located onshore, along the Ligurian coast (Ventimiglia canyon-head system). The modern Milazzo canyon head is located at the coastline and has a steep slope. The flanking deposits are equivalent to the oldest Gilbert delta foresets of the Ventimiglia canyon head as the delta progrades directly into the upper slope. A deeply entrenched channel and a large chute mark the mostly erosional area directly facing the mouths of the rivers that enter the Milazzo canyon head. Laterally, the upper part of the foresets slope is characterized by a bulge with swales and ridges topography. These geomorphic elements are interpreted to be formed by debris flows and turbidity currents as suggested by the upper part of the Ventimiglia foresets, where chaotic, massive or graded deposits are observed. The swales and ridges topography gradually disapper downslope; this area is dominated by turbulent processes due to flow expansion from a confined to a more unconfined setting. An high turbulent flow environment is also confirmed by the formation of plunge pools, due to hydraulic jump, at the foresets-toesets transition. Similar features in the outcrop are infilled by bedsets facies with grain-size coarser than the eroded surroundings. The modern Niceto canyon head is connected landwards to a delta system that stretches across a 1 km wide shelf. Channelized delta distributaries are similar to the topset strata of the youngest deltas of the Ventimiglia canyon head. Channels are up to 200 m wide and 50 m deep and show axial bedform trains confirming that large scale trough cross beds are an important facies of channel infill. Wave reworking in the upper part of the topsets is also suggested by both the modern and outcrop data.Our work shows how the nature of the infill and the depositional processes at the canyon heads are dependent on the shelf width and can give hints on the degree of evolution of the canyon itself. In addition, our work shows how the location and character of river entry points is important in dictating lateral facies variations within canyon heads.