Temporal linkages of explosive activity of Kolumbo and Santorini Volcanoes (Greece)

International Ocean Discovery Program (IODP) Expedition 372 combined two research topics, slow slip events (SSEs) on subduction faults (IODP Proposal 781A-Full) and actively deforming gas hydrate-bearing landslides (IODP Proposal 841-APL). Our study area on the Hikurangi margin, east of the coast of New Zealand, provided unique locations for addressing both research topics.SSEs at subduction zones are an enigmatic form of creeping fault behavior. They typically occur on subduction zones at depths beyond the capabilities of ocean floor drilling. However, at the northern Hikurangi subduction margin they are among the best-documented and shallowest on Earth. Here, SSEs may extend close to the trench, where clastic and pelagic sediments about 1.0-1.5 km thick overlie the subducting, seamount-studded Hikurangi Plateau. Geodetic data show that these SSEs recur about every 2 years and are associated with measurable seafloor displacement. The northern Hikurangi subduction margin thus provides an excellent setting to use IODP capabilities to discern the mechanisms behind slow slip fault behaviour.

In recent years, research funding agencies, universities, and governments have become increasingly concerned with promoting the reuse of research datasets. Enabling researchers to evaluate the trustworthiness and fitness-for-use of research datasets produced by others is critical for facilitating the reuse of these datasets. Understanding how researchers make these evaluations is crucial for developing digital infrastructure and tools, such as data repositories and metadata schema, in a way that better supports researchers in making these evaluations. Physical samples such as rocks are critical for generating datasets in many scientific domains. Often, samples are collected on field expeditions conducted by large infrastructural projects. These projects comprise many human and non-human components that affect the quality and integrity of samples. However, little is known about whether and how prospective dataset users evaluate the samples' trustworthiness and sample collection processes underlying these datasets. Researchers'strategies for evaluating sample trustworthiness are explored through a longitudinal qualitative case study (ethnographic observation, interviews (n = 66), and document analysis) of subseafloor biosphere research, an earth sciences domain. Domain researchers use rock samples collected on research cruises conducted by the International Ocean Discovery Program (IODP). Subseafloor biosphere researchers are primarily concerned about samples being compromised by microbiological contamination. Researchers vary regarding the components of IODP infrastructure they consider when evaluating sample trustworthiness. These components include methods to process samples, people handling samples, IODP policies and procedures, and IODP organizational politics. Researchers'strategies vary according to their disciplinary background, with microbiologists employing more fine-grained judgments about methods; whether researchers have participated in IODP expeditions, with those who have employing more fine-grained judgments about people involved; and whether researchers have ever been involved in organizing cruises or serving on IODP committees, with those who have employing more fine-grained judgments about many aspects of cruises. Researchers who make less complex decisions may be prone to erroneously trusting contaminated samples; researchers who make more complex decisions may be prone to erroneously discarding uncontaminated samples. The paper concludes by considering implications for the design of digital infrastructures to support researchers in evaluating sample trustworthiness.

<p>South China Sea (SCS) is not only the crucial pathway for transporting terrigenous materials from Eurasia to the Western Pacific Ocean since the early Oligocene, but also the dominant accumulation and preservation place as a result of limited material exchange between the semi-closed oceanic basin and the open ocean since the middle Miocene. Diverse factors, including global climate changes, eustatic sea level change, regional and local tectonic events, et al., controlled the sedimentary dispersal and accumulational patterns in the oceanic basin of the SCS, which can be revealed by the calculation of sediment budget at different geological times, as the sediment budget can illustrate directly the sediment influx, storage, loss in a basin system <em>(Hapke et.al, 2010).</em></p><p>By interpreting the multichannel seismic profiles covering the whole oceanic basin with constraints from International Ocean Discovery Program (IODP) Expeditions 349, 367 and 368, we reconstructed the sequence stratigraphy framework of the study area, and then calculated the sedimentary budget at different geological time. This work aims to quantitate the sedimentary dispersal and accumulation in the oceanic basin for the first time.</p><p>Until now we have completed the sequence boundary identification and dating, as well as the division of sedimentary units of all multichannel seismic profiles. The grid data of different sequence boundaries have been obtained and posted on the bathymetric map, and by the time-depth conversion with appropriate function in different region referred from the drilling results of IODP expeditions, we have figured out the thickness of each sedimentary unit. In the following we will do the decompaction correction before calculating the sedimentary budget of the whole oceanic basin at different times. This work could increase our understandings on the major controlling factors and possible material sources of the deposition process.</p><p> </p>

International Ocean Discovery Program (IODP) Expedition 360 was the first leg of Phase I of the SloMo (shorthand for nature of the lower crust and Moho at slower spreading ridges) Project, a multiphase drilling program that proposes to drill through the outermost of the global seismic velocity discontinuities, the Mohorovicic seismic discontinuity (Moho). The Moho corresponds to a compressional wave velocity increase, typically at ∼7 km beneath the oceans, and has generally been regarded as the boundary between crust and mantle. An alternative model, that the Moho is a hydration front in the mantle, has recently gained credence upon the discovery of abundant partially serpentinized peridotite on the seafloor and on the walls of fracture zones, such as at Atlantis Bank, an 11-13 My old elevated oceanic core complex massif adjacent to the Atlantis II Transform on the Southwest Indian Ridge. Hole U1473A was drilled on the summit of Atlantis Bank during IODP Expedition 360, 1-2 km away from two previous Ocean Drilling Program (ODP) holes: Hole 735B (drilled during ODP Leg 118 in 1987 and ODP Leg 176 in 1997) and Hole 1105A (drilled during ODP Leg 179 in 1998). A mantle peridotite/gabbro contact has been traced by dredging and diving along the transform wall for 40 km. The contact is located at ∼4200 m depth at the drill sites but shoals considerably 20 km to the south, where it was observed in outcrop at 2563 m depth. Moho reflections have, however, been found at ∼5-6 km beneath Atlantis Bank and <4 km beneath the transform wall, leading to the suggestion that the seismic discontinuity may not represent the crust/mantle boundary but rather an alteration (serpentinization) front. This then raises the interesting possibility that a whole new planetary biosphere may thrive due to methanogenesis associated with serpentinization. The SloMo Project seeks to test these two hypotheses at Atlantis Bank and evaluate carbon sequestration in the lower crust and uppermost mantle. A primary objective of SloMo Leg 1 was to explore the lateral variability of the stratigraphy established in Hole 735B. Comparison of Hole U1473A with Holes 735B and 1105A allows us to demonstrate a continuity of process and complex interplay of magmatic accretion and steady-state detachment faulting over a time period of ∼128 ky. Preliminary assessment indicates that these sections of lower crust are constructed by repeated cycles of intrusion, represented in Hole U1473A by approximately three upwardly differentiated hundreds of meter-scale bodies of olivine gabbro broadly similar to those encountered in the deeper parts of Hole 735B. Specific aims of Expedition 360 focused on gaining an understanding of how magmatism and tectonism interact in accommodating seafloor spreading, how magnetic reversal boundaries are expressed in the lower crust, assessing the role of the lower crust and shallow mantle in the global carbon cycle, and constraining the extent and nature of life at deep levels within the ocean lithosphere.

International Ocean Discovery Program (IODP) Expedition 353 (29 November 2014–29 January 2015) drilled six sites in the Bay of Bengal, recovering 4280 m of sediments during 32.9 days of on-site drilling. Recovery averaged 97%, including coring with the advanced piston corer, half-length advanced piston corer, and extended core barrel systems. The primary objective of Expedition 353 is to reconstruct changes in Indian monsoon circulation since the Miocene at tectonic to centennial timescales. Analysis of the sediment sections recovered will improve our understanding of how monsoonal climates respond to changes in forcing external to the Earth’s climate system (i.e., insolation) and changes in forcing internal to the Earth’s climate system, including changes in continental ice volume, greenhouse gases, sea level, and the ocean-atmosphere exchange of energy and moisture. All of these mechanisms play critical roles in current and future climate change in monsoonal regions. The primary signal targeted is the exceptionally low salinity surface waters that result, in roughly equal measure, from both direct summer monsoon precipitation to the Bay of Bengal and runoff from the numerous large river basins that drain into the Bay of Bengal. Changes in rainfall and surface ocean salinity are captured and preserved in a number of chemical, physical, isotopic, and biological components of sediments deposited in the Bay of Bengal. Expedition 353 sites are strategically located in key regions where these signals are the strongest and best preserved. Salinity changes at IODP Sites U1445 and U1446 (northeast Indian margin) result from direct precipitation as well as runoff from the Ganges-Brahmaputra river complex and the many river basins of peninsular India. Salinity changes at IODP Sites U1447 and U1448 (Andaman Sea) result from direct precipitation and runoff from the Irrawaddy and Salween river basins. IODP Site U1443 (Ninetyeast Ridge) is an open-ocean site with a modern surface water salinity very near the global mean but is documented to have recorded changes in monsoonal circulation over orbital to tectonic timescales. This site serves as an anchor for establishing the extent to which the north to south (19°N to 5°N) salinity gradient changes over time.

The fatigue resistance of a drill pipe is a critical factor affecting the performance of deep drillings. This study focused on the determination of fatigue strength, through full scale tests, on a selection of actual drill pipes, and the evaluation of the entire drill string fatigue resistance after the analysis of these test results. The fatigue tests cover a variety of drill pipes such as 165, 150 and 140 ksi grades with Delta, GPDS or DSTJ connection, new and used pipes. A resonant fatigue test machine was used to perform rotating fatigue tests on full scale drill pipe sections (or specimens) with dual measurements combined with a control software to keep stress amplitude constant. After these tests, the numbers of cycles to failure were experimentally evaluated along with the observation of the crack initiation locations that resulted to be dependent on several factors as discussed in the paper. Using these test results, the fatigue evaluation of drill string, planned for International Ocean Discovery Program (IODP) expedition 405 JTRACK operations, was examined by calculating the cumulative damage ratio to find the possible endurance of the operation. It was found that a specific type of drill pipe has higher fatigue strength than others, so the use of that drill pipe will contribute significantly to the prevention of fatigue failure during the offshore drilling expedition.

During International Ocean Discovery Program (IODP) expeditions, shipboard‐generated data provide the first insights into the cored sequences. The natural gamma radiation (NGR) of the recovered material, for example, is routinely measured on the ocean drilling research vessel DV JOIDES Resolution. At present, only total NGR counts are readily available as shipboard data, although full NGR spectra (counts as a function of gamma‐ray energy level) are produced and archived. These spectra contain unexploited information, as one can estimate the sedimentary contents of potassium (K), thorium (Th), and uranium (U) from the characteristic gamma‐ray energies of isotopes in the 40K, 232Th, and 238U radioactive decay series. Dunlea et al. (2013) quantified K, Th, and U contents in sediment from the South Pacific Gyre by integrating counts over specific energy levels of the NGR spectrum. However, the algorithm used in their study is unavailable to the wider scientific community due to commercial proprietary reasons. Here, we present a new MATLAB algorithm for the quantification of NGR spectra that is transparent and accessible to future NGR users. We demonstrate the algorithm's performance by comparing its results to shore‐based inductively coupled plasma‐mass spectrometry (ICP‐MS), inductively coupled plasma‐emission spectrometry (ICP‐ES), and quantitative wavelength‐dispersive X‐ray fluorescence (XRF) analyses. Samples for these comparisons come from eleven sites (U1341, U1343, U1366‐U1369, U1414, U1428‐U1430, and U1463) cored in two oceans during five expeditions. In short, our algorithm rapidly produces detailed high‐quality information on sediment properties during IODP expeditions at no extra cost.

&amp;lt;p&amp;gt;International Ocean Discovery Program (IODP) Expedition 386, Japan Trench Paleoseismology (offshore period: 13 April to 1 June 2021; Onshore Science Party: 14 February to 14 March 2022) was designed to test the concept of submarine paleoseismology in the Japan Trench, the area where the last, and globally only one out of four instrumentally-recorded, giant (i.e. magnitude 9 class) earthquake occurred back in 2011. &amp;amp;#8220;Submarine paleoseismology&amp;amp;#8221; is a promising approach to investigate deposits from the deep sea, where earthquakes leave traces preserved in the stratigraphic succession, to reconstruct the long-term history of earthquakes and to deliver observational data that help to reduce uncertainties in seismic hazard assessment for long return periods. This expedition marks the first time, giant piston coring (GPC) was used in IODP, and also the first time, partner IODP implementing organizations cooperated in jointly implementing a mission-specific platform expedition.&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;We successfully collected 29 GPCs at 15 sites (1 to 3 holes each; total core recovery 831 meters), recovering 20 to 40-meter-long, continuous, upper Pleistocene to Holocene stratigraphic successions of 11 individual trench-fill basins along an axis-parallel transect from 36&amp;amp;#176;N &amp;amp;#8211; 40.4&amp;amp;#176;N, at water depth between 7445-8023 m below sea level. These offshore expedition achievements reveal the first high-temporal and high spatial resolution investigation and sampling of a hadal oceanic trench,&amp;lt;strong&amp;gt; &amp;lt;/strong&amp;gt;that form the deepest and least explored environments on our planet.&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;The cores are currently being examined by multimethod applications to characterize and date hadal trench sediments and extreme event deposits, for which the detailed sedimentological, physical and (bio-)geochemical features, stratigraphic expressions and spatiotemporal distribution will be analyzed for proxy evidence of giant earthquakes and (bio-)geochemical cycling in deep sea sediments. Initial preliminary results presented in this EGU presentation reveal event-stratigraphic successions comprising several 10s of potentially giant-earthquake related event beds, revealing a fascinating record that will unravel the earthquake history of the different along-strike segments that is 10&amp;amp;#8211;100 times longer than currently available information. Post-Expedition research projects further analyzing these initial IODP data sets will (i) enable statistically robust assessment of the recurrence patterns of giant earthquakes, there while advancing our understanding of earthquake-induced geohazards along subduction zones and (ii) provide new constraints on sediment and carbon flux of event-triggered sediment mobilization to a deep-sea trench and its influence on the hadal environment.&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;&amp;amp;#160;&amp;lt;/p&amp;gt;

International Ocean Discovery program (IODP) Expedition 383 Dynamics of the Pacific Antarctic Circumpolar Current (DYNAPACC) (Lamy et al., 2019; 2021) drilled a series of cores from the Pacific sector of the Southern Ocean in order to explore atmosphere-ocean-cryosphere glacial-interglacial dynamics their implications for regional and global climate changes. IODP Expedition 383 sites constitute the first continuous drill cores at key locations of the Subantarctic Pacific Southern Ocean extending through the Pleistocene and back into the Pliocene.Here we focus on coccolith relative and absolute abundance as well as productivity variations for the last 0.5 Million year, in order to understand the nannofloral response to glacial-interglacial cycles and related changes in carbonate production and export. Our data has been generated at IODP Sites U1539 (56&amp;#176;09.0655&amp;#8242;S, 115&amp;#176;08.038&amp;#8242;W, ~1600 nmi west of the Strait of Magellan at 4070 m water depth) and U1540 (55&amp;#176;08.467&amp;#8242;S, 114&amp;#176;50.515&amp;#8242;W, ~1600 nmi west of the Strait of Magellan at 3580 m water depth), drilled at a southern and northern location in the central Pacific within the ACC, respectively. Coccolithophore diversity and coccolith numbers change dramatically in the studied cores, ranging from high values during interglacials (up to ca. 1011 coccoliths per gram of sediment, as in MIS11, Saavedra-Pellitero et al., 2017) to low values during the glacials, where they are outcompeted by siliceous microfossils, mostly diatoms.ReferencesLamy, F., Winckler, G., Alvarez Zarikian, C.A., and the Expedition 383 Scientists, 2019. Expedition 383 Preliminary Report: Dynamics of the Pacific Antarctic Circumpolar Current. International Ocean Discovery Program. https://doi.org/10.14379/iodp.pr.383.2019Lamy, F., Winckler, G., Alvarez Zarikian, C.A., and the Expedition 383 Scientists, 2021. Dynamics of the Pacific Antarctic Circumpolar Current. Proceedings of the International Ocean Discovery Program, 383: College Station, TX (International Ocean Discovery Program). https://doi.org/10.14379/iodp.proc.383.2021Saavedra-Pellitero M., Baumann K.-H., Lamy F., and K&amp;#246;hler P., 2017. Coccolithophore variability across Marine Isotope Stage 11 in the Pacific sector of the Southern Ocean and its potential impact on the carbon cycle. Paleoceanography, 32, 864&amp;#8211;880, doi:10.1002/2017PA003156.

Extended shallow carbonate platform, pelagic, and drift deposits were drilled during International Ocean Discovery Program (IODP) Expedition 359 in the Inner Sea of the Maldives. These sediments yield rich and well-diversified benthic, planktonic foraminiferal and nannofossil assemblages spanning from the early Oligocene to the Recent. We present here the shore-based revised integrated biostratigraphy of these microfossil groups at IODP Hole 359-U1468A together with the paleobathymetric reconstruction. Our data suggests the presence of a late Oligocene carbonate platform, marked by the shallowest water depths of the entire sequence of around 80 m. This carbonate platform sequence occurred from around 29 Ma, the extrapolated minimum age estimate, at least up to 27.5 Ma and possibly up to 25.4 Ma. Up the sequence, similar carbonate production conditions occurred until 22.5 Ma across the Oligocene–Miocene transition, equated at 23.04 Ma, with increased water depths &gt;120 m. Notably, in the time interval approximately from 24 to 21.5 Ma, orbitally induced sapropel layers indicate a change of open to restricted circulation. However, at around 22.5 Ma, pelagic deposition at a distal slope occurred with sedimentation rates of 3 cm/years. This initially occurred in water depths of &gt;350 m but gradually reached deposition in water depths of &gt;500 m, which persisted from 21.12 Ma until approximately the extrapolated age of 12.8 Ma. Sedimentation rates gradually increased to 10.5 cm/1000 years at around 450 m below sea floor, marking the initiation of the drift sequence as identified in seismic lines with an age estimate of 12.8 Ma. The initiation of the drift sequence is also marked by a drastic decrease in the preservation of benthic and planktonic foraminifera from good to very poor at around 12.8 Ma. The drift sequence essentially continued to the present day but was interrupted by two events: the deposition of distinct shallow water benthic shoals and a large hiatus. From 12.8 Ma, a shallowing upward bathymetry is suggested by the occurrence of shallow benthic foraminiferal assemblages that close to around 11.93 Ma reached a maximum water depth of 80 m. This shoal then prograded into the basin and persisted at least until 9.89 Ma. Basin conditions with water depths exceeding 500 m were re-established in the upper part of the sedimentary succession after a hiatus spanning approximately from 9.83 Ma to 2.39 Ma, implying that renewed open ocean conditions occurred in the Pliocene–Pleistocene part of the sedimentary record.

Evaluation of machine learning methods for lithology classification using geophysical data

&amp;lt;p&amp;gt;Short historical and even shorter instrumental records limit our perspective of earthquake maximum magnitude and recurrence, and thus are inadequate to fully characterize Earth&amp;amp;#8217;s complex and multiscale seismic behavior and its consequences. Examining prehistoric events preserved in the geological record is essential to reconstruct the long-term history of earthquakes and to deliver observational data that help to reduce uncertainties in seismic hazard assessment for long return periods. Motivated by the mission to fill the gap in long-term records of giant (Mw 9 class) earthquakes such as the Tohoku-Oki earthquake in 2011, International Ocean Discovery Program (IODP) Expedition 386, Japan Trench Paleoseismology, was designed to test and further develop submarine paleoseismology in the Japan Trench.&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;Earthquake rupture propagation to the trench and sediment remobilization related to the 2011 Mw 9.0 Tohoku-Oki earthquake, and the respective structures and deposits are preserved in trench basins formed by flexural bending of the subducting Pacific Plate. These basins are ideal study areas for testing event deposits for earthquake triggering as they have poorly connected sediment transport pathways from the shelf and experience high sedimentation rates and low benthos activity (and thus high preservation potential) in the ultra-deep water hadal environment. Results from conventional coring covering the last ~1,500 y reveal good agreement between the sedimentary record and historical documents. Subbottom profile data are consistent with basin-fill successions of episodic muddy turbidite deposition and thus define clear targets for paleoseismologic investigations on longer timescales accessible only by deeper coring.&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;In 2021, IODP Expedition 386 successfully collected 29 Giant Piston cores at 15 sites (1 to 3 holes each; total core recovery 831 meters), recovering 20 to 40-meter-long, continuous, upper Pleistocene to Holocene stratigraphic successions of 11 individual trench-fill basins along an axis-parallel transect from 36&amp;amp;#176;N &amp;amp;#8211; 40.4&amp;amp;#176;N, at water depth between 7445-8023 m below sea level. The cores are currently being examined by multimethod applications to characterize and date event deposits for which the detailed stratigraphic expressions and spatiotemporal distribution will be analyzed for proxy evidence of giant versus smaller earthquakes versus other driving mechanisms. Initial preliminary results presented in this EGU presentation reveal event-stratigraphic successions comprising several 10s of potentially giant-earthquake related event beds, revealing a fascinating record that will unravel the earthquake history of the different along-strike segments, that is 10&amp;amp;#8211;100 times longer than currently available information. The data set will enable a statistically robust assessment of the recurrence patterns of giant earthquakes as input for improved probabilistic seismic hazard assessment and advanced understanding of earthquake-induced geohazards globally.&amp;amp;#160;&amp;lt;/p&amp;gt;&amp;lt;p&amp;gt;&amp;amp;#160;&amp;lt;/p&amp;gt;

The consolidation state of sediments provides crucial information about the pore pressure in sediments, as well as the loading and unloading history of sedimentary basins. We performed consolidation tests on mudstones and calcareous oozes just below the thick volcaniclastics in the Hellenic Arc Volcanic Field, Greece. These sediments were sampled from the International Ocean Discovery Program (IODP) Expedition 398 in the Christiana, Santorini, and Kolumbo (CSK) volcanic field.To understand the in-situ stress and pore pressure, we compared the preconsolidation stress (pc) from the consolidation test with the in-situ effective overburden stress (&amp;#963;&amp;#8217;v) calculated from the shipboard bulk density measurement of core samples. The overconsolidation ratio (OCR = pc/&amp;#963;&amp;#8217;v) is used to identify the state of underconsolidation (OCR &lt; 1) or overconsolidation (OCR &gt; 1) at each drill site.In the IODP Sites U1589, U1590 and U1593 in the Anydros Basin, underconsolidation states were identified in the interval 200-600 m below sea floor (OCR = 0.59 to 0.85). A maximum of 40% of the effective in-situ overburden is supported by the excess pore pressure at 200 mbsf. These underconsolidated intervals are overlain by &gt;200 m of volcaniclastics derived from the Santorini and the Kolumbo volcanoes. Therefore, the rapid sediment supply (0.8-1.0 m/ky) from the submarine volcanoes apparently leads to the excess pore pressure, which can make sedimentary basins unstable.On the other hand, measurements from IODP Sites U1591 and U1598 in the Christiana Basin, and Sites U1592 and U1599 in the Anafi Basin showed normal consolidation (i.e., OCR = 1) and overconsolidation (OCR =1.27-2.52) states. Sediments which showed overconsolidation are mostly composed of dolomitic mudstones. The effect of cementation is identified from their consolidation curves, implying that the intergranular bonding contributes to the overconsolidation of sediments. In the presentation, the maximum amount of erosion is calculated to explain the overconsolidation states in the Cristiana and Anafi basins.

International Ocean Discovery Program (IODP) Expedition 395 recovered near-continuous sedimentary records from several major contourite drift bodies in the North Atlantic Ocean. These drifts deposits are influenced by deep-water currents, and studying their composition can inform us on past changes in ocean circulation. Drift sedimentation is a dynamic process that can lead to spatial variation in deposition and preservation through time. Here, we correlate on a glacial-interglacial timescale new IODP Expedition 395 records with Ocean Drilling Program (ODP) records previously cored nearby to assess the degree of variability between sites on the same drift body. We correlate IODP Site U1554 with ODP Site 984 for Bj&amp;#246;rn Drift, and IODP Site U1564 with ODP Site 983 for Gardar Drift. Variations in magnetic susceptibility measured on sediment cores show striking resemblances between the paired sites. The clearly expressed glacial-interglacial scale variability enables astronomical tuning of the records. Furthermore, we explore the possibility of using multiple volcanic ash layers as additional markers for stratigraphic correlation. This work will contribute to the construction of high-resolution age models for the Expedition 395 records, as well as to a better understanding of the evolution of Bj&amp;#246;rn and Gardar Drifts through space and time.

Three boreholes drilled during the International Ocean Discovery Program (IODP) Expedition&amp;#160;396 have yielded unexpected findings of altered granitic rocks covered by basalt flows, interbedded sediments, and glacial mud on the Kolga High situated near the continent-ocean transition on the mid-Norwegian margin. &amp;#160;To assess basin and basement structures near Kolga High in relation to the broader regional setting, a potential field forward modelling study was conducted. One specific goal was to evaluate the density distribution beneath the Kolga granite. The necessity of low-density crustal material beneath the Kolga High challenges the hypothesis of an old, thick, dense, and inherited basement high directly beneath the basalt, given the low gravity signal observed. In our potential field model, the rock density underneath the basalt remains relatively low (2.4 g.cm-3 in average). Based on onshore measurements, Caledonian or Precambrian &amp;#8216;fresh&amp;#8217; granitoids and other inherited basement rocks typically exhibit bulk densities usually exceeding 2.65-2.75 g.cm-3. The gravity signal observed on Kolga High, along with the low-density necessary to fit it, suggests that the inherited basement should be situated at a considerably greater depth (~up to 10 km), which is approximately 5-7 km deeper than the drilled Kolga granite/basalt interface. To unravel the weathering chronology for this enigmatic granite, the K-Ar method was selected to date fine-grained clay minerals. X-ray diffraction was performed on different grain size fractions to identify both protolithic and authigenically formed K-bearing minerals derived from the IODP rock samples (Holes U1565A and U1566A). K-Ar geochronology was then performed on five grain size fractions (