Specific computational tools assist geologists in identifying and sorting lithologies in well surveys and reducing operational costs and practical working time. This allows for the management of ...professional output, the efficient interpretation of data, and completion of scientific research on data collected in geologically distinct regions. Machine learning methods and applications integrate large sets of information with the goal of efficient pattern recognition and the capability of leveraging accurate decision making. The objective of this study is to apply machine learning methods to the supervised classification of lithologies using multivariate log parameter data from offshore wells from the International Ocean Discovery Program (IODP). According to the analysis of the lithologies proposed in the IODP Expeditions and for the application of our methods, the lithologies were divided into four groups. The IODP Expeditions were organized into four templates for better results in analyzing the set of expeditions and practical application of the methods. The templates were submitted to training, validation, and testing by multilayer perceptron (MLP), decision tree, random forest, and support vector machine (SVM) methods. The evaluation was randomly divided into training (70%), validation (10%), and testing (20%) using the classification methods as an evaluation of the results. In the results, it was observed that Template1 (IODP Expedition 362) obtained better results with the MLP method, Template2 (IODP Expeditions 354, 355, and 359) and Template3 (IODP Expeditions 354, 355, 359, and 362) obtained better results with the random forest method with greater than 80.00% accuracy. For cross-validation, the random forest method performed well in all scenarios. In the practical template, the G2 group obtained a better result with the MLP method with an average accuracy above 85.00%. It is expected that machine learning methods can help improve the study of geology with accurate and rapid answers related to interpreting collected data in different study regions.
•Machine learning methods were applied to standard and practical data templates for lithological classification.•RandomForest and MLP methods achieved the best results, with accuracy above 80.00%.•Methods for fast classification of offshore wells with multivariate data are provided.
As polar exploration reached its zenith, and in the same month
that Captain Robert Falcon Scott perished in Antarctica, four young
scientists from Zurich took ship for Greenland. Though they had
...little previous experience of arctic travel, their ambition was to
achieve the first west-to-east crossing of the northern
hemisphere's largest ice cap, making scientific observations along
the way. Few outside Switzerland have heard of this expedition or
its leader, the meteorologist Alfred de Quervain, in spite of its
success. In thirty-one days in the summer of 1912, the party
sledded across 640 kilometres of untracked snow and ice. Nobody
died or fell into a crevasse, although there were some near misses.
The voyage was more than a well-executed feat of arctic travel: de
Quervain and his colleagues collected data still used today by
scientists researching the effects of climate change on Greenland's
ice cap. De Quervain's popular account of his adventures, published
in German in 1914, is both a minor classic of exploration
literature and a sympathetic portrayal of life in Greenland's
remote coastal settlements in the early twentieth century.
Published to coincide with the expedition's 110th anniversary,
Across Greenland's Ice Cap includes the explorer's
original text, translated into English by his daughter and
son-in-law; a historical and biographical introduction by Martin
Hood; reflections on the journey's scientific legacy by the
geographers Andreas Vieli and Martin Lüthi; and a treasure trove of
hand-tinted lantern slides reproduced in full colour.
Marine sediments host an unexpectedly large microbial biosphere, suggesting unique microbial mechanisms for surviving burial and slow metabolic turnover. Although dormancy is generally considered an ...important survival strategy, its specific role in subsurface sediments remains unclear. We quantified dormant bacterial endospores in 331 marine sediment samples from diverse depositional types and geographical origins. The abundance of endospores relative to vegetative cells increased with burial depth and endospores became dominant below 25 m, with an estimated population of 2.5 × 10
to 1.9 × 10
endospores in the uppermost kilometer of sediment and a corresponding biomass carbon of 4.6 to 35 Pg surpassing that of vegetative cells. Our data further identify distinct endospore subgroups with divergent resistance to burial and aging. Endospores may shape the deep biosphere by providing a core population for colonization of new habitats and/or through low-frequency germination to sustain slow growth in this environment.
•We studied the rift-to-drift transition of the SCS.•Three types of basement domains have been identified.•The transition is composed of continental crust remnants with magmatic additions.•We ...interpreted the continental margin of the SCS as a magma-intermediate margin.
The South China Sea margins represent a critical natural laboratory to study the processes and parameters controlling the rift-to-drift transition. High quality seismic data previously suggested the occurrence of a relatively sharp transition between the continental and oceanic domains, a hypothesis recently validated by the results of the IODP Expedition 367&368 drilled in the northern South China Sea distal margin. Drilling results in this transition cored Mid-Ocean Ridge type basaltic basement (Site U1502), while its lateral equivalent showed continental affinities (Site U1499). Seismic data document the lateral evolution of this narrow transition zone (∼15 to 25 km wide) and tectono-magmatic context related to breakup. A short-period magmatic event occurred during the latest stage of continental rifting and intruded the edge of the thinned continental crust, triggering crustal breakup and onset of steady-state seafloor spreading. The architecture of the transitional domain documented in this work is in marked contrast with those interpreted as either magma-starved or magma-rich at breakup time, suggesting that the continental margin of the SCS is intermediate between the classical end-member magmatic archetypes. We propose that the magmatic event triggering continental breakup is related to decompression melting linked to the ascending asthenosphere. It is assumed that this event was rapid at geological time scale (<10 Ma) and was favored by a high mantle temperature.
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.
Key Points
New MATLAB algorithm quantifies K, U, and Th contents in marine sediments from NGR spectra
NGR‐derived element contents have good accuracy and satisfactory precision
The algorithm rapidly produces useful shipboard data (few minutes) at no extra cost
The International Ocean Discovery Program (IODP) conducted a series of expeditions between 2013 and 2016 that were designed to address the development of monsoon climate systems in Asia and ...Australia. Significant progress was made in recovering Neogene sections spanning the region from the Arabian Sea to the Sea of Japan and southward to western Australia. High recovery by advanced piston corer (APC) has provided a host of semi-continuous sections that have been used to examine monsoonal evolution. Use of the half-length APC was successful in sampling sand-rich sediment in Indian Ocean submarine fans. The records show that humidity and seasonality developed diachronously across the region, although most regions show drying since the middle Miocene and especially since ∼ 4 Ma, likely linked to global cooling. A transition from C3 to C4 vegetation often accompanied the drying but may be more linked to global cooling. Western Australia and possibly southern China diverge from the general trend in becoming wetter during the late Miocene, with the Australian monsoon being more affected by the Indonesian Throughflow, while the Asian monsoon is tied more to the rising Himalaya in South Asia and to the Tibetan Plateau in East Asia. The monsoon shows sensitivity to orbital forcing, with many regions having a weaker summer monsoon during times of northern hemispheric Glaciation. Stronger monsoons are associated with faster continental erosion but not weathering intensity, which either shows no trend or a decreasing strength since the middle Miocene in Asia. Marine productivity proxies and terrestrial chemical weathering, erosion, and vegetation proxies are often seen to diverge. Future work on the almost unknown Paleogene is needed, as well as the potential of carbonate platforms as archives of paleoceanographic conditions.
Southeast Asia is located in an important regional geodynamic intersection zone surrounded by inward subduction systems on three sides, consisting the largest and most complicated convergent ...subduction system in the earth. The deep circulation and ultimate destination of the subducted material have always been an elusive scientific mystery, lacking both systematic scientific observation and accepted theoretical models. In this review we present geophysical, geochemical and geodynamical models in last decades regarding the seismic tomographic deep structure, material exchanges and evolution history of the Curved Subduction System (CSS) in SE Asia, and identify remained challenges in constructing the deep mantle structure and quantifying the feedback between the subducting slab and the interior recycling materials relevant to the dynamic processes within the theme of mass and energy transfer. We propose that increased understanding of seismic tomography within the CSS, combined with geochemical analysis and computational geodynamic modeling, will aid clearer portrayal of the dynamic mechanisms controlling the evolution of such ring-shape subduction systems on Earth.
Magnetic surveys at tectonic windows that expose magnetic polarity boundaries provide the unique opportunity to explore the pattern of magnetization variations within the oceanic crust and determine ...the spatially averaged magnetizations of source layers that contribute to marine magnetic anomalies. Here we investigate the C2An.2n/C2An.2r polarity boundary in the tectonic window of Pito Deep, which has exposed a cross‐section through lavas, dikes, and the uppermost kilometer of gabbros at fast‐spread ocean crust. Near‐bottom magnetic anomaly surveys from two expeditions have been incorporated into a penalized least squares inversion method. The application of this method to magnetic data allows us to account for complex bathymetry and differing observation altitudes. When correlated with rock type, the magnetization solution shows median values of 4.4 ± 2.7 A/m for lavas, 2.0 ± 1.9 A/m for dikes, and 1.9 ± 1.9 A/m for gabbros. On a regional scale, lavas and dikes have a different polarity of magnetization than the underlying gabbros. The geometry of the polarity boundary is compatible with a large (~6 km) horizontal offset or very shallow dip of isotherms at the dike/gabbro boundary, and indicates that the zone of melt is significantly wider across axis than predicted from seismic tomography models that suggest pervasive cooling throughout the lower crust within a few kilometers of the spreading center.
Plain Language Summary
Over 30% of the Earth's ocean crust is created in fast‐spread environments like the East Pacific Rise, but there is no consensus on how the lower portion of the crust is formed and cooled. This is in part because it is difficult to access lower crustal gabbroic samples formed at fast‐spread ridges. Because ocean crustal rocks preserve a record of Earth's magnetic field at the time they cool, we can use magnetic data to help distinguish between different formation models. We use magnetic anomaly data in an exposed section of fast‐spread crust in order to determine the pattern of magnetization variations in these rocks. This new method solves for crustal magnetization over a ~10‐km wide survey area to determine a robust average magnetization of lavas, dikes, and gabbroic rocks. Our magnetizations agree with previous estimates for samples from fast‐spread crust. The survey area also includes a magnetic reversal, and the pattern of magnetization can only be reproduced if there is a large horizontal offset in temperature between the dike and gabbroic rocks, or the gabbroic section cools very slowly (meaning shallow isotherms). This means temperatures remain hotter in the gabbroic section of lower ocean crust further off axis.
Key Points
An application of the Occam inversion incorporates variable altitude anomaly data over complex topography to determine magnetic structure
We found spatially averaged remanence estimates for lavas (4.4 ± 2.7 A/m), dikes (2.0 ± 1.9 A/m), and uppermost gabbros (1.9 ± 1.9 A/m)
Results support shallowly dipping isotherms in the gabbros, or a large horizontal offset of isotherms near the dike‐gabbro transition
The physical properties of rock within Oceanic Core Complexes (OCC) provide information about the history of magmatism, deformation and alteration associated with detachment faulting and unroofing of ...their gabbroic sequences. New core and logging data from Atlantis Bank (AB) OCC are compared with prior deep sea drilling data from this site on the Southwest Indian Ridge, as well as from Atlantis Massif (AM) OCC on the Mid-Atlantic Ridge. The average seismic velocity at each site is typical for gabbroic rock. Downhole core and log variations are found to depend on both porosity and alteration. Porosity at millimeter to meter scale impacts P-wave velocities (6.0–6.4 km/s) in the upper several hundred meters at both OCC. Below ~ 600–800 m depth, in situ velocities are higher (6.6–6.9 km/s) for the remainder of the 1.5 km drilled to date, except in zones where alteration is significant. Variability of 0.5–1 km/s over depth intervals of a few meters is persistent where mineral alteration exceeds 10–20%, whereas variability drops to ± 0.1 km/s for intervals affected by little to no alteration. Seismic anisotropy is negligible overall, with just a few intervals showing consistent fast azimuth and magnitude of a few percent. The depth extent of alteration, probably related to the zone deformed below the detachment when active, is ~ 600–800 meters at both AB and AM.
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