Despite salt being regarded as an extremely efficient, low-permeability hydraulic seal, an increasing number of cross-evaporite fluid escape features have been documented in salt-bearing sedimentary basins. Because of this, it is clear that our understanding of how thick salt deposits impact fluid flow in sedimentary basins is incomplete. We here examine the causes and evolution of cross-evaporite fluid escape in the northern Levant Basin, Eastern Mediterranean. High-quality 3D seismic data offshore Lebanon image hundreds of supra-salt fluid escape pipes distributed widely along the margin. The pipes consistently originate at the crest of prominent sub-salt anticlines, where overlying salt is relatively thin. The fact the pipes crosscut the salt suggests that hydrofracturing occurred, permitting focused fluid flow. Sequential pipes from unique emission points are organized along trails that are several kilometres long, and which are progressively deformed due to basinward gravity gliding of salt and its overburden. Correlation of pipes in 12 trails suggests margin-wide fluid escape started in the Late Pliocene/Early Pleistocene, coincident with a major phase of uplift of the Levant margin. We interpret that the consequent transfer of overpressure from the central basin area, in addition to gas exsolution from hydrocarbons already trapped in sub-salt anticlines, triggered seal failure and cross-evaporite fluid flow. We infer that other causes of fluid escape in the Eastern Mediterranean, such as subsurface pressure changes driven by sea-level variations and salt deposition associated with the Messinian Salinity Crisis, played only a minor role in triggering cross-evaporite fluid flow in the northern Levant Basin. Further phases of fluid escape are unique to each anticline and cannot be easily correlated across the margin. Therefore, despite a common initial cause, long-term fluid escape proceeded according to structure-specific characteristics, such as local dynamics of fluid migration and anticline geometry. Our work shows that the mechanisms triggering cross-evaporite fluid flow in salt basins vary in time and space.

Since creation of spatial data is a costly and time consuming process, researchers, in this domain, in most of the cases rely on open source spatial attributes for their specific purpose. Likewise, the present research aims at mapping landslide susceptibility at the metropolitan area of Chittagong district of Bangladesh utilizing obtainable open source spatial data from various web portals. In this regard, we targeted a study region where rainfall induced landslides reportedly causes causalities as well as property damage each year. In this study, however, we employed multi-criteria evaluation (MCE) technique i.e., heuristic, a knowledge driven approach based on expert opinions from various discipline for landslide susceptibility mapping combining nine causative factors-geomorphology, geology, land use/land cover (LULC), slope, aspect, plan curvature, drainage distance, relative relief and vegetation in geographic information system (GIS) environment. The final susceptibility map was devised into five hazard classes viz., very low, low, moderate, high, and very high, representing 22 km 2 (13%), 90 km 2 (53%); 24 km 2 (15%); 22 km 2 (13%) and 10 km 2 (6%) areas respectively. This particular study might be beneficial to the local authorities and other stake-holders, concerned in disaster risk reduction and mitigation activities. Moreover this study can also be advantageous for risk sensitive land use planning in the study area.

<p>Hydrocarbon escape systems can be regionally active on multi-million-year timescales. However, reconstructing the timing and evolution of repeated escape events can be challenging because their expression may overlap in time and space. In the northern Levant Basin, eastern Mediterranean, distinct fluid escape episodes from common leakage points formed discrete, cross-evaporite fluid escape pipes, which are preserved in the stratigraphic record due to the coeval Messinian salt tectonics.</p><p>The pipes consistently originate at the crest of prominent sub-salt anticlines, where thinning and hydrofracturing of overlying salt permitted focused fluid flow. Sequential pipes are arranged in several kilometers-long trails that were progressively deformed due to basinward gravity-gliding of salt and its overburden. The correlation of the oldest pipes within 12 trails suggests that margin-wide fluid escape started in the Late Pliocene/Early Pleistocene, coincident with a major phase of uplift of the Levant margin. We interpret that the consequent transfer of overpressure from the deeper basin areas triggered seal failure and cross-evaporite fluid flow. We infer that other triggers, mainly associated with the Messinian Salinity Crisis and compressive tectonics, played a secondary role in the northern Levant Basin. Further phases of fluid escape are unique to each anticline and, despite a common initial cause, long-term fluid escape proceeded independently according to structure-specific characteristics, such as the local dynamics of fluid migration and anticline geometry.</p><p>Whereas cross-evaporite fluid escape in the southern Levant Basin is mainly attributed to the Messinian Salinity Crisis and compaction disequilibrium, we argue that these mechanisms do not apply to the northern Levant Basin; here, fluid escape was mainly driven by the tectonic evolution of the margin. Within this context, our study shows that the causes of cross-evaporite fluid escape can vary over time, act in synergy, and have different impacts in different areas of large salt basins.</p>

Over the last decade, there has been a resurgence of interest in the climatic and tectonic mechanisms that drove the Messinian salinity crisis (MSC) and the associated deposition of thick evaporites. The MSC represents an unprecedented palaeoceanographic change that led to a very short (c. 660 kyr) ecological and environmental crisis. However, across the Levantine offshore basin, the sedimentological nature of the top evaporitic units and the mechanisms that controlled the transition from a hypersaline evaporitic unit to brackish deposits (final MSC stage 3) are still disputed. Here, we re-evaluate the deposits associated with the terminal phase of the MSC, named in offshore Lebanon as the Nahr Menashe Unit (NMU).We describe the NMU seismic facies, characterize and map its internal seismic stratigraphy, and provide a new interpretation of its depositional environment, which persisted during the late Messinian and then evolved through a regional reflooding event. The base of the NMU overlies semi-circular depressions, randomly distributed linear marks and surface collapse features, which are indicative of a period of intense evaporite dissolution. The NMU seismic facies observed from the slope to the deep part of the basin support the interpretation of a layered salt-evaporite-sand depositional system subject to complex reworking, dissolution, deposition, and final erosion. A drainage network of valleys and complex tributary channels incising into the top NMU shows marked erosional characteristics, which indicate a dominant southwards sediment transfer following deposition of the NMU. This erosional drainage network formed due to the base-level fall associated with the last phase of the MSC. The base of the channel/valley network does not cut below the bottom of the Narh Menashe dissolution surfaces. The channel and valley network was subsequently infilled by layered sediments interpreted here to represent the post-MSC marine sediments deposited during reflooding. Our analysis challenges the previously proposed fluvial nature of the NMU and instead suggest that it is a mixed evaporite-siliciclastic unit deposited in a shallow marine or lacustrine environment during the tilting of the offshore Lebanese basoin . Only subsequently did the NMU experience a rapid erosional event followed by swift burial of transgressive/high-stand sediments.

In this work, Laser Induced Breakdown Spectroscopy (LIBS) has been used for investigating the presence of heavy mineral garnet (X3Y2(SiO4)3, where the X represent either of Ca 2+ , Mg 2+ , Fe 2+ , Mn 2+ and the Y site contain either of Fe 3+ , Cr 2+ , Al 3+ ) in beach sand samples collected from Sitakunda, Bangladesh. To achieve the goal, in the first attempt, a comprehensive spectral profiling of the laboratory grade garnet was done and the identified emission lines were employed as the reference lines for discovering the presence of the elements of garnet in the LIBS spectra of different sand samples and an arbitrary soil sample. The average intensity ratio for these reference lines of Mg, Al, Fe, Mn, Ca, estimated in different sand samples and the isolated garnet sample, is found to be about 60 % (against the average intensity ratio of about 20 % estimated for general soil sample and garnet), substantiating the presence of garnet in sand with significant concentration. Therefore, LIBS can be used as a useful alternative experimental tool for predicting the presence of minerals in the sand samples and for the exploration of new geological site in Bangladesh.