Stratigraphic Analysis Research Articles

A 121‐ka record of Western Andean fluvial response to suborbital climate cycles recorded by rhythmic grain size variations of the Lima fluvial fan

AbstractA complete, fluvial stratigraphic record for the last glacial period of the Western Andes in Peru is not available due to preservation issues and spatial variability in sedimentation. Deposits are typically restricted to incomplete records of fluvial terraces or localised occurrences of alluvial fans and landslides. These landforms are thought to have formed under a regime of climate cyclicity controlling increases in precipitation. Because of the fragmented preservation of these deposits, as well as dating uncertainties, it remains unclear if orbital climate cycles, such as the precession cycle, or suborbital cycles, such as the wet Heinrich events, are driving Andean sedimentation. In this paper, we try to answer this question through a sedimentological–stratigraphical analysis of a much more complete sedimentary sequence than usually found in the region. We present the results of a grain size analysis of 5000 clasts and 13 new luminescence ages of a 52‐m‐long, stratigraphic section of the Lima fluvial fan in Peru. Bayesian age–depth modelling resulted in a robust chronostratigraphic framework and derived sedimentation rates. The stratigraphic record registered sedimentation from 121.7 ± 4 to ka. Three major sedimentation periods occurred between 121.7 to , 87 ± 1 to , and to ka. These periods registered various unconformities and coarsening–fining upward sequences which chronologically correlate to suborbital pluvial periods, recognised from speleothems and lake records, that drove fluvial deposition. They also correlate with the timing of other recognised sedimentation events throughout the Western Andes. Marine regression resulted in fan progradation and not in incision. The Lima fan stratigraphy represents therefore the most complete, last glacial fluvial record for the Peruvian Western Andes to date and it highlights the potential of fluvial fans as recorders of suborbital climate variability.

Geological History Reconstruction using Stratigraphic Analysis: A Case Study of Kampung Baru, West Sumatra

The reconstruction of geological history includes the development of rocks and volcanic deposits on a depositional pattern consisting of various types of sedimentary materials accumulated over a long time, which involves depositional changes. Depositional changes require geological comprehension in analyzing and understanding the geological processes involved in their evolution. For this reason, stratigraphic analysis is a very relevant approach to discussing rock layers, including significant environmental changes during their geologic history. The purpose of this research is to find out the geological processes that have contributed to the formation of the earth in the past. The method in this research is a stratigraphic analysis carried out from field observation data carried out directly at the outcrop. Deposition began with the re-deposition of the Pre-Tertiary (Triassic)-aged Porphyry Quartz Dasite Formation. In the Late Oligocene Epoch, the Sawahtambang Formation was deposited, which formed in the braided river characterized by the presence of sedimentary structures in the form of lamination and cross lamination. In the Early Miocene to Middle Miocene, the transgression process occurred, where the change in deposition was caused by the supply of larger land sediments that caused the deposition of the Ombilin Formation to be deposited in the marine environment of the Transition-Nerritic Edge based on the bathymetry results. The research results are expected to enable geological information to gain in-depth knowledge and experience about the history of deposition and assist in geological modeling.

TAPHONOMIC ANALYSIS OF AN ARTICULATED BALEEN WHALE (CETACEA; MYSTICETI) FROM UPPER MIOCENE INNER SHELF DEPOSITS OF PENÍNSULA VALDÉS, PATAGONIA, ARGENTINA

Abstract Fieldwork at Península Valdés (Chubut, Argentina) in the Puerto Madryn Formation (Late Miocene) resulted in the discovery of a well-preserved, almost fully articulated, baleen whale (Cetacea, Mysticeti). This specimen, one of the most complete balaenid skeletons known from the Neogene of Argentina and worldwide, was the focus of a taphonomic analysis employing a multidisciplinary approach, integrating taxonomic, sedimentological, stratigraphic, and ichnological analyses, with the aim of reconstructing the taphonomic processes and the paleoenvironmental conditions that controlled preservation of the specimen. The skeleton belongs to the family Balaenidae (right whales). It displays a high degree of articulation, moderate pre-burial fragmentation, and relatively high completeness. Our results suggest that after death, the balaenid suffered a brief biostratinomic phase that can be summarized in four stages: (1) death at sea, with initial decomposition and positive buoyancy of the carcass; (2) internal accumulation of putrefaction gases, re-orientation, then gas loss; (3) sinking and deposition in a ventral-up position on the sea floor of the inner shelf; and (4) lateral re-orientation of the postcranial region due to physical and biological processes. The high degree of articulation and association of the skeletal elements, and the presence of both mandibles, indicate no lateral transport on the seabed and excludes refloating of the carcass at any stage. Finally, the data indicate a low-energy shelf environment with normal marine benthic oxygenation and salinity conditions, characterized by a soft bottom and a moderate sedimentation rate. The last, combined with high bioturbation, plus scour-induced self-burial, resulted in rapid burial of the carcass.

Stratigraphic and lithological-facies analysis of paleogene deposits of Central Asia and their relationship with mineral resources

Stratigraphic and lithological-facies analysis of paleogene deposits of Central Asia and their relationship with mineral resources

Osinskaya subformation of the Usolsky formation of the Lower Cambrian of the central and southern parts of the Nepa-Botuoba anteclise: structure, formation conditions and biostratigraphical characteristics

Relevance. Geological prospecting carried out recently throughout the Lena-Tunguska oil-and-gas province makes studies of carbonates of the Osinskaya subformation particularly relevant, as they make it possible to establish the patterns of hydrocarbon trap formation. Aim. To present the results of the lithological and facial, biostratigraphic and petrophysical studies of the Osinskaya subformation in the southern and central part of the Nepa-Botuoba anteclise. Objects. Carbonate rocks of the middle Osinskaya subformation of the Usolskiy Formation of the Lower Cambrian Tommotian Stage, studied from well cores. Methods. GIS complex, detailed lithological and sedimentological description of the core, sequential stratigraphic analysis, petrographic analysis of 300 samples and examination of paleontological remains taken from the core; analysis. Results. Based on these studies, three sedimentation zones were identified, traced, and described for the first time: deep-water, marginal, and shallow-water. The deep-water zone is characterized by uncompensated sedimentation, the presence of single reefs, and confinement to depressions and troughs. It was flanked by an edge zone of carbonate platform associated with elevated thicknesses of the subformation and distribution of reefs over the area. It was followed by a shallow-water zone, represented by medium and reduced thicknesses of the Osinskaya subformation, its sediments are composed of carbonate grained and clayey rocks with small single reefs. The localized marginal zone of the extended carbonate platform agrees with the previously identified Chambinsko-Altybsko-Mirninskaya and Verkhnetokhomsko-Katsko-Pilyudinskaya zones of distribution of reef-like organogenic structures. On the basis of the studied wells, the structure of three formations according to the lithologic-facial profile was described. The paper introduces the authors’ variant of conducting the boundaries of the members. It was revealed that in the deep-water zone the prospects of searching for reservoir rocks are associated with single carbonate structures, in the marginal zone with area bioherms, and in the shallow-water zone with detrital deposits and shallow bioherms. The paleontological finds are shown to be confined to the selected sedimentation zones and beds. It was determined that algae diagnosed in the boudstones (autochthonous) were involved in the formation of the second and third strata, the edge zone of the carbonate platform. Archaeocyaths were diagnosed in detrital carbonate rocks of the second pack (allochthonous) in well no. 7 and autochthonous in boudstones of well no. 2X. Cribriciates were diagnosed in the boudstones of the third member (autochthonous). Archaeocyaths, cribriciates, namacalatusses, and calcareous algae studied from the cores of wells West Yaractinian no. 45, 361, Bolshetyrskaya no. 7, 3X, 2X, 4X, 5X, 6X were major edificators of Early Cambrian organogenic structures (biostromes, bioherms, bioherms massifs, reef formations).

Influence of sedimentary architecture on static connectivity and geothermal doublet performance (Mezőberény, SE Hungary)

Although the Pannonian Basin in Hungary boasts significant geothermal potential, most geothermal wells in the region suffer from reinjection issues. The aim of this study is to examine the impact of the sedimentary architecture of a paralic lacustrine succession on the static connectivity of a geothermal aquifer. This problem was examined for a case-study geothermal doublet drilled in Mezőberény, southeast Hungary, which experienced injectivity problems shortly after commencing operations in 2012, ultimately leading to shut-in of the wells. A characterization of the architecture of the deltaic aquifer has been undertaken through a novel workflow that combines sedimentological and sequence stratigraphic analysis of the well-doublet and stochastic 3D modelling techniques to assess the likely static connectivity between the production and injection wells. Planform dimension of aquifer-forming mouth-bar elements and fluvial channel bodies were estimated from geological analogues, selected based on the thickness values of such sedimentary bodies interpreted on the gamma-ray logs of the well doublet and nearby hydrocarbon wells. In total five mouth-bar and two fluvial channel input geometry groups were selected, and fifty object-based realizations were constructed to analyse the static connectivity of different geological scenarios. The internal lithology of mouth-bar and fluvial-channel elements were modelled by sequential indicator simulations (ten realizations). Results of connected volume analysis indicate that the sandstone content of the aquifer is located within vertically segmented fluvial-channel and mouth-bar elements separated by mud-prone prodelta and lower delta-front deposits. This architectural configuration, in combination with low net-sandstone content suggests limited connectivity between the wells. Across the set of stochastic realizations, the volume of sandstone connecting the injection and production wells is ∼4% of the total aquifer volume, on average. Results of this study shows that simplified reservoir models can lead to over-estimation of connectivity of geothermal doublets. The proposed workflow combines sedimentological analysis and 3D modelling supported by geological analogues to predict sandstone reservoir connectivity of deltaic geothermal reservoirs. The described workflow can be carried out in target areas using existing boreholes to assist borehole planning.

3D static modeling and sequence stratigraphy using well logs and seismic data: An example of Abu Roash G member in Bahga oilfield

This research uses both three-dimensional (3D) modeling and geologic well control to piece back together the architectural parts of the Late Cretaceous formations. The goal is to figure out the sizes, directions, locations, and controls of the layers of the fluvial sandstone reservoirs. Sequence stratigraphy is essential for 3D reservoir modeling and petroleum geology understanding in the Bahga oilfield. The purpose of this work is to create a static model that shows the layers and facies distribution in the reservoir interval. We will use data from nine well logs and 22 seismic lines calibrated by the Abu Roash G Member reservoir core intervals to accomplish this. The petrophysical study discovered three parts in the Abu Roash G Member reservoir rock: channel fill that is affected by tides, channel fill that is dominated by tides (intertidal sands), and channel top with lenticular bedded sandstone. The model's findings point to the existence of an NNW-oriented sand body, which could be a prime location to produce hydrocarbons. The original oil in place (OOIP) is about 3,438,279 Stock Tank Barrels (STB), and the oil reserve reaches up to 1,031,484 (STB). Sequence stratigraphic analysis using seismic and well log information (SB) reveals that the Upper Cretaceous AR/G reservoir of the Bahga field is characterized by third- and fourth-order stratigraphic sequences, which are constrained by three Maximum Flooding Surfaces (MFS) and two Sequence Boundaries. The integration of the derived geological model and sequence stratigraphic results can lower future extraction risk by identifying the locations and trends of the geologic facies with the necessary petrophysical properties for the hydrocarbon accumulations.

Assessment of lake-level variations to decipher geological controlling factors and depositional architecture of Lake Fuxian, Yunnan Plateau: preliminary insights from geophysical data

Lake Fuxian is one of the deepest tectonic plateau freshwater lakes in the southeastern Tibetan Plateau, China. However, questions such as how old the lake is, how deep the total sedimentary thickness sequences are, and what landscape of the lake basin settings and geological structures are unknown. Here, based on fifteen seismic reflection profiles, we applied seismic facies and seismic sequence stratigraphic analyses to interpret the lake sequences. The results of the seismic response reveal that the maximum thickness of the sedimentation is ca. 1238 m and lies toward the NNE region of the lake basin on the L10-2 survey line. Lake sediments can be categorized into five seismic sequences and six seismic horizons. The oldest clinoforms in the deepest sequence (Sq-5) show that the depositional center was shifted to ~ 19 km from the NNE region to the SSW modern location and was ~ 930 m lower than the current lake floor. Multiple and complex tectonic activities strongly impacted on the lake basin, and a series of normal faults created an overall crustal extensional regime, resulting in the formation of many horst and graben structures.

Penelusuran sisa-sisa Kerajaan yang hilang dibalik Letusan Gunung Tambora di Situs Doro Bente

The archaeological research in the Tambora Peninsula was initiated by the National Archaeological Research Center in 2006, and from 2008 onwards, it was continued by the Archaeological Office in Denpasar-Bali until 2021. Numerous archaeological pieces of evidence have been successfully excavated from Mount Tambora's pyroclastic material. Recent research has been focused on the Doro Bente Site on the Teluk Saleh Peninsula. The research aims to understand the sequence of historical events on settlement centers based on artifact evidence resulting from the eruption of Mount Tambora in 1815. The study employs qualitative, descriptive methods, and a geoarchaeological approach. Data acquisition involves excavation, surveys, and literature studies. Stratigraphic analysis is conducted to identify sediment matrices and understand the deposition sequence. Excavation activities have uncovered significant artifacts such as ceramic fragments, pottery, animal bones, and shell fragments. Micro-scale deposition chronology in excavation box B28U18 indicates that the three lower layers, the oldest, were deposited in a marine environment, followed by five layers of pyroclastic material from the 1815 eruption of Mount Tambora. The geographical factors and available natural resources make Sumbawa Island a focal point for Chinese and European attention from the 13th to the 19th centuries AD.

Hydrologic remobilisation of tephra‐fall deposits: A sedimentological analysis throughout fluvio‐lacustrine systems of North‐West Patagonia

AbstractThis paper explores the response to Holocene ash inundation in different sub‐environments of two fluvio‐lacustrine systems, Las Piedritas and Totoral, focussing on the processes of volcaniclastic remobilisation. Sediment cores and outcrops were used to recognise three deposit types, noting how some differ from lahars, through sedimentological and stratigraphic analysis: (1) thick, laterally discontinuous, pumice‐dominated deposits occur overlying alluvial plain and lower terrace surfaces across both watersheds; (2) chaotic, extremely poorly sorted and matrix‐supported beds composed of both epiclastic and pyroclastic material occur as two conspicuous deposits at Las Piedritas outcrops, in a low‐gradient confined channel setting; and (3) layers with an exclusively pyroclastic composition and no flow sedimentary structures or fragment roundness were found draping each of the two chaotic intervals and intercalating with the background sediment in Las Piedritas prodelta. Thick pumice packages capping the floodplains resulted from the overflow of streams carrying a floating pumice load. Due to its positive buoyancy, the pumice is transported as a slowly moving overlying mantle without mixing with the streamflow. The disorganised pattern and poor sorting of the matrix‐rich polymictic beds are consistent with laminar, gravity‐driven, high‐concentration flows. They constitute secondary lahars, originating upstream from large run‐off processes that reworked a pyroclastic substrate. The lack of reworking features in the vitric‐rich units identified in the lake core retrieved from Las Piedritas prodelta, as well as the continuous and widespread occurrences of those interbedded in upstream outcrops, indicate an airfall origin. No reworked tephra unit is recognised in the prodelta sediment record, although various deposits from the hydrologic remobilisation of airfall tephra are found along the subaerial portion of both watersheds. Apparently, large amounts of flotation‐remobilised tephra were retained on the delta plain, while another considerable fraction would have been carried away from the creek mouth under the influence of dominant regional winds.

Terahertz time-domain imaging for the examination of gilded wooden artifacts

Terahertz imaging is unlocking unique capabilities for the analysis of cultural heritage artifacts. This paper uses terahertz time-domain imaging for the study of a gilded wooden artifact, providing a means to perform stratigraphic analysis, yielding information about the composition of the artifact, presence of certain materials identifiable through their THz spectral fingerprint, as well as alterations that have been performed over time. Due to the limited information that is available for many historic artifacts, the data that can be obtained through the presented technique can guide proper stewardship of the artifact, informing its long-term preservation.

Jurassic sedimentary migration characteristics and their geodynamic implications in the Dunhuang Basin and adjacent regions, Northwestern China

The Dunhuang Basin, situated in western China along the Altyn Tagh Fault (ATF) zone, intersects the Tethys and Paleo‐Asian Ocean tectonic domains. Influenced by both the ATF system and the far‐field effects of the Qiangtang‐Lhasa‐Eurasia collision during the Mesozoic, the mechanism of the Jurassic sedimentary migration of the basin in response to tectonic movements is unclear so far. The paper uses a comprehensive approach, including field geological surveys, lithologic and lithofacies discern, stratigraphic relationships analysis and 2D seismic profile interpretation, to examine the distribution of Jurassic residual strata in the basin. The comprehensive results of our study suggest that the Dunhuang Basin exists as an isolated block with unique tectonic and sedimentary evolution characteristics. In the Early Jurassic, the Dunhuang Basin underwent initial rifting, leading to the formation of small segmented intermontane sags. This phase was marked by the coarse particle sedimentary system of alluvial fans and braided rivers, represented the near source rapid deposition in the initial formation period of the basin. Stratigraphic distribution was primarily influenced by pre‐Jurassic basement topography and was not significantly constrained by faulting during this period. The formation of these isolated discontinuous small intermontane sags indicates the segmented activities of the ATF in the Early Jurassic period. In the Middle Jurassic period, influenced by the ATF dextral strike‐slip faulting, sedimentation extended eastward and the depocenter migrated clockwise compared with the distribution of the Middle Jurassic strata within the Dunhuang Basin. This period witnessed the development of coal measure strata at the basin's margins and lacustrine fine‐grained clastic deposition in the centre. The segmented fracture of the ATF gradually initiated a unified dextral strike‐slip tectonic movement. In the Late Jurassic period, sedimentary strata were locally present in the Wanyao Sag but absent in other sags. The depocenter migrated counterclockwise compared with the distribution of Middle Jurassic strata within the Dunhuang Basin, due to regional uplift accompanied by the ATF sinistral strike‐slip faulting caused by the collision between the Lhasa Block and the Eurasia Plate. The depocenter migration of the Dunhuang Basin constrained within the ATF system from the Early to Middle and Late Jurassic can be attributed to the transition of the ATF strike‐slip faulting in context of the stress relaxation and compression between the collision of the Qiangtang and Lhasa blocks to the Eurasia Plate, respectively.

A new lithostratigraphic scheme of the Ordovician Jeongseon Formation of the Yongtan Group in the Taebaeksan Basin and sequence stratigraphic analysis with discussion on basin geometry

A new lithostratigraphic scheme of the Ordovician Jeongseon Formation of the Yongtan Group in the Taebaeksan Basin and sequence stratigraphic analysis with discussion on basin geometry

Seismic stratigraphy and sediment cores reveal lake-level fluctuations in Lake Iznik (NW Turkey) over the past ∼70 ka

Our study aims to understand the palaeohydrological history of Lake Iznik and unravel the complex interplay between climatic, tectonic, and environmental factors that have shaped this Turkish basin. Through the analysis of seismic stratigraphy and sediment cores, we reveal a significant lowstand, indicating a lake level 60 m lower than today at ∼70 ka BP. Subsequently, a major phase of stepwise transgression is evidenced by 13 buried palaeoshorelines between ∼70 and 45 ka BP. From 45 to ∼10 ka cal BP, strong currents controlled the sedimentation in the lake, as evidenced by the occurrence of contourite drifts. Between ∼14 and 10 ka cal. BP, a major lowstand indicating a drier climate interrupted the current-controlled sedimentation regime. From ∼10 ka cal. BP, the subsequent increase in lake level occurred at the same time as the reconnection between the Mediterranean and Black seas. Archaeological evidence, including submerged structures of a basilica, establishes a link between lake-level changes and human settlement during the last millennium. The level of Lake Iznik has since continued to fluctuate due to climate change, tectonic events, and human activity.

Characterization of a marine mudstone confining unit at a proposed CO2 storage hub: Kemper county energy facility, Mississippi, USA

Cretaceous and Tertiary strata across Mississippi, Alabama, and the adjacent continental shelf constitute a widespread succession of sandstone, mudstone, and carbonate that have proven to be important objectives for deployment of geologic CO2 storage technology in saline formations. Analyses of stratigraphy, sedimentology, and reservoir properties indicate that the Cretaceous-age Paluxy Formation, Washita–Fredericksburg interval, and lower Tuscaloosa Group may provide a 1.4 gigatonne storage opportunity at the Kemper County Energy Facility in east-central Mississippi. The marine Tuscaloosa shale is a widespread reservoir seal in the deep subsurface of Mississippi and Alabama, and detailed geologic investigation of the shale includes integrated analysis of geophysical well logs and core that have yielded a multiscale analysis of the confining strata. Scanning electron microscopy (SEM) coupled with energy dispersive X-ray spectroscopy (EDS), quantitative X-ray diffraction (XRD), and permeability analyses from core were used to interpret microfabric, pore types, mineralogy and fluid properties within mudstone of the east-central Mississippi Embayment. This study has importance for identifying potential migration of fugitive CO2 into or across the shale. Results indicate that mudstone in the marine Tuscaloosa shale is an effective confining unit that is a key component of the storage complex in Kemper County. Water saturation in the marine Tuscaloosa shale units promotes rock ductility and contributes to low permeability, which is on the order of 10–100 nanodarcies (nD) as determined by pressure-decay permeametry. Accordingly, the marine Tuscaloosa shale is interpreted to prevent significant cross-stratal migration of injected CO2 from deeper sandstone reservoirs.

The Guangya submarine fan in the South China Sea: A distinctive channelized slope-through fan

Submarine fans play a crucial role in understanding deep-sea sedimentary processes, establishing source-to-sink linkages, and identifying deep-water hydrocarbon reservoirs. Various types of submarine fans have been documented. Here we present findings on the Guangya submarine fan in the Southwest subbasin (SWSB) of the South China Sea (SCS), by analyzing multibeam bathymetric and two-dimensional multichannel seismic data. Bathymetric data reveal that the Guangya fan, covering an area of ~22,500 km2, comprises seven leveed channels, leading to a large composite lobe off the channel mouths. Different from typical submarine fans, the Guangya fan exhibits an elongated shape, extending longitudinally from the shelf edge through the slope to the abyssal plain, while laterally confined within a trough-like morphology in the southwestern tip of the SWSB and beyond. Lacking a typical feeding canyon, the fan appears to be self-fed by the leveed channels that serve as the primary depositional element. In contrast to the radial channel pattern in typical fans, the channels within the Guangya fan form a unique braid to dendritic pattern, genetically linked to channel merging and intersecting effects. Long wavelength and low wave height cyclic steps are identified, highlighting the occurrence of energetic supercritical turbidity currents. Seismic stratigraphic analysis shows that the Guangya fan primarily consists of high-amplitude reflections, indicating its coarser-grained or sandy turbidite-dominated nature. The fan has been evolved since the Pliocene, and mainly comprises depositional elements including channel fills, levees, lobes, and mass transport deposits. The specific tectonic context at the convergence of the conjugate margins, bounding the funnel-shaped SWSB, significantly influences the development of the Guangya fan. The Guangya fan could be originated from a shelf-edge staging area predominantly fed by the Mekong River during sea-level lowstands.

Submarine pyroclastic deposits from 7.3 ka caldera-forming Kikai-Akahoya eruption

Extensive submarine pyroclastic deposits were discovered around the Kikai caldera, Southwest Japan, which originated from the caldera-forming Kikai-Akahoya (K-Ah) eruption that occurred at 7.3 ka. This submarine pyroclastic unit originated from a pyroclastic density current (PDC) that entered the sea and was transformed into a subaqueous density current. Our high-resolution marine seismic reflection surveys reveal that the uppermost unit exhibiting prominent seismic facies thins radially away from the caldera and covers >4500 km2 of the seafloor. The estimated volume of the submarine deposits is >71 km3 based on the isopach map. Seismic sequence stratigraphic analyses and correlation of shard glass compositions from the piston core and remotely operated vehicle samples with those from subaerial outcrops identified the unit as pyroclastic deposits produced by the K-Ah eruption. The geomorphological features of the unit indicate a long runout distance (i.e., 40 km), exponential thinning with increasing distance from the source, and a depression-filling nature of the deposits suggesting that the unit was formed predominantly by a density current that entered the water. The quantitative comparisons of geometric shape and its thinning rate, including that for non-volcanic density currents, indicate that the subaerial PDC entering into the water was transported as a dilute density current in the water. We propose that the formation of these dilute density currents transformed by PDCs probably requires sufficient water depth, as inferred also from previous analog experiments. Adding on-land ignimbrite of 5 km3 and widespread tephra of 249–374 km3, our estimate of submarine pyroclastic deposits of >71 km3 leads to a total bulk volume of the K-Ah eruption of 332–457 km3 (133–183 km3 in DRE), making it probably the largest eruption of the Holocene.

Hydrochemical stratigraphic analysis of the filling of the Meirama mine shaft I: monitoring and filling

The application of an old open-pit lignite mine as an auxiliary reservoir for the supply of the city of La Coruña has involved a detailed analysis of the chemical quality of the vertical profile. The study has shown that a stratified lake is formed where the shape of the filling (first with groundwater and later surface waters from the nearby rivers were added) has influenced the formation of the lake profile. The Meirama mine is an open-pit brown lignite mine located in NW Spain. Exploitation ended in March 2008, leaving a pit of approximately 146 hm3 with a maximum depth of 205 m. The rehabilitation of the pit consisted of the creation of a lake that will serve as an auxiliary water reservoir for the city of La Coruña. The filling process lasted approximately 8 years (March 2008–May 2016) with subterranean and surface contributions from the environment. The formation of an invariant chemocline and a seasonal thermocline was observed. Therefore, in this work, (the first of a series of two articles), an analysis of the evolution of various physicochemical parameters, elements, and compounds at certain heights (the surface, the first 2 m (2 mbs), at 59 masl, and at the bottom (2 masl)). In this first article, the physicochemical parameters of pH, dissolved oxygen, temperature, and some metallic elements (iron and manganese) are analysed. From the analyzed parameters it can be seen the creation of a surface thermocline and a chemocline at a depth of 59 masl with the beginning of the formation of anoxic conditions of the bottom of the pit through the consumption of oxygen.

Sandstone Layer Connectivity and Its Control on Coalbed Methane (CBM) Accumulation Based on Sequence Stratigraphic Analysis: A Case Study of the Lower Shihezi Formation in Qinan Coal Mine, Xuzhou–Suzhou Region, China

Sandstone Layer Connectivity and Its Control on Coalbed Methane (CBM) Accumulation Based on Sequence Stratigraphic Analysis: A Case Study of the Lower Shihezi Formation in Qinan Coal Mine, Xuzhou–Suzhou Region, China

Surface grain size of alluvial fans on Mars from thermal inertia, as an indicator of depositional style

The depositional history of alluvial fans on Mars provides insight into the climatic conditions during the time of fan formation in the late Hesperian to early Amazonian. However, traditional stratigraphic analysis of the alluvial fan deposits is not possible across most of Mars. This study assesses the use of thermal inertia data as a tool for sedimentologic interpretation of 437 Mars alluvial fans. Based on previous work demonstrating the relationship between depositional style, grain size, and thermophysical properties, this study uses analysis of the thermal inertia of alluvial fan surfaces across the global population of fans on Mars to make an assessment of depositional styles that built the alluvial fans. The thermal inertia values across the global population of fans are indicative of sand- to pebble-sized sediment. The variability of grain sizes across the global population is more homogenous than expected based on comparisons to terrestrial alluvial fans. Nearly all Mars alluvial fans have an average thermal inertia that corresponds to pebble and smaller grain size, and < 1% of Mars alluvial fans have an average thermal inertia that corresponds to cobble-sized grains. Spatial patterns of thermal inertia variability on alluvial fan surfaces show a small number of fans with evidence for either downslope fining or channelization, but the majority of fans show no recognizable geologic patterns in surface thermal inertia. The interpretation of the thermal inertia-derived grain size suggests that either there is widespread mantling of unconsolidated sand across the surface, or that Mars alluvial fans were built by primarily sand-sized sediment, which may be indicative of lower energy sediment transport events.