Mud Unit Research Articles

Performance of 3D printing biomimetic conch shell and pearl shell hybrid design composites under quasi-static three-point bending load

The failure process of biomimetic hybrid design composite composed of layers of conch shell and pearl shell was studied through quasi-static three-point bending experiments and numerical simulations. The biomimetic conch shell structure with inclined angles serves as the upper layer of the hybrid structure, while the biomimetic pearl shell structure with traditional brick and mud structure serves as the lower layer of the hybrid structure, forming a hybrid design structure. Four inclined angles were designed for the structural units of the conch shell, namely 15°, 30°, 45°, and 60°. Twenty-four specimens (six specimens for each inclined angle) were prepared using 3D printing technology using both soft and hard matrix materials. The influence of different inclined angles on the fracture strength, fracture toughness, and energy absorption of hybrid design structures was experimentally studied. The biomimetic hybrid design composite specimen with a notch is placed between two supporting rollers, and a loading indenter acts at mid-span. All twenty-four specimens were notched with a triangular tip and a rectangular bottom. A loading rate of 1 mm/min is used to avoid the viscoelastic effect of the composite materials. Details of the specimens, the experimental set-up and procedure are discussed in this paper. Complementary to the experimental studies, an extensive numerical investigation was carried out to study the influence of the aspect ratio of brick and mud units on the fracture initiation and failure of hybrid design structures. The causes of crack initiation and propagation, and failure modes in biomimetic hybrid design structures were postulated. These numerical findings help in reinforcing the experimental results and provide crucial information to enhance further research in this exciting area.

Holocene water levels of Silver Lake, Montana, and the hydroclimate history of the Inland Northwest

AbstractThe wettest portion of the interior of western North America centers on the mountainous region spanning western Montana, Idaho, British Columbia, and Alberta. Inland ranges there capture the remnants of Pacific storms. Steep east–west hydroclimate gradients make the region sensitive to changes in inland-penetrating moisture that may have varied greatly during the Holocene. To investigate potential hydroclimate change, we produced a 7600-yr lake-level reconstruction from Silver Lake, located on the Montana–Idaho border. Ground-penetrating radar profiles and a transect of four shallow-water sediment cores that were dated using radiocarbon dating and tephrachronology revealed substantial changes in moisture through time. An organic-rich mud unit indicating wet and similar to modern conditions prior to 7000 cal yr BP is overlain by an erosional surface signifying drier than modern conditions from 7000–2800 cal yr BP. A subsequent time-transgressive increase in water levels from 2800–2300 cal yr BP is indicated by a layer of late Holocene muds, and is consistent with glacier expansion and increases in the abundance of mesic tree taxa in the region. Millennial-scale trends were likely driven by variations in orbital-scale forcing during the Holocene, but the regional outcomes probably depended upon factors such as the strength of the Aleutian Low, Pacific sea-surface temperature variability, and the frequency of atmospheric rivers over western North America.

Sedimentary record of annual-decadal timescale reservoir dynamics: Anthropogenic stratigraphy of Lake Powell, Utah, U.S.A.

The tributaries of Lake Powell were impounded following construction of Glen Canyon Dam, resulting in deposition of reservoir sediment over a ∼650 km2 area since 1963. These units have been exposed through erosion as water storage in Lake Powell has decreased since 2000. This anthropogenic sedimentary record reflects the complex interplay among wet and dry periods of Colorado River runoff and the reservoir operating rules of Lake Powell. The relevant sedimentary exposures are mapped at reconnaissance level over 300 river-km above Glen Canyon Dam in canyons of the Colorado, San Juan, Escalante, and Dirty Devil Rivers. A detailed reference section measured in Calf Canyon, a tributary to the Colorado River, preserves more than 12 m of lacustrine, mainstem Colorado River, and local tributary sediment in an up-river location and elevation that is determined to have been inundated only during the highest reservoir level periods. At Calf Canyon, exposed reservoir sediment is comprised of cyclic sand-mud interbeds that record periods of deposition when reservoir level was at or above full pool. Six depositional cycles are identified in Calf Canyon, and each of these is interpreted to represent rapid sand deposition during Colorado River flood events (likely related to spring snowmelt runoff) followed by deposition of lacustrine mud while reservoir levels were high. The lacustrine mud units display significant pedogenic modification, indicating exposure and colonization dominated by tamarisk plants, prior to deposition of the next sand unit. High-precision elevation surveys of the 6 main lacustrine marker beds in Calf Canyon are correlated to multiple lake level highstands between 1975 and 2000. Preliminary observations suggest that age-equivalent strata are widespread within the reservoir-affected zones of all major tributaries including the Colorado and San Juan River arms as well as the Escalante and Dirty Devil Rivers. We predict that future mapping in other Lake Powell side canyons will demonstrate strong local control on sediment provenance, dictated by side canyon lithology, as well as time-transgressive deposition (and erosion) moving up and down the main canyons.

Depositional setup and characteristics of the storm deposit by the 2007 Cyclone Sidr on Kuakata Coast, Bangladesh

This study examines the sedimentary characteristics, provenance, and depositional processes of the storm deposits from 2007 Cyclone Sidr that have been identified on the southern coast of Bangladesh. Three sedimentary units up to 70 cm thick have been identified in fifteen geological core collected at a distance of 135–277 m from the coast. Laboratory analyses of grain size, TOC, TN, δ13C, and diatom assemblages were carried out to characterize the deposits. Massive to parallel laminated bluish gray mud underlies the storm overwash deposits. White to light gray, massive to parallel laminated, normal graded 1–17 cm thick sand overlies the mud unit with sharp to erosional contact. The mean grain size and thickness of this sand unit decrease landward with increasing sorting value, where grain size distribution of sand is comparable with modern beach sand. The unimodal sand that dominated the base of the storm deposits grades into bimodal olive-gray sandy silt in the upper part of the deposits. The grain size implies that the sand carried from the beaches and mud likely sourced from the suspended, nearshore sediment of the bay and adjacent rivers. TOC/TN, δ13C values and the presence of brackish mudflat origin diatoms with silty sand laminae in bluish gray mud indicate a tide-influenced environment. Post-storm sand and sandy silt sediments unit contain freshwater and marine-brackish diatoms that have likely been deposited from flooding caused by storm surge water from the bay and overbank flooded river water due to subsequent heavy rainfall. These sediments were sorted according to storm waves and settled over the study area. This study indicates that the low-lying delta coast gets the influences of high water levels both from the bay and the river during a storm. The modern storm deposit will help to characterize the paleo/prehistoric tropical cyclone in geological time for future studies in this area.

Study on the buried oyster reefs and environmental changes with the underlying muddy sediments on the Northwest Coast of Bohai Bay

The Electric Conductivity of Stirred Clayey sediments into Water (EC), pH values and micropalaeontological studies of the underlying muddy sediments of the buried oyster reefs in Dawuzhuang and Airport sites, northwest coastal plain of Bohai Bay revealed a difference of the depositional environments of the underlying mud units in two sites. In Dawuzhuang, from the underlying to the overlying muds, environment changed from subtidal to the lower intertidal zone, which presented a falling tendency of relative sea level. However, the underlying mud in Airport site occurred in the intertidal and changed upwards to the reef body as being lagoonal environment. These indicate that the relative sea level fall resulted in intertidal environment in Dawuzhuang and a change from the open intertidal to relatively isolated intertidal lagoon environment in Airport site as a diatom thriving as well during the mid-Holocene all form the important reasons for the oyster reef development.

Secular variation in the elemental composition of marine shales since 840 Ma: Tectonic and seawater influences

Marine shales, the most common lithology in the stratigraphic record, represent an archive of long-term changes in sediment production, weathering intensity, and seawater chemistry through Earth history whose potential has been underexploited to date. In this study, we compiled compositional data for 14,531 samples from 268 shale and mud units ranging in age from the early Cryogenian (840 Ma) to the Recent. We examined secular variation in the Al-normalized concentrations of ten elements (Mg, Na, K, Ba, Sr, Y, Th, Rb, Nb, and Zr) selected for (1) their presence in typical X-ray fluorescence (XRF) datasets (thus providing sufficient data), and (2) their lack of redox sensitivity (thus excluding elements whose primary control is aqueous redox conditions). Relationships among the study elements were quantified using principal component analysis (PCA) and cluster analysis (CA), revealing several significant groupings: (1) a subset of “detrital elements” (K, Rb, Th, Nb, Y, and Zr) whose concentrations are primarily controlled by subaerial weathering processes; (2) a subset of “hydrogenous elements” (Mg, Na, and Sr) whose concentrations are significantly influenced by seawater chemistry, and (3) Ba, which is subject to multiple controls. The dominant influence on the detrital elements appears to have been not chemical weathering intensity per se but the ratio of Al-poor silt to Al-rich clay in the particulate weathering flux. Although possibly modulated by factors such as climate and land plant evolution, silt:clay ratios appear most closely linked to tectonism, with higher values associated with major orogenic events. The concentrations of the hydrogenous elements in marine shales were likely related to their seawater inventories, which were modulated at long time scales by rates of submarine hydrothermal alteration. Ba in marine shales may have been significantly influenced by atmospheric pO2 and seawater sulfate levels via their control of barite saturation in seawater. In summary, our findings document significant relationships of marine shale composition to first-order geological controls, suggesting that long-term secular changes in sediment and seawater chemistry can be reconstructed from fine-grained siliciclastic sediments.

Sediment properties of lithologic units and their correlation within the lower delta plain of the Nakdong River Delta, southeast Korea

Multi-proxy sediment properties reveal that three cores (ND-01, ND-02, and ND-03) from the lower delta plain of the Nakdong River Delta, southeast Korea, are characterized by the same stratigraphic lithologic successions consisting of a upper sand unit (10–15 m thick and <1 ka), a middle mud unit (∼20 m thick and 1–9 ka), a lower sand unit (6–9 m thick and 9–10 ka), and a lower mud unit (10–15 m thick and >10 ka) overlying weathered gravelly fluvial sediments and weathered bedrock. The sediment properties of each lithologic unit are controlled by the balance between the marine influence from Holocene sea level rise and the freshwater influence from Nakdong River discharge. In particular, the middle mud unit is characterized by distinct peaks in CaCO3 content, P/T ratios (the ratio of planktonic foraminifera to the sum of benthic and planktonic foraminifera), total organic carbon and total nitrogen contents, and δ13Corg values at 7–8 ka, which indicates that the maximum marine forcing during the sea level rising and the greatest influence of the Tsushima Warm Current during the evolution of the river-mouth coastal depositional system from an estuarine to a deltaic environment. Although the vertical stacking of lithologic successions is stratigraphically consistent within the lower delta plain, the precise temporal evaluation and comprehensive depositional evolution in the Nakdong River Delta including the upper delta plain and the prodelta zones remain a topic of future investigation.

Holocene Evolution of Patos Lagoon, Brazil: The Role of Antecedent Topography

Bortolin, E.; Weschenfelder, J., and Cooper, A., 2019. Holocene evolution of Patos Lagoon, Brazil: The role of antecedent topography. Journal of Coastal Research, 35(2), 357–368. Coconut Creek (Florida), ISSN 0749-0208.The Patos Lagoon in Rio Grande do Sul, Brazil, is part of the largest barrier lagoon system in the world. It is enclosed by a 400-km-long composite late Pleistocene/Holocene sandy barrier and has a single tidal inlet. The modern lagoon is shallow (average < 5 m) and is dominated by silt deposition. More than 1000 km of shallow seismic data (3.5 kHz) indicate that the lagoon is underlain by several shore-normal incised valleys separated by interfluves. Each incised valley existed as an individual estuary since its first flooding during the mid-Holocene. The infill of these valleys contains a basal fluvial unit, a central estuarine mud unit, and locally developed tidal sand bodies associated with former tidal inlets. The contemporary lagoonal sediments form a blanketing upper unit. Ultimately, the interfluves were drowned and the contemporary lagoon was formed by the coalescence of the incised valley estuarine systems in the late Holocene. This expansion of accommodation space coincided with a dramatic reduction in vertical sedimentation rates. Seismic profiling reveals the contemporary sandy spits, and their subaqueous extensions coincide with the location of former interfluves, indicating that inherited topography exerts major control over the location and development of lagoon-marginal spits.

OSL chronology of the Huksan Mud Belt, south-eastern Yellow Sea, and its paleoenvironmental implications

The Huksan Mud Belt (HMB) is located in the south-eastern Yellow Sea. The radiocarbon (14C) and optically stimulated luminescence (OSL) age datings of the pre-Holocene HMB sediments were compared precisely. OSL dates for the uppermost HMB sediments showed the recent and short-term chronological development of the HMB. OSL and 14C ages of the Holocene sediment (HMB cores 101–103) were relatively consistent. By contrast, the OSL ages of the pre-Holocene sediment unit were considerably older than the 14C ages (by approximately 30%), where the OSL ages corresponded broadly to marine isotope stages (MIS) 5 and 4 (from about 125 ka to > 50 ka). An overall comparison of 14C and OSL dates suggests that the age of the Holocene mud unit is well constrained by 14C dating. However, 14C ages older than 40 ka may be unreliable. The surficial sedimentation rate and depositional ages for a 6.5-m-thick sequence of the uppermost unit (12HMB cores) were determined. Twenty OSL samples gave an age of approximately 8.5 ka. Most of the OSL ages for each site were in stratigraphic order. The surficial sediment ages for the 12 HMB cores were 2.6 ka for P-08, 7.7 ka for P-10, 7.3 ka for P-11, and 0.05 ka for P-14. The approximate surficial sediment ages of the uppermost unit of the HMB-101, -102, and −103 cores were 6.7 ka, 6.8 ka, and 1.1 ka, respectively. The spatiotemporal differences in deposition and erosion of the HMB Holocene muds, supposedly driven by changes in large, strong tidal forces and marine water depth, and an increase in ocean current velocity, could account for the various surficial deposition ages in the area.

Late Neogene foraminifera from the northern Namibian continental shelf and the transition to the Benguela Upwelling System

Middle Miocene to Plio-Pleistocene foraminifera provide insights into the palaeoenvironment on the northern Namibian continental shelf located at the far northern end of the present-day Benguela Upwelling System (BUS). Biostratigraphy and Strontium Isotope Stratigraphy (SIS) of the recovered basal olive-green mud unit indicate an age of 16 to 14 Ma. A sharp, erosional contact separates the basal mud from the overlying Plio-Pleistocene gravelly pelletal phosphorite sands. Grain size data, P/B ratios and benthic diversity indices indicate a change between the middle Miocene and overlying Plio-Pleistocene palaeoenvironments linked to the timing and conditions associated with the initiation of the BUS. The different lithological units and microfossil assemblages in the olive-green mud unit and the overlying pelletal phosphorite units support the late Miocene initiation of the BUS and the northwards migration of the Angola-Benguela Front. Planktic foraminifera indicate a shift from warmer surface water conditions to cooler conditions during the initiation of the BUS. Benthic palaeobathymetric ranges and P/B ratios are consistent with outer shelf water depths suggesting a deeper palaeoenvironment during the Mid-Miocene Climatic Optimum (MMCO) than today. Benthic foraminifera in the middle Miocene are dominated by large (>1 mm) taxa and adapted to oligotrophic environments before the initiation of the BUS. The benthic assemblage composition indicates that bottom water conditions changed to eutrophic conditions during the Plio-Pleistocene under intensified upwelling conditions.

How Could a Freshwater Swamp Produce a Chemical Signature Characteristic of a Saltmarsh?

Reduction–oxidation (redox) reaction conditions, which are of great importance for the soil chemistry of coastal marshes, can be temporally dynamic. We present a transect of cores from northwest Florida wherein radical postdepositional changes in the redox regime has created atypical geochemical profiles at the bottom of the sedimentary column. The stratigraphy is consistent along the transect, consisting of, from the bottom upward, carbonate bedrock, a gray clay, an organic mud section, a dense clay layer, and an upper organic mud unit representing the current saltwater marsh. However, the geochemical signature of the lower organic mud unit suggests pervasive redox reactions, although the interval has been identified as representing a freshwater marsh, an unlikely environment for such conditions. Analyses indicate that this discrepancy results from postdepositional diagenesis driven by millennial-scale environmental parameters. Rising sea level that led to the deposition of the capping clay layer, create...

Sedimentology in metamorphic rocks, the Willyama Supergroup, Broken Hill, Australia

ABSTRACTIn the upper greenschist to granulite grade rocks of the Willyama Supergroup at Broken Hill, Australia, earlier recognition of metamorphosed graded bedding in siliciclastic metasedimentary rocks led to interpretations of these rocks as deep-water turbidites. However, graded beds can also be deposited in shelfal environments below storm wave base. This study identified other tempestite features including wave oscillation ripples, hummocky cross-stratification and swaley cross-stratification indicating that deposition took place above the wave base of the larger storms.Albitised metasedimentary rocks of the upper Thackaringa Group show structures such as swaley cross-stratification typical of shallow-water conditions above fair-weather wave base. Deposition of the Broken Hill Group commenced with muddy Allendale Metasediments conformable on the Thackaringa Group. The Ettlewood Calc-Silicate Member, originally a dolomitic, siliceous sediment, is interpreted as coastal sabkha indicating onset of a marine transgression. The Parnell Gneiss represents a volcanic or volcaniclastic interruption, heralding gradually increasing input of sand in the Freyers Metasediments reaching a maximum in middle Freyers Metasediments, followed by an abrupt reversion to mud, still influenced by wave action. An open marine shelf is interpreted, possibly 30 m deep (no more than 100 m) in the final stage of a developing rift. The Broken Hill Group terminated with the massive Hores Gneiss volcanic unit.Sedimentation of the siliciclastic Sundown Group took place in similar conditions, commencing with a muddy interval overlying the Hores Gneiss. The shallowing produced by ∼90 m thickness of volcanic/volcaniclastic Hores Gneiss was compensated by subsidence.Paragon Group deposition commenced with substantial black mud, resulting from isolation from the sand supply and probably isolation from the sea. A fresh connection to the sea led first to the deposition of dolomitic carbonate (King Gunnia Calc-Silicate Member), then to deposition of parallel-laminated fine sand below wave base (upper Cartwrights Creek Metasediments), followed by ripple cross-laminated sand above wave base (Bijerkerno Metasediments). The Dalnit Bore Metasediments show abundant very thin graded silt–mud units possibly deposited below storm wave base, and thicker units of stacked wave oscillation ripples deposited above the wave base of larger storms.The Broken Hill orebody is hosted by altered Broken Hill Group metasedimentary rocks deposited at water depths of ∼30 m. Unless the ore fluid temperature was less than 150°C, it is likely that the orebody formed below the seafloor: at such shallow-water depths, the confining pressure would be inadequate to suppress boiling of hotter rising hydrothermal fluids.

The environmental conditions of MIS5 in the northern South China Sea, revealed by n-alkanes indices and alkenones from a 39 m-long sediment sequence

In order to reconstruct the environmental conditions of marine isotope stage (MIS) 5 in the coastal area of northern South China Sea, a sediment core was collected from the south coast of Hainan Island (18°16′57″N, 109°42′38″E), from which a thick marine mud unit (39 m) is found to be the deposit of MIS 5. According to the high abundance of alkenones, the thick mud sequence was deposited under marine conditions. The high TOC and n-alkanes concentrations (as normalized to TOC) suggest this was a period of high organic matter (OM) production, and the majority of OM came from terrestrial vascular plant sources. Comparatively, short chain n-alkanes (C18-22) and proportion of aquatic plant index (Paq) in the lower sub-unit appear higher than those in the middle and upper sub-units, suggesting a gradual increase in terrestrial OM supply throughout MIS 5e. The carbon preference index in long-chain n-alkanes (CPI25-33) implies high precipitation and/or temperature in this interval, whilst the average carbon length index in long-chain n-alkanes (ACL25-33) indicates a warm climate during MIS 5e.

Holocene glacial evolution of Mohnbukta in eastern Spitsbergen

Submarine geomorphology is one of the main tools for understanding past fluctuations of tidewater glaciers. In this study we investigate the glacial history of Mohnbukta, on the east coast of Spitsbergen, Svalbard, by combining multibeam‐bathymetric data, marine sediment cores and remote sensing data. Presently, three tidewater glaciers, Heuglinbreen, Königsbergbreen and Hayesbreen calve into Mohnbukta. Hayesbreen surged at the end of the Little Ice Age, between 1901 and 1910. The submarine landform assemblage in Mohnbukta contains two large transverse ridges, interpreted as terminal moraines, with debrisflow lobes on their distal slopes and sets of well‐preserved geometric networks of ridges, interpreted as crevasse‐squeeze ridges inshore of the moraines. The arrangement of crevasse‐squeeze ridges suggests that both landform sets were produced during surge‐type advances. The terminus position of the 1901–1910 Hayesbreen surge correlates with the inner (R.2) terminal moraine ridge suggesting that the R.1 ridge formed prior to 1901. Marine sediment cores display 14C ages between 5700–7700 cal. a BP derived from benthic foraminifera, from a clast‐rich mud unit. This unit represents pre‐surge unconsolidated Holocene sediments pushed in front of the glacier terminus and mixed up during the 1901 surge. An absence of retreat moraines in the deeper part of the inner basin and the observation of tabular icebergs calving off the glacier front during retreat suggest that the front of Hayesbreen was close to flotation, at least in the deeper parts of the basin. As the MOH15‐01 core does not penetrate into a subglacial till and the foraminifera in the samples were well preserved, the R.1 ridge is suggested to have formed prior to the deposition of the foraminifera. Based on these data we propose that a surge‐type advance occurred in Mohnbukta in the early Holocene, prior to 7700 cal. a BP, which in turn indicates that glaciers can switch to and from surge mode.

Gas hydrate reservoirs and gas migration mechanisms in the Terrebonne Basin, Gulf of Mexico

The interactions of microbial methane generation in fine-grained clay-rich sediments, methane migration, and gas hydrate accumulation in coarse-grained, sand-rich sediments are not yet fully understood. The Terrebonne Basin in the northern Gulf of Mexico provides an ideal setting to investigate the migration of methane resulting in the formation of hydrate in thin sand units interbedded with fractured muds.Using 3D seismic and well log data, we have identified several previously unidentified hydrate bearing units in the Terrebonne Basin. Two units are >100 m-thick fine-grained clay-rich units where gas hydrate occurs in near-vertical fractures. In some locations, these fine-grained units lack fracture features, and they contain 1–4-m thick hydrate bearing-sands. In addition, several other thin sand units were identified that contain gas hydrate, including one sand that was intersected by a well at the location of a discontinuous bottom-simulating reflector. Using correlation of well log data to seismic data, we have mapped and described these new units in detail across the extent of the available data, allowing us to determine the variation of seismic amplitudes and investigate the distribution of free gas and/or hydrate.We present several potential source-reservoir scenarios between the thick fractured mud units and thin hydrate bearing sands. We observe that hydrate preferentially forms within thin sand layers rather than fractures when sands are present in larger marine mud units. Based on regional mapping showing the patchy lateral extent of the thin sand layers, we propose that diffusive methane migration or short-migration of microbially generated methane from the marine mud units led to the formation of hydrate in these thin sands, as discontinuous sands would not be conducive to long-range migration of methane from deeper reservoirs.

Reconciling Log-Derived Water-Saturation and Saturation-Height Function Results

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 175053, “Reconciling Log-Derived-Water-Saturation and Saturation- Height-Function Results Through Resistivity Modeling, Core-Log Integration, and Image-Log Data: A Case Study From Deepwater Gulf of Mexico,” by Javier Miranda, Michael Rabinovich, Jeffry Hamman, and Maryam Mousavi, SPE, BP, prepared for the 2015 SPE Annual Technical Conference and Exhibition, Houston, 28–30 September. The paper has not been peer reviewed. Saturation-height functions (SHFs) play a key role in reservoir description and in quantifying oil in place. The functions must compare well with other sources of water saturation (Sw), such as core measurements and well-log interpretations, when they are available. The authors have reconciled different Sw sources through a reliable SHF function based on the Brooks-Corey model with parameters optimized for the Gulf of Mexico (GOM) Thunder Horse (TH) Field. The function is used to populate oil volumes in the 3D static and dynamic models. General Description of the Hydrocarbon Field TH is located in a six-block “lease unit” of the Mississippi Canyon (MC) area of the deepwater GOM. The field is approximately 69 miles from the Louisiana coastline in water depths ranging from 6,000 to 6,500 ft. The TH facility consists of a taut-wire-moored semisubmersible system with production, drilling, and quarters (PDQ). The PDQ is located near the southern boundary of MC 778. The PDQ is designed to handle 250,000 BOPD, 200 MMscf/D, and 140,000 B/D of produced water. The facility was also designed to handle 300,000 B/D of mixed seawater/produced water for injection. The TH wells are located in subsea drill centers, with additional satellite subsea-production wells located where the reservoir structure dictates. Sixteen producers have been brought on line since first oil on 14 June 2008. The total volume produced as of the end of 2014 is estimated at 300 million BOE. Oil and water rates (December 2014) are 100,000 BOPD and 26.500 BWPD, respectively. The TH discovery contains hydrocarbon resources in two structural closures commonly referred to as the TH South (THS) and TH North (THN). TH Reservoir Distribution and Architecture. The current depositional model for TH is that all three reservoir intervals are part of a stacked sequence of Miocene lower slope aprons. In a general architectural model for a single slope apron, the proximal region is dominated by amalgamated channels, bypass lags (acting as baffles and barriers), and lateral complexity. Net/gross ratio (NTG) can vary significantly in the proximal region, depending on the distance to sediment sources. The medial portion of the apron is dominated by more-sheet-like sands interspersed with the occasional silt- or mud-rich unit, and the distal portion of the apron is dominated by interlayered sand, silt, and mud units. In a vertical sequence, the apron model leads to an increase in system energy and channelization from bottom to top. After the apron healed the terrain, sediments began bypassing down the slope and were able to erode into the apron itself. This led to the formation of canyons and canyon-fill successions that segmented the original reservoirs and yielded isolated compartments and major production barriers.

A depositional model for seismo-turbidites in confined basins based on Ionian Sea deposits

This study investigates Ionian Sea seismo-turbidite (ST) deposits that we interpret to be triggered by major historic earthquakes and tsunamis in the Calabrian Arc. ST beds can be correlated with the AD 1908 Mw 7.24 Messina, AD 1693 Mw 7.41 Catania, and AD 1169 Mw 6.6 Eastern Sicily earthquakes while two previously unknown turbidites might have been generated by the AD 1818 Mw 6.23 Catania and AD 1542 Mw 6.77 Siracusa earthquakes.Textural, micropaleontological, geochemical and mineralogical signatures of STs reveal cyclic patterns of STa, STb, STc and STd sedimentary units for each earthquake with an associated tsunami. The STa unit contains multiple ST stacks with different mineralogy, geochemistry foraminiferal assemblages and sedimentary structures that are deposited from synchronous multiple slope failures and turbidity currents. The STb homogenite graded mud unit overlying the STa unit is deposited by the waning flows of the multiple turbidity currents that are trapped in the Ionian Sea confined basin. The STc laminated and marine-sourced unit results from seiching of the confined water mass that appears to be generated by earthquake ruptures combined with tsunami waves. The STd unit is a tsunamite cap deposited by the slow settling suspension cloud created by tsunami wave backwash erosion of the shoreline and continental shelf. This tsunami process interpretation is based on the textural gradation of the upper unit and a more continental source of the tsunamite cap which includes C/N>10 and the presence of inner shelf foraminifera with a lack of abyssal species. This interpretation is in agreement with the lack of a tsunamite cap for the turbidite likely linked to the AD 1542 historic earthquake that is not associated with a tsunami. The new sedimentologic criteria identifies the final seiche and tsunamite cap deposits of STs and provides a model that can now be tested in other locations to better understand the different depositional processes of seismo-turbidites in confined basins.

Iron behavior in a northern estuary: Large pools of non-sulfidized Fe(II) associated with organic matter

The estuaries of the Northern Baltic Sea (Gulf of Bothnia) receive an abundance of diagenetically reactive catchment-derived Fe, which is to a large degree complexed with organic matter or present as Fe (hydr-)oxides. However, our understanding of sedimentary Fe diagenesis in these estuaries is limited. To address this limitation, the present study examines Fe geochemistry in a 3.5-m-thick estuarine benthic mud layer and three samples of suspended particulate matter of a catchment on the eastern Gulf of Bothnia. The age–depth model of the mud, constructed on the basis of sedimentary features as well as 137Cs and aquatic plant 14C determinations, revealed a high average rate of sedimentation (5cm·yr−1) for the upper mud unit (0–182.5cm, corresponding to 1973–2011), in response to intensive land-use (ditching) in the catchment since the 1960s and 1970s. The intensive land-use has resulted in a strong increase in the Fe accumulation rates, but has not caused a recognizable impact on the diagenetic processes of Fe including features such as degree of sulfidization and solid-phase partitioning. Iron X-ray absorption spectroscopy (XAS) indicated that in the suspended particulate matter, large proportions (47–58%) of Fe occur as Fe(III)-organic complexes and 2-line ferrihydrite. In the mud, the former is completely reduced, and reactive Fe (defined via extraction with 1M HCl) was high throughout (52–68%, median=61%) and strongly dominated by Fe(II). This reactive Fe(II) pool was sulfidized to only a limited extent (degree of reactive sulfidization=11–26%, median=17%). This phenomenon is attributed to the brackish-water conditions (i.e. low in sulfate) and the abundant input of reactive Fe(III) from the catchment, leading to a surplus of dissolved Fe2+ over dissolved sulfide in the sediment. The low availability of dissolved sulfide, in combination with the high average sedimentation rate, limits the formation of intermediate reduced sulfur compounds at the water–sediment interface, thereby retarding the conversion of FeS into pyrite (ratios of pyrite-S to AVS=0.17–1.73, median=0.37; degree of pyritization=1–17%, median=3%). Iron XAS, in combination with wavelet transform analysis, of representative sediment segments from the upper and lower mud units suggests that the non-sulfidized Fe(II) pool is dominantly complexed by organic matter, with the remaining Fe(II) occurring as mackinawite. This has implications for the understanding of early Fe diagenesis in settings with a high input of organic matter and relatively low supply of sulfate.

Quaternary extensional and compressional tectonics revealed from Quaternary landforms along Kosi River valley, outer Kumaun Lesser Himalaya, Uttarakhand

A portion of the Kosi River in the outer Kumaun Lesser Himalaya is characterized by wide river course situated south of the Ramgarh Thrust, where huge thickness (~200 m) of the landslide deposits and two to three levels of unpaired fan terraces are present. Brittle normal faults, suggesting extensional tectonics, are recognized in the Quaternary deposits and bedrocks as further supported by surface morphology. Trending E–W, these faults measure from 3 to 5 km in length and are traced as discontinuous linear mini-horst and fault scarps (sackungen) exposed due to cutting across by streams. Active normal faults have displaced the coarsely laminated debris fan deposits at two sites located 550 m apart. At one of the sites, the faults look like bookshelf faulting with the maximum displacement of ~2 m and rotation of the Quaternary boulders along the fault plane is observed. At another site, the maximum displacement measures about 0.60 cm. Thick mud units deposited due to blocking of the streams by landslides are observed within and above the fan deposit. Landslide debris fans and terrace landforms are widely developed; the highest level of fan is observed ~1240 m above mean sea level. At some places, the reworking of the debris fans by streams is characterized by thick laminated sand body. Along the South Almora Thrust and Ramgarh Thrust zones, the valleys are narrow and V-shaped where Quaternary deposits are sparse due to relatively rapid uplift across these thrusts. Along the South Almora Thrust zone, three to four levels of fluvial terraces are observed and have been incised by river exposing the bedrocks due to recent movement along the RT and SAT. Abandoned channel, tilted mud deposits, incised meandering, deep-cut V-shaped valleys and strath terraces indicate rapid uplift of the area. Thick mud sequences in the Quaternary columns indicate damming of streams. A ~10-km-long north–south trending transverse Garampani Fault has offset the Ramgarh Thrust producing tectonic landforms.

Contrasting styles of deep-marine pyroclastic eruptions revealed from Axial Seamount push core records

A comprehensive understanding of explosive basaltic eruption processes in the deep-sea relies upon detailed analysis and comparison of the variety of volcaniclastic lithologies on the seafloor, which has been challenged by insufficient sample recovery. A dedicated ROV-based sampling approach using long push cores offers an unparalleled opportunity to fully characterize the diversity of unconsolidated volcaniclastic lithofacies on a recently active seamount. Lithofacies from Axial Seamount record two styles of pyroclastic eruptions, strombolian and phreatomagmatic, at 1.5 km water depth. Strombolian eruptions are represented by abundant fluidal and highly vesicular (up to 50%) vitriclasts within limu o Pele lapilli tuff and tuffaceous mud lithofacies. Lapilli-ash grain size, normal grading, good sorting, rip-up clasts and homogeneous glass geochemistry characterize individual limu o Pele lapilli tuff beds, and imply proximal deposition from a turbidity flow associated with a single eruption (i.e. event bed). Limu o Pele lapilli tuff beds are interbedded with poorly sorted, chemically heterogeneous and bioturbated tuffaceous mud units that preserve reworking and biologic habitation of more distal pyroclastic fallout and dilute turbidity flows. The phreatomagmatic eruption style is preserved by hydrothermal mineral-bearing muddy tuff that exhibits characteristics distinct from lapilli ash and tuffaceous mud lithofacies. Hydrothermal muddy tuff lithofacies are well-sorted and fine-grained with notable components of non-fluidal basaltic ash (∼45%), fluidal ash (∼30%) and accessory lithics (∼25%). Heterogeneous geochemistry of ash shards implies that juvenile components are minimal. The abundance, mineralogy and texture of lithic components (Fe–Mg clays, pyrite, epidote, actinolite, altered glass, basalt/diabase, hydrothermal breccia and agglutinate), and very fine-grain size of basaltic ash, are consistent with phreatomagmatic eruption deposits. A lack of bioturbation or other interbedded lithofacies, and presence of normal grading suggests prolonged eruption activity and deposition via turbidity flows or suspension fallout. The proximity of ancient hydrothermal muddy tuff lithofacies and active hydrothermal vents to caldera walls suggest that phreatomagmatic activity was linked to shallow circulation of fluids along caldera ring-faults rooted to underlying magma conduits and shallow reservoirs. This study provides evidence for two distinctly different pyroclastic eruption styles and provides a framework to further develop existing models of deep-sea explosive volcanism.