Coastal Depositional Environments Research Articles

Predicting natural arsenic enrichment in peat-bearing, alluvial and coastal depositional systems: A generalized model based on sequence stratigraphy

Hazardously high concentrations of arsenic exceeding the threshold limits for soils and drinking waters have been widely reported from Quaternary sedimentary successions and shallow aquifers of alluvial and coastal lowlands worldwide, raising public health concerns due to potential human exposure to arsenic. A combined sedimentological and geochemical analysis of subsurface deposits, 2.5–50 m deep, from the SE Po Plain (Italy) documents a systematic tendency for naturally-occurring arsenic to accumulate in peat-rich layers, with concentrations invariably greater than maximum permissible levels.A total of 366 bulk sediment samples from 40 cores that penetrated peat-bearing deposits were analysed by X-ray fluorescence. Arsenic concentrations associated with 7 peat-free lithofacies associations (fluvial-channel, levee/crevasse, floodplain, swamp, lagoon/bay, beach-barrier, and offshore/prodelta) exhibit background values invariably below threshold levels (<20 mg/kg). In contrast, total arsenic contents from peaty clay and peat showed 2–6 times larger As accumulation. A total of 204 near-surface (0–2.5 m) samples from modern alluvial and coastal depositional environments exhibit the same trends as their deeper counterparts, total arsenic peaking at peat horizons above the threshold values for contaminated soils.The arsenic-bearing, peat-rich Quaternary successions of the Po Plain accumulated under persisting reducing conditions in wetlands of backstepping estuarine and prograding deltaic depositional environments during the Early-Middle Holocene sea-level rise and subsequent stillstand. Contamination of the Holocene and underlying Pleistocene aquifer systems likely occurred through the release of As by microbially-mediated reductive dissolution. Using high-resolution sequence-stratigraphic concepts, we document that the Late Pleistocene-Holocene lithofacies architecture dictates the subsurface distribution of As. The “wetland trajectory”, i.e. the path taken by the landward/seaward shift of peat-rich depositional environments during the Holocene, may help predict spatial patterns of natural As distribution, delineating the highest As-hazard zones and providing a realistic view of aquifer contamination even in unknown areas.

Meta‐analysis of the long‐term stratigraphic evolution of rifted margin basins: The GeoDyNamical Analysis approach applied to the South Atlantic Ocean

AbstractModels of the formation of rifted margins have significantly evolved over the last decades by identifying new styles of crustal thinning and magmatic production. However, the expression of these different processes in the depositional environments of the overlying basins remains to be determined. Using only published data, we integrated the sedimentary evolution of 21 basins of the Equatorial, Central and South segments of the South Atlantic that record various styles of crustal thinning and magmatic production. To compare these basins that underwent rifting at different times, we developed a new type of analysis allowing to evaluate statistically the (dis)similarities in depositional environment trends by normalizing them to the tectonic phases of the basin (syn‐rift, transition and post‐rift) rather than the stratigraphic or absolute ages: The GeoDyNamical Analysis. We show that the timing of the long‐term retrograding mega‐sequence driven by lithosphere thinning depends on the deformation style and magma production. Along oblique margins of the Equatorial Segment, deepening initiated during syn‐rift because their narrow crustal thinning style favours rapid tectonic subsidence surpassing sediment supply. Along wide margins of the Central Segment, deepening is initiated later, at the end of the transition phase, because depth‐dependent thinning favours slow tectonic subsidence and late break‐up. Along magma‐rich margins of the South Segment, deepening is initiated during the transition phase, after volcanics stopped filling accommodation created by subsidence. In the Central Segment, evaporites accumulated during the second half of the transition phase, when crustal thinning ceased in the proximal margin and migrated to its distal part. Immediately before and during evaporites accumulation, sediments recorded continental and coastal depositional environments resulting from the limited thermal subsidence in the proximal margin domain. Evaporite deposition lasted until the initiation of retrograding mega‐sequence, at the onset of the post‐rift phase and the end of crustal thinning in the distal margin.

Sedimentary molybdenum and uranium: Improving proxies for deoxygenation in coastal depositional environments

Sedimentary molybdenum (Mo) and uranium (U) enrichments are widely used to reconstruct changes in bottom water oxygen conditions in aquatic environments. Until now, most studies using Mo and U have focused on restricted suboxic-euxinic basins and continental margin oxygen minimum zones (OMZs), leaving mildly reducing and oxic (but eutrophic) coastal depositional environments vastly understudied. Currently, it is unknown: (1) to what extent Mo and U enrichment factors (Mo- and U-EFs) can accurately reconstruct oxygen conditions in coastal sites experiencing mild deoxygenation, and (2) to what degree secondary (depositional environmental) factors impact Mo- and U-EFs. Here we investigate 18 coastal sites with varying bottom water redox conditions, which we define by means of five “redox bins”, ranging from persistently oxic to persistently euxinic, from a variety of depositional environments. Our results demonstrate that Mo- and U-EF-based redox proxies and sedimentary Mo and U contents can be used to differentiate bottom water oxygen concentration among a range of modern coastal depositional environments. This is underpinned by the contrasting EFs of Mo and U along the redox gradient, which shows a substantial difference of Mo-EFs between redox bins 3–5 (ir/regularly suboxic – ir/regularly dysoxic – persistently oxic) and of U-EFs between redox bins 1–2 (persistently euxinic – ir/regularly euxinic). Surprisingly, we observe comparatively low redox proxy potential for U in environments of mild deoxygenation (redox bins 3–5). Further, we found that secondary factors can bias Mo-and U-EFs to such an extent that EFs do not reliably reflect bottom water redox conditions. We investigate the impact of limited Mo sedimentary sequestration in sulfidic depositional environments (i.e., the “basin reservoir effect”, equilibrium with FeMoS4), Fe/Mn-(oxy)(hydr)oxide “shuttling”, oxidative dissolution, the sulfate methane transition zone in the sediment, sedimentation rate, and the local Al background on Mo- and U-EFs.

Facies analysis and depositional environment of the Carboniferous Singa Formation: Case study

Due to limited information, this paper aims to present a detailed facies analysis and depositional environment of the Carboniferous age, Singa Formation at Pulau Ular, Langkawi, Kedah. One exposed outcrop at Hill C was examined in detail, and one sedimentary log was created. The log is categorized bed by bed into several facies according to lithology and sedimentary structures. The focus was to identify the facies succession and to analyze the depositional environment as Singa Formation. This study is vital to reconstructing the pattern of past glacial as it will provide the crucial link between glacial processes and history, ice masses, and a more comprehensive Earth system. The Singa Formation is concluded into coarsening upward facies successions based on the facies succession grades upward from offshore facies. The depositional environment of Pulau Ular is interpreted as a coastal and a glacier depositional environment. Eight facies have been recognized; shale (FC1), shale with burrows (FC2), siltstone (FC3), shale with burrows, clay to silt (FC4), laminated shale with dropstone (FC5), sandstone that consists of dropstone (FC6), shale consists of dropstone (FC7) and sandstone with diamictite rock (FC8). Facies shale, sandstone, and siltstone proved that the study area is a coastal depositional environment, while facies consisting of dropstones and diamictite show that the study area is a glacier depositional environment.

Holocene foraminifera from the outer zone of the Bahía Blanca Estuary, Argentina (South America)

In this study, Holocene paleoenvironmental changes were interpreted based on benthic foraminifers from a core (39°20′S-61°27′W) extracted from the Argentine Continental Shelf close to the Bahia Blanca Estuary, in the south of Buenos Aires Province. Foraminiferal fauna was determined, and found to include 44 species of 22 genera. From micropaleontological and sedimentological analysis, paleoenvironmental changes during the middle-late Holocene were recognized. Two stages were determined: from 8319–8045 to 7836-7623 Cal. yrs BP, the sediments reflected a shallow environment with estuarine conditions and low energy, enabling determination of a coastal depositional environment. As from ca. 7836–7623 up to ca. 651-557 Cal. yrs BP, the sediments indicated a passage towards to a shallow shelf environment with great marine influence, displaying a high degree of energy and oxygenation, which may have been related to a rise in sea level ca. 7836 -7623 Cal. yrs BP. The detailed study of the benthic foraminiferal fauna presented herein and the sedimentological and chronological analysis performed on the continental shelf next to the Bahía Blanca Estuary provide further proof of the relative location of the mean sea level during the middle Holocene transgressive hemicycle in Argentina.

Textural Characteristics of the Holocene Sandy Ridges in the Eastern Venetian Coastal Plain (North Adriatic Sea, Italy)

In the lower Piave river coastal plain (northeast of the Venice Lagoon, Italy), evidences of ancient sandy ridges testify to both the local coastline progradation and retrogradation that occurred during the Holocene. Their arrangement is recognizable in aerial photographs as they appear as groups of parallel sandy strips. The orientation of each group of ridges differs from the orientation of the others. Even if the ridges have not preserved their original relief and morphology, weak undulations are still locally present. Through the joint interpretation of textural parameters and geomorphological observations and measurements, an attempt has been made to define the depositional processes responsible for the formation of these sandy ridges. The results from grain-size analyses have given evidence of the foreshore and the backshore environments. They have confirmed the presence of both aeolian deposits in most of the sampled sandy ridges and fine-grained filling sediments containing organic matter in the old inter-ridge depressions. The investigations have also confirmed the existence of a well-preserved abandoned Piave river delta and four subsequent main stages of coastal progradation interrupted by episodes of coastal retreat. Therefore, this research has provided new insights into the evolution of the Holocene Venetian coastal plain by adding new information on the different coastal depositional environments and transporting agents.

Quaternary Coastal Landscape Evolution and Sea-Level Rise: An Example from South-East Sicily

Coastal depositional environments are the site of complex interactions between continental and marine processes. Barrier islands are highly dynamic coastal systems, typical of these transitional environments, and are affected by sea level changes and the accumulation of transgressive deposits with the landwards migration of the coast. The offshore of Marzamemi (Syracuse Province, Sicily), in the south-eastern portion of the Hyblean foreland, represents an excellent site for the study of transgressive deposits and their connection with the sea-level changes. The available dataset consisted of new high-resolution bathymetry (Multibeam), whose description and interpretation through a Digital Elevation Model (DEM) was integrated with a grid of eighteen seismic profiles (SPARKER). In the investigated bathymetric range, from about −5 m to −60 m, a sensibly different morphological setting between the northern and southern sectors was evident. Within the whole study area, three bathymetric contours (−45 m, −35 m and −20 m) were identified and assumed as the markers of the main locations of the paleo-coastlines during the recent changes in the sea level. Along the northern sector, three submerged barrier-lagoon systems developed on a calcarenite substratum, marking important steps of the Late Quaternary sea-level rise. They coexisted with numerous karst forms (poljes and dolines). In the southern sector the transgressive environmental evolution was significantly different and submerged lagoons did not form. Here the outcropping calcarenite substratum was affected by the development of paleo-rivers and karsts structures, a tract in common along with many Mediterranean carbonate coastal areas.

The youngest dinosaur footprints from England and their palaeoenvironmental implications

Newly discovered dinosaur footprints from the Lower Cretaceous (Albian) Folkestone Formation (Lower Greensand Group) of Kent in S.E. England can be referred to theropod, ornithopod and possibly ankylosaur dinosaurs. The occurrence of dinosaur footprints, together with fossil wood and oysters in a matrix of well-rounded quartz grains indicates a coastal depositional environment of an extremely shallow depth, perhaps with short periods of subaerial exposure. This is the first record of dinosaur footprints from the Folkestone Formation, and it represents the youngest association of dinosaur footprints from England. The moderately diverse dinosaur ichnoassemblage of theropods, ornithopods, ankylosaurs and previously documented fossils indicate deposition on a sandy beach setting.

Sedimentological and Lithostratigraphic Study of the Senonian Series in Timstiguite Region, Central High Atals, Morocco

In this paper, we present the sedimentological, stratigraphic and paleogeographic aspect of the Upper Cretaceous red formations (Senonian series) of Timstiguite region (Central High Atlas of Morocco). The formations were measured bed by bed and sampled in a very detailed way. An exoscopic analysis of the quartz grains was carried out by a systematic prospecting of the grains relief and theirs surface characteristic, this led us to characterize their origin and consequently to determine the different paleoenvironnements. The clay sediments of these formations seem to be a favorable prospect in point of view: evolution of the clay and non-clay sediments in this central basin of the High Atlas will depend mainly on the conjugation of tectonic, eustatic, climatic and other influences. The senonian thickness is more important than other sub basins (Albban and Imider) where it shows a very reduced thickness. The Senonian of Timstiguite corresponds to a succession of detrital and evaporitic carbonate facies, which confirms a coastal depositional environment with passages of some periods of marine emersions.

Changes in depositional environment of the Savitri (tropical) estuary, central west coast of India

Transformation of coastal regions as a result of recent climate change and localised human influences is of concern. Thus, understanding of the changes that have already occurred, the processes responsible for these changes, and their impact on coastal depositional environment is important. Large and well-developed intertidal mudflats of Savitri estuary of central west coast of India are well suited for this purpose. The distribution of sediment components, total organic carbon, total nitrogen, total phosphorous, sedimentary organic carbon isotope ratios (δ13Corg), diatoms, pH, and metals (Fe, Mn, Al, Ni, Cr, Co, Zn, Pb) of two mudflat sediment cores, S-18 from lower estuary and S-41 from middle estuary of Savitri estuary, are presented in this paper. The enrichment of δ13Corg values from bottom to surface as well as dominance of marine diatom species towards the surface of core S-18 was attributed to the decrease in freshwater inflow to the estuary as a result of decreased rainfall, and runoff, while, increase in organic nutrient load in cores S-18 and S-41, was may be due to input from anthropogenic activities in recent years and changes in depositional environment of Savitri estuary.

Evaluation of the hydrocarbon generation potential of the Pimenteiras Formation, Parnaiba Basin (Brazil) based on total organic carbon content and Rock-Eval pyrolysis data

The Parnaiba Basin is a Paleozoic to Mesozoic intraplate volcano-sedimentary basin where the Pimenteiras Formation (Devonian) is the main sequence with potential of hydrocarbon generation, mostly natural gas. The present paper evaluates the potential of hydrocarbon generation of Pimenteiras Formation based on Total Organic Carbon (TOC) and Rock-Eval pyrolysis parameters. In this work, 1077 shale samples of the Pimenteiras Formation distributed in 32 wells were evaluated. The TOC content varies between 0.1 to 4.7 wt.%, partially reflecting the accumulation and preservation rates of the organic matter in marine and coastal depositional environments controlled by regressive-transgressive cycles. The oxic and anoxic conditions vary significantly with deposition in this situation, which were evidenced by HI and OI variations through sample profiles. In the north and center of the basin, the Pimenteiras Formation has a higher potential for hydrocarbon generation relative to the south, probably due to higher anoxic conditions during deposition. The Hydrogen Index indicates the predominance of kerogen types II and III with minor occurrences of types I and IV. The Tmax values indicate general immature conditions and locally postmature, where the lowest temperatures represent the basin´s burial history, whereas the higher ones were influenced by igneous intrusions and thermogenic anomalies related to the Transbrasiliano Lineament. In addition, the excessive heat around the intrusions altered the Rock-Eval pyrolysis parameters as well as the type of organic matter, resulting in a relative increase of the kerogen types III and IV, which explains the great potential for gas generation in this basin.

River avulsions and sedimentary evolution of the Luanhe fan-delta system (North China) since the late Pleistocene

The Luanhe Fan-Delta (LFD) is one of the most important coastal deltas in North China. Numerous investigations on the late Quaternary evolution of this fan-delta system have been implemented during the 1980s. However, few detailed sedimentologic studies have been undertaken. Based on comprehensive analysis of sedimentary facies, grain size, microfossils, radiocarbon dates (AMS14C) and optically stimulated luminescence (OSL) ages from three ~30 m-long cores, along with recent reports from a series of cores and seismic profiles from the coastal areas, we reconstructed the detailed late Quaternary sedimentary evolution of the northern Bohai coast, which evolved from a coastal barrier-lagoon system during MIS5 to an alluvial plain, with river channels and floodplains between MIS4 and the Early Holocene. A variety of transgressive coastal depositional environments (freshwater marshes, beach ridges, sandy barriers, shallow seas) developed during the early Holocene. These environments were followed by delta progradation. The delta system then gradually turned into a coastal barrier-lagoon system under the combined impact of prevailing wave-driven currents and local subsidence. Two dramatic 90-degree diversions of the lower Luanhe River course likely influenced the sedimentary evolution of the LFD in its inner portion. The first avulsion took place in Qianxi, probably at the end of the Late Pleistocene (~15,000 cal a BP). It led to the abandonment of the Luanhe alluvial fan in the western part of the northern Bohai coastal plain (NBCP), and to the formation of a new alluvial fan in the eastern NBCP. This alluvial fan evolved into a fan-delta system (7000–3500 cal a BP) during the Holocene transgression. The second avulsion occurred at Zhuacun during the Late Holocene, probably at 3600 ± 100 cal a BP. Following this latter avulsion, the Luanhe River shifted toward the east and formed a new fan-delta system (~3700 cal a BP–present), with its apex in Luanzhou. Abrupt tectonic uplift in this highly seismic region likely controlled the two avulsions and the dramatic shift of the alluvial-fan complexes. Climate and sea-level changes may also have partly influenced the development of the LFD.

Modern Analogue of Shaly Sand Reservoir on Coastal Plain in Selat Baru, Bengkalis Island, Indonesia

Coastal environment is one of main reservoir depositional system in the oil industry and becomes the main challenges in defining its characteristic, especially in lateral correlation. Research conducted in Bengkalis Island which has a unique characteristic of coastal depositional environment that affected by a tidal system related to modern analogue for reservoir characterization. The method used for this research is analysing lithofacies from drilled core data, surface sampling, and lateral measurement from foreshore to the tidal limit. It is confirmed from core data that research area consists of sand, shale, and peat with lamination, cross laminations sedimentary structure and also filled with organism activity, which clustered into eight lithofacies. By integrating the core data with surface sampling and lateral measurement, it is interpreted that facies is changing only in near distance (about 30 – 40 m) with sloping 1 – 2 degrees in the surface, so by defining the same characteristic on lithofacies, correlation can clearly define on a shaly sand reservoir in the tidal coastal environment.

Late Holocene to Recent aragonite‐cemented transgressive lag deposits in the Abu Dhabi lagoon and intertidal sabkha

AbstractModern cemented intervals (beachrock, firmgrounds to hardgrounds and concretionary layers) form in the lagoon and intertidal sabkha of Abu Dhabi. Seafloor lithification actively occurs in open, current‐swept channels in low‐lying areas between ooid shoals, in the intertidal zone of the middle lagoon, some centimetres beneath the inner lagoonal seafloor (i.e. within the sediment column) and at the sediment surface the intertidal sabkha. The concept of ‘concretionary sub‐hardgrounds’, i.e. laminar cementation of sediments formed within the sediment column beneath the shallow redox boundary, is introduced and discussed. Based on calibrated radiocarbon ages, seafloor lithification commenced during the Middle to Late Holocene (ca 9000 cal yr bp), and proceeds to the present‐day. Lithification occurs in the context of the actualistic relative sea‐level rise shifting the coastline landward across the extremely low‐angle carbonate ramp. The cemented intervals are interpreted as parasequence boundaries in the sense of ‘marine flooding surfaces’, but in most cases the sedimentary cover overlying the transgressive surface has not yet been deposited. Aragonite, (micritic) calcite and, less commonly, gypsum cements lithify the firmground/hardground intervals. Cements are described and placed into context with their depositional and marine diagenetic environments and characterized by means of scanning electron microscope petrography, cathodoluminescence microscopy and Raman spectroscopy. The morphology of aragonitic cements changes from needle‐shaped forms in lithified decapod burrows of the outer lagoon ooidal shoals to complex columnar, lath and platy crystals in the inner lagoon. Precipitation experiments provide first tentative evidence for the parameters that induce changes in aragonite cement morphology. Data shown here shed light on ancient, formerly aragonite‐cemented seafloors, now altered to diagenetic calcites, but also document the complexity of highly dynamic near coastal depositional environments.

Late-Holocene coastal depositional environments and climate changes in the Gulf of Corinth, Greece

Multidisciplinary studies in coastal systems of the eastern Mediterranean region have proven to be excellent tools in understanding paleoenvironmental, paleoecological, and paleoclimatic changes that took place during the Holocene period, and how these changes interacted with urban development and growth. This paper presents sedimentological, high-resolution x-ray fluorescence (XRF scanning), micropaleontological, and x-ray diffraction (XRD) data from three shallow sediment cores that were retrieved from Aliki (ancient Siphai or Tipha) salt pond. The study area is located in a unique, highly tectonic geographical region, at the northeast part of the Gulf of Corinth in Greece. Beachrock deposits that form a barrier between the salt pond and the marine environment seem to play an important role in the evolution of the area. The chronological framework was set at around 3100 cal. BP by four 14C radiocarbon dates, and the evolutionary model that was established indicates four different changes taking place during this period at the study area. From around 3100 to 1600 cal. BP, a transition from a closed to an open lagoonal environment was identified, interrupted by a fluvial terrestrial deposit at around 2500 cal. BP. A shift toward a closed lagoonal system at around 1600 cal. BP and the establishment of a salt pond environment seem to correlate with tectonic activity. The study provides important information about the evolution of coastal landscape in such a tectonic active region and points the interaction between regional human activity and climatic changes during the late-Holocene period.

Organic petrography, Rock\u2013Eval pyrolysis and biomarker geochemistry of Maastrichtian Gombe Formation, Gongola Basin, Nigeria

The Maastrichtian Gombe Formation is located within one of the inland basins of Nigeria (Gongola Basin). Surface and borehole samples of coal and interbedded shale of this formation were evaluated to determine the organic matter richness, quality, maturity, source and depositional environment through organic geochemical techniques such as total organic carbon (TOC) determination, Rock–Eval pyrolysis, chromatography and organic petrography. The genetic potential and average TOC value of the coals, shales and coaly shales are 38.03 wt%, 3.14 wt% and 12.1 wt%, respectively, indicating moderate-to-good source potential. HIs are less than 200 mgHC/gTOC for all the samples indicating Type III kerogen for most of the samples (gas prone) and plant contributions from terrestrial sources. The source rocks were characterized by high molecular weight n-alkanes which range from C10–C41 in the coals and C9–C41 in the shales. The n-alkanes distributions in the coals maximize at C29 indicating terrestrial sourced organic matter, while the shales maximize at C16 and C29 indicating mixed sources. Pr/Ph of the coals and shales ranges from (2.15–3.51) to (0.95–2.37), respectively, suggesting fluvio-deltaic deltaic and coastal swamp depositional environments. The predominance of pristane over phytane suggests humic origin of the organic matter. The sterane/hopane values (< 0.6) indicate incorporation of bacterial inputs commonly associated with terrigenous organic matter in the coals. The CPI is greater than unity, Tmax is generally < 435 °C and vitrinite reflectance less than 0.55 Ro for most of the samples and suggest the samples are of low maturity status to expel liquid hydrocarbon.

GPR trace analysis for coastal depositional environments of southern Brazil

Ground penetrating radar (GPR) is increasingly used for subsurface detection of structures due to nondestructive characteristics. Use of the method for studies of coastal depositional environments is growing in southern Brazil. In this paper, we propose an analysis of traces in the variation in signal amplitude, integrated with the degree of compaction determined in the drill hole, for the characterization of depositional environments in regressive barriers. Signal attenuation with depth was interpreted from the least squares method for two cases of contrast in volume of rainfall. Results show efficiency of the methodology in determination of contacts between different deposits at depth, showing an increase in signal amplitude at the contact between the original deposits from low to high compaction. Precipitation is not relevant for signal attenuation in the sandy deposits studied.

New longirostrine crocodylomorph remains from the Blesa Formation (Barremian) in the Iberian Peninsula (Spain)

Crocodylomorpha has been a highly morphologically and ecologically diverse clade over time. During the Mesozoic and Cenozoic, several crocodylomorph lineages colonized the marine environment; however, by the late Early Cretaceous the extinction of Thalattosuchia and the origination of new marine forms occur, and the “Middle” Cretaceous is a period of time where marine crocodylomorphs are poorly known. Here we describe two rostrum fragments (MPZ 2016/78 and MPZ 2016/79) collected in the upper part of the Blesa Formation (Barremian, Lower Cretaceous) in Teruel (Spain). The “Upper” Blesa Fm has been interpreted as a coastal–transitional depositional environment. The specimens correspond to long-snouted crocodylomorphs. MPZ 2016/78 is the left half of a fragmentary rostrum with heterodonty in dentition size, M4? and M5? being the largest alveoli. This suggests that it belongs to a crocodylomorph with a generalist diet. By contrast, MPZ 2016/79 is a fragmentary right half of a more gracile and slender long rostrum. It is homodont in size, with several small teeth, common in animals specialized for ichthyophagy. MPZ 2016/78 and MPZ 2016/79 have been assigned to Crocodylomorpha indet. This new crocodylomorph material, together with the fossil remains of marine vertebrates previously found in the same region (plesiosaurs, chelonians, osteichthyans, chondrichthyans and a new crocodylomorph), suggests that the “Upper” Blesa Formation was a coastal zone with a great wealth of fauna, making it an interesting area for the study of Barremian marine vertebrates.

Metal pollutants in Indian continental coastal marine sediment along a 3700 km transect: An electron paramagnetic resonance spectroscopic study

We report the analysis and geographical distribution of anthropogenically impacted marine surficial sediments along a 3700km transect around the continental shelf of India. Sediments have been studied using a mixed analytical approach; high sensitivity electron paramagnetic resonance (EPR), chemical analysis and environmental magnetism. Indian coastal marine deposits are heavily influenced by monsoon rains flushing sediment of geological and anthropogenic origin out of the subcontinental river systems. That is, climatic, hydro-, geo- and anthropogenic spheres couple strongly to determine the nature of Indian coastal sediments. Enrichment of Ni, Cu and Cr is observed in shelf sediments along both east and west coasts associated with industrialised activities in major urban areas. In the Gulf of Cambay and the Krishna and Visakhapatnam deltaic regions, levels of Ni and Cr pollutants (≥80 and ≥120ppm respectively) are observed, sufficient to cause at least medium adverse biological effects in the marine ecosystem. In these areas sediment EPR spectra differ in characteristic from those of less impacted ones. Modelling enables deconvolution of EPR spectra. In conjunction with environmental magnetism techniques, EPR has been used to characterise species composition in coastal depositional environments. Paramagnetic species can be identified and their relative concentrations determined. EPR g-values provide information about the chemical and magnetic environment of metals. We observe g-values of up to 5.5 and large g-shifts indicative of the presences of a number of para and ferrimagnetic impurities in the sediments. EPR has enabled the characterisation of species composition in coastal depositional environments, yielding marine sediment environmental ‘fingerprints’. The approach demonstrates the potential of EPR spectroscopy in the mapping and evaluation of the concentration and chemical speciation in paramagnetic metals in sediments from marine shelf environments and their potential for source apportionment and environmental impact assessment.

Near Shore -Shallow Marine (Ophiomorpha and Margaritichnus) Trace Fossils from Fatehgarh Formation of Barmer Basin, Western Rajasthan, India

Two trace fossils namely Ophiomorpha and Margaritichnus have been reported from the Bariyara section of the Fatehgarh Formation of Barmer Basin. Here the Margaritichnus trace fossil sp. is the first record from the western Rajasthan. The present study area is located about 6 km south of Fatehgarh town and 70 kms north of Barmer on Bramer–Jaisalmer road. The Ophiomorpha trace fossils are found in white fine grained calcareous sandstone from lower siliciclastic sequence while Margaritichnus trace fossils occurs in dark brown medium to fine grained ferruginous sandstone of middle phosphorite - siliciclastic sequence of the Fatehgarh Formation of Barmer Basin. The Ophiomorpha trace fossils were considered as crustaceans and shrimps whereas Margaritichnus were mainly produced by worm–like deposits feeders such as sipunculids and priapulids or possibly hydrozoa. The ichnological and sedimentological investigations suggests near - coastal shallow marine depositional environment for the Fatehgarh Formation of the Barmer Basin. It is difficult to attribute a more specific age of Bariyara section of Fatehgarh Formation because of the long stratigraphic range of Margaritichnus (Permian-Cretaceous) and Ophiomorpha (Permian-Recent) as attributed the Fatehgarh Formation to the Cretaceous age on the basis of microvertebrate assemblages recorded from the same Bariyara section.