Brackish Marine Environments Research Articles

Geochemical Characteristic of the Carbonaceous Sediments of the Upper Paleozoic Kuantan Group, Malaysia

The geochemical parameters discussed in this paper are based on an average values of twelve outcrop carbonaceous samples, mainly black shales, were determined using X-Ray Fluorescence (XRF) and Inductively Coupled Plasma-Mass Spectrometer (ICP-MS) techniques, representative of Charu, Sagor, and Permian formations.The aim of this study is to define and discuss their characteristics, the distribution abundance of major and minor elements, investigation the dominant mineralogical composition and reconstruct the depositional environment for these sediments.The bulk chemical result showed that, the average values of the major elements are 65.83%, 64.82 %, 71.4 % SiO2, 18.27 %, 22.2 %, 15.66 % Al2O3, 1.53 %, 0.99 %, 2.49 % Fe2O3. 4.06 %, 6.25 %, 3.66 % K2O , whereas in the case of the miner elements, the results read values of 524.4 ppm, 758.8 ppm, 446.3 ppm Ba , 366 ppm, 399.3 ppm, 257.3 ppm Rb, 88 ppm, 67.3 ppm, 47.3 ppm Sr , 308 ppm, 288.8 ppm, 327ppm Zr for the Charu, Sagor, and Permian formations respectively. The major oxides reflect the dominant mineralogical composition of quartz and other silicate minerals (e.g. illite, kaolinte, smectite) and deficiency in carbonates.The high Rb/K ratio suggests brackish marine environment or rapid depositions that prevent equilibrium between Rb and K in these study shales and marine environment. The high Rb/Sr ratios of 4.16, 5.89 and 5.44 for the Charu, Sagor, and Permian formations respectively possibly attributed to the lowest contents of Sr content due to reducing environment prevailing during deposition of these sediments.

Geochemical Characteristic of the Carbonaceous Sediments of the Upper Paleozoic Kuantan Group, Malaysia

The geochemical parameters discussed in this paper are based on the analysis of twelve outcrop carbonaceous samples, mainly black shales, using X-Ray Fluorescence (XRF) and Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) techniques. These samples are representative of the Charu, Sagor, and Permian formations. The aim of this study is to define and discuss their characteristics, the distribution abundance of major and minor elements, investigate the dominant mineralogical composition, and reconstruct the depositional environment for these sediments. The bulk chemical results showed that the average values of the major elements are 65.83%, 64.82%, and 71.4% SiO?; 18.27%, 22.2%, and 15.66% Al?O?; 1.53%, 0.99%, and 2.49% Fe?O?; and 4.06%, 6.25%, and 3.66% K?O for the Charu, Sagor, and Permian formations, respectively. The minor elements recorded values of 524.4 ppm, 758.8 ppm, and 446.3 ppm Ba; 366 ppm, 399.3 ppm, and 257.3 ppm Rb; 88 ppm, 67.3 ppm, and 47.3 ppm Sr; and 308 ppm, 288.8 ppm, and 327 ppm Zr for the Charu, Sagor, and Permian formations, respectively. The major oxides reflect the dominant mineralogical composition of quartz and other silicate minerals (e.g., illite, kaolinite, smectite) and a deficiency in carbonates. The high Rb/K ratio suggests a brackish marine environment or rapid deposition that prevented equilibrium between Rb and K in these shales. The high Rb/Sr ratios of 4.16, 5.89, and 5.44 for the Charu, Sagor, and Permian formations, respectively, are possibly attributed to the low Sr content due to reducing conditions prevailing during the deposition of these sediments.

Degradation Rates and Bacterial Community Compositions Vary among Commonly Used Bioplastic Materials in a Brackish Marine Environment.

Plastic pollution threatens both terrestrial and aquatic ecosystems. As a result of the pressures of replacing oil-based materials and reducing the accumulation of litter in the environment, the use of bioplastics is increasing, despite little being known about their accurate biodegradation in natural conditions. Here, we investigated the weight attrition and degradation behavior of four different bioplastic materials compared to conventional oil-based polyethylene during a 1-year in situ incubation in the brackish Baltic Sea and in controlled 1 month biodegradation experiments in the laboratory. Bacterial communities were also investigated to verify whether putative plastic-degrading bacteria are enriched on bioplastics. Poly-l-lactic acid showed no signs of degradation, whereas poly(3-hydroxybutyrate/3-hydroxyvalerate) (PHB/HV), plasticized starch (PR), and cellulose acetate (CA) degraded completely or almost completely during 1-year in situ incubations. In accordance, bacterial taxa potentially capable of using complex carbon substrates and belonging, e.g., to class Gammaproteobacteria were significantly enriched on PHB/HV, PR, and CA. An increase in gammaproteobacterial abundance was also observed in the biodegradation experiments. The results show substantial differences in the persistence and biodegradation rates among bioplastics, thus highlighting the need for carefully selecting materials for applications with risk of becoming marine litter.

Facies transition and depositional architecture of the Late Eocene tide-dominated delta in northern coast of Birket Qarun, Fayum, Egypt

Late Eocene successions in the Fayum Depression display notable facies transition from open-marine to brackish-marine realms. Stratigraphic and sedimentologic characteristics of the depositional facies are integrated with ichnological data for the recognition of four facies associations (FA1 to FA4). The transition from open-marine sandstones (FA1) to the brackish-marine deposits (FA2) heralds a transgressive – regressive dislocation. The shallowing- and coarsening-upward progradation from the basal prodelta mudstone-dominated facies (FA2a) to deltafront heterolithics (FA2b) and sandstone facies (FA2c) are overlain by finning-upward delta plain deposits which are expressed by the delta plain mudstone (FA2d) and erosive-based distributary channel fills (FA4). Prodelta/deltfront deposits of FA2 are arranged in thinning- and coarsening-upward parasequences which are stacked in a shallowing-upward progressive cycle. Shallow-marine fossiliferous sandstones (FA3) mark the basal part of each parasequence. Stratigraphic and depositional architectures reflect a tide-dominated delta rather than an estuarine and incised valley (IV) model. This can be evinced by the progressive facies architecture, absence of basal regional incision or a subaerial unconformity and the stratigraphic position above a maximum flooding surface (MFS), in addition to the presence of multiple tidally-influenced distributary channels. Stratigraphic and depositional characteristics of the suggested model resemble those of modern tide-dominated deltaic systems. Accordingly, this model contributes to our understanding of the depositional models for analogous brackish-marine environments, particularly tide-dominated deltas in the rock record.

Stepwise post-glacial transgression in the Rhône Delta area as revealed by high-resolution core data

Integrated sedimentological and micropalaeontological (benthic foraminifers and ostracods) analyses of two continuous cores (40m and 50m long, respectively) recovered in the lower delta plain of modern Petit Rhône Delta, along with data from the previously studied Core SF, enable detailed reconstruction of the late Pleistocene–Holocene palaeoenvironmental evolution of the Rhône Delta system. Through identification of nine microfossil assemblages and with the aid of 28 radiocarbon dates, a high-resolution picture of stratigraphic architecture is offered for the first time for the entire post-glacial succession. Above late Pleistocene fluvial-channel gravels, a retrograding pattern of swamp and estuarine/bay deposits (lower transgressive systems tract — TST) is overlain by vertically stacked, late transgressive nearshore deposits (upper TST). This succession reflects the progressive landward migration of the palaeoshoreline driven by the rapid post-glacial sea-level rise, which took place in the study area between ca. 12 and 7cal ky BP. The following deceleration in sea-level rise (highstand phase) induced the onset of deltaic sedimentation, as evidenced by superposition of middle–late Holocene prodelta, delta-front and delta-plain deposits within the cored succession. At distal location the occurrence, within prodelta deposits, of a distinctive microfossil assemblage dominated by opportunistic benthic foraminifer Valvulineria bradyana marks the onset of the Rhône Delta mud-belt around 4cal ky BP. Identification and lateral tracking of six separate flooding surfaces within the TST enable the characterization of five short-term (millennial to sub millennial-scale) depositional cycles with distinctive transgressive–regressive internal architecture (T–R 1–5). The lower, transgressive portions of cycles 1–3 (11.8–9.8cal ky BP) mark abrupt shifts from freshwater to increasingly mixed, brackish-marine environments under conditions of rapid sea-level rise. In contrast, the upper, ‘regressive’ portions represent the filling of newly formed accommodation space via extensive crevasse to bay-head delta processes. Cycles 4 and 5 (9.8–8.2cal ky BP) and the uppermost transgressive deposit below the maximum flooding surface document three distinct landward shifts of the shoreline that took place under conditions of rapidly increasing sea-level rise. The vertical stacking of these millennial-scale cycles is interpreted to reflect the stratigraphic response to stepwise sea-level rise during the early Holocene. The youngest flooding surface may represent the sea-level signature of the 8.2ka climate event.

Holocene marine ingressions in the coastal zone of the pomeranian bay based on radiocarbon assays

Abstract In recent years, a team at the Geology and Paleogeography Unit, Marine Sciences Institute, University of Szczecin, has been performing geological, geochronological and paleogeographic surveys in (i) the Szczecin Lagoon and Świna Gate Sandbar and (ii) the estuary section of the Rega river valley near Mrzeżyno. These studies have helped to examine and identify not only the distribution of fossil marine sediments but also their lithological and sedimentological characteristics. The age of marine ingressions and regressions in the coastal zone of the Pomeranian Bay were determined using approximately 170 radiocarbon assays. It was found that the marine ingression associated with the ‘Littorina transgression’ was not synchronous at these two areas. It started earlier in the Mrzeżyno area, ca. 8300-8200 cal BP. In that first phase, marine sediments developed as tightly packed sands containing a few fragments of shells. In several profiles, these deposits were separated from the bottom and top with layers of peat, thus allowing an indirect determination of their age. The next phase of ingression began about 7300 cal BP. These younger marine sediments already contained quite numerous shells of marine malacofauna, especially Cardium glaucum, often found in a life position. In the area of the Szczecin Lagoon and Swina Gate Sandbar, the oldest marine ingression started as early as about 7350 cal BP. The quite clear trace is a considerably thicker series of marine sands with numerous sea shells representing marine and brackish-marine environments, including Cardium glaucum shells in a life position, which made it possible to identify the age and the rate of accumulation of marine sands.

Reconstruction of Holocene palaeoenvironment and sedimentation history of the Ombrone alluvial plain (South Tuscany, Italy)

The late Holocene sedimentological and palaeoecological evolution of the Grosseto alluvial plain was studied. About one hundred boreholes were drilled, following a 6-km long NW/SE transect. The lithology of the upper 9 m was studied and a reconstruction of environmental changes was undertaken based on palaeoecological macro- and microfossil analysis. Local environmental conditions around the site changed from a brackish-marine environment, which persisted until 2800 cal yr BP, when temporarily fresh-water conditions prevailed. A renewed marine influence led to the development of salt marsh conditions. A second short period of fresh-water conditions is reflected from the record from near the top of the boreholes. Mean sedimentation rates were in the order of 0.76 mm/yr before human impact and subsequently rose to ca. 1.1 mm/yr. There is evidence for a temporary cessation of sea-level rise shortly after 2800 cal. yr BP, which may be linked to cooler, wetter climatic conditions and a decline of solar activity. Thermal contraction of ocean water during the early Subatlantic may have played a role.

Carbon and nitrogen isotope compositions of organic matter in coastal marine sediments (the Gulf of Trieste, N Adriatic Sea): indicators of sources and preservation

Terrestrial organic carbon (OC) preserved in marine sediments is an important reservoir in the global carbon cycle, but remains poorly constrained. We determined the elemental and C- and N-isotopic compositions of organic material (OM) in surface sediments and sediment cores from the Gulf of Trieste (N Adriatic), an area characterized by relatively high riverine input. This multiple tracer approach permits evaluation of how sensitive each tracer is for constraining the terrestrial component of OM. Using the relevant terrestrial and marine OM end-members, we estimate that the terrestrial contribution ranges from about 90% at the mouth of the Isonzo River and decreases to ≤10% in the center of the Gulf. In the southern part of the Gulf, 32–44% of terrestrial OC is contributed from smaller rivers, while the δ 15N values of OM reflect more effective nutrient utilization. Analyses of different size fractions show that smaller particles are consistently more organic-rich and tend to be transported further from the river mouth, depending on river discharge. In the size fraction 2–16 μm, elemental ratios and δ 13C org and δ 15N isotopic signatures are consistent with a sedimentary OM pool dominated by bacterially derived biomass. Radiocarbon analyses of sedimentary OC yield depleted Δ 14C values (−338.7‰ to −429.4‰), indicating a significant fraction of relatively old OC. The natural abundance of 13C and 14C tracers suggests a two-component mixture of ancient and modern C in the sediments down to approximately 60 cm sub-bottom, with an estimated ∼45% of sedimentary OC probably being derived from ancient sedimentary OC (kerogen). In addition, there is a significant change in the source of organic material downcore in these sediments which, along with geological evidence, indicate contributions from freshwater swamps typical of coastal lakes with intermittent connections to the sea (brackish) prior to ∼9000 BP. Depth variations in a core from a salt marsh further indicate temporal variability of OM deposition and transformations in a changing brackish-marine environment in the past.

Palynostratigraphy and palaeoenvironment of the Middle Jurassic Sortehat Formation (Neill Klinter Group), Jameson Land, East Greenland

The grey–black mudstones of the Sortehat Formation form part of the Middle Jurassic fill of the Jameson Land Basin in East Greenland. The formation is exposed in the southernmost part of the north–south-trending, Mesozoic rift system in East Greenland that was part of the epeiric seaway between East Greenland and Norway. Sedimentological observations of the Sortehat Formation indicate deposition in an offshore marine setting that was typically low energy and periodically oxygen-deficient but was influenced by storm currents on occasion. Detailed palynological studies of the Sortehat Formation have resulted in the definition of three palynological assemblage zones recognised at four localities, namely Enhjørningen Dal and Pelion (north Jameson Land), the type section at Sortehat (central Jameson Land) and Albuen at Neill Klinter along Hurry Inlet (south-east Jameson Land). In stratigraphic order, these zones are termed the Botryococcus Assemblage Zone, the Nannoceratopsis gracilis – Nannoceratopsis senex Assemblage Zone, and the Sentusidinium pelionense Assemblage Zone. They are recognised on the basis of the identification of approximately 110 species of palynomorphs, including 45 species of spores, 30 of pollen, 22 of dinoflagellate cysts, 10 acritarch species, two species of algae, and some fungal spores. An Aalenian – ?Early Bajocian age is suggested for the Sortehat Formation on the basis of the palynoflora. Interpretation of the palynomorph assemblages suggests that the formation accumulated in a shallow, brackish marine environment. A significant terrestrial input, including the freshwater green alga Botryococcus, is recorded in the lower part of the formation and interpreted as an allochthonous accumulation in an offshore marine environment related to transgression of a low-lying coastal plain. A marked shift in the palynomorph assemblage seen by diversification of marine microplankton above the base of the formation, indicates an increase in the marine signal probably related to the onset of highstand conditions following the marine transgression.

Origin of the Sea of Marmara as Deduced from Neogene to Quaternary Paleogeographic Evolution of its Frame

The Sea of Marmara Basin (SMB) is connected to the fully marine Mediterranean by the Dardanelles strait and to the brackish Black Sea by the Thracian Bosporus. This linkage to two different marine realms with contrasting water chemistry has been a prime control on the sedimentary history of the SMB, which in turn was controlled by its tectonics. Isolation from any of these realms resulted in drastic changes in its paleoceanographic conditions and made it a part either of the global ocean system or of a brackish-marine environment, depending on the realm from which the connection was severed. The SMB represents the inundated part of the northwestern Anatolian graben system that resulted from the interaction between the North Anatolian fault (NAF) zone and the present N-S extensional tectonic regime of the Aegean. The geologic history of this basin began during the late Serravallian when the NAF was initiated. The first inundation of the basin coincided in both time and space with this initiation. The invading sea was the Mediterranean, which stayed there for a short period and subsequently was replaced by the Paratethys during the late Miocene. Paratethyan conditions prevailed in the basin until the latest Pliocene, when the second flooding from the Mediterranean occurred through the Dardanelles. Owing to glacio-eustatic sea-level changes during the Pleistocene, Paratethyan/Black Sea and Mediterranean conditions alternated. In the last (Würm) glaciation, the SMB was completely isolated and turned into a euxinic lacustrine environment, similar to the Black Sea at that time. Following the Würm glaciation, the Mediterranean Sea broke its way once more into the SMB and filled it with salt water. When sea level in the basin rose above the Bosporous sill at 7.5 Ka B.P., the present dual flow regime was established.

Messinian event in the black sea

Three holes were drilled during the 1975 DSDP Leg 42B drilling the Black Sea. A section from Hole 380, at 2107 m water depth on the western edge of the abyssal plain, is 1074 m thick, and provides the most complete stratigraphic section. Dating of the sediments is based upon (1) fossil evidence from pollen, crustaceans, benthic foraminifera, and diatoms, (2) correlation with climatic changes and with unusual isochronous events that have been dated elsewhere, (3) paleomagnetic data, and (4) estimates of sedimentation rate. The history of Black Sea sedimentation recorded by the DSDP cores includes black shale sedimentation during the Late Miocene, followed by periodic chemical sedimentation from Late Miocene to Early Quaternary, and a change to dominantly terrigenous sedimentation from the Middle Quaternary. These hemipelagic and turbiditic sediments were deposited in lacustrine and brackish marine environments. The Messinian sediments, however, consist of stromatolitic dolomite, oolitic sands, and coarse gravels, deposited in supratidal and intertidal environments. The intercalation of the shallow-water sediments in a deep-water sequence suggests a drastic lowering of the water-level within the Black Sea basin during the Messinian so that the edge of the present abyssal plain was then the edge of a shallow lake. The Messinian draw-down phase of the Black Sea was in existence for about 100,000 years during the Lago-Mare stage of the salinity crisis. The evaporated waters formed an alkaline lake before it was drowned by a brackish marine transgression correlative to the Trubi transgression of the Mediterranean.

Ostracods from the Purbeck-Wealden Beds in Bornholm

An account of the Purbeck-Wealden beds in Bornholm and a brief summary of similar beds in the Scanian-Pomeranian area are given.Two faunas are described from the Jydegaard Formation. A Cypridea-fauna is correlated with Wealden 3 in Northwest Germany. It is followed by an ostracod-assemblage, known from Northwest Germany, indicating brackish-marine environments corresponding to Wealden 3 or 4 of the German subdivision. Two new ostracod species are described.Two other faunas have moreover been identified, a brackish one in the Rabekke Formation and a brackish-marine one in the inlier at Salene. The former contains elements suggesting a Middle Purbeck age.