Deposition Of Marine Sediments Research Articles

Geochemical Characteristics of Trace Elements and Mineralization Model of the Ediacaran-Early Cambrian Phosphorites, South China.

As a nonrenewable resource, phosphate rock is an important support for the development and survival of the national economy. The regional distribution and output of phosphate rock in China are extremely uneven, and the amount of high-quality ore resources is relatively poor, which seriously restricts the development and utilization of phosphate rock resources in China. This paper briefly summarizes the distribution characteristics of phosphate rock resources and summarizes the characteristics and research progress of Ediacaran-early Cambrian phosphorus mineralization types, geological characteristics, and deposit genesis of the Yangtze platform in South China. The Ediacaran-early Cambrian sedimentary phosphorite deposits in China are mainly distributed in Yunnan, Guizhou, Hubei, Sichuan and Hunan provinces of the Yangtze platform, in which the early Cambrian phosphate deposits are also rich in rare earth elements, associated with uranium, nickel, molybdenum, vanadium, and other beneficial metal elements. The increase of atmospheric oxygen content at the Ediacaran-Cambrian boundary may have promoted the extensive oxygenation of the late Neoproterozoic oceans, so the Ediacaran-early Cambrian oceans generally showed a reductive environment, and there may be dynamic chemical stratification of the oxidation zone-sulfide zone-iron zone. Up to the early Cambrian, the redox stratified structure of Precambrian seawater may still be inherited, showing that the surface water is an oxidizing environment, changing to a reduction environment, and even wedge-shaped sulfide water is developed at the bottom of the deep basin. The main phosphorus sources are deep phosphorus-rich seawater, continental weathering, and deep hydrothermal activity of Ediacaran-early Cambrian marine sedimentary phosphorite deposits in South China. The genetic mechanisms of phosphorite deposits in the Yangtze platform in South China are mainly biogenic, upwelling phosphorus-forming theory, mechanical mineralization, and syn-sedimentary hot water mixed genesis. In the future, it is still necessary to further explore the internal relationship between phosphorus deposits and major geological events, the in situ analysis of microstructure of phosphate rock ores, and the genetic mechanism of phosphate deposits and the reconstruction of paleo-marine environment.

Assessment of Salinity in Fresh and Saline Aquifers in the Coastal Area of Jiangsu Province

Within the littoral alluvial expanse of the Yangtze River Delta, the phreatic zone encompassing the aquifer represents a prolific ecosystem, which has been subjected to an enduring epoch of marine sediment deposition, and is conspicuously susceptible to the escalating phenomenon of urbanization. The prodigious abstraction of the groundwater reserves has engendered a recent encroachment of seawater and leakage of connate saline water, culminating in the salinization of freshwater sources. For an incisive comprehension of the gradations of salinity (viz., fresh, brackish, and saline) and to execute evaluations of the groundwater’s quality, the spatial distributions of the total dissolved solids (TDS) were interpolated employing bifurcate power functions that establish a relationship between the Vertical Electrical Sounding (VES)-predicated transformation average resistivity and the assayed TDS from the systematically sampled boreholes corresponding to the aquifer stratum. The scrutiny of the groundwater’s physicochemical attributes is of paramount significance to efficaciously steer the exploitation and management of hydric resources within the area under investigation.

Peperites

Peperites are volcanosedimentary materials generated by the mingling of magma and unconsolidated wet sediments. They have unique insights into submarine volcanisms and the tectonic environments where they form. For the 1st time, the authors identified two types of peperites (blocky and fluidal) hosted by micritic limestone rocks in the Walash Volcanosedimentary Group of the Mawat area, Kurdistan Region-Iraq. They are designated as peperitic facies one and two (PF1 and PF2) and consist of black basaltic rocks mixed with chocolate-brown micritic limestone rocks. Their abundance demonstrates the contemporaneity of deep marine sediment deposition and submarine volcanism during Walash’s nascent arc. Despite hydrothermal alteration, the basaltic rocks retained their magmatic textures. Basaltic rocks comprise mainly albite, anorthite, diopside, hematite, and alkali-feldspar. Calcite dominates micritic limestone rocks, while quartz is minor. Based on geochemical data, igneous sections are basaltic rocks with tholeiitic series that are strongly enriched in Light Rare Earth Elements with low concentration ratios of (La/Yb) and (Sr/Y), indicating geochemical affinity to normal island arc basalt with a primitive arc signature. Furthermore, their formation is thought to be caused by partial melting of subducted slabs deep within 30 km and the associated derived fluids above the subducted slab. Thirteen species of planktonic foraminifera (Morozovella) are identified through paleontological research and biostratigraphy. Using these various tools lead the authors to illustrate the tectonic setting of the formation of peperitic rocks in arc fronts of the subducted Walash arc during the Middle to Late Paleocene (60 Ma).

Mitigation of the diagenesis risk in biological apatite δ18O interpretation

The assessment of the potential blurring effect of diagenetic processes represents the greatest challenge for geochemists whose purpose is to reconstruct environmental parameters based on isotopic proxies. Numerous studies performed on phosphatic remains from terrestrial and marine sedimentary deposits have shown post-depositional isotopic modifications due to exchange reactions with surrounding waters. If diagenesis may be diagnosed through several lines of evidence such as mineralogical or chemical modifications of the pristine in vivo apatite after burial in soils and sediments, diagenesis does not prove that bioapatite phosphate exchanged oxygen isotopes with aqueous fluids. Therefore, we propose a new method of detection of diagenetic alteration of bioapatite phosphate based on a statistical approach designed to analyze sample collections. The approach requires that phosphatic remains belonged to animals living during a short time interval and within an environment characterized by steady air or water temperature and the δ18O of ambient water. We show that the distribution of bioapatite phosphate δ18O follows a normal distribution resulting from the combination of independent factors such as those related to the genetics, environment and analytical measurements. In the case of oxygen isotope exchange between the bioapatite phosphate and various amounts of circulating aqueous fluids, our numerical simulations reveal that the distributions of bioapatite phosphate δ18O are asymmetric with shapes depending on the temperature of reaction and the composition of the reacting aqueous fluid. This new statistical tool based on mass balance equations and Monte Carlo simulations is considered valuable to mitigate the diagenesis risk in the interpretation of bioapatite phosphate δ18O as paleoecological and paleoclimatic proxies.

The Zunyi manganese deposit, South China: A consequence of climatic-oceanic changes triggered by the eruption of Emeishan large Igneous Province?

South China hosts a large number of Middle Permian marine sedimentary Mn deposits (MSMDs) coeval to the eruption of the Emeishan Large Igneous Province (ELIP). The linkage between these MSMDs and ELIP eruption remains unclear. Here, we observed anomalously high Hg concentrations and Hg/TOC ratios, and a shift of Δ199Hg to near-zero at the base of the Middle Permian Zunyi MSMD. These results suggest ELIP eruption as a possible driving force for the deposition of the Zunyi MSMD. Principal component analysis (PCA) of trace element concentrations of the Zunyi MSMD samples revealed three clusters of trace elements. Cluster A elements (Cr, Zn, Mo, Sb, and Tl) are anomalously high at the basal of the Zunyi MSMD, confirming ELIP as a driver for the formation of this deposit. Cluster B elements (Ba, Rb, and Cu) are high in the entire deposit, supporting elevated oceanic productivity. A stepwise increase in Cluster C elements (Li, Ga, Sn, Zr, Nb, Hf, Ta, and W) concentrations in the Zunyi MSMD suggests enhanced terrestrial weathering. We infer that the ELIP eruption triggered an increased input of terrestrial nutrients to the ocean, causing increased oceanic productivity and rising dissolved O2 levels in the surface water of the middle Permian ocean in South China, favoring Mn deposition and MSMDs formation.

Synchrotron Microanalytical Characterization and K/Ar Dating of the GL-O-1 Glauconite Reference Material at the Single Pellet Scale and Reassessment of the Age of Visually Mature Pellets

The K/Ar chronology of glauconite pellets is a long-used method for directly dating marine sedimentary deposits. Many papers have explored the processes that form glauconite and the factors that lead to greater reliability in the ages. Although K/Ar ages of glauconite are generally in agreement with other measures of stratigraphic age, there are examples of occurrences with ages too old and examples with ages too young. This paper seeks to build on the accumulated knowledge of glauconite, using synchrotron radiation to non-destructively characterize individual pellets and then consecutively measure the argon and potassium to obtain a K/Ar age. This strategy provides the advantage of measurements on a single aliquot while avoiding recoil loss of 40Ar in the nuclear reactor during irradiation for 40Ar/39Ar dating. We have used the glauconite reference material GL-O-1 to showcase several non-destructive methods for evaluating the maturity of individual pellets. In our argon measurements, we have found that the radiogenic argon concentration of large bulk samples underestimates the values for individual visually mature pellets, and we determined a K/Ar age of 101.0 ± 0.3 Ma (1σ SEM), M.S.W.D. 0.54 from 15 of 16 visually mature individual pellets. This age is 6% older than the reference value of 95.03 ± 1.11 Ma (1σ), and it is in good agreement with constraints from the U-Pb dating of volcanic minerals near the Albian–Cenomanian boundary.

Late-Holocene wildfire record from the Stagmo peat section, Leh valley, NW Himalaya

Wildfire is an integral component of the terrestrial ecosystem that plays a significant role in regulating the vegetation cover. The paleofire records stored in lacustrine, peat, or marine sedimentary deposits along with environmental proxy records provide temporal information on fire activity and contemporary climatic conditions on a regional scale. A ~2.8m long peat sedimentary profile from Stagmo, Indus Valley, Ladakh Himalaya was examined for sedimentology and charcoal microfossil contents to investigate fire characteristics and reconstruct wildfires which are compared with paleoclimatic changes and past human activities to assess their significance in biomass burning. Charcoal count (CC) analysis provides a suitable method for investigating climatic and vegetation changes with human intervention when no direct evidence is available in the Late-Holocene Trans Himalaya records. The results bring new insight into the interaction between vegetation, fire, and human activity in the Ladakh Himalaya during the past ~2.8 cal kyr BP. An event characterized by high CC at ~2.8 cal kyr BP is distinct from the whole sequence and cannot easily be explained as only the result of a climatic event. This first high charcoal count phase (2.81–2.55 cal kyr BP) could be a natural response to the expansion of forest and dense vegetation with human management interruption. This paleo wildfire event likely corresponds with the time of the Tibetan Plateau’s immediate human occupation. In the second phase, a relatively low charcoal count (1.65–1.54 cal kyr BP) is supported by the high fuel availability during a transitional phase. The third phase of wildfire reconstruction in Ladakh Himalaya is identified at ~1.38 cal kyr BP. This phase can be correlated with the intensified Indian Summer Monsoon (ISM) advancing to Trans-Himalaya leading to increased human settlement in the region.

Estimation of the Spring Tide Bedload Transport at the Eastern Entrance of the Qiongzhou Strait

Marine sediment deposits near the Qiongzhou Strait have great potential as sources for beach nourishment and infrastructure industry aggregates. Estimation of bedload transport during the spring tide improves the understanding of the sediment movement characteristic under dynamic conditions, which would further favor the assessment and mining of marine sand resources. To study the bedload transport at the eastern entrance of the Qiongzhou Strait, the surficial sediment distributions were obtained through hundreds of sediment samples from field work. A semi-implicit cross-scale hydrological science integrated system model was adopted and validated to simulate the tidal currents in the Qiongzhou Strait. With field observation and simulated data, we estimated the spring tide bedload transport in the study area using the Bagnold Model. The transport rate in the study area was found to have large temporal and spatial variation. The net transport direction during the spring tide cycle was eastward in the southern parts of the strait and westward in the northern strait. Our research has important implications for regional engineering and marine resources management.

Grain size and mineral variability of glacial marine sediments

ABSTRACT Glacial marine sediment deposition varies both spatially and temporally, but nearly all studies evaluate down-core (∼ time) variations in sediment variables with little consideration for across core variability, or even the consistency of a data set over distance scales of 1 to 1000 m. Grain size and quantitative X-ray diffraction (qXRD) methods require only ≤ 1 g of sediment and thus analyses assume that the identification of coarse sand (i.e., ice-rafted debris) and sediment mineral composition are representative of the depth intervals. This assumption was tested for grain size and mineral weight % on core MD99-2317, off East Greenland. Samples were taken from two sections of the core that had contrasting coarse-sand content. A total of fourteen samples were taken consisting of seven (vertical) and two (horizontal) samples, with five replicates per sample for qXRD analyses and ∼ 10 to 20 replicates for grain size. They had an average dry weight of 10.5 ± 0.5 g and are compared with two previous sets of sediment samples that averaged 54.1 ± 18.9 g and 20.77 ± 5.8 g dry weight. The results indicated some significant differences between the pairs of samples for grain-size parameters (mean sortable silt, and median grain size) but little difference in the estimates of mineral weight percentages. Out of 84 paired mineral and grain-size comparisons only 17 were significantly different at p = < 0.05 in the post-hoc Scheffe test, all of which were linked to grain-size attributes.

DECCAN VOLCANIC OF MALWA, STRATIGRAPHY AND CORRELATION OF BASALTIC LAVA FLOWS USING MEGACRYST BEARING HORIZON AS TOOL, PARTS OF WESTERN M.P. INDIA

A review of earlier studies of the Deccan Trap occurrences of parts of Ratlam, Mandsaur, Jhabua, Dhar, Khargone, Indore, Ujjain and Shajapur districts of Madhya Pradesh, India was carried out of the area falling between latitudes 220 0000 to 2400000N and longitudes 7400000 to 7600000 in Survey of India Quadrangle sheet Nos. 46I, 46J, 46M and 46N.The main objectives of the study were to synthesize the data on the Deccan Trap basaltic lava flows , their types ,their diagnostic characteristics with special emphasis on delineating and identifying the various megacryst horizons , their levels with specific elevation above m.s.l. to build up the litho-stratigraphy for regional correlation. Broadly the area exhibits the Proterozoic Aravalli Supergroup, the Cretaceous, Bagh and Lameta Groups and the Deccan basaltic lava flows with intruded dykes and sills. The Aravalli Supergroup is represented by the Udaipur, Lunavada and Champaner Groups. The Udaipur Group consists mainly of hornblende gneiss, marble and calc-silicate, carbonaceous phyllites and chlorite schist. The Lunavada Group comprises dolomitic limestone (Phosphate bearing), quartzite, muscovite quartzite, quartz muscovite schist, feldspathised quartzite, gneissic feldspathic rock and biotitic gneiss. The Champaner Group is represented by dolomite, phyllite, slates and basic intrusives. The Aravalli Super group of rocks is also intruded by serpentinite, pyroxinite, granite and basic rocks. The Aravalli Supergroup of rocks is unconformably overlain by Cretaceous marine sedimentary deposits of Bagh Group. It includes Lower arenaceous and Upper calcareous units and occurs as discontinuous outcrops. These are almost horizontally to sub horizontally disposed. The Bagh Group is represented by three units / Formations i.e. Nimar sandstone overlain by nodular limestone and subsequently by coralline limestone. The Lameta Group of rocks is noticed in the area east and South East of Bagh exposures, overlying the Nimar sandstones. These rocks predominantly consist of limestone, gritty sandstone and conglomerate and generally exhibit hummocky topography and sometimes display solution channels. These are mostly horizontally to sub-horizontally disposed with an average thickness of 5- 6 m. The Deccan Trap has occupied a very long stretch of area which consists of a sequence of 121 basaltic lava flows with a cumulative thickness of about 610 m. These flows represent a sequence of cyclic lava eruptions with fine to medium grained a aphyric to sparsely / moderately / highly / mega porphyritic lava. About two third of the total flows exhibit Aa characters and the rest are compound and simple Pahoehoe. Some of these flows consist of megacryst units containing feldspar laths varying in size round two to five cm. These megacryst horizons have been identified at different elevations in Quadrangles 46I, J, M, N and on the basis of these horizons, various flows have been grouped into to six Formations which have specific nomenclatures and stratigraphic status. These formations are in the order of antiquity 1) Mandleshwar formation, 2) Choral formation,3) Dhar formations 4) Indore Formation 5) Bargonda Formation and 6) Singarchori Formation. Full sequence is exposed only in quadrangle 46N whereas the Quadrangles 46I, J, M do not exhibit Bargonda and Singarchori Formations. An attempt has been made to correlate the various Formations in degree sheets 46 I, J, M, N with the surroundings Geological Quadrangles. The Megacryst bearing lava- flows act as marker horizons for this purpose. A large number of dykes and dyke swamps of basaltic as well as doleritic compositions have been marked around the Narmada River. The intensity of the dykes is more in the oldest Mandleshwar Formations and it gradually decreases in increasing order of antiquity towards the younger Bargonda and Singarchori Formations. The general trend of these dykes varies from East North East – West South West to E-W running sub parallel to the Narmada lineament, besides a few dykes also cut across this lineament trend and oriented along NNW-SSE to N-S direction. The Length of these dykes varies from about 200 m to 20 Km with width varying from a few meters to as much as 200 m. The possibility exists that these dykes may have been actually feeders through which periodic eruptions of tholiitic basaltic lava took place resulting in formation of such a thick pile of lava flows. Besides as many as seven Intertrapean fossiliferous sedimentary horizons have been recognized within the basal part of the flows. These demonstrate episodic nature of volcanic activity, long periods of quiescence and resilience. The overall study of various lava flow s and their interrelations their relative dispositions thinning /swelling and pinching nature. Their relative elevations, occurrence of marker megacryst units, change in lava characters, overall gradient of lava flows and their relation to preexisting topography and slope elements reveals that the sources of lava eruptions of Older Formations are situated somewhere in the west and south west whereas those of Younger Formations are located in the Eastern part of Mhow of the area studied.

Ventilation Changes Drive Orbital‐Scale Deoxygenation Trends in the Late Cretaceous Ocean

AbstractMechanisms that drive cyclicity in marine sediment deposits during hothouse climate periods in response to Earth's orbit variations remain debated. Orbital cycles fingerprint in the oceanographic records results from the combined effect of terrestrial (e.g., Weathering derived nutrient supply, freshwater discharge) and oceanic (e.g., productivity, oxygenation) processes, whose respective contribution remains to be clarified. Here we investigate the effect of extreme orbital configurations on the oxygenation state of the ocean using marine biogeochemistry simulations with the IPSL‐CM5A2 Earth System Model under Cenomanian‐Turonian boundary conditions. Our simulations show that small changes in ocean ventilation triggered by orbitally induced variations in deep water formation have a strong impact on the spatial distribution of dissolved oxygen. This phenomena is amplified in enclosed and already poorly oxygenated basins, such as the proto‐Atlantic ocean, where up to 50% of the water volume become anoxic for some of the configurations.

Investigation of coastal environmental change at Ruddons Point, Fife, SE Scotland

Ruddons Point, on the Firth of Forth coastline, Scotland, is a laterally extensive terrace of glacial and marine sediment deposits raised above current sea-level, situated near to Kincraig Point, a key site that records a series of stepped erosional platforms carved into the local bedrock, interpreted as post Last Glacial Maximum palaeoshorelines. The deposits at Ruddons Point continue inland, with exposures of the raised sands and gravels cut by the local river, the Cocklemill Burn. The site provides an opportunity to examine the depositional history through the Late Devensian and Holocene. Geophysical survey aided in interpreting characteristics of subsurface sediments such as the transition between the younger saltmarsh sediments and older underlying sands and clays below, which slope in a northerly direction. A chronology obtained through optically stimulated luminescence (OSL) dating spans from c. 29 ka for sands and clays at an elevation of −0.66 mOD to surface windblown sands at <300 years, at an elevation of 8.45 mOD. A basal peat, dated by radiocarbon dating to the early Holocene at c. 9.2 ka, formed prior to the Main Postglacial Transgression. Dating of inland raised marine deposits along the Cocklemill Burn records dates ranging from c. 8.9 to c. 4.3 ka. The raised marine deposits of Ruddons Point range from c. 8.1 to c. 2.9 ka, deposited unconformably on glacial tills and clays. This multidisciplinary field study builds depositional scenarios utilizing two dating methods, spanning the last c. 29 ka, to better understand coastal evolution for a region which has experienced complex relative sea-level variations. Supplementary material : Supplementary data related to this research article is available at https://doi.org/10.6084/m9.figshare.c.6080999 Thematic collection: This article is part of the Early Career Research collection available at: https://www.lyellcollection.org/topic/collections/early-career-research

Kerch ironstones as unconventional Nd and MREE resources:
 features and prospects

Based on the mineralogy and major and trace element
 composition (including REE+Y) of bulk samples
 and in separate size fractions of the ore, the contribution
 of different REE+Y species to the total REE budget of
 ironstones from the Kamysh-Burun trough was estimated.
 Kerch ores have the structure of REE+Y accumulation
 typical for marine sedimentary iron ore deposits.
 Light REEs form independent mineralization of authigenic
 phosphates (rhabdophane-type LREE(PO4)∙nH2O
 phases) enriched in La, Pr, Nd, and Ca. Medium REEs
 are mainly adsorbed on Fe3+-(oxy)hydroxides forms. The
 coexisting Nd and MREE enrichment combined with Th
 and U depletion allow considering the Kerch ironstones
 as commercially attractive unconventional resources of
 rare-earth elements.

Sulfur and lead isotope geochemical characteristics of Pb-Zn deposits in the Khau Loc zone, northeastern Vietnam, and their significance

In northeastern Vietnam, the Khau Loc zone is considered to have high potential for lead-zinc mineralization. The lead isotope data for 18 galena samples and 18 ones of δ34S isotope data (including galena and pyrite samples) were collected from lead-zinc ore deposits in some areas in the Khau Loc zone, including Phia Dam, Khuoi Man, Ban Lin, Lung Dam, and Ta Pan. These were employed to investigate the sulfur and lead isotope geochemical characteristics of Pb-Zn deposits and their significance in this study. The samples were analyzed using the LA-ICP-MS to show that the Pb isotopic ratios of 206Pb/204Pb, 207Pb/204Pb, and 208Pb/204Pb in the galena samples range from 17.8908 to 18.6012, 15.5794 to 16.1025, 38.4420 to 39.2118, with the average values of 18.296, 15.749, and 38.812, respectively. The pyrite and galena samples had the δ34S isotope, ranging from 9.0 to 15.106. The sulfur isotope systematics implies that most of the lead-zinc ore formations originated from marine sedimentary evaporation deposits and magmatic intrusion-volcanic eruption sources rich in silica. The distribution of lead isotopic ratios had a well-defined cluster for each deposit, indicating the formation of lead-zinc deposits and lower crust and orogen trends. In addition, these findings of lead isotopic ratios and δ 34S isotopes proved that the Khau Loc zone is an activated structure with continuous growth in continental crust thickness during the early Proterozoic and Cenozoic periods. Furthermore, the study results also presented the evolution of material sources involved in the formation of lead-zinc ores in the Khau Loc zone.

Young soils of a temperate barrier island under the impact of formation and resetting by tides and wind

The island Spiekeroog (Germany) at the southern North Sea coast exhibits an island tail (Ostplate) of which large parts formed after 1860 by gradual eastward deposition of marine sediments. This study aimed to (i) provide a first overview of soils on the Ostplate, (ii) verify whether soil formation stages in different landscape elements (dune chain, dune slacks, saltmarsh, pioneer zone) are linked to the island’s gradual development and (iii) to assess the impact of tides and winds on soil formation. Standard physicochemical properties of dune -and dune slack topsoils and 19 pedons (i.a. pH, total organic carbon (TOC), total inorganic carbon (TIC), total nitrogen (TN), and mean weight diameter (MWD) of water stable aggregates) were analyzed. Soils of the dune slacks, the saltmarsh and the pioneer zone classified as Gleysols which showed no trend towards differences along the Ostplate. The dune chain exhibited Protic Arenosols that were initially acidified in lee positions (min. pH = 5.1). Carbon (C) and nitrogen (N) isotopes (δ13C, δ15N) signatures of saltmarsh sediments were used as a proxy for the tidal influence on soil formation. In addition, sulfur (S) isotope (δ34S) signatures revealed insights on sulfur sources in the saltmarsh. The δ13C signatures of organic matter (OM) decreased and TOC/TN -and TOC/total sulfur (TS) ratios increased with increasing elevation and decreasing flooding frequency. At higher flooding frequency, δ15N resembled the dominant input of OM from the southern North Sea, at a lower interaction level, mixing of a wider range of sources was indicated. S isotopes indicated dissolved sulfate and reduced species as sulfur sources. It was concluded that an ongoing impact of wind-induced sand movement at the dunes, and flooding-induced sediment movement in the saltmarsh and the pioneer zone, repealed any potential disparities in soil formation stages, which might have existed along the Ostplate.

Upper Cretaceous paleoenvironmental changes and petrophysical responses in lacustrine record (Songliao Basin, NE China) and marine sedimentary deposit (Goban Spur Basin, NW Europe)

AbstractThe Cretaceous interval is marked by several important geological changes whose prints are buried in both continental and marine sytems. Although significant paleoenvironmental details of this period have been inferred from biological and geochemical indicators, little is known about the physical proxies. Through scientific borehole data, petrophysical properties of Upper Cretaceous Songliao Basin (SB) in NE China and Goban Spur Basin (GSB) in NW Europe were intercorrelated to investigate the critical geological paleoenvironmental shifts and their petrophysical responses, through statistical, wavelet and spectral approaches. The results demonstrated that petrophysical features, particularly gamma-ray and resistivity reactivities, were responsive to past environmental changes in both terrestrial and marine systems. Shifts in organic-rich shale deposition and brine bearing shale showed a correlation to a probable period of seawater incursion in SB, while the gamma log, resistivity and density reactivities were interrelated to the basin paleo-structuration. At GSB, the gamma-ray and resistivity reactivities are tied-up to the Mid-Atlantic seabed motion, marine-water level shifts and paleoceanographic instabilities. In both paleo-basins, a decrease in the gamma-ray reactivity occurred from Turonian to Maastrichtian and is consistent with a regional or global increase in hydrodynamic energy. The oceanic/lacustrine anoxic events related to low sedimentation rate occurred in both basins and are associated with high gamma-ray and resistivity signals (SB); high gamma-ray and low resistivity signals (GSB). These changes correlated with geochemical evidence, suggesting that gamma-ray and resistivity can represent alternative means for marine and continental paleoenvironmental comparison.

Toxicology of Heavy Metals to Subsurface Lithofacies and Drillers during Drilling of Hydrocarbon Wells

This study investigates the toxicological effects of heavy metals on lithofacies of the subsurface in a drilled hydrocarbon well as well as, to the drilling crew and people in an environment. The pollution levels of selected heavy metals were considered alongside their ecological effects during dry and wet seasons. The health hazard potential of human exposures to the metals, were estimated in terms of intensity and time using the USEPA recommended model. The heavy metal concentration for each layer decreased across the lithofacies as follows; Layer 5> Layer 4> Layer 3> Layer 2> Layer 1. The average concentrations of the heavy metals present in the samples obtained from the formation zone, varied significantly and decreased in the order of Al> Zn> Ni> Pb> Cr> Cu> Cd> As> Hg. The highest concentration of Al, Cu, and Zn in this present study were within the maximum allowable limits whereas, those of As, Cd, Hg and Ni were all above their maximum allowable limits. Among the transition metals analysed, the maximum mean daily dose of Pb (9.18 × 10−6 mg/kg/d) and Cr (1.42 × 10−6 mg/kg/d) were confirmed susceptible to human carcinogens and environmental toxins. The estimated hazard quotient shows that the dermal pathway is the most likely route via which the drilling crew and people in the environment can get contaminated. The cancer risk values for the Pb (7.72 × 10−4), Cd (1.35 × 10−1), Ni (9.97 × 10−3), As (1.50 × 10−1) and Cr (3.16 × 10−3) are all above the acceptable values. The cancer risk contribution for each metal was in the order of As> Cd> Ni> Cr> Pb. Layer 5 had the maximum Geo-accumulation index for the heavy metals considered. This higher Geo-accumulation index noted at the depth in Layer 5 may be attributed to the effect of water basin with turbidity currents, deltas, and shallow marine sediment deposits with storm impacted conditions. Also, the pollution from lead (Pb) in the dry season was maximum with an Igeo value> 5 for all the lithofacies considered because of the low background concentration of the metal. During the wet season, the heavy metal pollution rate was moderate for Zn whereas, it was extremely polluted with respect to Pb. The ecological risk potential of Pb shows that the associated ecological risks range from 536 – 664 in the wet season (i.e. extremely strong) and 2810 – 3480 in dry season (extremely strong). The high level of Pb pollution found in the area at such shallow depth may be due to the sedimentary folds possibly caused by the full spectrum of metamorphic rocks and primary flow structures at shallow depths. This was used to identify the environmental sensitivities of the heavy metals during the dry and wet seasons.

Sea-level responses to rapid sediment erosion and deposition in Taiwan

Numerous studies have shown that sediment deposition can perturb sea level by several meters over millennial timescales by modifying the gravity field, crustal elevation, and sediment thickness. Relatively few studies have focused on the complementary role of erosion on sea-level change despite its effects on the same quantities, partly because many rapidly eroding mountains are too far from shorelines to strongly perturb sea level at the coast. Taiwan, a mountainous island eroding rapidly within tens of km of the coast, offers an opportunity to investigate the joint influences of rapid onshore erosion and rapid offshore deposition on sea-level change. Here we develop a sediment loading history for Taiwan since the previous interglacial (∼120 ka) by compiling published erosion and deposition rate measurements and by applying a geometric marine sediment deposition and compaction model for sites without deposition rate measurements. We use the resulting sediment redistribution history to drive sea-level responses in a gravitationally self-consistent sea-level model. Our simulations show that the effects of rapid onshore erosion outweigh the effects of rapid offshore deposition along Taiwan's east coast. Along the east coast of Taiwan, sediment redistribution induces rapid sea-level fall, a response that differs in sign from the coastal sea-level rise induced by rapid sediment redistribution in many other river systems around the world. The spatial extent of the modeled sea-level fall is sensitive to the Earth model, particularly the effective elastic thickness of the lithosphere, a sensitivity that we describe in further detail in the Discussion. These results suggest that sediment redistribution could have generated sea-level changes of >10m on the east coast of Taiwan since 10 ka and >100m since 120 ka. This can account for some of the discrepancy between observed and modeled paleo-sea-level marker elevations, which reduces estimates of tectonically driven rock uplift rates inferred from the elevation differences between paleo-sea-level markers and modeled sea level. This highlights the importance of accounting for erosional unloading in interpretations of paleo-sea-level reconstructions and associated estimates of tectonically driven uplift rates.

Geomorphology and substrate of Galway Bay, Western Ireland

ABSTRACT A combination of multibeam bathymetry and backscatter, LiDAR altimetry and bathymetry, satellite images, and hydrodynamic model outputs were used to map the seafloor and coastline of Galway Bay (western Ireland). This is the first time these multiple datasets have been integrated into a single combined geomorphological and substrate map. The substrate of the bay is predominantly mud and sand with bedrock outcropping extensively around the coastline. The main depositional features are dunes, while the main erosional features are scours and outcropping bedrock. Hydrodynamic model outputs show good correlation between the direction and intensity of prevailing currents and the location and shape of the features in the bay. This indicates that although Galway Bay was shaped glacially through the passage of the British-Irish Ice Sheet across the bay and ensuing glacial and marine sediment deposition, many of the mapped seafloor landforms are modern and current-induced.

Zygadelphus aetheus gen. et sp. nov., an unusual fossil flower from mid-Cretaceous Myanmar amber

The flower described here as Zygadelphus aetheus gen. et sp. nov. was obtained from amber mines in Myanmar, preserved in marine sedimentary deposits dating to the mid-Cretaceous Period, ca. 99 My in age. The perianth consists of ca. 10 spirally arranged tepals that vary in size and shape. The stigmatic tips of two styles are visible, the remainder of the gynoecium being hidden from view by the crowding of stamens and perianth parts toward the center of the flower. There is a whorl of 4 stamens, the anthers of which have the feature, probably unique among angiosperms, of possessing a small but complete accessory stamen arising as an appendage on their dorsal surface. Anthers of both types of stamens are bilocular and dehisce by dorsally hinged valves. Presence of pollen in the accessory anthers indicates that they functioned in reproduction. Under the assumption that the fossil is not merely a teratological mutant in an otherwise normal-flowered species, it is here given taxonomic status as representing a peculiar type of floral development, now extinct, that existed during an earlier stage of angiosperm evolution.