Shallow-water Settings Research Articles

A record of fossil shallow-water whale falls from Italy

Danise, S. & Dominici, S. 2014: A record of fossil shallow-water whale falls from Italy.Lethaia, DOI: 10.1111/let.12054.Twenty-five Neogene–Quaternary whales hosted in Italian museum collections andtheir associated fauna were analysed for evidence of whale-fall community develop-ment in shallow-water settings. The degree of bone articulation, completeness of theskeleton and lithology of the embedding sediments were used to gather informationon relative water depth, water energy, sedimentation rate and overall environmentalpredictability around the bones. Shark teeth and hard-shelled invertebrates with anecrophagous diet in close association with the bones were used as evidence of scav-enging. Fossil bone bioerosion, microbially mediated cementation and other molluscshells in the proximity of the remains informed on past biological activity around thebones. The results are consistent with the hypothesis that shallow-water whale falls dif-fer from their deep-water counterparts. Taphonomic pathways are more variable onthe shelf and whale carcasses may not go through all steps of the ecological successionas recognised in the deep sea. Whilst the mobile scavenger and the enrichment oppor-tunistic stages are well represented, chemosynthetic taxa typical of the sulphophilicstage were recovered only in one instance. The presence of a generalist fauna amongthe suspension feeding bivalves and carnivorous gastropods, and the extreme rarity ofchemosynthetic taxa, suggest that predatory pressure rules out whale-fall specialistsfrom shallow shelf settings as in analogous cold seep and vent shallow-water commu-nities.

Larger benthic foraminifera: a tool for biostratigraphy, facies analysis and paleoenvironmental interpretations of the Oligo-Miocene carbonates, NW Central Zagros Basin, Iran

The facies distribution and the biogenic components of the study carbonates in the Ghale Nar oil field in the central part of the Zagros basin were used to reconstruct and interpret the depositional environment of the Asmari Formation. The sediments of the formation consist mainly of limestone, dolomite, dolomitic limestone and are dominated by larger benthic foraminifers (LBF) and corallinacean assemblages. Based on the LBFs, the Asmari formation in the study section is Oligocene (Rupelian–Chattian) to Early Miocene (Burdigalian) in age. Fourteen facies representing upward gradual shallowing trend of an open marine (F1 (the Pabdeh Formation) to 3), shoal (F4–5), semi-restricted and restricted lagoon (F6–12) and near-shore lagoon (F13–14) environments were identified. The facies analysis and the paleoenvironmental interpretations revealed that the carbonate sediments of the Asmari Formation were deposited in a homoclinal ramp consisting of inner, middle and outer zones. The F1 facies (top of the Pabdeh Formation) with planktonic foraminifers represents an outer ramp. The F2–3 facies with planktonic, large and small hyaline benthic foraminifers and corallin algal indicate a distal to proximal middle ramp setting. The F 4–14 facies were characterized by the occurrence of porcelaneous benthic foraminifers representing a shallow-water setting of distal to proximal inner ramp influenced by wave and tide processes. The carbonate ramp developed in tropical waters, under oligotrophic to slightly mesotrophic conditions. Our results from the facies and paleoecological analysis revealed that the Asmari Formation was deposited on a carbonate open ramp dominated by heterozoan and subordinate photozoan skeletal assemblages.

Facies analysis and sequence stratigraphy of the Asmari Formation in the northern area of Dezful Embayment, south-west Iran

This paper concerns the sequence stratigraphy of the Oligocene (Rupelian–Chattian)–Early Miocene (Burdigalian) Asmari Formation based on microfacies analysis of the sediments in the Ghale Nar Oilfield, central area of Zagros fold-thrust belt. Fourteen facies types typical for upward shallowing trend from open marine (MF 1–3), to shoal (MF 4-5), semi-restricted and restricted lagoon (MF 6–12) and finally to near-shore lagoon (MF 13-14) depositional environments were identified. Based on the environmental interpretations, we reconstructed a homoclinal ramp mainly represented by its inner and middle sectors. Facies types MF 4–14 are characterized by the occurrence of large and small porcelaneous benthic foraminifera representing a shallow-water setting of an inner ramp influenced by wave and tide processes. MF1 (Pabdeh Formation), and 2 -3 with planktonic, large and small hyaline benthic foraminifera represent between FWWB and SWB. Four third-order depositional sequences were recognized. In this study, in order to better correlate the identified sequences with pre-defined sequences of the Asmari Formation in the Dezful Embayment and the Izeh zone that are chronologically well-defined, we use their number instead of their name. Sequence 2 mainly consists of an open marine environment in the base, followed by semi-restricted to restricted lagoonal facies. Sequences 36 are characterized by semi-restricted to restricted lagoonal facies. Moreover, the regional relative sea-level change curves correlate well with the global sea-level change curves.

Fossil semi-endophytic species of Lithophyllum (Corallinaceae, Rhodophyta) from Tahiti, including L. kenjikonishii sp. nov., and their taphonomic signatures

Woelkerling W.J., Iryu Y. and Bassi D. 2013. Fossil semi-endophytic species of Lithophyllum (Corallinaceae, Rhodophyta) from Tahiti, including L. kenjikonishii sp. nov., and their taphonomic signatures. Phycologia 52: 387–397. DOI: 10.2216/13–129.1Fossil specimens of two semi-endophytic species of Lithophyllum, L. kenjikonishii sp. nov. and L. cuneatum (Corallinaceae, Rhodophyta), were discovered in thin sections of ocean floor cores of the last deglacial period (c. 20,000–10,000 years before present) obtained from Tahiti, French Polynesia, during Expedition 310 of the Integrated Ocean Drilling Program. Detailed morphological–anatomical accounts of both species are provided, and their placement in Lithophyllum and the subfamily Lithophylloideae is discussed in relation to recent classification proposals. Lithophyllum kenjikonishii, recorded only from fossil thalli, and L. cuneatum, known from fossil and nonfossil thalli, are readily distinguished in tetrasporangial conceptacle pore canal anatomy and on differences in spermatangial conceptacle chamber anatomy. Both species are semi-endophytic in Hydrolithon onkodes, another species of Corallinaceae. Taphonomic signatures evident in thin sections suggest that the occurrence of L. kenjikonishii, L. cuneatum, or Hydrolithon braganum (another semi-endophyte) growing in H. onkodes may be a reliable reference for identifying shallow-water settings (fore reef, reef flat and lagoon) in coral reef depositional systems within Pleistocene to last deglacial sedimentary successions in the Pacific Ocean. Taphonomic signatures thus have considerable potential as a palaeoecologic proxy in interpreting reef growth history.

A unique condition for early diversification of small shelly fossils in the lowermost Cambrian in Chengjiang, South China: Enrichment of phosphorus in restricted embayments

In the earliest Cambrian the major diversification of small shelly fossils (SSFs) was the first episode of the so-called Cambrian Explosion. In order to clarify the background environmental conditions of this event, we examined the lowermost Cambrian strata with bedded phosphorites in the Chengjiang area, South China. The lowermost Cambrian (the Zhongyicun Mb of the Zhujiaqing Fm) in eastern Yunnan is composed of bedded phosphorites and phosphatic limestones with diverse SSFs. We investigated 3 sections within the Chengjiang area at Hongjiachong, Maotianshan, and Xiaolantian. Detailed lithostratigraphic analysis of outcrops and drill cores at Hongjiachong indicates that the Zhongyicun Mb consists of 5 distinct units, A to E in ascending order. The presence of 15 genera of SSFs in 20 horizons shows that the Zhongyicun Mb yields two distinct SSF assemblages of Fortunian age (earliest Cambrian; 541–529Ma); i.e. the first assemblage with simple-shape SSFs (Anabarites, Protohertzina) from basal Unit A, and the second assemblage with various molluscan shells (Paracarinachites, Ocruranus–Eohalobia) from Units C–E. As well as abundant phosphate grains, all SSFs occur as clastic grains, suggesting that phosphorite was primarily formed in extreme shallow-water settings, as were the small shelly animals. We established that the first occurrence of the second SSF assemblage is at least 5m lower (ca. 1–2myr earlier in age) than previously reported in Chengjiang, and we speculate that the major diversification in SSF assemblage likely occurred during the Fortunian, at least before ca. 534Ma. Judging from the rift-related tectonic setting and relevant paleogeography of western South China, we further speculate that the Zhongyicun Mb was primarily deposited in restricted embayments in the Kangdian rift basin, and that the rapid SSF diversification in the Fortunian occurred in a unique setting in highly phosphorus-rich seawater.

A shallow water record of the onset of the Messinian salinity crisis in the Adriatic foredeep (Legnagnone section, Northern Apennines)

The Legnagnone section (North-eastern Apennines) represents one of the few shallow water records of the onset of the Messinian salinity crisis. Here we present a detailed description of a ~200kyr time interval encompassing the pre-/syn-evaporitic transition based on a multidisciplinary approach, integrating sedimentological, bio-magnetostratigraphical, palaeontological and stable isotope data. Such a shallow water setting is potentially more sensitive to the palaeoenvironmental change leading to the MSC than the more often studied deeper Mediterranean basin. The aquatic palaeoenvironmental reconstruction proposed here is based on the study of foraminifer, ostracod and mollusc assemblages. It depicts a change from infralittoral (20–50m) to inner circalittoral environment (60–100m) that, since 6.12Ma, was progressively affected by a reduction of oxygen at the sea floor punctuated by short-lived anoxic events. At least three cooling events have been recognized on the basis of relative abundance data in mid to high altitude pollen, which, before 6.03Ma, are in phase with abundance peaks of Turborotalia spp., a taxon indicating eutrophic and cool surface waters. The absence of stress-tolerant benthic foraminifers during these peaks points to strong ventilation episodes triggered by a generally cooler climate. The proximity of a deltaic system and the consequent riverine input probably caused a salinity decrease of the surface waters, hindering the proliferation of planktonic foraminifers in the water column, which prevalently occur in short influxes and disappear at ca. 6Ma. Our results suggest that the onset of the crisis occurred during a phase of relative sea level high stand, whereas no evidences of sea level drop can be envisaged. The palaeoclimatic reconstruction based on palynological data indicates the dominance of a “subtropical humid forest” vegetation type, where fresh water swamps are well represented. From 6.03Ma onward, the transition to the salinity crisis is marked by more pronounced cyclical expansions of the temperate broad-leaved deciduous forest, along with herbaceous taxa. The establishment of the strongly evaporative condition at the crisis onset is not associated with major vegetational changes towards drier conditions, but linked to a sudden increase of δ18O and the disappearance of benthic foraminifers just prior to the deposition of the 1st laminated carbonate, which represents the base of the Primary Lower Gypsum unit.

Production, preservation, and biological processing of mass-independent sulfur isotope fractionation in the Archean surface environment

Mass-independent fractionation of sulfur isotopes (S MIF) in Archean and Paleoproterozoic rocks provides strong evidence for an anoxic atmosphere before ~2,400 Ma. However, the origin of this isotopic anomaly remains unclear, as does the identity of the molecules that carried it from the atmosphere to Earth's surface. Irrespective of the origin of S MIF, processes in the biogeochemical sulfur cycle modify the primary signal and strongly influence the S MIF preserved and observed in the geological record. Here, a detailed model of the marine sulfur cycle is used to propagate and distribute atmospherically derived S MIF from its delivery to the ocean to its preservation in the sediment. Bulk pyrite in most sediments carries weak S MIF because of microbial reduction of most sulfur compounds to form isotopically homogeneous sulfide. Locally, differential incorporation of sulfur compounds into pyrite leads to preservation of S MIF, which is predicted to be most highly variable in nonmarine and shallow-water settings. The Archean ocean is efficient in diluting primary atmospheric S MIF in the marine pools of sulfate and elemental sulfur with inputs from SO2 and H2S, respectively. Preservation of S MIF with the observed range of magnitudes requires the S MIF production mechanism to be moderately fractionating ( 20-40‰). Constraints from the marine sulfur cycle allow that either elemental sulfur or organosulfur compounds (or both) carried S MIF to the surface, with opposite sign to S MIF in SO2 and H2SO4. Optimal progress requires observations from nonmarine and shallow-water environments and experimental constraints on the reaction of photoexcited SO2 with atmospheric hydrocarbons.

Facies analysis and sequence stratigraphy of the evaporite bearing Sachun Formation at the type locality, South East Zagros Basin, Iran

The Paleocene-Early Eocene Sachun Formation across the interior Fars in the SE of the Zagros Basin (Iran) consists of carbonates, evaporites and siliciclastic sediments. Lithostratigraphic evidence shows that the Sachun Formation can be divided into three units: lower evaporite (unit 1), middle limestone and marl (unit 2), and upper evaporite (unit 3). The lower and upper evaporate units are represented by gypsum-anhydrite layers that are interbedded with thin-bedded dolomite and red marl layers. In the evaporites of the Sachun Formation, brecciated gypsum, nodular, nodular-banded gypsum and laminated-banded gypsum with chicken-wire fabrics are identified. These associations indicate a sabkha or shallow-water setting, such as a lagoon. Petrographic studies led to the identification of twelve carbonate facies types that have been formed in four different types of depositional settings, across a ramp with a gentle dip, including; supratidal sabkha, shallow subtidal lagoons, barrier and shallow open-marine. The mixed carbonate and siliciclastic lithofacies are composed of red and gray marl which both are interbedded with carbonate and evaporite deposits. Three depositional sequences (A, B and C) are recognized from deepening to shallowing trends in the depositional facies, changes in cycle stacking patterns and sequence boundary features. Sequences A and C are evaporite-dominated shallowing-upward cycles and sequence B consists of carbonate-dominated shallowing-upward cycles.

Evidence for shallow-water ‘Upper Kellwasser’ anoxia in the Frasnian–Famennian reefs of Alberta, Canada

The Frasnian–Famennian extinction witnessed the global devastation of both level-bottom and reef communities in low latitudes. Marine extinctions in offshore level-bottom communities are associated with two widespread, transgressive, anoxic ‘Kellwasser Events’ that support an anoxia–extinction link. Typical Kellwasser facies of bituminous limestones and shales are not obviously recorded in shallow-water settings, and thus, it is unclear whether anoxia played a role in reef losses. We evaluate geochemical, petrographic and facies evidence for oxygen restriction from an extremely shallow-water carbonate platform in Alberta. Sequence stratigraphy places the Frasnian–Famennian boundary at a sequence boundary that tops a laminated mudstone and interrupts carbonate platform deposition. Two transgressive pulses have been identified, one of which is associated with the second, major transgression of T-R cycle IId of the Devonian eustatic sea-level curve. Geochemical proxies indicate that these transgressions were accompanied by influx of dysoxic or anoxic waters. Organic carbon and U enrichment in the Frasnian, particularly just below the Frasnian–Famennian boundary, points to episodic dysoxic conditions that probably persisted into the basal Famennian and were coincidental with the global Upper Kellwasser Event. This study provides the first evidence for the smoking gun of an anoxia-driven extinction in very shallow waters, implicating this potent killer in the demise of the Devonian reefs.

Taxonomic composition and environmental distribution of post-extinction rhynchonelliform brachiopod faunas: Constraints on short-term survival and the role of anoxia in the end-Permian mass extinction

Marine taxonomic losses during the end-Permian mass extinction were driven by physiological stresses from ocean warming, acidification, and anoxia that ultimately resulted from CO2 release from Siberian Traps flood volcanism. Despite abundant proxy evidence for anoxia, its role is not well resolved because the timing and selectivity of the extinction are better explained by warming and ocean acidification. We studied the taxonomic composition and spatial and temporal distribution of brachiopod-rich post-extinction faunas, which contain short-lived Permian survivors that lived at a key time during and immediately after the peak of the extinction, to elucidate the controls on survival and the role of anoxia. Holdover brachiopods primarily belong to extinct families and orders, not to long-term survivors, and their probability of short-term survival was a function of pre-extinction metapopulation size. Although short-term survival appears to have been stochastic, likely because of intraspecific variation in tolerance within larger metapopulations, opportunistic and possibly dysaerobic-tolerant genera thrived locally. Rhynchonelliform brachiopod distribution was patchy, both environmentally and temporally. They were more abundant in shallow-water settings, consistent with an oxygenated habitable zone, and their local demise often corresponded with the local development of low-oxygen conditions. Thus, although warming and acidification may have been the primary triggers of taxonomic loss, the addition of spatially and temporally variable anoxic conditions exacerbated physiological stress and contributed to ultimate extinction of short-lived survivors. The combination of the three stresses—warming, acidification, and anoxia—which act synergistically to negatively affect respiratory physiology of marine invertebrates, may explain the severity of the end-Permian extinction and provides a sobering analogue for modern ocean acidification and anoxic dead zones.

Changes in area of shallow siliciclastic marine habitat in response to sediment deposition: implications for onshore-offshore paleobiologic patterns

Models presented here of shallow-marine siliciclastic deposition show that the widths of depth-defined regions differ markedly in response to sea-level change. These models add to recent studies that have emphasized the highly specific response of habitat area to sea-level change. Collectively, these studies indicate that a particular bathymetric zone on a particular margin may vary substantially in area during a sea-level change, while other such zones and margins may experience little or even opposite responses. In the models presented here, intermediate-depth and deep-water regions tend to show sinusoidal variations in width, with widening during relative falls in sea level and narrowing during relative rises. The shallow-water region displays markedly non-sinusoidal change and is consistently characterized by abrupt widening at the beginning of the highstand systems tract and an equally abrupt narrowing at the onset of sea-level fall at the beginning of the falling-stage systems tract. These onshore-offshore differences in how width and area change with sea level may explain why taxa in shallow-water settings tend to be more abundant, eurytopic, and widespread than those in deeper-water settings. Likewise, these models suggest that the evolution of novelty in nearshore habitats may be a response to wide variation in shallow-marine area during sea-level change.

The Early Sarmatian bryozoan Celleporina medoborensis sp. nov. from the Medobory reefs of western Ukraine (Central Paratethys)

Moundlike, globular to hemispherical bryozoan colonies of Celleporina medoborensis sp. nov. are documented from the calcareous organodetrital, slightly marly facies of the Lower Sarmatian (Volhynian) serpulid-microbialite reefs, in the Polupanivka and Ditkivtsi quarries (Medobory Hills), located at the northeastern margin of the Carpathian Foreland Basin (Central Paratethys) in western Ukraine. The colonies of C. medoborensis are multilamellar, often with a subcircular hole and occur together with numerous cyclostome bryozoans (crisiids, tubuliporinids, branching colonies of entalophoroids) as well as schizoporellid and cryptosulid cheilostomes, accompanied by a few macro- and micro-fossil taxa. The combination of morphological characters such as: thick radial ribs in the pseudoporous, variably-shaped area of the ovicell, and one or two small adventitious oral, as well as large vicarious avicularia are the main characteristic features of species. The rich occurrence of the celleporiform colonies of C. medoborensis sp. nov. within the fine-grained calcareous sands of Polupanivka and Ditkivtsi suggests a shallow-water setting and high availability of soft substrates, probably dominated by calcareous algae upon which the bryozoans may have settled in the Medobory reef biota during the Early Sarmatian.

Gastropods and tergomyans from the Upper Ordovician (Viru–Harju) of the Fågelsång area, Scania, southern Sweden

A diverse tergomyan and gastropod assemblage is described from the Global Boundary Stratotype Section and Point (GSSP) section of the Sandbian Stage, Upper Ordovician, in the Fågelsång area, Scania, southern Sweden. Deep water graptolitic mudstone and shale comprise the succession, and previously only one gastropod species was known. The new material spans the Sularp Formation through the Lindegård Mudstone (Nemagraptus gracilis–Dicellograptus complanatus biozones). Fourteen species are described: two tergomyan, five bellerophontoid gastropods, and seven anisostrophically coiled gastropods. Three species are new: Peelerophon hodites, Tetranota scanica and Lophospira sandbiana. Three taxa (Tritonophon subtrilobatus, Tetranota scanica and Holopea mobergi) are found high in the Lindegård Mudstone (Vormsi–Pirgu stages). Cyrtodiscus, Peelerophon and Tritonophon are recorded for the first time in Baltoscandia. Some taxa may have been transported from shallower water settings, whereas species of Peelerophon, Joleaudella, Mestoronema and Sinuites may have been part of the local benthos. Except for Bucania erratica, no species are shared with the fauna of the coeval Dalby Limestone in Sweden. Deaechospira elliptica, common in the Dalby Limestone, is not recorded at Fågelsång, although two closely related species are found (Deaechospira rotunda and Deaechospira? sp.). The Fågelsång assemblage has more in common with the older to coeval fauna of the Elnes and Arnestad formations in the Oslo Region, Norway (e.g. sharing Joleaudella, Sinuites, Mestoronema and Pararaphistoma). The Sandbian fauna of Fågelsång includes peri-Gondwanan taxa, e.g. Cyrtodiscus, Peelerophon and Deaechospira. Nevertheless, cluster analysis reveals that the faunas of Baltica and Laurentia were most similar, whereas faunas from Perunica and Baltica remained distinct and separated during the Darriwilian–Sandbian. The few similarities may result from spread of a temperate fauna supplementing rather than replacing taxa in deep water assemblages. The main Fågelsång assemblage coincides both with the Baltoscandian Middle Caradoc Faunal Turnover and the Gutenberg Carbon Isotope Excursion. http://zoobank.org/urn:lsid:zoobank.org:pub:093F6504-B3FA-42A4-94C2-FF460D549F18

Arsenic in marine hydrothermal fluids

Hydrothermal fluids emerging at the seafloor near mid-ocean ridges (MOR) or in back-arc basins (BAB) and island arc (IA) settings are known to contain a considerable amount of dissolved metals (e.g. Fe, Zn, Cu, Cd) due to water–rock interaction at elevated temperatures and potentially magmatic degassing. The chemical input from these fluids plays an important role for ocean chemistry and the cycling of elements. Despite its notoriety as an environmental toxin and its abundance in hydrothermal ore deposits in combination with gold, arsenic (As) is one of the few elements, which has been rarely investigated.Compared to the amount of As in open ocean seawater of around 1.7μgL−1, hydrothermal fluids can have significantly higher concentrations. Fluids from MOR hydrothermal systems such as the East Pacific Rise can contain up to 80.5μgL−1 As and at the Mid-Atlantic Ridge the highest values were around 24μgL−1. Those values, although elevated are surpassed by As concentrations in BAB and IA hosted hydrothermal systems, which can be as high as 1386µgL−1 in BAB settings and even higher with values up to 5850µgL−1 (~3900-times seawater) in IA shallow-water settings, occurring near shore hydrothermal systems.The most important factors controlling the amount of As in hydrothermal fluids are the different – mostly physicochemical – conditions at and beneath the seafloor. These include temperature (controlling phase separation of the fluids and leaching processes in the host rock), pressure as a function of depth, pH directly influencing leaching processes, As mobility and speciation, reaction time and maturity of the system in combination with redox reactions and diverse chemical reactions like adsorption and desorption. The concentration of As in the underlying host rock may also play a role, although its mineralogical association may be more important than bulk rock concentration. Additional input of As could be caused by degassing magmatic metal-rich volatiles or sediment-fluid interaction in sediment covered hydrothermal systems. The contribution from magmatic volatiles is hard to quantify and therefore often neglected in calculations and discussions. Of the two As redox species, arsenate (AsV) and arsenite (AsIII), arsenite is easier transported in the vapor phase. However, As speciation has not been traditionally part of chemical analyses. Prior to discharge at the seafloor, the concentration of As in hydrothermal fluids may decrease rapidly, if precipitation of As-bearing and As-scavenging minerals, such as pyrite, orpiment, claudetite and hydrous ferric/manganese oxides, occurs in the shallow subsurface as shown by thermodynamic calculations. This is consistent to the observation that those hydrothermal fluids high in Fe and Mn are often low in As.Arsenic concentrations in fluids from shallow BAB/IA hydrothermal systems are higher than those in deep situated MOR hydrothermal systems most likely due to their different physicochemical conditions. Basaltic host rocks (MOR) and dacitic/andesitic host rocks (BAB/IA) have As concentrations which are more or less identical and cannot account for the huge differences in fluid As concentration.Arsenic is one of the few trace elements whose concentration in seawater is higher than in river water, which could be caused by the flux of As from hydrothermal systems. Estimating that between 3.0×103 and 1.25×108kg As could be discharged at the MOR annually, which is a substantial amount compared to 53.9×106kg transported annually by rivers. Higher flux can be expected at BAB and IA settings, however data is sparse. A single IA system, confined to a very small area of 60 by 100m (Tutum Bay, Papua New Guinea), discharges around 5.5×102kg As annually.

Discrimination of Seagrass Species and Cover Classes within situHyperspectral Data

ABSTRACT Pu, R.; Bell, S.; Baggett, L.; Meyer, C., and Zhao, Y., 2012. Discrimination of seagrass species and cover classes with in situ hyperspectral data. Seagrass habitats support a variety of ecosystem functions and an increasing interest has emerged for utilizing remote sensing to acquire information on the spatial extent and abundance of seagrass vegetation. Here we report on hyperspectral data collected from a combined laboratory and field-based study to examine the spectral qualities of seagrass species and evaluate whether seagrass species and levels of seagrass cover could be distinguished using true in situ hyperspectral data collected by a spectrometer overlying sea-grass-dominated vegetation in a shallow water setting in the central west coast of Florida. We also analyzed hyperspectral data measured in the lab to compare with those from in situ collections. Using a set of 97 field measurements we compared spectra qualities for different seagrass species, levels of seagrass cover, water depths...

Foraminiferal assemblages and trophic state in coastal sediments of the Adriatic Sea

The environmental variables that influence the abundance and biodiversity of foraminifera in shallow-water settings are poorly understood. In order to help address this problem, we investigated abundance, biomass and biodiversity of living (as Rose-Bengal stained) benthic foraminifera together with the quantity and biochemical composition (in terms of phytopigment, protein, lipid, carbohydrate and biopolymeric carbon) of the organic matter in coastal sediments of the Central Adriatic Sea. Sediment samples were collected in the Portonovo Bay in May, July and October 2008 and February 2009, and the organic matter quantity and biochemical composition and benthic foraminiferal abundance and assemblage composition were analysed in the top 1cm. Uni- and multi-variate analyses of variance revealed clear temporal variability of all the investigated variables as well as relationships between the composition of the foraminiferal assemblages and the quantity and quality of the food sources. The foraminiferal abundance and species composition changed significantly between the four sampling periods, reflecting the temporal (seasonal) variability in the quantity and nutritional quality of the food sources. Lipids, among all other organic compounds, explain significant portions of the variance of both foraminiferal abundance and biomass. In winter, a strong phytoplankton bloom led to an increased quantity of nutritionally available organic matter on the sea floor, which in turn was associated with a bloom of Leptohalysis scottii and Psammophaga sp. 1. These two foraminiferal species thus displayed an opportunistic behaviour in response to the pulse of organic carbon of high nutritional quality. We suggest that these species can be used as indicators of benthic eutrophication in shallow waters.

Tectonic evolution of the northern Bonaparte Basin: impact on continental shelf architecture and sediment distribution during the Pleistocene

The Bonaparte Basin (NW Australia) forms a rare, recent example where Neogene deformation shaped a very wide platform (630 km wide) in which a mixed carbonate-silliciclastic sedimentary sequence developed. This study combines structural and stratigraphic analysis and provides new insights as to the role of tectonics in controlling platform shape and sediment distribution in wide shallow water settings. Detailed analysis of the structure and stratigraphy of the northern part of the Bonaparte Basin allowed identification of the main regimes and phases of deformation and their control on sedimentation during the Neogene. The results reveal that the distribution of Neogene sediments across the northern Bonaparte Basin is mainly controlled by flexure-induced deformation mechanisms associated locally with extensional faults and low-strain, left-lateral strike-slip. These processes ultimately shaped the geometry and sedimentary architecture of the wide continental shelf. They led to the development of two different types of tectonically induced shelf depocentres that controlled the gross distribution of Quaternary sediments. In particular, deformation processes enhanced the formation of the carbonate-dominated, ∼200 m-deep Malita intra-shelf basin. The Bonaparte Basin is a prime natural laboratory to describe the links between tectonics and sedimentation along a very large, mixed carbonate/clastic platform and could be used as a modern analogue to similar settings in the past Earth's history.

Rb-Sr and K-Ar isotopic systems of the Upper Devonian sediments in the Pripyat Trough, Belarus

The results of Rb-Sr and K-Ar isotope studies of the Famennian upper salt and suprasalt complexes sampled from the core material of exploratory boreholes drilled at the northwestern margin of the Pripyat Trough (Belarus) are presented. The suprasalt and saliferous portions of the sequence define an age of approximately 470 Ma. Despite multiple reworking of the material, we interpret this value as preservation of the provenance “memory.” Regardless of the Sr content in sample, the strontium isotope ratios obtained for low-Rb minerals (celestine, carbonate, and halite) varies throughout the section within 0.7083–0.7095, indicating the preservation of some primary features of the matter. The lowest isotope values obtained are slightly higher than those inferred for the upper Famennian. This fact confirms the concept that the studied complex was formed in a shallow-water setting. Data on sylvites show that the present-day isotopic characteristics of potassium salts were formed significantly later.

Chemostratigraphic constraints on early Ediacaran carbonate ramp dynamics, Río de la Plata craton, Uruguay

C- and Sr-isotope data for marine carbonates can provide a detailed record of isotopic variations in seawater through time and have proven to be a valuable tool for interpreting biogeochemical events and correlating Neoproterozoic sedimentary successions worldwide. Negative carbon isotope excursion to values as low as −4.5‰ in the Ediacaran Polanco Limestones Formation, Uruguay has been interpreted as recording the aftermath of a post-Gaskiers glacial event occurred elsewhere on southwest Gondwana. The record of both deep- and shallow-water settings in the Polanco Limestone Formation provides an opportunity to examine δ13C variability across the platform and to evaluate whether the carbon isotope values reflect local or global processes. Herein we provide high-resolution δ13C-chemostratigraphy and Sr-isotope data from stratigraphic sections comprising proximal and distal settings on the carbonate platform. Carbon isotopic values are negative in deep-water facies but progressively rise towards positive values in shallow-water settings. This previously unrecognized trend suggests that deposition of Polanco carbonates occurred in a stratified marine basin where degradation of organic matter below the redox boundary led to lower δ13C values at greater depths. The negative δ13C excursion is restricted to specific horizons in shallow-water facies and is interpreted as being originated due to higher levels of reworking under storm-dominated conditions, which produced a strong local oxidation of organic matter and ultimately, the negative carbon isotope signatures. 87Sr/86Sr and δ13C chemostratigraphy coupled with new radiometric data allow us to revise the previously proposed age for the unit. This new data support an age between 590 and 560Ma for the deposition of the Polanco Limestones Formation.

Late Holocene sedimentary changes in shallow water settings: the case of the Sele river offshore in the Salerno Gulf (south-eastern Tyrrhenian Sea, Italy)

A complementary data set consisting of sedimentological, petrophysical, geochronologic and seismo-stratigraphic analysis was used to detect the sedimentary changes in the inner shelf record in a mostly stable region, over the last 3 ky cal BP, that is since the sea level attained its present day position. This study has been carried out within the VULCOST project on the Salerno Gulf (south-eastern Tyrrhenian Sea, Italy), to learn more about the impact of minor morpho-climatic changes and anthropogenic disturbances on the shelf sedimentary record. Some decimeter-thick sandy beds deposited on the inner shelf, off the Sele river mouth, in the time span corresponding to the Little Ice Age (LIA), despite the fact that, at the time, the coastline at that time was farther inland with respect to its present day position. Since the beginning of the 20th century, mainly fine grained sediment settled, possibly owing to the restoration of mild climatic conditions, changes in the rivers’ regime and land-use. The analysis of the marine cores, collected off the coast, also reveals a litho-stratigraphic mismatch among coeval intervals, possibly driven by the different response of the catchments to the morpho-climatic variations. High resolution seismic data shows that the sediment bypass area, shaped by wave action, is much deeper than the estimated limit, if computed on the base of fair-weather wave length and sedimentologic analysis. Indeed, toplap terminations of reflectors are recognizable as deep as 25 m in the southern sector of the Gulf and suggest an intense reworking of the seabed over long periods, much deeper than the outer limit of the beach. This evidence is also supported by the state of pyroclastic layers in the core record, which proves sediment reworking in the marine setting, down to 24 m of depth. The high resolution sedimentologic and stratigraphic reconstructions point to a non linear relation between depth, distance from the coast and sand deposition over the time. This suggests a complex picture of coastal dynamics within the same basin, with a remarkable outcome regarding the wave-cut terraces as proxies of sea level stands.