Marine Basin Research Articles

Geochemistry and paleogeography of the Rajang Group, Northwest Borneo, Malaysia

The Late Cretaceous to Late Eocene Rajang Group in Borneo is one of the world's largest deep-sea sedimentary fans. The volume of the Rajang Group cannot be explained by erosion of the Schwaner Mountains in SW Borneo and the Malay Peninsula. To identify other contributing sources, this study examined the provenance history of the Rajang Group and the overlying Tatau Formation. A combination of bulk rock geochemistry, zircon morphological analysis and U–Pb geochronology is used to better constrain the provenance of the Rajang Group. Bulk rock Nd data, supported by detrital zircon data indicates that a late Mesozoic magmatic belt include the Schwaner Mountains was an important source before the Paleocene, after which sediment supply was dominated by older crustal sources, consistent with the Malay Peninsula. The increased contribution from older crustal material is considered to be the consequence of collapse of the magmatic arc and collision between Australian microcontinental fragment(s) and the southern margin of Sundaland. Paleocene river systems that flowed through the Malay Peninsula, transported large amounts of sediments to the marine basins including the deep-sea Rajang Group. A strong signal of sediment recycling for the Tatau Formation indicates uplift and denudation of lower Rajang Group in Late Eocene.

Characteristics and Long-Term Variability of Occurrences of Storm Surges in the Baltic Sea

Understanding the characteristics of storm surges is especially important in the context of ongoing climate changes, which often lead to catastrophic events in the coastal zones of seas and oceans. For this reason, this paper presents the characteristics of the Baltic Sea storm surges and trends in their occurrences through the past 60 years. The study material was based on hourly sea level readings, spanning the years 1961–2020, retrieved from 45 Baltic Sea tide gauges, as well as air pressure and wind field data. Owing to the analysis and visualization of storm situations, two main types of storm surges were identified and characterized: a surge driven by wind and a surge driven by subpressure associated with an active low pressure area. This paper also discusses a third, mixed type of storm surge. Further analyses have indicated that through the past 60 years in the Baltic Sea, the duration of high sea level has increased by 1/3, the average number of storm surges has increased from 3.1 to 5.5 per year, and the maximum annual sea levels have increased—with a trend value of 0.28 cm/year. These processes, also observed in other marine basins, provide strong evidence for contemporary climate change.

The Delta of Shatt Al-Arab River, Framework and Evolution

Shatt Al-Arab Delta was built at the northern end of the Arabian Gulf (AG) on the top of a longitudinal shallow marine basin shape. Today the hydrologic regime of Shatt Al-Arab River is suffering from many changes caused by anthropogenic activity impacts, led to a significant decrease in water feeding about 1000 m3/sec in 1990 into less than 50m3/sec in 2016. Many previous studies have been discussed as well as performing a marine geophysical surveys to assess the evolution of Shatt Al-Arab Delta during the history. Many phenomenon and progradational parts of the Delta: Prodelta, distributary channel, bay fill, and beach ridge have been identified from marine geophysical survey. The lower reflector is appear as irregular surface, which could indicate the presence of an ancient beach that appear as a terraces region due to fluctuation in the sea level. The second reflector appear as a layer have had variation depth, which may represent a beginning of the ancient delta creation after of the sea level stability (< 5000 years ago). The top layers have been deposited, which represent the present day delta. This present result suggests that there are three phases of delta evolution during history, the first phase represents the beginning of the modern origin of this delta during 1000-2000 yr. ago when the Tigris and Euphrates Rivers are connected together, at that time the delta was not so large and have been formed by the excess sediment that coming from the marshes after the two Rivers dumping most of their sedimentary load there. The second phase represents the activation of this delta with stabilized coastline, especially after the manmade connection between Karun and Shatt Al-Arab Rivers, which occurred before thousand years ago. The third phase represents the last half of the previous century when several factors contributed on the evolution of Shatt Al-Arab delta, including hydrological, climatological and anthropogenic factors.

A stratigraphic record from syn to post subduction sedimentation in Marlborough, New Zealand, and implications for Gondwana breakup

Sediments that accumulate within marine basins at convergent plate margins can provide important insights into the evolution and tectonic stability of the subduction wedge. Long-term sediment dispersal and stratigraphic patterns can also be influenced by geodynamic reconfigurations of the plate margin, such as changes in plate dip or velocity, or the subduction of anomalous oceanic crust. An understanding of tectonic context and complexity is therefore critical for any interpretation of convergent margin stratigraphy. Unfortunately, ongoing subduction and wedge deformation tends to obscure or destroy the stratigraphic record of such events as sediments become progressively incorporated into the wedge.The Awatere Valley in New Zealand's South Island contains well-preserved forearc stratigraphic record that accumulated within coastal-plain and marine basins during the final stages of East Gondwana subduction. We assign seven facies associations (FA) to characterise post-subduction units, showing that a transition from syn to post-subduction deposition is contained within largely marine strata from the New Zealand Urutawan to Ngaterian stages (c. 108 to 95 Ma). In contrast to previous accounts of deposition within nascent rift-basins, restored basin geometries are most consistent with those of terraced subduction wedges. We find no evidence that extension affected deposition prior to 95 Ma. Our results instead document a transition from highly deformed sedimentary wedge (pre 108 Ma) to largely undeformed sedimentary cover units (∼100 Ma) that is predominantly gradational.Up to 2 km of basin fill documents a relative sea-level (RSL) rise and fall between 108 and 95 Ma. A period of relative sediment starvation during the Urutawan (108–103 Ma) was abruptly terminated by synchronous mass-wasting, including the remobilisation of metre-scale blocks and rafts, that signals a dramatic increase in depositional energy relative to preceding patterns. Within the context of a large RSL fluctuation, diminishing compressional tectonism and forearc volcanism (from 98 Ma), this increase is anomalous and appears to signal a significant change in underlying subduction dynamics.

Characteristics and environmental significance of concretions in the Lower Cambrian Qiongzhusi Formation in the Middle–Upper Yangtze region, China

Based on the outcrop and drilling data of the Sichuan Basin and its periphery, this paper reveals the concretion development characteristics of the Lower Cambrian Qiongzhusi Formation and its significance to the environment. Three preliminary conclusions are drawn as follows. (1) The exposure layers and lithofacies characteristics of the concretions in the Qiongzhusi Formation are very different from area to area. In the eastern Sichuan-western Hubei-Hunan & Guizhou and southern Sichuan depression areas, the concretionsare developed in the section of SQ1, and are mainly composed of calcareous siliceous mixed shale facies, siliceous shale facies, dolomitic shale facies and dolomite facies. The clay content is generally less than 25% and is significantly less than the surrounding rocks, and the TOC is generally higher in the lower concretion layers and less in the upper concretion layers. In the central Sichuan and northern Sichuan depression areas, the concretions appear in the sections of SQ1 and SQ2, and are dominated by calcareous shale facies and marl facies. The calcic content is obviously higher than that of surrounding rocks, and the clay content is less than that of surrounding rocks, and the TOC is less than 1.50%. Because mineral composition difference is high, most of the GR curves of the concretions show trough response characteristics, reflecting the central region enriched with calcium or siliceous, and the edge enriched with clay and organic matter. (2) The concretion layers generally occur in carbonaceous shale, silty shale and siliceous shale with a TOC over 0.7%, and are especially developed in carbonaceous shale and siliceous shale of SQ1, and occasionally appear in grey silty shale with a TOC over 0.2%, showing that the concretion layers are basically symbiotic with grey shale (especially with high-quality shale). (3) The concretions are a kind of important sedimentary response of rifting activities in Yangtze marine basin. According to the distribution characteristics of concretions and black shale in the Qiongzhusi Formation, the rifting activities of Yangtze marine basin can be divided into three periods including development period (SQ1), adjustment period (SQ2) and abortion period (SQ3). In the period of SQ1, controlled by massive rifting and upwelling ocean currents in Yangtze marine basin, the concretions and organic-rich shale were widely developed in the Lower Qiongzhusi Formation. In the periods of SQ2 and SQ3, while rifting activity of Yangtze marine basin decreased and aborted, and while sea level fell and upwelling ocean currents receded to the southeast, the concretions and organic-rich shale just appeared in the local depression areas in small scale.

Remarkably coherent population structure for a dominant Antarctic Chlorobium species

BackgroundIn Antarctica, summer sunlight enables phototrophic microorganisms to drive primary production, thereby “feeding” ecosystems to enable their persistence through the long, dark winter months. In Ace Lake, a stratified marine-derived system in the Vestfold Hills of East Antarctica, a Chlorobium species of green sulphur bacteria (GSB) is the dominant phototroph, although its seasonal abundance changes more than 100-fold. Here, we analysed 413 Gb of Antarctic metagenome data including 59 Chlorobium metagenome-assembled genomes (MAGs) from Ace Lake and nearby stratified marine basins to determine how genome variation and population structure across a 7-year period impacted ecosystem function.ResultsA single species, Candidatus Chlorobium antarcticum (most similar to Chlorobium phaeovibrioides DSM265) prevails in all three aquatic systems and harbours very little genomic variation (≥ 99% average nucleotide identity). A notable feature of variation that did exist related to the genomic capacity to biosynthesize cobalamin. The abundance of phylotypes with this capacity changed seasonally ~ 2-fold, consistent with the population balancing the value of a bolstered photosynthetic capacity in summer against an energetic cost in winter. The very high GSB concentration (> 108 cells ml−1 in Ace Lake) and seasonal cycle of cell lysis likely make Ca. Chlorobium antarcticum a major provider of cobalamin to the food web. Analysis of Ca. Chlorobium antarcticum viruses revealed the species to be infected by generalist (rather than specialist) viruses with a broad host range (e.g., infecting Gammaproteobacteria) that were present in diverse Antarctic lakes. The marked seasonal decrease in Ca. Chlorobium antarcticum abundance may restrict specialist viruses from establishing effective lifecycles, whereas generalist viruses may augment their proliferation using other hosts.ConclusionThe factors shaping Antarctic microbial communities are gradually being defined. In addition to the cold, the annual variation in sunlight hours dictates which phototrophic species can grow and the extent to which they contribute to ecosystem processes. The Chlorobium population studied was inferred to provide cobalamin, in addition to carbon, nitrogen, hydrogen, and sulphur cycling, as critical ecosystem services. The specific Antarctic environmental factors and major ecosystem benefits afforded by this GSB likely explain why such a coherent population structure has developed in this Chlorobium species.FJebgLEuwcBu4fPtsFrHHTVideo abstract

The Subhercynian Basin: an example of an intraplate foreland basin due to a broken plate

Abstract. The Late Cretaceous intraplate shortening event in central western Europe is associated with a number of marine basins of relatively high amplitude and short wavelength (2–3 km depth and 20–100 km width). In particular, the Harz Mountains, a basement uplift on a single, relatively steeply dipping basement thrust, have filled the adjacent Subhercynian Cretaceous Basin with their erosive product, proving that the two were related and synchronous. The problem of generating subsidence of this general style and geometry in an intraplate setting is dealt with here by using an elastic flexural model conditioned to take account of basement thrusts as weak zones in the lithosphere. Using a relatively simple configuration of this kind, we reproduce many of the basic features of the Subhercynian Cretaceous Basin and related basement thrusts. As a result, we suggest that overall, it shares many characteristics with larger-scale foreland basins associated with collisional orogens on plate boundaries.

Contrasting nutrient availability between marine and brackish waters in the late Mesoproterozoic: Evidence from the Paranoá Group, Brazil.

Understanding the delayed rise of eukaryotic life on Earth is one of the most fundamental questions about biological evolution. Numerous studies have presented evidence for oxygen and nutrient limitations in seawater during the Mesoproterozoic era, indicating that open marine settings may not have been able to sustain a eukaryotic biosphere with complex, multicellular organisms. However, many of these data sets represent restricted marine basins, which may bias our view of habitability. Furthermore, it remains untested whether rivers could have supplied significant nutrient fluxes to coastal habitats. To better characterize the sources of the major nutrients nitrogen and phosphorus, we turned to the late Mesoproterozoic Paranoá Group in Brazil (~1.1Ga), which was deposited on a passive margin of the São Francisco craton. We present carbon, nitrogen and sulphur isotope data from an open shelf setting (Fazenda Funil) and from a brackish-water environment with significant riverine input (São Gabriel). Our results show that waters were well-oxygenated and nitrate was bioavailable in the open ocean setting at Fazenda Funil; the redoxcline appears to have been deeper and further offshore compared to restricted marine basins elsewhere in the Mesoproterozoic. In contrast, the brackish site at São Gabriel received only limited input of marine nitrate and sulphate. Nevertheless, previous reports of acritarchs reveal that this brackish-water setting was habitable to eukaryotic life. Paired with previously published cadmium isotope data, which can be used as a proxy for phosphorus cycling, our results suggest that complex organisms were perhaps not strictly dependent on marine nutrient supplies. Riverine influxes of P and possibly other nutrients likely rendered coastal waters perhaps equally habitable to the Mesoproterozoic open ocean. This conclusion supports the notion that eukaryotic organisms may have thrived in brackish or perhaps even freshwater environments.

Analysis of trends and features of seaports’ development in the Russian Federation

The article analyses the economic state and prospects for the development of modern seaports in the context of the development of the transport infrastructure of the Russian Federation as a key factor in increasing the economic efficiency of public production. A review of the seaports of the Russian Federation of the Russian Federation, which includes 67 ports in five marine pools is presented: the Arctic, the Baltic, the Azov-Black Sea, the Caspian and the Far East. The main stages of development of the seaports are highlighted and the characteristic features of each marine basin are noted. The analysis of the economic indicators of the activities of marine ports is carried out: cargo turnover, volume of cargo handling and bulk vessels in the seaports of the Russian Federation. The main problems of the development of seaports in Russia are revealed, the objectives of state regulation and the system of state support are considered. The directions of increasing the competitiveness of seaports in the world market are determined.

ИЗУЧЕНИЕ РАКОВИННОГО ВЕЩЕСТВА СОВРЕМЕННЫХ И ПЛЕЙСТОЦЕНОВЫХ МОЛЛЮСКОВ РОДА DIDACNA

One of the ways to study the reactions of marine invertebrates to the external effects of changes in temperature and salinity is the biogeochemical analysis of skeletal parts, which are consistently built up during ontogenesis and record a variety of information about these changes. The most studied shells of mollusks, sea urchin shells and skeletal parts of corals. Information about the chemical composition of modern and fossil mollusk shells is widely used in solving geological and biological problems, including determining the temperature and salinity of ancient marine basins, studying the diagenesis of carbonate sediments, and the biochemical evolution of invertebrates. X-ray diffraction analysis of the shell matter of didacnae belonging to the Cardiidae showed an aragonite composition. The quantitative determination of elements in mollusk shells by microprobe analysis of spot scanning and spectrometric method is carried out. Samples were taken in successive layers of shell growth within the annual ring, and the seasonal dynamics of strontium changes were detected. For Didacna, strontium is the main element-indicator of seasonal and ontogenetic growth, is included in the crystal lattice of aragonite and forms strong compounds in the process of shell formation during the life of these bivalves. The variability of seasonal, ontogenetic, and taxonomic differences in a number of indicator elements in living and Pleistocene bivalves of the genus Didacna was studied.

Early Neoproterozoic tectonic evolution of northern Yangtze Block: Insights from sedimentary sequences from the Dahongshan area

Precambrian sedimentary strata are widely distributed along the periphery of the Yangtze Block. However, the age, provenance and tectonic setting of the sedimentary successions on the northern margin still remain unclear, which exerted considerable influence on the understanding of Precambrian crustal evolution of the Yangtze Block. Here we report integrated detrital zircon U-Pb dates and Lu-Hf isotopes from the Dahongshan area to the northeast of the nuclei (i.e. the Kongling Complex) of the Yangtze Block. The youngest U-Pb dates of 995 Ma and 810 Ma of detrital zircon grains place constraints on the maximum depositional ages of the underlying Dagushi Group and the overlying Huashan Group, respectively. Both groups show pre-Mesoproterozoic age populations at ca. 2050 Ma and ca. 2700 Ma and corresponding εHf(t) values varying from –24.1 to + 2.3, consistent with counterparts of the Kongling Complex and Yangpo Complex in northern Yangtze Block. The εHf(t) values of Neoproterozoic (1000–800 Ma) detrital zircon grains in the Huashan Group show a decrease after ca. 880 Ma (from + 13.5 to –18.5), possibly indicating a transition from arc-continent collision to continental arc setting on the northern margin of the Yangtze Block. In combination with sedimentary characteristics and the new isotopic results, the Dagushi Group probably formed in a shallow marine basin setting and received dominant detritus from the Kongling and Yangpo complexes. In contrast, the Huashan Group received sediments recycled from the underlying Dagushi Group and contemporary igneous rocks in the Dahongshan and Kongling areas. The changes in provenance and tectonic setting recorded in the two sedimentary sequences suggest a tectonic transition from late Mesoproterozoic passive continental margin to Neoproterozoic subduction and accretion in response to the amalgamation of Rodinia supercontinent. On the basis of distinct location and history, Pre-Nanhua Neoproterozoic sedimentary sequences distributed in the periphery of Yangtze Block are dispersed into four separate domains. Through bivariate kernel density estimates and bootstrap resampling method, we have identified that these domains were characterized by asynchronous igneous impulse and heterogeneous character of igneous activity in early Neoproterozoic along with varying degrees of integration of crustal growth and reworking.

Sr–Nd isotopic constraints on carbonates, conodonts, and brachiopods of Early-Middle Pennsylvanian Itaituba and Nova Olinda formations, Amazonas Basin, Brazil

Isotopic signatures presented in carbonates and fossils herein are one of the first attempts to obtain Sr and Nd data for the Early – Middle Pennsylvanian of the Itaituba epeiric sea and to evaluate the paleoseawater and paleotectonic of the Amazonas Basin. 87Sr/86Sr data range from 0.708330 ± 0.000018 to 0.708850 ± 0.000046, with ΔSW varying from −60 to −87 reflecting the marine sedimentation, while ΔSW varying from −33 to −51 suggest a post-depositional alteration. These values are in general agreement with the 87Sr/86Sr global seawater curve evolution for this time. The increasing influx of Sr from landmasses in a restricted marine basin, the Itaituba Epicontinental Sea, reflecting enhanced continental weathering during low stand sea level is a potential explanation for the Amazonas Basin during this time. Plotted in the εNd(t = 310 Ma) isotopic global seawater curve evolution data for the Itaituba and the Nova Olinda formations shift to lower values of εNd(t = 310 Ma), when compared to the Panthalassa Ocean. Nd isotopic signature suggests an incoming of seawater masses also from other oceans (e.g. Paleo-Tethys), instead of a unique Panthalassa Ocean provenance of water during the Pennsylvanian in the Amazonas Basin. 143Nd/144Nd isotopic values showed scattered 0.511608 ± 0.000077 to 0.512270 ± 0.000012. Nd-TDM around 1.5 Ga and εNd present-day values around −15 support an old continental Nd provenance to the ancient seawater, similar to those present in the rocks from Amazonian Craton.

High Preservation Potential Volcaniclastic Sedimentation in the Serravallian Sequence of the Amantea Basin (Coastal Chain, North-Western Calabria)

Evidence of volcaniclastic sedimentation occurs in the first depositional sequence of the sedimentary succession of the Amantea Basin. Volcaniclastic deposits are intercalated in the upper part of a sandstone formation and these show a maximum thickness of about 8 m. The Amantea Basin is a Neogene depozone located along the Tyrrhenian margin of Calabria whose onset started during the Upper Serravallian. The source volcano to these materials had to have been located within or near to the marine basin in order to supply it with significant amounts of pyroclastic fragments emplaced by either pyroclastic fall/or flows during one or more explosive eruptions. The marine environment of volcaniclastic flows made up of pyroclastic fragments mixed with minor siliciclastic and carbonate material. The textural and structural features of the deposits and the composition of the volcanic glass fragments indicate an origin from a sub-aerial coeval explosive eruption, with initial sedimentation in a shallow marine environment, mixing with non-volcanic materials, reworking and final re-sedimentation into the basin. The age of the volcaniclastic/sedimentary sequence makes these deposits a marker for the geodynamic evolution of the area, and the lack of such horizons in the other coeval peri-Tyrrhenian basins allows us to consider the Amantea Basin as a confined elongated coastal basin area, whose tectonostratigraphic architecture denotes a structural partitioning of the eastern nascent Tyrrhenian Basin.

Early Jurassic Trigoniida (Bivalvia) from Argentina

AbstractBivalves of the Order Trigoniida were abundant and diverse in the Andean Early Jurassic shallow-marine paleoenvironments. Based on extensive collections with detailed stratigraphic information from 40 localities in central-western Argentina, we describe 20 species (4 new) belonging to 11 genera (3 new) and 5 families (Groeberellidae, Trigoniidae, Prosogyrotrigoniidae, Frenguelliellidae, and Myophorellidae). The abundant material allows the description of ontogenetic development and intraspecific variability, highlighting the likely phylogenetic significance of previously underestimated features. Within Frenguelliellidae, we show that the stratigraphic range ofFrenguelliellaLeanza in the region is restricted to the Sinemurian–Pliensbachian. We proposePoultoniellanew genus for some late Pliensbachian–Toarcian species.JaworskiellaLeanza is limited to its type species, whereas for certain convergent forms we proposeMoerickellanew genus (most likely the oldest Myophorellidae).Pseudovaugonianew genus likely descended fromMoerickellan. gen., rather than from the highly diversePromyophorellaKobayashi and Tamura, and is unrelated toVaugoniaCrickmay.Frenguelliella chubutensis(Feruglio) andPromyophorella basoaltorumnew species are the most frequently occurring species. Some species were probably endemic (e.g.,Promyophorella?sanjuaninanew species), although a few (such asFrenguelliella eopacificanew species andPoultoniella jaworskiinew genus new species) had a wide paleolatitudinal range and occur throughout the Pacific coasts and terranes of the Americas, revealing a significant faunal interchange among marine basins during Hettangian–Pliensbachian times. The well-documented Argentinian Early Jurassic record shows a rapid recovery and radiation of the Trigoniida after the Triassic/Jurassic extinction. Many of the new taxa that evolved in America eventually dispersed worldwide by Toarcian and Middle Jurassic times.UUID:http://zoobank.org/82c0d95e-f147-4736-a417-ebc252911181.

Diverse gas composition controls the Moby-Dick gas hydrate system in the Gulf of Mexico

AbstractIn marine basins, gas hydrate systems are usually identified by a bottom simulating reflection (BSR) that parallels the seafloor and coincides with the base of the gas hydrate stability zone (GHSZ). We present a newly discovered gas hydrate system, Moby-Dick, located in the Ship Basin in the northern Gulf of Mexico. In the seismic data, we observe a channel-levee complex with a consistent phase reversal and a BSR extending over an area of ∼14.2 km2, strongly suggesting the presence of gas hydrate. In contrast to classical observations, the Moby-Dick BSR abnormally shoals 150 m toward the seafloor from west to east, which contradicts the northward-shallowing seafloor. We argue that the likely cause of the shoaling BSR is a gradually changing gas mix across the basin, with gas containing heavier hydrocarbons in the west transitioning to methane gas in the east. Our study indicates that such abnormal BSRs can be controlled by gradual changes in the gas mix influencing the shape of the GHSZ over kilometers on a basin scale.

Foraminiferal stratigraphy and paleoenvironments of a high latitude marginal marine basin – A Late Cretaceous record from IODP Site U1512 (Great Australian Bight)

The 690 m core recovered at IODP Site U1512 offers unparalleled insights into climate during the peak and demise of the Cretaceous hothouse from the southern high latitudes. A new high-resolution micropaleontological record (notably deep water agglutinated foraminifera, DWAF) combined with additional geochemical data was produced from this locality, with the goal of recognizing benthic foraminiferal biozones, their relationship to the Tethyan realm and associated paleoenvironmental changes.We document a diverse benthic foraminiferal assemblage consisting of 162 taxa (110 agglutinated and 52 calcareous). The most common elements of the DWAF assemblage are tubular (i.e., Kalamopsis grzybowskii, Bathysiphon spp.) and planispiral forms (i.e., Ammodiscus spp., Haplophragmoides spp., Buzasina sp., Labrospira spp.). The Turonian strata yield abundant Bulbobaculites problematicus and Spiroplectammina navarroana. The presence of Uvigerinammina jankoi provides a tie point to the Tethyan DWAF biozonation of Geroch and Nowak (1984). The calcareous foraminiferal assemblage is composed of cosmopolitan deep-water forms including Lenticulina, Dentalina, Gavelinella/Anomalinoides, Praebulimina and Pseudobolivina.Organic geochemical data (notably steranes/hopanes ratios), foraminiferal assemblages, together with an increasing abundance of radiolaria reveal a complex and constantly changing marginal marine paleoenvironment. The prevailing regime (oxic or dysoxic, marine, or terrestrially influenced) was strongly influenced by paleobathymetry, unstable oceanic circulation and terrestrial runoff. These factors caused the paleoenvironment to change five times over 10 million years, each lasting <2 Ma. A major increase in the abundance of radiolaria (>50%) after the mid-Turonian followed a peak in the abundance of tubular epifaunal foraminifera during the lower to mid-Turonian. This is possibly related to an increase in bathymetry, that could correspond to a preceding sea level lowstand, and associated changes in ocean chemistry, such as changes in organic flux or salinity. Foraminiferal and geochemical evidence from Site U1512 allow for far-reaching interpretations of the paleoenvironments of the Great Australian Bight during the Late Cretaceous.

High Species Richness and Extremely Low Abundance of Cumacean Communities Along the Shelf and Slope of the Gulf of Guinea (West Africa)

The Gulf of Guinea belongs to the most scarcely sampled marine basins in the oceans of the world. We have analyzed diversity and distribution patterns of cumacean communities on the shelf and slope, along the coast of Ghana. The material was collected in October and November of 2012 using a van Veen grab (0.1 m2) on nine transects. Six stations were located at each transect (25, 50, 100, 250, 500, and 1,000 m). Sixty-three species of Cumacea were recorded withLeuconandEocumaas the most speciose genera, with 12 and eight species, respectively. Comparisons of species richness with literature data pointed that the Ghanaian coast hosts very diverse communities. About 95% of species were new to science, and the number of cumacean species known from the West Africa increased by over 100%. Nevertheless, most of the species had extremely low abundance, 13 singletons and 15 doubletons were found. Mean density of cumaceans was estimated at only 1.5 ind./0.1 m2. Species accumulation curve did not reach the asymptotic level, suggesting undersampling, despite the fact that sampling effort was high (250 samples). The highest species richness was recorded in the inner shelf (25–50 m) and on the slope (1,000 m). Cluster analysis separated shallow water communities from deeper regions on the shelf and upper slope. The most unique species composition was found at 1,000 m. Principal component analysis showed the importance of oxygen, sediments, and human-related disturbance for distribution of cumacean communities. In the shallows, oxygen content and presence of gravel were the most important factors structuring communities. In the deeper bottom areas (250–1,000 m), cumacean fauna was affected by local pollution, mainly by higher concentration of barium, other heavy metals, and THC.

Evidence for widespread wildfires and their environmental impact in the Late Cretaceous Canadian Arctic

Wildfires are important in modern ecology but the complex interplay between wildfires and vegetation or climate is less well understood in ancient environments, in particular those of the Arctic regions. This includes the impacts of paleo-wildfires on surrounding marine basins by affecting sedimentation rates and nutrient input via soil degeneration and intensification of continental run-off. The Late Cretaceous was an important time of global climate shift, with the rise of angiosperm vegetation marking a turning point in global flora, and globally abundant wildfires due to high atmospheric oxygen levels and elevated temperatures. This study investigates Late Cretaceous samples from the Canadian Arctic Islands to examine the evidence for widespread wildfires and how these wildfires may have influenced or been influenced by contemporaneous climate and vegetation shifts. Organic geochemical, and organic petrological data show evidence of enhanced wildfires beginning in the Turonian, including increases in semi-fusinite macerals and pyrogenic PAH (polycyclic aromatic hydrocarbon) indicators of natural combustion. This increasing wildfire influence corresponds with a rise in broad-leafed Arctic forests, as evidenced by angiosperm-derived terpenoid biomarkers, with both wildfire and angiosperm abundances peaking in the Early Campanian. Additionally, geochemical and petrographic data shows a shift in the type of organic matter deposited over time, correlating to the evidence of increased wildfire activity. This study proposes that the distance between wildfire region and marine depocenter is assessed via a new provenance method based on the degree of photo-oxic degradation of selected PAH isomers upon airborne transport. The increasing effects of wildfires on the Arctic ecosystem over the Turonian-Campanian were likely driven by relatively warm temperatures, elevated atmospheric oxygen, volcanism related to the High Arctic Large Igneous Province (HALIP), and abundant fuel availability. Widespread wildfires are proposed to have fostered the expansion of angiosperm vegetation into the Canadian Arctic in the Late Cretaceous by allowing them to outcompete gymnosperms in post-fire regrowth. Intensified erosion and continental run-off associated with the destruction of the vegetation cover by wildfires is thought to have acted as a driving force in the increasing terrigenous organic matter deposition in the Sverdrup Basin during the Late Cretaceous. Taken together, the results of this study suggest that increasing wildfires related to global climatic conditions in the Late Cretaceous contributed to the expansion of angiosperm flora in the Arctic, and had a substantial impact on the deposition of sediments in the surrounding Sverdrup Basin.

U-Pb Detrital Zircon Ages and Geochemical Features of the Jingxing Formation, (Qamdo Basin, Tibet: Implications): Inferences for the Metallogenic Model of the East Tethys Evaporite

Qamdo basin is located between the suture zone of Jinsha River (Ailao Mountains) and that of Ban Gong Lake (Nujiang) in the eastern Tethys. Part of the Jingxing Formation is deposited in the southwest of the basin. In this study, two profiles were investigated from the north and south of Qamdo basin. The characteristics of detrital zircon LA-ICP-MS U-Pb age, and the main and trace elements of sandstone were analyzed. The characteristics of major and trace elements showed that the tectonic setting of the study area is mainly composed of a relatively stable active continental margin and a passive continental margin, showing characteristics of a continental island arc. The weathering degree of Jingxing Formation in the Qamdo area is lower than that in the Lanping-Simao area, which may be closer to the origin. The age distribution characteristics of detrital zircon grains indicate that the Qiangtang Block, Youjiang basin, and Yangtze area jointly constitute the provenance of the Qamdo-Lanping-Simao basin. Both basins may be part of a large marine basin with unified water conservancy connection before evaporite deposition. Metamorphic seawater from the Qamdo basin may migrate to the Lanping-Simao basin and even the Khorat basin, where evaporite was deposited.

Refining the depositional model of the lower Permian Carynginia Formation in the northern Perth Basin: anatomy of an ancient mouth bar

The late early Permian coincided with a short-lived cold episode in Western Australia, which occurred long after the demise of late Paleozoic ice sheets, and is manifested by conspicuous dropstones in corresponding marine strata. In the northern Perth Basin, this time interval is represented by the Carynginia Formation, which has long been regarded as a record of low-energy marginal-marine sedimentation. The low-diversity body-fossil content and impoverished trace-fossil assemblages in the formation were recognised as evidence of low salinities, low dissolved-oxygen levels and high suspended-sediment concentrations presumably related to freshwater influxes into a restricted basin. However, sedimentary facies indicative of river processes have yet to be documented to explain the sedimentological and paleontological character of the formation. This study examines an overlooked sandstone-rich interval of the Carynginia Formation in the Irwin Sub-basin, a marginal half graben faulted against crystalline basement of the Yilgarn Craton and forming part of a series of late Paleozoic intracratonic rift basins in Western Australia. Facies analysis indicates that the lower part of the interval is dominated by storm-generated deposits containing extraformational pebbles and boulders. These deposits are interpreted as recording lower-shoreface sedimentation under the influence of seasonal sea ice, and constitute a shallower, sandstone-rich equivalent of mudstone-prone strata that otherwise characterise the Carynginia Formation. The upper part of the interval consists of river-borne deposits representing friction-dominated deposition of a river-mouth bar, the first direct record of deltaic sedimentation in the Carynginia Formation. The stratal organisation of mouth-bar bedsets is likely the result of successive sediment-laden pulses related to seasonal floods in a shallow marine basin, and the autogenic evolution of the mouth-bar complex in response to fluctuating river discharge and compensational stacking. Formative runoff events were arguably responsible for reductions in salinity and the introduction of turbid buoyant plumes into the shallow sea that were adverse to faunal development. A fluvial influence may explain the sedimentary character and fossil content of coeval mudstone-prone formations in Western Australian rift basins, especially in the vicinity of cratonic margins. KEY POINTS The lower Permian (late Artinskian–Kungurian) mudstone-prone Carynginia Formation in the northern Perth Basin has long been regarded as the record of low-energy, marginal-marine conditions in a cold-water seaway. The low-diversity fossil content in the lower part of the formation indicates stressed physico-chemical conditions influenced by freshwater, sediment-laden influxes. The described mouth-bar deposits are the first direct evidence of deltaic sedimentation in the Carynginia Formation, demonstrating that river outflows likely controlled water chemistry and impacted faunal development.