Early Marine Research Articles

Increasing terrigenous input into the continental margin seawater during the late Ediacaran, North China

The late Ediacaran period encompasses widespread glacial deposits and early animal radiation. The temporal and spatial context of these events is not well established. The possible links between the glacial deposits and late Ediacaran fossils are critical for understanding the co-evolution of early animals and marine environments. This study presents a detailed geochemical reconstruction from the Tuerkeng Formation on the western margin and the Dongpo Formation on the southern margin along the North China Craton (NCC). The two fossiliferous late Ediacaran formations cover a critical interval between the end of the Zhengmuguan-Luoquan glaciation and the occurrence of late Ediacaran tubular fossils (e.g., Shaanxilithes). The two formations' similar and intermediate CIA values indicate moderate weathering under a warm and humid climate. Stratigraphic covariation of water-insoluble elements in samples from Tuerkeng and Dongpo formations suggest a rapid input of terrestrial materials at the beginning of deglaciation, and these terrestrial materials continued to be input into the shallow marine environment along the western and southern margins of NCC during the deposition of the two formations. Accompanied by the continental weathering and erosion of fresh rocks during the postglacial period of late Ediacaran, abundant nutrients as well as the terrigenous materials would be continuously transported into the continental margin seawater, which may ultimately lead to the rise of the Ediacaran biota. Our results provide new insights into paleoenvironment conditions along the continental margin of NCC and highlight the critical role of the postglacial terrigenous input in the evolution of early animals.

Lower to Middle Triassic conodont biostratigraphy and carbonate carbon isotope chemostratigraphy of the Zuodeng area, Guangxi, South China, and its relevance for stratigraphic correlation from the Induan to the Anisian

The Nanpanjiang Basin in South China is a vital area for studying the Early Triassic marine ecosystem recovery in the aftermath of the end-Permian mass extinction (EPME). The Zuodeng sections (A, B, and C) are located on the Debao platform, one of the isolated shallow-water platforms within the Nanpanjiang Basin. This area preserves a relatively complete conodont succession from the Lower Triassic to the lower Middle Triassic. Here, a total of 12 conodont zones and 4 subzones are established, namely, the Hindeodus postparvus Zone, the Hindeodus sosioensis Zone, the Neoclarkina krystyni Zone, the Neoclarkina discreta Zone, the Neospathodus dieneri Zone (including the Neospathodus dieneri M1 and Neospathodus dieneri M3 subzones), the Neospathodus cristagalli Zone, the Neospathodus pakistanensis Zone, the Novispathodus waageni eowaageni Subzone, the Novispathodus waageni waageni Subzone, the Neospathodus yangtzeensis-Novispathodus shani Zone, the Novispathodus pingdingshanensis Zone, the Triassospathodus homeri Zone, the Neospathodus triangularis Zone and the Chiosella timorensis Zone.The Permian-Triassic boundary is placed at the base of Bed 48 in the Zuodeng A section, coinciding with the base of the widespread microbialite beds and the carbon isotope excursion. The Induan-Olenekian boundary is placed at the bases of Bed 86 and Bed 21 in the Zuodeng A and Zuodeng B sections, respectively, where Nv. ex gr. waageni occurs at or slightly below the peak of the positive δ13Ccarb excursion. The Smithian-Spathian boundary is recognized at the bases of Bed 92 and Bed 33 in the Zuodeng A and Zuodeng B sections, respectively, based on the first occurrence (FO) of Nv. pingdingshanensis near the middle point of the positive δ13Ccarb excursion. The Olenekian-Anisian boundary is drawn at the top of Bed 5 in the Zuodeng C section based on the FO of Ch. timorensis. The conodont zones recognized in the Zuodeng area correlate well with sections in South China and elsewhere worldwide. The Ns. yangtzeensis-Nv. shani Zone is newly established, and the recognition of this zone in several sections significantly improves the accuracy of stratigraphic subdivision and correlation of the Smithian. The conodont zones in the Zuodeng area thus provide a high-precision time scale for future studies on marine ecosystem recovery in the aftermath of the EPME and environmental events during the Early Triassic.

Depositional evolution in response to long-term marine transgression in the northern South China Sea

Research on the interaction between depositional evolution process and marine transgression is critical to understanding the transform mechanism of sedimentary systems and guiding hydrocarbon exploration. The early Miocene witnessed the most significant sea-level rise since the Cenomanian, which resulted in extensive marine-influenced deposits worldwide. However, the relationship between the process of depositional evolution and long-term marine transgressions (>1 Ma) remains poorly understood. The Pearl River Mouth Basin in the South China Sea offers a comprehensive deposition record of the early Miocene marine transgression. This study employs high-quality 3D seismic, well-logging, and core data to investigate the impact of the early Miocene transgression on the evolutionary dynamics of the sedimentary system. The regional sea level exhibited a prolonged rise of at least 100 m during the deposition period of the Miocene Zhujiang Formation, corresponding to the long-term marine transgressive in the South China Sea. Throughout this marine transgression, depositional systems developed in the study area include tidal flats, fan deltas, meandering river deltas, and shallow marine shelf sand bodies. The marine transgression process resulted in a significant change in depositional system types, which can be divided into seven units from Unit 1 at the bottom to Unit 7 at the top. The predominant deposition environment transitioned from tidal flats in Units 1-3 to meandering river deltas in Units 4-5, and finally to shallow marine shelf systems in Units 6-7. In the early stage (Units 1-3), the regional uplifts hindered sea level transgression and caused erosion, leading to the development of small-scale proximal fan deltas. In the middle stage (Units 4-5), these regional uplifts submerged, and meandering river deltas dominated with sediments derived from distant extrabasinal sources. During the late stage (Units 6-7), regional sea levels reached their peak, transforming the entire basin into a shallow marine shelf system. Additionally, this marine transgression significantly influenced the distribution of hydrocarbon resources. Notably, the shallow marine shelf sand bodies in Units 6-7 warrant substantial attention for future exploration. This study outlines the complicated transitional processes within depositional systems during long-term marine transgression events, holding relevance for the global evolution of marginal sea basins.

Sedimentary evolution and lake level fluctuations of Urmia Lake (north‐west Iran) over the past 50 000 years; insights from Artemia faecal pellet records

AbstractA 25 m long sediment core from hypersaline Urmia Lake (north‐west Iran) was studied for the Late Quaternary depositional history and palaeoclimate variations using the abundance and compositional characteristics of Artemia faecal pellets. Sediment analysis is supported by scanning electron microscopy – energy dispersive X‐ray spectroscopy, organic and inorganic carbon content measurements, and stable isotopes (δ13C and δ18O) from faecal pellet carbonates. The imprecise chronology of the core back to 50 kyr bp is supported by ten radiocarbon ages from faecal pellets and bulk sediments. The palaeoenvironmental record is subdivided into four periods: (i) During much of Marine Isotope Stage 3, a period of lake level lowering is characterized by a decreasing amount of faecal pellets, and an increasing amount of coated grains, sulphate minerals and reworked shell fragments. (ii) During late Marine Isotope Stage 3 and early Marine Isotope Stage 2 a lake level lowstand and a lake floor exposure is interpreted based on the relatively low abundance of pellets, which are multicoloured and appear together with volcanic lithics and rounded sulphate minerals. (iii) During late Marine Isotope Stage 2 the record is devoid of pellets but dominated by large sulphate crystals suggesting a prolonged low lake level. (iv) During Marine Isotope Stage 1 a relative lake level highstand is rapidly established with sediments that are highly abundant in fresh pellets. The modern lake level lowstand is represented by a salt crust. The δ13C and δ18O records measured from faecal pellet carbonates suggest a link with the precipitation versus evaporation balance in the lake over time. From bottom to top the linear trend towards more negative delta values illustrates the increasing amount of precipitation arriving at the lake from the Late Pleistocene to the Holocene. Two prominent isotope minima during the Late Pleistocene and one prominent minimum in the early Holocene mark relative high lake levels, which can also be linked to Lake Van in Turkey.

A clumped isotope diagenetic framework for the Ediacaran dolomites: Insights to fabric‐specific geochemical variabilities

AbstractWhile marine dolomites formed under near surface conditions have been considered to be potentially reliable archives of past oceanic conditions, this interpretation comes with significant challenges because diagenetic alteration frequently produces diverse fabrics with large geochemical variability. It has been suggested that the Ediacaran dolomites in South China (Hamajing Member, Dengying Formation) recorded the oceanic conditions present at the time they formed, yet these dolomites are composed of five different fabrics (stromatolitic, micritic, oolitic, saddle dolomites and fibrous–radial dolomite cements) and show large variations in multiple geochemical isotope proxies (carbon, oxygen, clumped, magnesium and the sulphur of carbonate‐associated sulphate). This study establishes a paragenetic sequence for these dolomites by combining the clumped and the oxygen isotopic compositions, thereby assessing whether they are geochemically representative of the original seawater. Using this diagenetic framework, the micritic and stromatolitic dolomites show a closed‐system behaviour (low water–rock ratios; <0.3) and are largely resistant to the hydrothermal alteration during late diagenesis. In contrast, the ooid and cement fabrics have been affected by the hydrothermal fluid precipitating saddle dolomite in the open‐system condition with the high stimulated water–rock ratios (>1). Furthermore, in a closed‐system environment, the elevated δ24Mg and δ34S values in the stromatolitic dolomite reflect the isotopic Rayleigh fractionation that enriches the 26Mg and 34S through rock‐buffered recrystallization, coupled with microbial sulphate reduction. These results demonstrate that the complex signals in early marine dolomite should be carefully evaluated when used as a palaeoproxy.

First Early Cretaceous sharks from India

ABSTRACT A small assemblage of first Early Cretaceous (Aptian) sharks from India is described from the Habur Formation of Jaisalmer Basin, Rajasthan state, western India. Based on isolated teeth, five lamniform genera, namely Cretalamna, Dwardius, Leptostyrax, Squalicorax, and ? Eostriatolamia are identified. Of these, the records of Dwardius and ? Eostriatolamia may possibly be amongst the globally oldest, and therefore paleobiogeographically significant. These finds open up new possibilities for collection and study of Early Cretaceous marine vertebrates from India.

Holocene geomorphological evolution of a sediment-starved coastal embayment in response to sea level change: Insights from the Qing'ao Embayment, southern China

Aiming to gain a better understanding of the response of sediment-starved coastal systems to the climate-driven sea level change, this study examines the Holocene evolution history of Qing'ao Embayment, southern China, as a case study. Results suggest three distinct stages of the evolution history: Stage 1 (8400–6000 cal yr BP) records an initial sedimentation phase associated with the early Holocene marine transgression into the embayment. Stage 2 (6000–3000 cal yr BP) records early sediment deposition under relatively strong hydrodynamic inshore/open-bay environment during early marine regression. Stage 3 (3000 cal yr BP to present) records two substages: Stage 3a relates to the semi-enclosed bay, intertidal and lagoonal salt marsh facies between 3000 and 1300 cal yr BP, and Stage 3b records the final infilling of the embayment into a lagoonal plain. This evolution model suggests that the rates of sea level change and sediment accretion are the two major controlling factors for the Holocene geomorphological evolution of sediment-starving coastal systems.Comparison of the evolution of Qing'ao embayment with sediment-supply rich large-river estuary/deltas reveals unique features in the response to Holocene sea level change of this sediment-starved embayment: During the early Holocene marine transgression, sediment starts to accumulate in the small embayment around 8400 cal yr BP, hundreds of years later than in large river estuaries. During 8400–6000 cal yr BP, sediment accretion rate remains dramatically lower than sea level rise rate, which results in the quick growth of sediment accommodation space during this stage. Around 6000 cal yr BP, though sea level has remained relatively stable and large-river deltas have been growing for about 1000 years, the sediment-starved embayment was still under shallow marine and/or open bay conditions. At 3000 cal yr BP, shoreline started to prograde in sediment-starved embayment, which is about 3000 years later than large river deltas. Finally, agricultural activity started around 1300 cal yr BP in the embayment, thousands of years later than large river deltas. Limited or minimal fluvial sediment supply to the small embayment has constrained the land expansion during the sea level stabilization since mid-Holocene, and the limited living space might result in the much later agricultural activity in such coastal system.Due to the different balances between sea level change and sediment flux, sediment-starved coasts are expected to be under higher risks than large river deltas. However, earlier and more extensive human activities in large river basins have resulted in the reduction of sediment discharge that heighten the risks of large river deltas against future sea level rise. Thus, more attention should be paid to the coastal sediment supply budgets in the context of the background of rising sea level.

Early Oligocene marine transgression and organic matter accumulation recorded in the upper Eocene to lower Oligocene Enping Formation of the Baiyun Sag, Pearl River Mouth Basin, South China Sea

The upper Eocene to lower Oligocene Enping Formation provides the primary source rocks for hydrocarbon accumulation in the Baiyun Sag, Pearl River Mouth Basin, South China Sea. Nevertheless, the depositional environment of this formation has been a subject of debate. This study confirms that the lower to middle members of the Enping Formation predominantly consist of lacustrine deposits, and a marine transgression occurred during the deposition of the Enping Formation’s upper member in the Early Oligocene period. This transgression is supported by an increase in paleosalinity proxies (B/Ga, Sr/Ba), greater negative S isotopic values of pyrite, and an increase in triaromatic dinosteroid concentrations in the upper member samples. A series of indicators (chemical alteration index, V/Cr and Ni/Co ratios) suggest that mudstones from the lower–middle member and the upper member were all deposited under warm-humid climate with the dysoxic-oxic water conditions. The mudstones from the lower–middle member and upper member were formed with low-to-moderate primary productivity under relatively strong dilution condition. The paleoredox and paleoproductivity were minimally influenced by marine transgression. Additionally, there is a weak correlation between the total organic carbon content and indicators of these depositional conditions. The input of terrigenous organic matter is a pivotal factor in regulating the accumulation of organic material within the Enping Formation. The multi-stage deltas likely played a significant role in supplying terrigenous organic matter, thereby influencing the distribution of organic-rich mudstone in the Baiyun Sag.

The Coupled Ice Sheet–Earth System Model Bern3D v3.0

Abstract Understanding climate variability from millennial to glacial–interglacial time scales remains challenging due to the complex and nonlinear feedbacks between ice, ocean, sediments, biosphere, and atmosphere. Complex climate models generally struggle to dynamically and comprehensively simulate such long time periods as a result of the large computational costs. Here, we therefore coupled a dynamical ice sheet model to the Bern3D Earth system model of intermediate complexity, which allows for simulating multiple glacial–interglacial cycles. The performance of the model is first validated against modern observations and its response to abrupt perturbations, such as atmospheric CO2 changes and North Atlantic freshwater hosing, is investigated. To further test the fully coupled model, the climate evolution over the entire last glacial cycle is explored in a transient simulation forced by variations in the orbital configuration and greenhouse gases and aerosols. The model simulates global mean surface temperature in fair agreement with reconstructions, exhibiting a gradual cooling trend since the last interglacial that is interrupted by two more rapid cooling events during the early Marine Isotope Stage (MIS) 4 and Last Glacial Maximum (LGM). Simulated Northern Hemispheric ice sheets show pronounced variability on orbital time scales, and ice volume more than doubles from MIS3 to the LGM in good agreement with recent sea level reconstructions. At the LGM, the Atlantic overturning has a strength of about 14 Sv (1 Sv ≡ 106 m3 s−1), which is a reduction by about one-quarter compared to the preindustrial. We thus demonstrate that the new coupled model is able to simulate large-scale aspects of glacial–interglacial cycles.

Bioproductivity and vegetation changes documented in Eifel maar lake sediments (western Germany) compared with speleothem growth indicating three warm phases during the last glacial cycle

Understanding supra-regional climate variability such as the changes in the North Atlantic realm is important to identify the drivers of the climate system. In this study maar lake sediments from the Eifel (western Germany) were analysed with a multi-proxy approach and compared to central and western European speleothem growth phases.Corg (chlorins) and the pollen assemblage were analysed from two sediment cores of the Hoher List infilled maar lake. To generate Corg (chlorins) and pollen records covering the entire last 130,000 yr b2k (years before year 2000 CE), the data from this study were stacked with published data from other Eifel maar lake sediment cores (Sirocko et al., 2013, 2021, 2022). The sediment cores from Hoher List infilled maar lake were dated by marker tephra layers giving chronological anchor points and the precise dating of the sediment cores was performed by the tuning of the Corg (chlorins) records to the NGRIP δ18O record (Rasmussen et al., 2014). The speleothems, whose growth phases are compared to the lake sediment proxy records, were compiled from the literature as well as speleothems from Dechencave (western Germany) dated by the 230Th/U-method in this study.The Corg (chlorins) variability shows the bioproductivity in the maar lake, which is related to water temperature and corresponds to the Greenland Interstadials (GIs) in the NGRIP δ18O record indicates its dependence on supra-regional climate variations in the North Atlantic. The pollen record shows three periods of forest with temperate forest species, during the Eemian, early Marine Isotope Stage (MIS) 3, and the Holocene. Speleothem growth in four caves in central and western Europe (Dechencave, Spannagel Cave, Hölloch Cave, Villars Cave) is predominantly sensitive to cold periods with glaciers and/or permafrost conditions above the caves inhibiting speleothem growth. The forested phases and phases of high bioproductivity in the Eifel correspond well with phases of speleothem growth indicating three warm phases in central Europe during the last glacial cycle.

Late Triassic–Jurassic bivalve biochronology, palaeogeography and palaeoenvironment of the Junggar Basin, NW China

Abstract The middle Mesozoic of the southern Junggar Basin is a source of abundant Late Triassic–Jurassic non-marine and Early Jurassic marine–littoral bivalves. The bivalve chronology provides a framework for dating the strata and documents Early Jurassic transgressions and the end-Triassic mass extinction in the Junggar Basin. The first occurrences (FOs) and last occurrences (LOs) of Utschamiella cf. tungussica and Utschamiella cf. obrutschevi lie in the basal upper Rhaetian. The FOs of Ferganoconcha sibirica , Ferganoconcha subcentralis , Unio manasensis , Unio mirabilis and Waagenoperna are at, and the FOs of Margaritifera isfarensis , Tutuella rotunda and Tutuella chachlovi adjoin, the base of the middle Sinemurian. The LOs of Yananoconcha hengshanensis and Waagenoperna are at the Lower–Middle Jurassic boundary. The LOs of Psilunio , Cuneopsis and F . subcentralis are near the Middle–Upper Jurassic boundary. Non-marine bivalves disappeared in the late Rhaetian, due to a sudden Norian–Rhaetian temperature drop. New forms did not return until the Sinemurian, when the climate warmed. The transgressions created low-relief terrestrial environments, in which organisms including bivalves thrived, leading to the formation of large quantities of coal, oil and gas. The Junggar Basin shifted from Arctic to subtropical latitudes in the Northern Hemisphere between the Early and Middle Jurassic.

Age and Tectonic Setting of Layered Lead–Zinc Ore Bodies in the Xiaohongshilazi Deposit: Constraints from Geochronology and Geochemistry of the Volcanic Rocks in Central Jilin Province, NE China

The newly discovered Xiaohongshilazi deposit located in Panshi City, central Jilin Province, NE China, is a medium-scale Pb–Zn–(Ag) deposit. The Pb–Zn–(Ag) orebodies are divided into layered and vein-type orebodies, which have different ore geneses. The layered Pb–Zn orebodies are mainly hosted within and spatially controlled by the volcanic rocks. To constrain the age and tectonic setting of the layered Pb–Zn mineralization, we completed laser-ablation–ICP–MS zircon U–Pb dating and whole-rock major and trace element analyses of the ore-bearing volcanic rocks. The dacite samples were confirmed as belonging to the Daheshen Formation and were the main ore-bearing volcanic rocks for the layered orebodies. They yielded concordia U–Pb ages of 278.1 ± 1.8 Ma and 278.3 ± 1.8 Ma, respectively, indicating that the volcanic rocks from the Daheshen Formation and related layered Pb–Zn mineralization were formed in the early Permian. The andesite and rhyolite located above the layered orebodies yielded concordia U–Pb ages of 225.0 ± 1.1 Ma, 225.3 ± 1.5 Ma, and 224.7 ± 1.2 Ma, respectively; these substances are considered to be of the Sihetun Formation and were first reported in the area. The dacite samples associated with layered Pb–Zn mineralization were high in SiO2 (62.54–65.02 wt.%), enriched in LREEs and LILEs (e.g., Rb, Ba, and K), and showed depletion in HFSEs (e.g., P and Ti). It showed slightly negative Eu anomalies (δEu = 0.60–0.65) and negative Nb anomalies, with Th/Nb (1.12–1.21) and La/Nb (2.8–4.7) ratios, presenting subduction-related arc magma affinity formed in an active continental margin setting. In agreement with previous studies on zircon Hf isotopes (εHf (t) = +0.23~ +10.60) of the volcanic rocks from the Daheshen Formation, we infer that they were derived from the partial melting of the depleted lower crust. In conclusion, mineralization characteristics, geochronological data, geochemical features, and regional tectonic evolution suggest that two Pb–Zn–(Ag) mineralization stages from the Xiaohongshilazi deposit occurred: the layered VMS-type Pb–Zn mineralization associated with the marine volcanic rocks from the early Permian Daheshen Formation, which was induced by the subduction of the Paleo-Asian oceanic plate beneath the northern margin of the North China Craton, and the vein-type Pb–Zn–(Ag) mineralization caused by the subduction of the Paleo-Pacific Plate in the early Jurassic. Considering this, along with the mineralization characteristics of the same-type polymetallic deposits in this region, we propose that the early Permian marine volcanic rocks have great prospecting potential for the VMS-type Pb–Zn polymetallic deposits.

Oxygenation of the Baltoscandian shelf linked to Ordovician biodiversification

AbstractMarine biodiversity increased markedly during the Ordovician Period (~487–443 million years ago). Some intervals within the Ordovician were associated with unusually rapid and prominent rises in taxonomic richness, the reasons for which remain debated. Links between increased oxygenation and biodiversification have been proposed, although supporting marine oxygen proxy data are limited. Here we present an expansive multi-site iodine-to-calcium (I/Ca) record from Lower–Middle Ordovician marine carbonates in Baltoscandia that provides a detailed account of the spatio-temporal development of oxygen conditions across this palaeoshelf. The data document progressive oxygenation of regional seafloor environments, with well-oxygenated waters sourced from the palaeoequatorward Iapetus Ocean and peak I/Ca values (that is, dissolved oxygen concentrations) coinciding with the most pronounced biodiversity increases and ecosystem reorganizations during this time interval. This occurred while the climate cooled, global sea level dropped and carbonate deposits became regionally dominant. The results suggest that ventilation of shelves played a critical role in regulating early Palaeozoic marine biodiversity via development of ecospace and aerobic–metabolic conditions.

Beringian Freshwater Mussel Beringiana beringiana (Unionidae) in Northeast Asia

The origin of the fauna of Beringia is a notable biogeographical puzzle. Large mussels of the genus Beringiana inhabit both Northeast Asia and the northwestern part of North America and thus provide an important model to investigate the paleobiogeography of Beringia and the past and current intercontinental species exchanges. Data on Beringiana distribution, morphology, genetics, and taxonomy are fragmentary or questionable. In this study, we summarized the data on its distribution in Northeast Asia, performed genetic analysis (cox1), and studied the variation in the shell morphology in samples from four isolated populations, including the putative sympatric species. Over ten large enclaves of Beringiana are currently known in Northeast Asia (east to the Verkhoyansk Range), mostly in the lower reaches of large rivers in northeastern Yakutia, Kamchatka, Magadan Oblast, and Khabarovsk Krai. These enclaves are far apart (several hundreds of kilometers) because the mussel is associated with muddy sand or pebbly sand bottom substrates and spreads through its glochidia, which are parasitic on the fish. Shell morphology can be highly variable even in a single population, overlapping the diagnoses of several Beringiana species (which are currently not recognized as valid). Our analysis of the cox1 sequence in four populations identified all individuals as B. beringiana. We evaluated the possible current and probable Late Pleistocene–Early Holocene freshwater and marine pathways of B. beringiana dispersal through the area of former Beringia, including the current intercontinental migration of glochidia on fish.

First report of the genus Thorectichthys (Ellimmichthyiformes) in America, from the Cenomanian deposits of the Cintalapa Formation, Chiapas, southeastern Mexico

The El Chango quarry is an outstanding paleontological site of Mexico. The marine limestones of this site represent a small outcrop of the Cintalapa Formation and bear a significant assemblage of Early Cenomanian continental plants plus marine crustaceans, decapods, mollusks, and fishes. This paper includes the description of a double-armored herring species from El Chango, which is named Thorectichthys fideli and belongs to the family Paraclupeidae, in the order Ellimmichthyiformes. This new species shares the diagnostic generic features with T. marocensis and T. rhadinus, two slightly younger North African species previously discovered in Cenomanian–Turonian deposits of the Akrabou Formation, Morocco. The new species has a couple of peculiar features never before observed in the ellimmichthyiforms; the caudal skeleton of this fish has four uroneurals, and the horizontal limb of the preopercle is dorsally notched allowing the superficial lateral exposure of a broad and massive posterior process of the quadrate. Including this species in a comprehensive phylogenetic analysis confirms the monophyletic nature of Thorectichthys and its inclusion as a basal clade of the family Paraclupeidae. Thorectichthys fideli sp. nov. adds to an increasing assemblage of Mexican Cretaceous ellimmichthyiforms that includes ancestral as well as more derivatives species that shows the broad Albian–Cenomanian distribution of the ellimmichthyiforms, along the epicontinental environments of the Tethys Sea.

A multi-population approach supports common patterns in marine growth and maturation decision in Atlantic salmon (Salmo salar L.) from southern Europe.

This study provides a regional picture of long-term changes in Atlantic salmon growth at the southern edge of their distribution, using a multi-population approach spanning 49 years and five populations. We provide empirical evidence of salmon life history being influenced by a combination of common signals in the marine environment and population-specific signals. We identified an abrupt decline in growth from 1976 and a more recent decline after 2005. As these declines have also been recorded in northern European populations, our study significantly expands a pattern of declining marine growth to include southern European populations, thereby revealing a large-scale synchrony in marine growth patterns for almost five decades. Growth increments during their sea sojourn were characterized by distinct temporal dynamics. At a coarse temporal resolution, growth during the first winter at sea seemed to gradually improve over the study period. However, the analysis of finer seasonal growth patterns revealed ecological bottlenecks of salmon life histories at sea in time and space. Our study reinforces existing evidence of an impact of early marine growth on maturation decision, with small-sized individuals at the end of the first summer at sea being more likely to delay maturation. However, each population was characterized by a specific probabilistic maturation reaction norm, and a local component of growth at sea in which some populations have better growth in some years might further amplify differences in maturation rate. Differences between populations were smaller than those between sexes, suggesting that the sex-specific growth threshold for maturation is a well-conserved evolutionary phenomenon in salmon. Finally, our results illustrate that although most of the gain in length occurs during the first summer at sea, the temporal variability in body length at return is buffered against the decrease in post-smolt growth conditions. The intricate combination of growth over successive seasons, and its interplay with the maturation decision, could be regulating body length by maintaining diversity in early growth trajectories, life histories, and the composition of salmon populations.

Biodeterioration and Chemical Corrosion of Concrete in the Marine Environment: Too Complex for Prediction.

Concrete is the most utilized construction material worldwide. In the marine environment, it is subject to chemical degradation through reactions with chloride (the most important ion), and sulfate and magnesium ions in seawater, and to biodeterioration resulting from biological (initially microbiological) activities, principally acid production. These two types of corrosions are reviewed and the failure of attempts to predict the degree of deterioration resulting from each is noted. Chemical (abiotic) corrosion is greatest in the splash zone of coastal constructions, while phenomenological evidence suggests that biodeterioration is greatest in tidal zones. There have been no comparative experiments to determine the rates and types of microbial biofilm formation in these zones. Both chemical and microbiological concrete deteriorations are complex and have not been successfully modeled. The interaction between abiotic corrosion and biofilm formation is considered. EPS can maintain surface hydration, potentially reducing abiotic corrosion. The early marine biofilm contains relatively specific bacterial colonizers, including cyanobacteria and proteobacteria; these change over time, producing a generic concrete biofilm, but the adhesion of microorganisms to concrete in the oceans has been little investigated. The colonization of artificial reefs is briefly discussed. Concrete appears to be a relatively prescriptive substrate, with modifications necessary to increase colonization for the required goal of increasing biological diversity.

Early marine carbonate cementation in a relict shelf-edge coral reef North of Miami, Florida: Pseudo-coupled depositional and diagenetic modeling

Carbonate depositional and early diagenetic processes overlap in time because of the high chemical reactivity of calcite. Previous studies have modeled early diagenesis in a static depositional framework. They followed a rule-based modeling approach instead of applying rigorous thermodynamics and reaction kinetics.This study has developed a pseudo-coupled approach based on a dynamic depositional framework and reactive transport modeling for diagenesis. It has been tested for the “Pompano” reef north of Miami, Florida. The model includes five reef parasequences deposited over 9.0 kyr with five facies zones. After deposition of the first parasequence, diagenetic processes are modeled. The resulting framework forms the starting condition for depositing the next parasequence. Subsequently, its diagenetic overprint and the continued overprint in the underlying parasequence(s) are modeled. These workflow steps are repeated until all five parasequences are covered.The results show the spatial and temporal development of calcite cementation and porosity distribution. During the reef catch-up phase, cement mainly developed at the depositional surface (up to 10% of the total sediment volume). During the keep-up phase, cement abundance increases to a maximum value of ∼17%. After the reef's demise, cement forms a crust at the sediment-water interface with up to 38% of the total sediment volume. In general, controlling factors of cement distribution include facies-specific flow velocities, reef facies, relative sea-level changes, depositional gaps, and seawater salinity.The modeling results of this study are well aligned with the actual cement and porosity distribution in the Pompano reef and with other sub-recent and ancient examples described in the literature. Pseudo-coupled depositional-diagenetic modeling represents a suitable approach for quantitative porosity prediction in comparable depositional and diagenetic settings. It reduces uncertainties in prediction at inter-well to prospect scale for oil and gas exploration, geothermal exploration, and subsurface storage of CO2.

Controls on preservation of organic matter during the Cenomanian Ocean Anoxic Event II (OAE2) and Turonian global sea-level rise: Agadir Basin, Morocco

The Ocean Anoxic Event II (OAE2) was a significant global event associated with a positive carbon isotope excursion, occurring from the Late Cenomanian to the Early Turonian (C/T). It has been commonly associated with enhanced organic carbon preservation. Carbon isotopic analysis carried out over the C/T interval in the Agadir Basin, Morocco, integrated with previous biostratigraphic data, allows a refined correlation of the OAE2 interval. Detailed sedimentary facies analysis identifies ten lithofacies that record the transition from shallow marine environments in the Late Cenomanian to relatively deeper conditions in the Early Turonian. The variation in lithofacies can be correlated to relative sea level changes that show a correlation to the global eustatic curve.The OAE2 interval comprises dark grey mudstones beds that display low total organic carbon (TOC) values. Trace element and facies analysis suggest dilution from high detrital influx, along with oxic water conditions and low productivity. OM-rich black mudstones are identified in post-OAE2 Early Turonian strata. Trace element analysis suggests this increase in organic matter accumulation was related to increased sea surface productivity and oxygen-depleted bottom water conditions, which facilitated organic matter preservation. Deposition of OM-rich black mudstones is widely reported during the global Early Turonian marine transgression, suggesting the very high sea level was a major control on organic matter generation and preservation.

Constraining the elemental stoichiometry of early marine life

Abstract The relative proportions of carbon, nitrogen, and phosphorus, commonly referred to as the Redfield ratio (106:16:1), have likely varied dramatically through Earth’s history in response to changes in oceanic redox state and nutrient availability. However, there have been few attempts to track long-term secular patterns in the elemental stoichiometry of marine life. We use a sediment reactive-transport (diagenetic) modeling approach to provide new constraints on the elemental stoichiometry of marine ecosystems during Earth’s early history, by simulating environmental conditions associated with the formation and deposition of suites of Archean sedimentary iron and phosphorus-bearing minerals. Our results suggest that siderite formation in porewaters linked to dissimilatory iron reduction but limited formation of authigenic P phases can only be reproduced when C to P ratios in marine biomass are at least 500 (mol/mol), approximately five times higher than the values that characterize the modern ocean. This constraint indicates that Archean oceans were strongly nutrient-limited.