Marine Rocks Research Articles

Depositional sequences and sea level changes during Bathonian-Oxfordian, Kutch (Kachchh) Basin, Gujarat, India

The Kutch sedimentary basin is situated at extreme west of Indian Peninsula is an excellent example of cyclic sedimentation in Mesozoic shallow marine regime. The Bathonian to Santonian shallow marine rocks crops out in the Kutch Mainland extending for ~ 193 km from Habo in the east to Lakhpat in the west. Based on detail field studies in the Jhura dome, Kutch Mainland and laboratory investigations of 43 carbonate rock samples, the 370 m succession of carbonate-dominated rocks is stacked into three depositional sequences of regional importance. The 84 m Transgressive sequence-I of Bathonian age consisting of four microfacies assemblages represents an upward deepening facies succession. The 130 m regressive sequence of Callovian age composed of five microfacies assemblages showing upward shoaling facies succession. It was deposited during stillstand period followed by gradual increase in sediment supply. The 155 m transgressive sequence II of Early Oxfordian age consists of four microfacies assemblages that deposited during highstand of sea level in the basin together with episodic and less sediment supply. The relative sea level curves indicate high-order sea level variation during whole sequence before to major drop in sea level at the end of the transgressive sequence-II. The microfacies study reveals that these high order sequences are regionally comparable and might have been controlled by an active tectonic mechanism together with global sea level change.

Transgression–regression cycles drive correlations in Ediacaran–Cambrian rock and fossil records

AbstractStrata of the Ediacaran Period (635–538.8 Ma) yield the oldest known fossils of complex, macroscopic organisms in the geologic record. These “Ediacaran-type” macrofossils (known as the Ediacaran biota) first appear in mid-Ediacaran strata, experience an apparent decline through the terminal Ediacaran, and directly precede the Cambrian (538.8–485.4 Ma) radiation of animals. Existing hypotheses for the origin and demise of the Ediacaran biota include: changing oceanic redox states, biotic replacement by succeeding Cambrian-type fauna, and mass extinction driven by environmental change. Few studies frame trends in Ediacaran and Cambrian macroevolution from the perspective of the sedimentary rock record, despite well-documented Phanerozoic covariation of macroevolutionary patterns and sedimentary rock quantity. Here we present a quantitative analysis of North American Ediacaran–Cambrian rock and fossil records from Macrostrat and the Paleobiology Database. Marine sedimentary rock quantity increases nearly monotonically and by more than a factor of five from the latest Ediacaran to the late Cambrian. Ediacaran–Cambrian fossil quantities exhibit a comparable trajectory and have strong (rs > 0.8) positive correlations with marine sedimentary area and volume flux at multiple temporal resolutions. Even so, Ediacaran fossil quantities are dramatically reduced in comparison to the Cambrian when normalized by the quantity of preserved marine rock. Although aspects of these results are consistent with the expectations of a simple fossil preservation–induced sampling bias, together they suggest that transgression–regression and a large expansion of marine shelf environments coincided with the diversification of animals during a dramatic transition that is starkly evident in both the sedimentary rock and fossil records.

Silver, cobalt and nickel mineralogy and geochemistry of shale ore in the sediment-hosted stratiform Nowa Sól copper–silver deposit, SW Poland

The Nowa Sól deposit is a part of the newly discovered Northern Copper Belt and is situated some 30 km NW of the Lubin–Sieroszowice mining district (the so-called New Copper District) in SW Poland. The ore horizon spans across the upper part of the Lower Permian (Rotliegend) terrestrial redbeds and the lower part of the Upper Permian (Zechstein) marine rocks. It comprises three lithotypes: sandstone, shale and carbonate. The high-grade shale ore has polymetallic characteristics and is a crucial host for by-product metals such as Ag, Co and Ni (studied in this paper), but also Mo, V and Re. The results of bulk-rock and electron microprobe as well as mineralogical (optical and scanning electron microscope) data of the mineralized, organic-rich shale ore from the Nowa Sól deposit are presented. This thin stratigraphic horizon, ranging from 0.06 to 0.59 m, shows notable concentrations of critical metals, including on average 15.9 wt% Cu, 715 grams per tonne (g t -1 ) Ag, 318 g t -1 Co and 345 g t -1 Ni. It constitutes less than 10% of the total ore mass, but accounts for 36% of the Ag, 40% of the Ni and 42% of the Co found within the deposit. The ore sulfides in the mineralized shale in the Nowa Sól deposit include chalcocite, djurleite and bornite, accompanied by digenite, covellite, tennantite, galena, sphalerite and pyrite. The Ag content within the Cu sulfides exhibits a linear decrease: chalcocite > djurleite > bornite. Three primary Ag minerals are identified within the shale ore, namely native Ag, Ag amalgam and stromeyerite. Two types of Ag amalgam are observed: Hg-rich and Hg-poor. Cobaltite and gersdorffite represent the primary Co and Ni minerals, occurring as micrometre-sized inclusions within chalcocite and djurleite. Textural observations suggest that the Ag, Co and Ni mineralization postdates the major phase of Cu sulfide precipitation. It is shown that in the Nowa Sól deposit, the Kupferschiefer horizon has acted as a geochemical barrier for the above-mentioned metals during protracted time, from early syndepositional to late epigenetic stage of basin evolution. Supplementary material: The supplementary material contains the results of the electron microprobe analyses and the specific experimental conditions employed for these analyses – available at https://doi.org/10.6084/m9.figshare.c.6873631

Elemental and Sr–Nd isotopic evidence for unravelling the origin of the low-temperature geothermal fluids of Tivoli Terme (Latium, central Italy) between erosional S4 and S3 phases (upper Pleistocene) and neotectonics implications

Sr and Nd isotopic ratios along with (REE + Y) and other trace elements were measured in bedded travertines from three quarries at Tivoli Terme, Latium, aimed at deciphering their chemical and isotopic characteristics for the origin and evolution of fluids. Travertines, which were deposited between ∼81 and ∼54 ka BP, display high Sr and low REY contents along with REYPAAS patterns, supporting their fluid origin mainly from marine rocks, in particular the Upper Triassic Burano Evaporite Fm. This has been confirmed by the narrow ranges of δ87Sr and εNd values, close to those of that formation and other Mesozoic marine carbonates from central Italy. A sample of today's thermal water from Tivoli Terme provided a REYPAAS pattern and a δ87Sr value comparable with travertines, both features supporting that today's water is analog to past hydrothermal fluids. The overlap of the chemical and Sr–Nd isotopic compositions of coeval travertines and thermal waters from Tivoli and Acquasanta Terme, Marche, suggests a common fluid origin, ruling out any significant contribution from magmatic fluids/rocks to Tivoli travertines, yet deposited at the periphery of the Alban Hills volcano. Lastly, the geochemical results provide implications for regional neotectonics and the role of CO2-rich fluid pressure in fault activation, even in mildly active to almost inactive tectonic domains.

Hapalosiphonacean cyanobacteria (Nostocales) thrived amid emerging embryophytes in an early Devonian (407-million-year-old) landscape

Cyanobacteria have a long evolutionary history, well documented in marine rocks. They are also abundant and diverse in terrestrial environments; however, although phylogenies suggest that the group colonized land early in its history, paleontological documentation of this remains limited. The Rhynie chert (407Ma), our best preserved record of early terrestrial ecosystems, provides an opportunity to illuminate aspects of cyanobacterial diversity and ecology as plants began to radiate across the land surface. We used light microscopy and super-resolution confocal laser scanning microscopy to study a new population of Rhynie cyanobacteria; we also reinvestigated previously described specimens that resemble the new fossils. Our study demonstrates that all are part of a single fossil species belonging to the Hapalosiphonaceae (Nostocales). Along with other Rhynie microfossils, these remains show that the accommodation of morphologically complex cyanobacteria to terrestrial ecosystems transformed by embryophytes was well underway more than 400 million years ago.

Compound-specific carbon isotope measurements of individual lipid biomarkers from immature Ediacaran rocks of Baltica

Compound-specific carbon isotope ratios (CSIA) were measured for a suite of lipid biomarker compounds extracted from immature, late Ediacaran sedimentary rocks from drill cores sampled across Baltica. Using a newly developed picomolar‐scale CSIA (pico‐CSIA) method, we measured carbon isotope compositions of the abundant n-alkanes and hopanes, as well as C29 sterane, pristane, and phytane. Total organic carbon (TOC) of the Kotlin Regional Horizon in Baltica (Saint Petersburg area, Utkina Zavod drill core), from a low-salinity coastal environment, is consistently enriched in 13C by up to 10‰, compared to that for Redkino and Kotlin marine rocks from other locations in Baltica. This 13C enrichment is also recorded by the n-alkanes, hopanes, phytane, and C29 sterane. In all locations, the δ13C values of the C29 sterane are within 2‰ of the bacterial hopane δ13C values and within 0.7‰ of δ13CTOC, suggesting that the abundant hopanes within these sediments could be derived from RuBisCO Calvin-Benson-Bassham pathway-utilizing organisms, as well as from bacterial heterotrophs. Since δ13Clipid signature tracks δ13CTOC values for the Kotlin Regional Horizon samples from Utkina Zavod location, the significant 13C enrichments in this interval reflect either the δ13C composition of DIC used for autotrophy or a muted magnitude of carbon isotope fractionation during lipid biosynthesis, but are not due to enhanced preservation of organic compounds and geopolymers derived from 13C-enriched biochemicals. Pico-CSIA and biomarker data provide evidence for both regional environmental heterogeneity and secular changes in carbon cycling during deposition of sediments of the Kotlin and Redkino Regional Horizon intervals.

TYMKIVIA PRIMITIVA GEN. NOV. SP. NOV., A NEW TYPE OF FOSSILS FROM THE LATE EDIACARAN (VENDIAN) KANYLIVKA GROUP IN PODOLIA, UKRAINE

A thick sequence of Ediacaran (Vendian) deposits is exposed in the southwestern part of Ukraine along the valley of the Dniester River and its left tributaries. The stratigraphy and lithology of these deposits have been studied in some detail, but information on the fossil record is still very scarce. The Kanilovka Group sedimentary sequence has the lowest level of exploration. Tymkivia primitiva gen. nov. sp. nov. is described from Late Ediacaran shallow-water marine rocks of the Podolia region. The fossils are casts of the inner surface and imprints on the surface of bacterial mats (“death masks”) of small, sedentary sac-like organisms. Numerous imprints on the surface of mudstone and siltstone slabs testify to the existence of mass settlements of these organisms in the Volyn-Podilsky sedimentary basin in the Late Ediacaran. Morphological details that could be interpreted as a mouth, anus, and internal organs are not found in the fossils. Tymkivia was found in association with bacterial mat remains and the carbonaceous compressions of Vendotaenia, Kanilovia, and the problematic rod-shaped Harlaniella. Tymkivia is interpreted as possible remains of benthic plants; it is morphologically similar to some modern green algae. The option of interpretation as a fossilized record of the polyp stage of Medusozoa (Cnidaria) cannot be ruled out either. The appearance and disappearance of these organisms are the benchmarks of the stage of sedimentation of the Kanylivka Group.

Nitzschia captiva sp. nov. (Bacillariophyta), the essential prey diatom of the kleptoplastic dinoflagellate Durinskia capensis, compared with N. agnita, N. kuetzingioides and other species

ABSTRACT Durinskia capensis is a kleptoplastic dinoflagellate species from high intertidal marine rock pools, which can use a variety of diatoms for photosynthesis. However, very few of the diatoms permit indefinite survival of the dinoflagellate and rbcL sequences show that D. capensis isolated from nature contains one of two closely related Nitzschia species as its kleptoplastids. In culture, without a supply of these ‘essential’ Nitzschia cells to replenish the intracellular store of diatom plastids and other organelles, D. capensis eventually loses all its kleptoplastids and dies. Inside Durinskia, diatoms do not possess frustules and so cannot be compared morphologically with free-living forms. Recently, one of the essential Nitzschia species was isolated from the type locality of D. capensis and grown in culture, allowing comparison with similar Nitzschia species, particularly N. agnita and N. kuetzingioides, examined from type material. We conclude that the ‘essential diatom’ of D. capensis differs morphologically from these and other Nitzschia species and it is therefore described as N. captiva sp. nov. Nitzschia agnita and N. kuetzingioides, on the other hand, are conspecific and N. agnita has priority. Nitzschia captiva and N. agnita are extremely similar in valve shape, dimensions, pattern and ultrastructure, but can be separated by their girdle structure. Nitzschia agnita appears to be a freshwater species, though somewhat salt-tolerant. In contrast, N. captiva, which is known principally from records of the kleptoplastids of D. capensis rather than from frustules, is so far marine.

Integrated Characterization of Mudstones in the Andes of Colombia: Understanding Its Complexities for Risk Mitigation

This article presents a comprehensive vision of particularities and constraints of the Paja Formation in the Northern Andes of Colombia, supported by personal, institutional, and academic experiences, including a doctoral thesis in completion (geomorphology and risks research line). Such fine-grained marine rocks cause severe damage in diverse zones, with little spread, and are very unfavorable, especially within the Eastern Cordillera (departments of Santander and Cundinamarca), whose socio-environmental problems motivated a popular legal action in the municipality of Vélez due to the cracking and collapse of houses, damage to roads and landslides in the urban area, as well as flows, subsidence, and high hydrogeochemical dynamism or rare earths, although they also presented spontaneous ignition at the rural area. Understanding how these problems originate and interrelate is the main objective of the work. At the beginning, we include some brief definitions, terms, and key approaches to understand the consolidated geomaterials, location, and background of the problem; then, the results of meso–macro–micro studies, obtained by combining the field techniques and conventional instrumental laboratory analyses (tests on the chemistry of water and soil, description of samples with magnifying glasses, petrography with a polarized light microscope, micromorphology of regoliths–colluvions) of nanoscientists (emphasizing RXD-RXF, SEM, IR-Raman spectroscopy, TOC-TS) are presented. These characterizations and new knowledge must be socially and institutionally appropriated and applied in land use planning and risk management for the sustainability of challenging environments with the stratiforms of Lower Cretaceous rocks and associated Quaternary deposits in populated mountainous areas and contrasting intertropical hydroclimatological regimes, geologically active, so unstable and insecure.

Hydrocarbon generation and potential of marine source rocks in supercritical water

Water, in ultra-deep layers of the earth and in layers receiving abnormally high heat, can exist in a supercritical state. Supercritical water (SCW) can participate in the transformations of organic compounds not only as a solvent but also as a reactant, influencing petroleum formation and the evolution of sedimentary organic matter. Here, we carried out hydrous pyrolysis experiments in both SCW and water vapor (WV) using two organic-rich marine rocks under closed conditions, to quantitatively evaluate the generation potential of hydrocarbons in a supercritical state and to clarify the effect of water phase on hydrous pyrolysis experiments. The results showed that SCW promoted gaseous and liquid hydrocarbon generation and facilitated the cracking of aliphatic hydrocarbons. For gaseous hydrocarbons, the action of SCW became stronger as the temperature increased. For liquid hydrocarbons, the peak yields of bitumen were enhanced by the SCW, and the temperature corresponding to peak yield in SCW was lower than that in WV. These results were attributed to the supply of hydrogen and oxygen from SCW for the petroleum formation and cracking. The δ13C and δD values of gases were also influenced by SCW. However, these values obtained in SCW did not always become positive as their yields increased. Generally, methane (CH4) was enriched in 12C and 1H. The influence of SCW on the isotopic fractionation of ethane (C2H6) and propane (C3H8) was more complex. The water phase is an important factor affecting the experimental results of hydrous pyrolysis. From these findings, it can be concluded that SCW allowed for increased conversion of sedimentary organic matter to gaseous and liquid hydrocarbons in ultra-deep layers and layers affected by volcanic-hydrothermal activity.

Preservation of biotic and palaeoenvironmental signatures in organosulfur compounds of immature fine-grained sedimentary rocks

Organosulfur compounds (OSCs) in sedimentary rocks are considered to have formed primarily by abiotic incorporation of inorganic sulfur species into biogenetic functionalized molecules during early diagenesis, thus preserving carbon skeletons of appropriate biomolecules. OSCs could be characterized at a molecular level by Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) even when they are small in amounts and large in molecular weights. Herein, to reveal the palaeoecological and palaeoenvironmental information that OSCs have recorded but might not be contained in other biomarkers, OSCs’ composition in solvent extracts of rocks with different geological histories were determined utilizing FT-ICR-MS. The analyzed natural laboratories are the marine Schöneck, Dynow and Posidonia formations and the lacustrine Wealden Formation which are in the late diagenetic or early catagenetic stages.The prevailing iron-deficient sulfidic depositional settings of the marine Posidonia and Schöneck formations are reflected by abundant OSCs bearing up to three sulfur atoms. The high ratios of reduced relative to oxidized forms (Sz versus SzOx) further illustrate the restricted presence of oxidants at the oxic-anoxic interfaces. The high average oxygen numbers of S1Ox compounds and the exclusive presence of nitrogenous OSCs (SzNy and SzNyOx) found in the marine rock extracts document the high abundances of polyoxygenated compounds and proteinaceous moieties in marine organisms that can be sulfurized. In contrast, the lacustrine organisms contain abundant sulfurizable aliphatic moieties.The observed prominent enrichment of Sz and SzOx compounds containing 40, 35, 30, 25 carbon atoms are associated with the selective and efficient preservation of polyfunctionalized biomolecules via sulfurization, such as C40 carotenoids, C35 bacteriohopanepolyols, C30 unsaturated tetracyclic polyprenoid alcohols, or C25 or C30 highly branched isoprenoid (HBI) polyenes. The strong enrichment of sulfurized C35 bacteriohopanepolyols can be developed as an indicator of the low levels of oxygen exposure prior to sulfurization, which occur only in the Dynow and Schöneck formations. The prominent enrichment of sulfurized carotenoids is generally associated with high primary productivity. While the strongly enriched sulfurized HBI polyenes in the Upper Schöneck Formation is indicative for diatom blooms, the precursors of C30 pentacyclic polyprenoid organosulfur compounds are more abundant in fresh/brackish water algae.

Cultivating marine bacteria under laboratory conditions: Overcoming the "unculturable" dogma.

Underexplored seawater environments may contain biological resources with potential for new biotechnological applications. Metagenomic techniques revolutionized the study of bacterial communities but culture dependent methods will still be important to help the biodiscovery of new products and enzymes from marine bacteria. In this context, we promoted the growth of bacteria from a marine rock pond by culture dependent techniques and compared the results with culture independent methods. The total number of bacteria and diversity were studied in different agar plate media during 6 weeks. Agar plate counting was of the same order of magnitude of direct microscopy counts. The highest efficiency of cultivation was 45% attained in marine agar medium. Molecular analysis revealed 10 different phyla of which only four were isolated by the culture dependent method. On the other hand, four taxonomic orders were detected by cultivation but not by the molecular technique. These include bacteria from the phyla Bacillota and Actinomycetota. Our study shows that it is possible to grow more than the traditionally considered 1% of bacteria from a seawater sample using standard agar plate techniques and laboratorial conditions. The results also demonstrate the importance of culture methods to grow bacteria not detected by molecular approaches for future biotechnological applications.

Reservoir Characteristics of Fine‐grained Sedimentary Rocks in Saline Lakes in the Cenozoic Upper Ganchaigou Formation, Southwestern Qaidam Basin, NW China

AbstractCenozoic fine‐grained sedimentary rocks in the southwestern Qaidam Basin, as typical salinized lacustrine sediments, are significantly different from those in other freshwater lakes under the impact of the high salinity in the lake. Many fine‐grained sedimentary rock samples were selected from the lower member of Neogene (N1) in the Gaskule Oilfield, Qaidam Basin, northwest China, with the aim to analyze and test their petrology, pore structure, and organic geochemical characteristics and determine its genesis and geological significance. Based on previous results, a new genesis of mixed sedimentary rocks is proposed. The Cenozoic lacustrine fine‐grained sedimentary rocks in SW Qaidam Basin belong to mixed sedimentary rocks, which can be divided into three types, including carbonate and terrigenous clastic‐bearing mudstone, carbonate‐bearing to terrigenous clastic mixed sedimentary rocks, and carbonate‐terrigenous clastic mixed sedimentary rocks. The geneses of mixing are quite different from that of mixed marine rocks. According to the sedimentary characteristics of the salinized lakes, three new geneses of mixed deposits are proposed: syn‐sedimentary mixing, varve interbedded mixing, and biogenic mixing. The reservoir spaces of the Cenozoic lacustrine fine‐grained sedimentary rocks in SW Qaidam Basin include residual intergranular pores, intercrystalline pores, microfractures, and minor dissolved pores. The reservoirs have super‐low porosity and ultra‐low permeability, with a porosity of 1.82%–21.04%, averaging 7.71%, and permeability of (0.0028–254.86) × 10–3 μm2, averaging 2.82 × 10–3 μm2. The test results of total organic carbon (TOC) content show that the highest content of organic carbon reached 1.41%, and those of vitrinite reflectance show that Ro ranges from 0.525%–0.824%, with an average of 0.806%. The organic geochemical characteristics show that the fine‐grained mixed sedimentary rocks of SW Qaidam Basin have the potential for self‐generation and self‐storage. As an unconventional reservoir, it has potential industrial value. This is the first study of fine‐grained sedimentary rocks in the Qaidam Basin, which offers certain theoretical and practical values.

The retention of precursor biotic signatures in the organonitrogen and organooxygen compounds of immature fine-grained sedimentary rocks

To reveal the impact of biomass input (marine algae, terrestrial plants and lacustrine Botryococcus braunii) on the composition of high molecular weight organooxygen and organonitrogen compounds (Ox, Ny and NyOx), solvent extracts of immature–early mature rock and coal samples were systematically characterized by Fourier transform ion cyclotron resonance mass spectrometry using different ionization modes. In total, 16 samples from the marine Schöneck, Dynow and Posidonia formations, the lacustrine Wealden Formation and the terrestrial New Zealand coals were investigated.Coals as the in-situ deposits of terrestrial plants consist to a great degree of aromatic polyoxygenated Ox and N1Ox compounds, representing the degradation products of lignin like phenolic ketones and carboxylic acids as well as their condensation products with the degradation intermediates of labile organonitrogen compounds. Aliphatic Ox moieties derived from plant protective constituents principally waxes and cutan show a pronounced even or odd carbon number predominance of the C23–C33 species with C26, 28, 30 or C27, 29, 31 as the major homologs. In contrast, marine and lacustrine microbial communities contribute plentiful middle-chain C22, C24 or C23, C25 Ox compounds. Marine rock extracts are characterized by abundant organonitrogen compounds, especially N2 and N2Ox classes, interpreted as signatures of protein-rich marine algae that were successfully preserved via a degradation-recondensation pathway, whereas the low protein content of lacustrine Botryococcus braunii is reflected by a low amount of N1Ox and N1 classes. Highly aliphatic algaenan of Botryococcus braunii sterically protected its oxygen-bearing groups from degradation, leading to a great abundance of Ox compounds, furthermore, it characterizes the Botryococcus braunii source by substantial heteroatomic species containing more than 40 carbon atoms.

Integrated correlation of the Camaquã Basin (Southernmost Brazil) with other Ediacaran units of southwestern Proto-Gondwana

Ediacaran organic-walled microfossils (OWM) were recently reported for the Camaquã Basin. Sphaeromorphic acritarchs, such as Leiosphaeridia sp, Lophosphaeridium sp. and Germinosphaera, as well as one kind of ornamented microfossil (Tanarium irregulare) were extracted from rocks of either marine (Maricá Group) or continental (Bom Jardim, Santa Bárbara groups) depositional systems. The stratigraphic distribution of organic-walled microfossils within well age-constrained siliciclastic successions made it possible to correlate these microfossils with other coeval Ediacaran assemblages in the world, especially in southwestern Proto-Gondwana. This comparison has shown similarities and differences among them. The Camaquã Basin microfossils register a more extended time interval, but present a smaller diversification than the other assemblages, probably due to have lived within more stressing environments. These differences led us to create a new microfossil assemblage, the CAMBAP (Camaquã Basin Palynoflora) Assemblage, which represents an ecozone, with cosmopolitan microfossils living closely associated with microbial mats.

A nutrient control on expanded anoxia and global cooling during the Late Ordovician mass extinction

Expanded ocean anoxia and global cooling have been invoked as major causal mechanisms for the Late Ordovician mass extinction, but the factors underpinning the extinction remain unresolved. Here, we document two intervals of particularly intense phosphorus recycling in marine rocks deposited across a bathymetric transect in the Yangtze Shelf Sea. The first occurred during the initial phase of the extinction and, coincident with global cooling, drove the development of ocean euxinia on the shelf. The second re-established shelf euxinia after the peak of glaciation, leading to the second phase of extinction. Integration of these data into a global biogeochemical model indicates that phosphorus recycling would have doubled the long-term burial rate of organic carbon, driving ~4°C of global cooling. Thus, through its impact on both the spread of anoxia and global cooling, extensive redox-promoted phosphorus recycling was a critical factor in Earth’s first catastrophic loss of animal life.

Introduced predators and nest competitors shape distribution and breeding performance of seabirds: feral pigeons as a new threat

Petrels are particularly sensitive to predation by introduced species. Many populations have reduced their breeding ranges, currently mainly occupying predator-free sites. Breeding range reduction leads to interspecific competition for nesting sites, which can be detrimental to petrels. Here, we evaluate how the presence of introduced mammals (cats Felis catus and rats Rattus spp.) and potential competitors for nest sites (Cory’s shearwaters Calonectris borealis and feral rock pigeons Columba livia) shape the distribution, breeding density, and breeding performance of Bulwer’s petrel Bulweria bulwerii on Tenerife, the largest and most densely human populated of the Canary Islands. We estimated nest density, assessed the role of nest location and physical characteristics of nests on breeding success, and determined causes of breeding failure by introduced predators and competitors. Nest density was higher in predator-free colonies on marine rocks. Cat presence was the best predictor of nest density, but it was not correlated with either presence or abundance of competitors. Breeding success varied between years and colonies but was not related to nest characteristics. Pigeon competition for nests was the most frequent cause of breeding failure (7.3%), followed by rat predation (6.3%). We also compared petrel and pigeon nest cavities and found considerable overlap in the physical size of nest sites. Our study provides insights into an overlooked impact of the invasive rock pigeon: nest competition with small seabirds. We encourage more research on the effects of pigeons on nest density, as well as disease and pathogen transmission, and vegetation changes within seabird colonies.

Geoheritage in the Minett UNESCO Biosphere (Southern Luxembourg): Inventory, Evaluation, and Conservation Aspects of Representative Geosites

The southwestern part of Luxembourg, known as Minett in the local language use, exposes an exceptionally high diversity of marine near-shore sediment rocks from the Early to Middle Jurassic, owing to its proximal position at the north-eastern margins of the Paris Basin. The iconic Minette ironstone formation is known as the worldwide largest oolitic ironstone deposit from the last 500 my and the abandoned open cast mines are nowadays protected sites with a high biodiversity, intrinsically linked to geodiversity. The schistes bitumineux unit, a lateral equivalent of the well-known Posidonienschiefer of the Holzmaden region (South Germany), is frequently studied for its exceptionally preserved fossils of marine vertebrates, cephalopods, and insect remains, deserving its status as a Fossil-Lagerstätte of international relevance. Of regional importance are the Rumelange limestones, with coral patch-reef paleo-environments. The geomorphological main feature of the region is the Cuesta of the Middle Jurassic (‘Dogger-Schichtstufe’), with several outliers (‘Zeugenberge’) that represent widely visible landmarks in the landscape. In this paper, 16 geosites, representative of the geological, palaeontological, geomorphological, and hydrogeological heritage in the Minett UNESCO biosphere, are presented and evaluated according to scientific, educational, and geotouristic criteria.

Kinematics and Ar–Ar illite age of deformation in the late Paleozoic Chicomuselo Fold-Thrust Belt (CFTB), Chiapas, Mexico and tectonic implications

The Chicomuselo fold-thrust belt (CFTB) is perhaps the less known cover orogen in Mexico. It is exposed in southernmost Mexico, Guatemala and Belize, along a fringe of about 500 km long and 50–100 km wide, on the southern edge of the Maya tectonostratigraphic terrane. The CFTB is constituted by a succession of sedimentary late Paleozoic marine rocks that include the Santa Rosa Inferior, the Santa Rosa Superior, the Grupera and the Paso Hondo formations. Based on the fossil content of the Santa Rosa Inferior and Paso Hondo formations, the age of these units was constrained from the Mississippian to the late Wolfcampian (early Permian). These successions are folded and thrusted, affecting the two more competent upper formations, whereas the two finer-grained lower units are also highly foliated. Folds, thrusts, and axial-plane foliation (S1) are more consistent with a NE-SW shortening direction and the asymmetry indicates a vergence towards the NE. Such structures are unconformably covered by red-beds of the Middle Jurassic Todos Santos Formation. No angular unconformity was found among the Paleozoic formations, as reported in previous works, which indicates that shortening deformation may have occurred in an orogenic cycle that took place between the latest Permian and Triassic. Structures related to such deformation are cut by kink bands and lateral faults (both dextral and sinistral), spaced across the belt. In order to constrain the thermal conditions of deformation in the CFTB, about 53 samples of phyllite, slate and shale were collected, and their illite crystallinity index (ICI) determined along the belt axis. Calibrated ICI's indicate that deformation occurred between low epizone to the upper diagenetic zone (Kübler index between 0.2 and 1 Δ°2θ angle), with a slow increase in crystallite size from the lower to the upper units, along and across the belt. Deformation-related illite from the Santa Rosa Inferior and Paso Hondo formations was dated with the 40Ar-39Ar method. In the first sample, mica fish of tens of microns dominate the fabric, though a finer-grained illite parallel to the axial plane of late kink bands overgrows such fabric. In the second sample, only one generation of micrometric size illite is visible under the SEM. However, the characterization and dating of several clay size fractions (0.2–0.5, 0.5–1 and 1–2 μm, in addition to 2–4 μm in the first sample) indicate that both samples contain the same two end-member generations of illite, one formed during a first event of intense shortening at 252.3 ± 8.1 Ma, and another associated to spaced faulting formed at 175.1 ± 6.5 Ma. All these data indicate that all sedimentary units within the CFTB were shortened simultaneously during an orogeny that started in the Permian-Triassic threshold and were presumably affected by Middle Jurassic faulting during the opening of the Gulf of Mexico.

Cranium of an Eocene/Oligocene pheasant-sized galliform bird from western North America, with the description of a vascular autapomorphy of the Galliformes

We describe the fossil cranium of a pheasant-sized galliform land bird from latest Eocene or earliest Oligocene marine rocks of the Jansen Creek Member, Makah Formation (Washington State, USA), which is the only three-dimensionally preserved cranium of a Paleogene representative of the Galliformes. The specimen was freed from a hard calcareous nodule with dilute formic acid. Micro-computed tomography provided further osteological details and a virtual cranial endocast. The fossil exhibits a plesiomorphic temporal morphology, lacking an ossified aponeurosis zygomatica, a feature characterizing some extant Cracidae and most Odontophoridae and Phasianidae. Overall, the fossil is most similar to the skull of the Asian phasianid taxon Arborophila, but this resemblance may well be plesiomorphic for a more inclusive clade. Still, we consider it possible that the fossil represents an archaic member of the Phasianoidea, in which case it would be the earliest record of this taxon from the New World. The fossil exhibits a previously unnoticed cranial autapomorphy of galliforms, a foramen in the temporal region that enables the vena profunda to enter the braincase, for which the name foramen temporale venosum is here introduced. Consistently present in all studied extant galliform taxa and absent in all other extant birds, this foramen enables a vascular connection between the brain and the ophthalmic rete, the latter playing an important role in thermoregulation of the avian brain.