Sedimentary Features Research Articles

Seismic geomorphology and evolution of the Melville Bugt trough mouth fan, northwest Greenland

Trough mouth fans on glaciated margins are a common sedimentary feature that contain a record of ice sheet advance and retreat across the continental shelf. This study uses 2D and 3D seismic reflection data across the Melville Bugt Trough Mouth Fan (MB-TMF), offshore northwest Greenland, to document its stratigraphic architecture, glacigenic landforms, and marine deposits. The MB-TMF stratigraphy is characterised by rapid progradation of the continental shelf (over 100 km since ∼2.7 Ma) and heterogeneous truncation or subsidence of topset strata. The variable topset character relates to the repeated growth and retreat of the Greenland Ice Sheet across the shelf since ∼2.7 Ma. Seismic geomorphology and facies analysis of the prograding clinoforms show repeated sequences of debris flow deposits and gullies that are taken to infer gravity-driven processes and the presence of meltwater-related hyperpycnal flows in areas proximal to the ice sheet on the outer shelf. Several sets of mega-scale glacial lineations confirm the presence and flow pathways of successive ice streams since ∼1.3 Ma. Evolution of the MB-TMF can be summarised into four stages that were controlled by variations in ice sheet erosion, topographic forcing of ice stream flow, and changes in accommodation related to glacigenic deposition and tectonic subsidence. These results show that during the Middle Pleistocene Transition there is an apparent switch from a meltwater-dominated depositional regime, to one with greater emplacement of materials by ice directly at the palaeo-shelf edge. These results provide significant new detail about the large-scale glacigenic and marine depositional processes during the repeated fluctuations of the northwest Greenland Ice Sheet into Melville Bugt since ∼2.7 Ma.

Migrated hybrid turbidite-contourite channel-lobe complex of the late Eocene Rovuma Basin, East Africa

Analysis of 3D seismic data and well log data from the Rovuma Basin in East Africa reveals the presence of a late Eocene channel-lobe complex on its slope. The first two channels, denoted as channel-1 and channel-2, are initiated within a topographic low on the slope but come to a premature end when they are blocked by a topographic high in the northwest region of the basin. New channels migrate southeastward from channel-1 to channel-6 due to the region’s sufficient sediment supply and stripping caused by bottom currents. The primary factors controlling the development of the channel complex include its initial paleo-topographic of seafloor, the property of gravity flows, the direction of the bottom current, and the stacking and expansion of its levees. The transition zone from channel to lobe can also be clearly identified from seismic sections by its pond-shaped structure. At a certain point, thest systems record a transiton from erosive features to sedimentary features, and record a transition from a confined environment to an open environment. Channels and lobes can be differentiated by their morphologies: thick slump-debris flows are partly developed under channel sand sheets, whereas these slump-debris flows are not very well developed in lobes. Well log responses also record different characteristics between channels and lobes. The interpreted shale volume throughout the main channel records a box-shaped curve, thereby implying that confined channel complexes record high energy currents and abundant sand supply, whereas the interpreted shale volume throughout the lobe records an upward-fining shape curve, thereby indicating the presence of a reduced-energy current in a relatively open environment. Within the Rovuma Basin of East Africa, the average width of the Rovuma shelf is less than 10 km, the width of the slope is only approximately 40 km, and the slope gradient is 2°–4°. Due to this steep slope gradient, the sand-rich top sheet within the channel also likely contributes to the straight feature of the channel system. It is currently unclear whether the bottom current has any effect on its sinuosity.

The Bawang Member, a unique unit of Belaga Formation in the Miri Zone, Central Sarawak, NW Borneo Malaysia: Revised stratigraphic and sedimentological characteristics

Bawang Member (Unit 4) of Late Eocene age is the fifth and the youngest member of Belaga Formation. In general, the Late Cretaceous to Late Eocene turbidite sequence of Rajang Group in the lower Rajang area (Central Sarawak) is characterized by Belaga Formation. This member is unique and is only exposed in the vicinity of the Tatau area (Arip valley and Tatau High region) with limited exposures. In this research we present new evidence, to support its position on the stratigraphic column, based on field observations (stratigraphic and sedimentological characteristics) and lab analysis (TOC). Numerous recently exposed sections were visited in the study area. Four litho-facies were identified in the Bawang Member based on sedimentological observations; (1) Massive sandstone facies (SF1), (2) Medium to thick-bedded sandstone facies (SF2), (3) Thin bedded heterolithic facies (SF3), and (4) Mudstone or Shale facies (SF4). Reddish maroon and green shales exposed in Tatau High region are only exposed in another member of Belaga Formation i.e. Kapit Member. The Bawang Member sediments differ from the Tatau High region sediments in absence of cleavage and internal sedimentary features (rip-up clasts), the occurrence of bioturbation, and with lesser exposures of mud facies. On the contrary, the Tatau High sediments show higher ratios of mud facies, presence of cleavage in shales and even in few sandstones, and absence of major bioturbation of strata. The presence of internal sedimentary features (rip-up clasts) in Tatau High and in Kapit Member supports the idea that these are the parts of the same rock unit. Furthermore, contrasting TOC values between these two units (Bawang and Tatau High), and the similarity of TOC among Tatau High and Kapit Member are also in support of the same idea. Based on the differences of facies (rock) types, the effect of cleavage, absence of rip-up clasts, the occurrence of bioturbations and different TOC values, we confirm that the Tatau High rocks must be older than most of Bawang Member exposures and are actually the faulted blocks of Kapit Member.

Monogenetic volcanoes with initial phreatomagmatic phases in the Ceboruco graben, western Mexico: The cases of Potrerillo I, Potrerillo II, and San Juanito

Potrerillo I, Potrerillo II, and San Juanito volcanoes are part of the 28 Late Quaternary monogenetic eruptive vents concentrated along a ~2-km-wide and ~30-km-long stripe in the vicinity of Ceboruco stratovolcano (western Mexican Volcanic Belt). The studied volcanoes are closely spaced and located within a ~12 km2 sub-drainage basin, northwest of Ceboruco's edifice. Eruptive dynamics were inferred from sedimentary, stratigraphic, and pyroclast characteristics. Unlike Potrerillo I, which was formed by an entirely dry explosive magmatic eruption, evidence for the prevalence of initial short-lived phreatomagmatic phases was found for the Potrerillo II and the San Juanito eruptions that ended effusively.In this study we examine the nature and proportion of different types of pyroclasts within the exposed deposits of these three volcanoes, as well as their sedimentary features to better understand the initiation and progression of their eruptions. Our results indicate that both Potrerillo II and San Juanito tephra ring deposits show dominantly atypical, crudely bedded, coarse-grained deposits where the evidence for energetic, diluted pyroclastic density currents is scarce or subordinated. Instead, low energy, shallow seated, phreatomagmatic explosions generated medium-to-coarse grain-sized pyroclasts that were transported within dense tephra jets that were ballistically ejected, which on deposition formed non-turbulent currents with non-extensive lateral movement. The nature of such eruptive style was controlled by the substrate hydrogeology conditions that prevailed at the time of the eruption. So, magmas of different composition (dacitic for Potrerillo II, and basaltic andesite for San Juanito) followed similar dynamics when interacting with water. We propose that fractured aquifers with shallow water tables (or even surface water) existed at the time of both eruptions and interacted explosively with the magmas.In contrast, the construction of Potrerillo I scoria cone, which is related exclusively to explosive magmatic activity, does not show evidence of phreatomagmatic activity. This eruption may have occurred when the water table was deep, or surface water was unavailable. The variations in the depth of phreatomagmatic explosions, the availability of the water involved in the phreatomagmatic phases, and the absence or presence of these phases in the studied volcanoes were probably strongly influenced by the water-bearing conditions of the aquifers at the time of the eruption, which in turn, depended on the amount and distribution of annual rainfall.This study improves our understanding of phreatomagmatic eruptions of diverse magmatic compositions in similar settings. The recognition of associated hazards will allow to further define eruptive scenarios of monogenetic eruptions and help update the volcanic hazard map of the Ceboruco volcano area in the future.

Applying deep learning for identifying bioturbation from core photographs

Advances and availability of deep learning (DL) software have recently allowed the development, testing, and deployment of automated image classification schemes for sedimentary features from core images. The development of these methods is especially relevant for extracting useful geological features from otherwise unused core photographs. This paper demonstrates and tests the use of a DL workflow for the automated extraction of bioturbation data from a core photograph data set. The proposed workflow includes extracting image tiles from core photographs along a grid and referencing each tile with collected sedimentary data. Each labeled image tile is then used as a training and testing input for a machine learning algorithm. This method allows users to quickly generate thousands of labeled training images. To demonstrate and test this workflow, a data set was collected using PyCHNO™, an open-source software specifically designed to collect sedimentary data from core photographs. The resulting data set comprising 13,545 tiles of 128 × 128 pixel resolution is used to train a DL algorithm to automatically predict if a core photograph contains evidence of bioturbation. The trained model was able to predict whether or not an image demonstrated evidence of bioturbation with up to 88% accuracy. The workflow demonstrates one of many possible applications for automatically extracting biogenic or physical sedimentary structure data from core photographs. Models built using this approach can be used to “seed” wells from a given area or interval, which can therefore significantly increase the value of core photograph data sets with relative ease.

Denitrification, Nitrogen Uptake, and Organic Matter Quality Undergo Different Seasonality in Sandy and Muddy Sediments of a Turbid Estuary.

The interaction between microbial communities and benthic algae as nitrogen (N) regulators in poorly illuminated sediments is scarcely investigated in the literature. The role of sediments as sources or sinks of N was analyzed in spring and summer in sandy and muddy sediments in a turbid freshwater estuary, the Curonian Lagoon, Lithuania. Seasonality in this ecosystem is strongly marked by phytoplankton community succession with diatoms dominating in spring and cyanobacteria dominating in summer. Fluxes of dissolved gas and inorganic N and rates of denitrification of water column nitrate (Dw) and of nitrate produced by nitrification (Dn) and sedimentary features, including the macromolecular quality of organic matter (OM), were measured. Shallow/sandy sites had benthic diatoms, while at deep/muddy sites, settled pelagic microalgae were found. The OM in surface sediments was always higher at muddy than at sandy sites, and biochemical analyses revealed that at muddy sites the OM nutritional value changed seasonally. In spring, sandy sediments were net autotrophic and retained N, while muddy sediments were net heterotrophic and displayed higher rates of denitrification, mostly sustained by Dw. In summer, benthic oxygen demand increased dramatically, whereas denitrification, mostly sustained by Dn, decreased in muddy and remained unchanged in sandy sediments. The ratio between denitrification and oxygen demand was significantly lower in sandy compared with muddy sediments and in summer compared with spring. Muddy sediments displayed seasonally distinct biochemical composition with a larger fraction of lipids coinciding with cyanobacteria blooms and a seasonal switch from inorganic N sink to source. Sandy sediments had similar composition in both seasons and retained inorganic N also in summer. Nitrogen uptake by microphytobenthos at sandy sites always exceeded the amount loss via denitrification, and benthic diatoms appeared to inhibit denitrification, even in the dark and under conditions of elevated N availability. In spring, denitrification attenuated N delivery from the estuary to the coastal area by nearly 35%. In summer, denitrification was comparable (~100%) with the much lower N export from the watershed, but N loss was probably offset by large rates of N-fixation.

PROCESSOS FLUVIOMARINHOS ASSOCIADOS À FORMAÇÃO DA ILHA RASA, SUL DA BAÍA DE MARAPATÁ, NORDESTE DO PARÁ, BRASIL

As ilhas assumem expressivo destaque na paisagem estuarina paraense; contudo, a maior parte delas apresenta gênese não claramente definida. A fim de investigar os fatores de formação da ilha Rasa, situada na foz do rio Tocantins, estuário do rio Pará, o presente trabalho se apoia em feições sedimentares identificadas em um testemunho de sedimento coletado no interior da ilha. Neste trabalho, a integração faciológica e a interpretação de seus ambientes deposicionais, em associação aos eventos climáticos reportados para a região, subsidiaram a proposição de modelo morfogenético. O modelo aqui proposto sugere que a ilha Rasa possui idade tardio-holocênica e consistia, incialmente, de barras arenosasque evoluíram sob o efeito de processos fluviais, inerentes à rede de drenagem e marinhos, articulados às mudanças no clima e nível do mar. Esses processos afetaram o suprimento de sedimento e a distribuição da cobertura vegetal, influenciando a configuração do setor estuarino e contribuindo para a formação de ilhas proximais.
 Palavras-chave: barra arenosa, estuário, nível relativo do mar, ambiente sedimentar, rioTocantins.

Isolation of the South China Sea from the North Pacific Subtropical Gyre since the latest Miocene due to formation of the Luzon Strait

The North Pacific subtropical gyre (NPSG) plays a major role in present global ocean circulation. At times, the gyre has coursed through the South China Sea, but its role in the evolutionary development of that Sea remains uncertain. This work systematically describes a major shift in NPSG paleo-circulation evident from sedimentary features observed in seismic and bathymetric data. These data outline two contourite depositional systems—a buried one formed in the late Miocene, and a latest Miocene to present-day system. The two are divided by a prominent regional discontinuity that represents a major shift in paleo-circulation during the latest Miocene (~ 6.5 Ma). The shift coincides with the further restriction of the South China Sea with respect to the North Pacific due to the formation of the Luzon Strait as a consequence of further northwest movement of the Philippine Sea plate. Before that restriction, data indicate vigorous NPSG circulation in the South China Sea. Semi-closure, however, established a new oceanographic circulation regime in the latest Miocene. This work demonstrates the significant role of recent plate tectonics, gateway development, and marginal seas in the establishment of modern global ocean circulation.

Extra-large grains in Late Glacial – Early Holocene aeolian inland dune deposits of cold climate, European Sand Belt, Poland: An evidence of hurricane-speed frontal winds

Only exceptionally, grains larger than 2–3 mm are involved in dune-forming processes. In 16 Late Glacial – Early Holocene inland dunes deposits from three regions of the northern and central Poland, beds, layers, laminae and lenses containing extra-large grains, up to 20.5 × 12.5 × 11 mm in the longest axes, are present. Occurrences of the extra-large grains are documented in the dunes dispersed in three distinct physiographic regions, Biebrza Basin, Central Poland Lowlands, Przedbórz Upland and the adjacent part of the Włoszczowa - Nida Basin. An aeolian genesis of these deposits is proven by sedimentary features and morphology of the landforms, including simple forms of parabolic, longitudinal and transverse dunes, as well as large, complex depositional forms. The extra-large grains occur at various depths in the sandpit sections, ranging from a few tens of centimetres just the above contact of dune deposits with the substrate up to a few tens of centimetres below the top of the dune section. Outcrops with the extra-large grains are located on both lee and stoss sides in the dune landforms. Deposits bearing extra-large grains show nearly horizontal and low angle lamination, which is typical of the dune stoss sides, to high angle foresets, which are typical of lee sides of dune landforms. Several sites display up to seven layers of the extra-large grains, indicating a few episodes of extremely strong and relatively steady wind during the dune-forming period. Estimation of the wind velocity threshold for such coarse material shows values between 23 and 82 m s−1, for speeds 1 m above the surface. On the basis of measured dimensions and volumes of particular pebbles, a principal component analysis demonstrates that the distribution of grain dimensions is clearly heterogeneous between the three physiographic regions of northern and central Poland. The concentration of values from the Central Poland Lowlands dataset is significantly higher than in the other two regions. This might have been caused by the lack of wind-flow terrain constraints in the mostly flat area of the Central Poland Lowlands. In contrast, the relatively high variance of grain dimension parameters could have been caused by the inconstancy of wind velocity and direction over the undulated morphology of the other two regions. The prevailing western direction of transportation points to frontal, episodically hurricane-speed winds (>20–40 m s−1), which were able to transport the extra-large grains during Late Glacial – Early Holocene times, in the area south of the Scandinavian ice sheet. The relatively rare occurrence of layers and laminae with extra-large grains in the investigated dune deposits suggests specific processes leading to their formation. However, reports of 16 outcrops with the extra-large grains imply that aeolian transport of very coarse material is not only a scientific curiosity, but a process occurring on a broader scale.

Study on sedimentary facies characteristics of Xujiahe Formation in Sichuan Basin

Sedimentary facies is the summation of all primary sedimentary features in a sedimentary unit, which is the product of sedimentation in a specific environment. It emphasizes the material performance of sediment formation conditions, including mineralogy, petrology, paleontology, geochemistry and geophysics. Therefore, it has unique sedimentary features in this environment. In this paper, the types and units of sedimentary facies which can reflect the basic characteristics and geometry of sedimentary system are established, and based on the comprehensive analysis of rock types, lithological assemblages, sedimentary structures, palaeontological assemblages and section structures, the sedimentary facies types of Xujiahe formation of Upper Triassic in the study area mainly include semi-arid flooded basin facies, delta facies, beach bar-lagoon system and lake facies, among which delta facies and beach bar-lagoon system are the main sedimentary facies types. Because sedimentary facies is the historical product of basin formation, evolution and extinction, it can not only reflect the formation conditions, temporal and spatial distribution and evolution law of related strata and rock types, but also be the basis for analyzing the nature and structural background of sedimentary basin. At the same time, the analysis of sedimentary facies is of great significance for understanding and analyzing the evolution history of basin and guiding the exploration and development of related oil and gas resources.

GAS SIPS AND SHALLOW ACCUMULATIONS OF GAS ON THE SHELF OF TURKEY IN THE BLACK SEA

It has been suggested that shelf and slope sediments of high deposition rate are methane sources, whereas the deep basin is methane sink. The methane production and migration in sediments may cause massive slope failures so methane is geologically important. Methane production is also economically important as methane seeps may indicate the presence at depth of hydrocarbon reservoirs, and methane hydrate may be an important source of energy. Recent studies in marine geology indicate potential geo-resources in the Turkish coast of Black Sea. The Black Sea sediments are rich in calcite and organic carbon, the latter showing a high degree of preservation due to anoxia in the waters below 100-150 m. Different marine geophysical surveys at different times were carried out in order to understand the sedimentary features of gas-saturated sediments in the Black Sea. Multibeam, side scan sonar, sub-bottom profiler and multi-channel seismic data were collected to make both high-resolution bathymetric and reflectivity maps of the seafloor. In some cruises, deep-tow combined side scan sonar and subbottom profiler was used to obtain acoustic images of both the seafloor surface and subbottom sediments. Several different structures were observed in the Black Sea basin as slumps, pockmarks, faults, gas chimneys, shallow gas accumulations and dome-like structures. Structures, which contain gas hydrates, are present on the seismic sections as strong acoustic reflections.

Topographic and geomorphological features and tectogenesis of the southern section of the Kyushu-Palau Ridge (KPR) and its adjacent areas

The Philippine Sea is the largest marginal sea in the Western Pacific Ocean and is divided into two parts by the Kyushu-Palau Ridge (KPR). The western part is the West Philippine Basin, and the eastern part consists of the Shikoku and Parece Vela basins. Based on surveyed data of massive high-resolution multibeam bathymetric data and sub-bottom profiles data collected from the southern section of the KPR from 2018 to 2021, this paper analyzes the topographic and geomorphological features, shallow sedimentary features, and tectonic genesis of the southern section of the KPR, obtaining the following conclusions. The southern section of the KPR has complex and rugged topography, with positive and negative topography alternatingly distributed and a maximum height difference of 4086 m. The slope of seamounts in this section generally exceeds 10° and is up to a maximum of 59°. All these contribute noticeably discontinuous topography. There are primarily nine geomorphological types in the southern section of the KPR, including seamounts, ridges, and intermontane valleys, etc. Among them, seven independent seamount groups are divided by five large troughs, forming an overall geomorphological pattern of seven abyssal seamount groups and five troughs. This reflects the geomorphological features of a deep oceanic ridge. Intramontane basins and intermontane valleys in the southern section of the KPR are covered by evenly thick sediments. In contrast, sediments in ridges and seamounts in this section are thin or even missing, with slumps developing locally. Therefore, the sediments are discontinuous and unevenly developed. The KPR formed under the control of tectonism such as volcanic activities and plate movements. In addition, exogenic forces such as underflow scouring and sedimentation also play a certain role in shaping seafloor landforms in the KPR.©2021 China Geology Editorial Office.

The Precambrian Hazara Formation from Hazara Mountains, Northern Pakistan

The late Neoproterozoic Hazara Formation along the Lora Maqsood Road near Haripur, Lesser Himalayas, North Pakistan, is studied for sedimentology, petrography, and major and trace element analysis to determine the paleoenvironment, provenance, paleoweathring intensity, and tectonic settings. The Hazara Formation is characterized by greywacke sandstone, siltstone, shale, argillite, claystone, limestone, and coarsening and finning upward turbidite lithofacies. Based on bedding style, grain size, and sedimentary structures, 11 types of lithofacies were identified within the sequence. The macroscopic studies indicate that the sequence has undergone through slight metamorphism although the texture is altered sedimentary features and bed geometries are well preserved. Compaction seems to affect the part of argillaceous sediments of an enormous thickness of the Hazara Formation to make slate-like appearance which may preferably be called argillites. The same effect is seen on sandstone to make it so hard to name it orthoquartzite. Petrographic analysis of limestone reveals that the limestone is micritic in nature; stylolites and pressure solution structures are also present in the limestone. The petrographic analysis of sandstone categorized it as feldspathic greywacke in the QFR diagram. The quartz content is higher in sandstone and may reach to 70% which indicates a weathered felsic source. The petrographic analysis suggests a continental block provenance with stable craton and an uplifted basement source. The Chemical Index of Alteration and the Chemical Index of Weathering values indicate moderate to high weathering conditions with a warm and moist climate in the source region. A sedimentary-tectonic model based on the geochemical data of sandstone indicates deposition along with active continental margin tectonic settings. The paleocurrent flow analysis indicates that the dominant source region of the sediments of the Hazara Formation was situated south to southeast, which may probably be the central Indian craton, Aravali orogeny, and Bundelkhand craton of southern India.

Responses of fluvial terrace formation to monsoon climate changes in the north-eastern Tibetan Plateau: Evidence from pollen and sedimentary records

Climate factors, including precipitation and related vegetation cover, which are vital features of monsoon climates, differ across global/regional areas and are highly variable on a catchment scale. The correlation between fluvial processes and the phases of monsoon climate change are poorly understood in the north-eastern Tibetan Plateau (NETP), partially because direct monsoon climatic proxies from fluvial sediment are lacking. In this study, we compared the fluvial activity with monsoon climate changes reconstructed from pollen analysis, optically stimulated luminescence (OSL) dating, and sedimentary features of terrace sediments in the Datong catchment. The results show that pollen from upstream, for example, 20–30 km from the sample site and transported by water flow, makes the greatest contribution to the pollen assemblages of overbank sediments, which provides reliable regional climatic information. The overbank sediments of the fourth terrace (T4) are dated to around 57.1 ka; beneath these, the lower braided-river gravel was likely deposited during the early part of the Marine Isotope Stage (MIS) 4. The pollen-inferred vegetation is forest-steppe, reflecting a strong monsoon under warm and wet climate conditions during the deposition in the middle sediment unit, possibly during MIS 3. Afterwards, alluvium aggradation ended, and pronounced incision and abandonment was observed in the terrace surface followed by loess deposition which likely occurred during MIS 3–2, at the initiation of the decline of the monsoon. The basal sediment unit of the second terrace (T2) was dated to approximately 6.5–5.0 ka, indicating the start of alluvial aggradation during the Holocene Optimum. Relatively high arboreal pollen from the basal sediment unit of T2 shows a relatively strong monsoon with a warm and wet climate. This was followed by the deposition of the middle sediment unit when the climate was relatively drier with a weak monsoon, recorded by herbaceous vegetation dominated by Artemisia and Chenopodiaceae. It was deduced that during the following cold–warm transition, the river could incise deeply, and this terrace was formed under increasing monsoon conditions. The deep incision and formation of the two studied terraces correlate with different phases of climate change: a warm-to-cold climate transition (decreasing monsoon) for T4 and a cold-to-warm climate transition (increasing monsoon) for T2. We argue that the extreme climatic events at millennial–centennial scales during the Holocene, in addition to orbital-scale changes of monsoon variation, might have led to fluvial thresholds being crossed, causing intense incision and terrace formation. However, the correlation of fluvial processes in the NETP as a response to the East Asian monsoon at different temporal scales could be highly variable.

Fire as an Artifact\u2014Advances in Paleolithic Combustion Structure Studies: Introduction to the Special Issue

Hearths present sedimentary features, artifacts, and direct evidence for maintained and controlled fire in the past. The use of hearths reflects regular access to fire and its diverse benefits. Among these benefits are cooked food, protection from the cold and from predators, and fire’s transformative power regarding raw materials. Hearths may have also served as focal points of activity at Paleolithic campsites and triggered changes in social structures. As sedimentary features, combustion structures function as behavioral as well as paleoenvironmental archives. The papers in this special issue focus on the former aspect, how combustion feature can serve as transmitters of behavior, and with what tools we can explore them. We here briefly present an overview on the range of topics explored in these papers, which include ethnoarchaeological research on fire use among recent hunter-gatherer groups, spatial analysis of burnt lithics, actualistic experiments regarding fire function and fire use in tool production.

Brachiopods from the Palaeogene clastic deposits of north-western Italy

Four brachiopod species, i. e. Erymnaria bolcensis ( Massalongo , 1850), Gryphus cf. minor (Philippi, 1836), Terebratulina tenuistriata (Leymerie, 1846), and Megathiris detruncata (Gmelin, 1791) have been identified in the Oligocene deposits of NW Italy. The species G. cf. minor and T. tenuistriata dominate in the studied material. This is the first record of M. detruncata from the Oligocene of Italy, although it has been noted both from the Eocene and Miocene of Italy. The stratigraphic ranges of E. bolcensis and T. tenuistriata have been extended. The studied assemblage differs considerably from the majority of the Palaeogene and Neogene assemblages of Europe dominated by micromorphic megathyridids. Geological context and sedimentary features point to mass-flow deposits of fan deltas, indicating that the assemblage has been transported within the sediment down a slope.

VERTEBRATE TAPHONOMY, PALEONTOLOGY, SEDIMENTOLOGY, AND PALYNOLOGY OF A FOSSILIFEROUS LATE DEVONIAN FLUVIAL SUCCESSION, CATSKILL FORMATION, NORTH-CENTRAL PENNSYLVANIA, USA

ABSTRACT The fluvial facies of the Catskill Formation record important ecological events that occurred during Late Devonian time. A well-exposed section between the towns of Blossburg and Covington, in north-central Pennsylvania, contains abundant macrofossils and sedimentary features, making it well-suited for linking Upper Devonian fossil occurrences with depositional environments and sedimentary processes. Strata consist of two distinct fluvial facies: floodplain lithofacies consist of mudrocks, with evidence of pedogenic overprinting and sharp-based sandstones interpreted as crevasse splays; channel-bar lithofacies consist of single- and multi-storied cross-stratified lenticular sandstone bodies interpreted as fluvial channel-bar complexes. Macrofossils occur in 22 discrete horizons spanning > 240 m of stratigraphic succession that include Archanodon bivalve shell impressions, two genera of “placoderms” (Bothriolepis, Phyllolepis), an unidentified acanthodian, and several taxa of sarcopterygian fishes, including lungfish (Dipnoi indet.), Holoptychius, Langlieria, and Sauripterus. Most vertebrate macrofossils are preserved as disarticulated, abraded plates, scales, and bone fragments in sandstone channel-bar deposits. Articulated, unabraded remains are preserved in proximal floodplain deposits. Miospores recovered from Catskill Formation fossil sites in the Blossburg-Covington section belong to the COR subzone of the VCo (Diducites versabilis-Grandispora cornuta) palynological zone, indicating deposition ca. 362 to 361.8 Ma during the late Famennian stage of the Late Devonian. Catskill Formation fluvial strata exposed tens of kilometers to the south and west yield latest Famennian palynomorphs. These broadly contemporaneous continental depositional environments supported Late Devonian vertebrate evolution, including the fin-to-limb transition in tetrapodomorphs, and the possible euryhalinity of vertebrates occupying marine-to-nonmarine transitional habitats.

Evaluation of sedimentary features and biomarkers in the Paleogene Niubao formation in the Lunpola basin, Tibetan plateau: implications for the oil source rocks and exploration

The Paleogene Niubao formation is mainly exposed in the central part of the Lunpola basin in the hinterland of the Tibetan Plateau and has high potential for oil and gas exploration and development. The biomarkers of source rocks are systematically studied by selecting representative samples. The middle and upper Niubao formation contain rhythmically inter-bedded mudstone and sandstone that show periodic variations characteristic of the lake water environment. Additionally, the large volumes of muddy dolomite in the upper Niubao formation (UNF) are associated with high salinity in the lake environment under a hot and arid climate. The organic geochemical analysis shows that the middle Niubao formation (MNF) and UNF have high organic abundance (total organic carbon (TOC) contents of 1.48–8.96% in the MNF and 1.52–12.83% in the UNF) and type I–II kerogen. The analysis shows that the UNF was deposited in a persistent, anoxic, stratified and highly saline paleo-lake environment, which was beneficial to the preservation of organic matter. The high phytoalkane and γ-paraffin contents in the UNF indicate a strongly reducing and highly saline lacustrine depositional environment. The high pregnane contents and ascending sterane in the source rocks in the MNF indicate high maturity, and the distribution of n-alkanes and regular sterane indicates the input of some terrestrial organic matter. The high maturity indicates that the source rock in the MNF may represent the main hydrocarbon-generating layer in the basin.

The undisclosed paleoclimatic record of northern mesoamerica: A pedostratigraphic approach for environmental reconstruction

This article presents the results of a research on paleosols formation conditions in the Aguascalientes Valley, northern Mesoamerica, where paleoenvironmental reconstructions have been scarce. Records of environmental and climatic changes, as well as the alteration of the landscape are expressed in the memory of the soil. Soil micromorphology is the most efficient method to identify these changes. In paleosols, micromorphological features reflecting a certain soil forming process can be related to environments in which those processes took place. Paleoenvironmental reconstruction of the region consisted in identifying pedofeatures and other present soil attributes, grouping features into pedogenic facies under constant environmental conditions, examining the groundmass in order to detect features caused by erosion or sedimentation, and finally establishing a hierarchy between the different pedogenic facies, including erosional and sedimentary features if necessary. Specific statistical data analysis disclosed stratigraphical relationships. The results we obtained, such as illuvial clay coatings, redoximorphic nodules, and hypocoatings, revealed the most representative pedofeatures that developed under humid climate. Under a semiarid climate, representative pedofeatures that were revealed included micritic coatings and hypocoatings. A paleosol with ferruginous nodules and hypocoatings in groundmass, and at least one phase of dusty and high-birefringence yellow clay illuviation is proposed as stratigraphic marker for this area of the Aguascalientes Valley. Evidence indicates the sequence of events in the area was: (i) a large period of humid climate; (ii) a short period of climate change, from humid to semiarid, followed by subhumid; and (iii) a large period of semiarid climate, including the current one. The paleosols of the Aguascalientes Valley to a large extent preserve major trends in history and provide further evidence to define the 11 phases of stability (pedogenesis) in 8 cycles and to detect the interlayer phases of instability (sediment transport/deposition).

The March 2015 catastrophic flood event and its impacts in the city of Copiapó (southern Atacama Desert). An integrated analysis to mitigate future mudflow derived damages

The March 2015 extraordinary hydrometeorological event in the Andes cordillera caused severe floods in the southern Atacama Desert. One of the most affected cities was Copiapó (northern Chile) located downstream of the junction between the Copiapó river and its ephemeral tributary Quebrada Paipote. This work analyses the features of this catastrophic flood and relates them with the identified impacts. A large volume of water mixed with fine sediments overflowed the tributary channel generating a flood that affected 72% of the urban area. The rheological (velocity, density and flow regime) and sedimentary features of the flow reveal the occurrence of massive mudflows that infilled the space available inside the buildings, buried the streets with a sandy mud deposit of more than 30 cm medium thickness and collapsed the sewer network. The post-event survey carried out by the Ministry of Housing and Urban Planning (MINVU) was used for the development of fragility curves that allows modelling the probability of damage. Results indicate that the greatest probability of building damage is generated by the accumulation of sediments instead of by the flow depth. On the other hand, once the very fine grain sediments of the top of the deposit dried up, it increased the concentration of post-event suspension particulate matter, causing a health issue. This work highlights the need to understand mudflow processes and their consequences in arid environments to improve urban planning and mitigate future damages since their impacts strongly affect infrastructures and communities.