Sedimentary Context Research Articles

Heavily eroded Pleistocene landscape and site-forming processes of the Acheulean artifacts-bearing Holocene sediments, Eastern Desert, Sudan

Since the Middle Pleistocene, the Sahara region has undergone strong environmental changes resulting from climate changes. Dry periods, constituting an ecological barrier to human presence, alternated with wet periods when the Sahara area was covered with green savanna and an extensive network of watercourses, allowing the area to be occupied by hunter-gatherer groups. Responding to the Quaternary climatic changes, hominin dispersal was channeled through vegetated corridors. Such evidence for human settlements connected to Pleistocene green corridors in the Sahara region has been discovered in the research area called EDAR (Eastern Desert Atbara River). This area comprises a cluster of Acheulean and Middle Stone Age (MSA) sites discovered in the fluvial sedimentary context. This manuscript discusses the occurrence of Middle Pleistocene Acheulean artifacts in much younger sediments documented at the site EDAR 6. These Acheulean artifacts are present within thick Holocene calcareous sandy silts formed between 2.7 ka and 8.7 ka based on an optically stimulated luminescence (OSL) chronology, which is also supported by paleomagnetic analysis. The stone gravelly artifacts mantled above the eolian deposits have been known in other Paleolithic sites under the desert environment of Northern Africa. We propose that the relocation of the Palaeolithic artifacts was due to long-lasting erosional and redepositional processes affecting the Acheulean artifacts-bearing sediments since the Middle Pleistocene. We interpret that the cumulative results of the two processes, i.e., the gravel framework dilation and the gravel overpassing, allowed the stone artifacts to be exposed at the surface or incorporated in the Holocene sediment layers.

Geochemical Characteristics and Sedimentary Paleoenvironment of the Coal-Bearing Strata in the Xishanyao Formation: A Case Study of the Yihua Coal Mine in the Zhundong Coalfield, Xinjiang

The eastern Junggar Basin in Xinjiang harbors abundant coal resources within the Middle Jurassic Xishanyao Formation. However, the formation environment associated with these coal-bearing strata remains unclear. Geochemical characteristics serve as crucial geological indicators of the sedimentary period. Therefore, it is imperative to explore the geochemical attributes and sedimentary context of the coal-rich layers within the Middle Jurassic Xishanyao Formation in the Zhundong region to enhance the prospects of coal extraction and utilization. The elemental compositions, both major and trace, of the Xishanyao Formation were analyzed through X-ray fluorescence spectrometry (XRF) and inductively coupled plasma mass spectrometry (ICP-MS). A comprehensive analysis was conducted on the sediment provenance, tectonic background, and depositional environment of the coal-bearing strata in the Xishanyao Formation. Moreover, through the utilization of a range of discrimination indices, including Sr/Cu, B/Ga, Sr/Ba, V/Cr, Ni/Co, and δCe, the paleo-depositional setting of the coal-containing layers was reconstructed. The findings suggest that the primary source rocks of the coal-bearing beds in the Xishanyao Formation consist of continental tholeiites, with the predominant material composition in the source region being felsic volcanic rocks originating from the upper crust. The tectonic backdrop of the source region is marked by a continental island arc environment. During the sedimentation period of the Xishanyao Formation, the depositional environment was characterized by a freshwater oxidizing setting. Additionally, it experienced a transition from arid-hot to humid-hot before returning to arid-hot conditions.

Earth's earliest forest: fossilized trees and vegetation-induced sedimentary structures from the Middle Devonian (Eifelian) Hangman Sandstone Formation, Somerset and Devon, SW England

The evolution of trees and forests through the Devonian Period fundamentally changed the Earth's land biosphere, as well as impacting physical environments and geomorphology by stabilizing sediments and interacting with flowing air and water. From the mid-Givetian Age onwards, lignophyte flora are known to have been key parts of the machinery in the so-called Devonian landscape factory, but the impact of earlier forests, dominated by less woody cladoxylopsids, are not as well understood. We report here evidence for a previously unrecognized cladoxylopsid forest landscape, archived within the Eifelian Hangman Sandstone Formation of Somerset and Devon, SW England. This unit has previously been considered palaeobotanically depauperate, but is here shown to contain the earliest fossil evidence for such trees in the British record, as well as the oldest known evidence globally for the relative position of standing trees: in common parlance, a fossil forest. In addition to abundant fossil material attributable to the cladoxylopsid tree Calamophyton , and other early Mid-Devonian flora, the sedimentary context of the plant remains sheds light on the biogeomorphic impacts of these earliest forests. The trees colonized a sizeable distributive fluvial system that was prone to seasonal disturbance events. The nature of the sedimentary system has created a bias to those facies where biogeomorphic signatures are most frequently recorded (from the distal parts of the system), but across the whole system there is evidence of plant–sediment interactions in the form of vegetation-induced sedimentary structures, rooting features and accumulations of plant debris. Plant remains are also found in nearshore facies adjacent to the distributive fluvial system, attesting to the development of a novel non-marine/marine teleconnection from the production and export of new biological sedimentary particles. The Hangman Sandstone Formation is illustrative of the revolutionary power of cladoxylopsid trees as biogeomorphic agents, forming densely spaced forests and shedding exceptionally abundant plant debris, while also impacting local landforms and sediment accumulations and profoundly changing landform resilience against flood disturbance events. These findings provide evidence that the Eifelian Stage (393.3–387.7 Ma) marks the onset of tree-driven changes to physical environments that would forever change Earth's non-marine landscapes and biosphere. Supplementary material: Details of sedimentary facies and additional images of plant fossils are available at https://doi.org/10.6084/m9.figshare.c.7084873

Influences of lithofacies on fluid mobility in mixed sedimentary rocks: Insights from NMR analysis of the middle Permian Lucaogou Formation, Junggar Basin

The multi-source mixed sedimentation resulted in a unique series of mixed fine-grained sedimentary rocks evolved within the Permian Lucaogou Formation in the Jimusar Sag, located in the southeastern Junggar Basin, China. The variety of lithofacies within this series resulted in pronounced heterogeneity of pore structures, complicating the analysis of fluid occurrence space and state within reservoirs. As a result, the impact of lithofacies on fluid mobility remains ambiguous. In this study, we employed qualitative methods, such as field emission scanning electron microscopy (FE-SEM) and thin section observation, and quantitative analyses, including X-ray diffraction (XRD), total organic carbon (TOC), vitrinite reflectance (Ro), high-pressure mercury intrusion (HPMI) porosimetry, and nuclear magnetic resonance (NMR), along with linear and grey correlation analyses. This approach helped delineate the effective pore characteristics and principal factors influencing movable fluids in the fine-grained mixed rocks of the Lucaogou Formation in the Jimusar Sag, Junggar Basin. The findings indicate the development of three fundamental lithologies within the Lucaogou Formation: fine sandstone, siltstone, and mudstone. Siltstones exhibit the highest movable fluid saturation (MFS), followed by fine sandstones and mudstones sequentially. Fluid mobility is predominantly governed by the content of brittle minerals, the sorting coefficient (Sc), effective pore connectivity (EPC), and the fractal dimension (D2). High content of brittle minerals favors the preservation of intergranular pores and the generation of microcracks, thus offering more occurrence space for movable fluids. A moderate Sc indicates the presence of larger connecting throats between pores, enhancing fluid mobility. Elevated EPC suggests more interconnected pore throat spaces, facilitating fluid movement. A higher D2 implies a more intricate effective pore structure, increasing the surface area of the rough pores and thereby impeding fluid mobility. Ultimately, this study developed a conceptual model that illustrates fluid distribution patterns across different reservoirs in the Lucaogou Formation, incorporating sedimentary contexts. This model also serves as a theoretical framework for assessing fluid mobility and devising engineering strategies for hydrocarbon exploitation in mixed fine-grained sedimentary rocks.

Magnetic micro-archaeology: a method for conducting rock magnetic microfacies analysis on archaeological soil micromorphology samples, with a case study from El Salt, Alcoy, Spain

For geoarchaeologists the use of multiproxy and multimethod integrative approaches has become common for studying the sedimentary context of archaeological materials. In this paper, we introduce a novel approach that combines rock magnetic analysis with micromorphological analysis. We first conduct a brief examination of the magnetic properties of organic resins used in micromorphology to understand the potential impact of the resin and manufacturing process on the magnetic signature. It is crucial to understand the original production of the samples to ensure that endothermic reactions do not compromise the magnetic data. We illustrate the advantages of this approach through a case study of a pit hearth from the Neanderthal archaeological site of El Salt in Alcoi, Spain. This study utilises archived micromorphological samples of a pit hearth (combustion structure H77) initially described by Leierer et al. (J Archaeol Sci 123:105237, 2020). Rock magnetic analysis of multiple magnetic parameters—including magnetic susceptibility, natural remanent magnetization, and progressive isothermal remanent magnetization—reveals that each microfacies type exhibits a unique magnetic pattern, even if there is overlapping in signatures across some magnetic parameters. The interpretation of the magnetic data aligns with the results and microfacies descriptions previously provided by Leierer et al. (J Archaeol Sci 123:105237, 2020), further supporting the interpretation of the combustion feature as being in situ with a history of repeated use. The approach presented here offers an enhanced tool for micromorphologists to better understand the magnetic characteristics of microfacies units in higher resolution and establish direct connections to the micromorphological results.

Geochemical characterization of Lokoja-Basange Sandstone at Imiegba and Okpekpe areas, Benin flank of Anambra basin, Nigeria: implications for provenance, tectonic setting and source-rock weathering

This study investigates the geochemical attributes of the Lokoja-Basange Sandstone situated in Okpekpe and Imiegba areas of the Benin Flank of Anambra Basin, Nigeria. The aim of this study is to unveil its provenance, tectonic setting, and source rock weathering extent. Using energy dispersive x-ray fluorescence (EDXRF) "Minipal 4" spectrometer analysis, nine outcrop samples were examined for major oxide concentrations. The results show significant average SiO2 (77.09 wt. %), Al2O3 (12.10 wt. %), Fe2O3 (2.72 wt. %), Na2O (1.64 wt. %), K2O (2.41 wt. %), while TiO2, MnO, MgO, CaO, P2O5, LOI had average concentrations of less than 1.00 wt. %. Bivariate plots of log [Fe2O3/K2O] versus log [SiO2/Al2O3] indicate 77.80% litharenites and 22.20% arkose sediments. The [Al2O3]-[CaO+Na2O]-[K2O] ternary plot, the tectonic discriminant diagrams of [SiO2/20]-[K2O+Na2O]-[TiO2+Fe2O3+MgO], log [K2O/Na2O] versus SiO2, [SiO2/Al2O3] versus log [K2O/Na2O] and bivariate discriminant functions plot indicate that the sediments have felsic igneous provenance and quartzose sedimentary origin, within a passive margin tectonic setting and the source-area underwent moderate to near complete chemical weathering in semi-arid to humid climatic conditions with increasing chemical maturity. Conclusively, the chemical alteration index (CIA) ranges from 65.4% to 74.2%, averaging 70.70%; the chemical index of weathering (CIW) averages 82.37%; the plagioclase index of alteration (PIA) averages 78.88%; and the mineralogical index of alteration (MIA) averages 41.43%. These data signify extensive weathering of felsic igneous source rocks, highlighting mineralogical maturity of Lokoja-Basange Sandstone. In essence, this study enriches insights into the sandstone's origins, sedimentary context, and weathering history.

Automated rapid artefact surface area measurement from imagery with computer vision

Automated surface area measurements have been of interest to archaeologists since digital imagery began allowing researchers to remotely collect artefact metrics. We present a method of automatically measuring 2D surface area from artefact planform images employing computer vision in Python. The Python script, provided as a .py file in supplementary data, creates boundaries around regions of relatively homogeneous pixels (artefacts) in the image. These bounded regions are called contours. A count of the number of pixels within each contour provides a surface area in pixels. A circular reference object provides a conversion factor for the contours, as well as a point of reference for geometric accuracy of outputs.
 Measurements of 2D artefact surface area can be used in combination with measurements of length, width, thickness, and mass, or in some cases, replace such measurements. As presented, this technique provides utility to archaeology with applications to new documentation of artefacts, archived artefact images containing a scale, as well as landscape geoarchaeology and sedimentary contexts. Limitations of this type of surface area measurement include the requirement of the image background being of a solid colour heavily contrasting the artefacts being measured. Effectively, the background requirement limits deployment supporting collection of rapid field measurements from in-situ surface scatters without modification to the script or manipulation of the artefacts. Analytical applications utilizing this technique include studies of relative artefact abundance, shape and size class characterizations in artefact scatters, and redistribution of artefacts by geomorphological processes.

Magnetostratigraphy of the Pliocene Masol Formation, Siwalik Frontal Range, India: Implications for the age of intentional cut-marked fossil bones

The sedimentary Masol Formation, at least 165 m thick, is located in the Indian Siwalik Frontal Range and outcrops in the Chandigarh Anticline. It includes a fossiliferous zone called the Quranwala Zone (QZ) in its lower part. These fossils are characteristic of the Late Pliocene (Tatrot). Previous magnetostratigraphy showed that the QZ was deposited during the Gauss chron, with a short magnetic excursion at the base of the QZ, but the Gauss-Matuyama reversal was imprecisely identified in the stratigraphy of the Masol Formation. Following cut marks on fossil bones discovered in the QZ, we conducted a new magnetostratigraphy study to clarify their age. Our results indicate that detrital hematite is the main magnetic carrier and confirm that the entire Masol Formation was deposited during the Gauss Chron, whereas the Gauss-Matuyama reversal is outside the study area. Comparison between the magnetic excursion previously found at the base of the QZ and others identified elsewhere in a different sedimentary context and dated between 2.62 and 2.95 Ma, gave a range of sedimentation rates between 0.41 and 3.75 m.kyr-1 for the minimum thickness of the Gauss chron recorded in the Masol Formation. However, only rates less than 1 m.kyr-1 are consistent with the Late Pliocene deposits observed in the Siwalik. Magnetostratigraphy and obtained sedimentation rates conclude that the cut and percussion marks on the fossil bones have a minimum age of 2.68 Ma and a maximum age of 2.95 Ma. This evidence of intentional hominin activity is thus the oldest known in Asia.

Basal sauropodomorph locomotion: ichnological lessons from the Late Triassic trackways of bipeds and quadrupeds (Elliot Formation, main Karoo Basin).

Using modern ichnological and stratigraphic tools, we reinvestigate two iconic sauropodomorph-attributed tetradactyl ichnogenera, Pseudotetrasauropus and Tetrasauropus, and their stratigraphic occurrences in the middle Upper Triassic of Lesotho. These tracks have been reaffirmed and are stratigraphically well-constrained to the lower Elliot Formation (Stormberg Group, Karoo Basin) with a maximum depositional age range of <219-209 Ma (Norian). This represents the earliest record of basal sauropodomorph trackways in Gondwana, if not globally. Track and trackway morphology, the sedimentary context of the tracks, and unique features (e.g., drag traces) have enabled us to discuss the likely limb postures and gaits of the trackmakers. Pseudotetrasauropus has bipedal (P. bipedoida) and quadrupedal (P. jaquesi) trackway states, with the oldest quadrupedal Pseudotetrasauropus track and trackway parameters suggestive of a columnar, graviportal limb posture in the trackmaker. Moreover, an irregularity in the intermanus distance and manus orientation and morphology, in combination with drag traces, is indicative of a non-uniform locomotory suite or facultative quadrupedality. Contrastingly, Tetrasauropus, the youngest trackway, has distinctive medially deflected, robust pedal and manual claw traces and a wide and uniform intermanus distance relative to the interpedal. These traits suggest a quadrupedal trackmaker with clawed and fleshy feet and forelimbs held in a wide, flexed posture. Altogether, these trackways pinpoint the start of the southern African ichnological record of basal sauropodomorphs with bipedal and quadrupedal locomotory habits to, at least, c. 215 Ma in the middle Late Triassic.

Reconstructing formation processes at the Canary Islands indigenous site of Belmaco Cave (La Palma, Spain) through a multiproxy geoarchaeological approach

AbstractThe indigenous populations of La Palma (Canary Islands), who arrived on the island from Northwest Africa ca. 2000 years B.P., were predominantly pastoralists. Yet, many aspects of their subsistence economy such as the procurement, management, and use of wild plant resources remain largely unknown. To explore this, we studied the 600–1100‐year‐old archaeological site of Belmaco Cave, which comprises a stratified sedimentary deposit representative of a fumier. Here, we present a high‐resolution, multiproxy geoarchaeological study combining soil micromorphology, lipid biomarker analysis, X‐ray diffraction, μ‐X‐ray diffraction, μ‐X‐ray fluorescence, Fourier transform infrared spectroscopy, and μ‐Fourier transform infrared spectroscopy, to characterize formation processes and explore plant sources. Recurrent goat/sheep habitation and maintenance activities are represented by interstratified layers of unburned dung, charcoal‐rich sediment, and dung ash. Lipid biomarker data show a herd diet mainly composed of herbaceous plants, which is key to understanding the mobility of indigenous shepherds. Our results also revealed an unusual suite of authigenic minerals including hazenite, aragonite, and sylvite, possibly formed through diagenetic processes involving interaction between ash, dung, urine, volcanogenic components, and bacterial activity, coupled with arid and alkaline conditions. Our study shows the potential of a multiproxy approach to a fumier deposit in a volcanogenic sedimentary context.

New Insights into the Platform-to-basin Anatomy of the Urgonian Bas-Vivarais Domain (Lower Cretaceous; SE France)

This paper offers a new contribution to our ongoing harmonization efforts concerning the chronostratigraphic model of the southern France Urgonian-type carbonate platforms, which surrounded the Vocontian Basin during the Early Cretaceous. A multi-stratigraphic approach on the classical sections of the Ardèche River gorges and the Saint-Remèze Plateau have been used for reconstructing the evolution of the Bas-Vivarais Urgonian domain along an inner-to-outer platform profile; the latter being nearly perpendicular to the eastern Vocontian platform margin. In our transect, the installation and first developments of the Urgonian platform domain occured during the early Barremian Taveraidiscus hugii and Kotetishvilia nicklesi ammonite zones. This first platform stage was interrupted at a brief emersion episode that lasted through the Nicklesia pulchella ammonite zone, and resulted in the deposition of a sedimentary wedge with limited gradual downward, basinward shift in inner platform facies. This was followed by the regional deposition of shallow-water communities dominated by corals, echinoids, and orbitolinids, which passes basinward into open-marine, ammonite-bearing marly deposits in the Saint-Remèze Plateau outcrops. This change in facies was previously referred to as the Serre de Tourre Beds (STB), and dated to the Kotetishvilia compressissima and Moutoniceras moutonianum ammonite zones. The STB are further identified to as the local sedimentary expression of the Mid-Barremian Event recording a brief warming climate pulse testified by the presence of Offneria simplex, a caprinid rudist of Caribbean origin. Above, there is a regional recovery of inner platform Urgonian facies during the early late Barremian showing a striking progradational basinward trend. The latter, and its subsequent developments are in need of investigations. Taken together, the general evolution of the Urgonian Bas-Vivarais domain shows strong similarities with the sedimentary context of the nearby Subalpine Urgonian platform during the early Barremian. The finding of common sedimentary signals is more difficult with the Provence platform domain at that time.

Compound-specific carbon isotope analysis of short-chain fatty acids from Pine tissues: characterizing paleo-fire residues and plant exudates

Different types of plant tissues and resin can account for the wax lipids found in sedimentary contexts and archaeological samples. Consequently, there is increasing research to characterize the fatty acid carbon isotope ratios of different plant anatomical parts and their plant exudates (resin). With the aim to explore isotopic differences between plant tissues, state of the fine organic matter, effect of thermal degradation, and to identify plant residues we measured the δ13C values of short-chain fatty acids (δ13C16:0 and δ13C18:0) in: i) dead and fresh (collected and immediately dried) pine needles and branches (Pinus canariensis) and pine resin from laboratory-controlled heating experiments and ii) sediment and charred pine tissue samples from a wild pine forest fire. Our results are compared to previously published experimental open-air fire experiments and pine-fuelled archaeological combustion features. We found that for both fatty acid types, there are differences in δ13C signatures among anatomical parts and initial moisture content. These data allow us to characterize the isotopic signature of pine tissue and the effect of degradation on isotopic biomarkers, as well as to estimate combustion temperatures in pine-fuelled anthropogenic fires.

Upper Barremian−lower Aptian charophyte biostratigraphy from Arrifes section (Algarve Basin, Southern Portugal): correlation with dinoflagellate cyst biostratigraphy

The Arrifes section (Algarve Basin, Southern Portugal) has been studied from the viewpoint of charophyte biostratigraphy. The previous sedimentological studies in this section showed that it is built of the interbedding of continental and marine facies that contain both marine and continental palynomorphs (pollen, spores, and dinoflagellates), providing an excellent sedimentary context to perform direct correlations between marine and continental domains. In the present work, the identified charophyte biozones have been correlated with dinoflagellate biozones previously recognized in the Arrifes section, being the first time that these two biochronologies can be directly correlated. From the charophyte biostratigraphy viewpoint, two assemblages are distinguished. The older one is found between 65 and 135 m of the stratigraphic section, and it is composed of the species Echinochara lazarii, Atopochara trivolvis var. triquetra, A. trivolvis var. trivolvis, Clavator grovesii var. jiuquanensis, Clavator harrisii var. harrisii, C. harrisii var. reyi, and C. harrisii var. zavialensis. This assemblage belongs to the upper Barremian–lower Aptian Clavator grovesii var. jiuquanensis Eurasian biozone and also to the Ascidiellacruciata-Pseudoglobatorpaucibracteatus European biozone and it is described in beds with the dinoflagellate cyst Subtilisphaera scabrata (lower to lowermost upper Barremian) and Odontochitina operculata (from upper Barremian upwards). The younger charophyte assemblage is found between 135 and 155 m of the stratigraphic section, and it is composed of the species A. trivolvis var. trivolvis, Clavator grovesii var. corrugatus, Clavator harrisii var. harrisii, C. harrisii var. reyi, and C. harrisii var. zavialensis. This assemblage belongs to Clavator grovesii var. corrugatus biozone, previously assigned to upper Aptian (Clavator grovesii var. lusitanicus biozone). However, in the Arrifes section, this assemblage is found in beds assigned to the dinoflagellate cyst Odontochitina operculata (from upper Barremian–lower Aptian). The direct correlation of the base of the C. grovesii var. corrugatus biozone with the dinoflagellate cyst O. operculata, indicates that the base of the Clavator grovesii var. corrugatus biozone is in the upper lower Aptian, which is slightly older than was previously suggested, and it is extended until the middle Albian.

Finding Medieval Medicine Through Archaeobotany: An Ontological Approach

ABSTRACT An ontological approach to medieval archaeobotany could assist in uncovering otherwise obscure evidence of complex human-plant interactions. In particular, archaeobotanical remains could contribute more toward research on medieval medicine and understandings of human and environmental health. This article considers ways in which current archaeobotanical methods and practices may be limiting interpretations of medieval plant remains. We argue that increased immersion in both ontological and sedimentary contexts can improve archaeobotanical research by integrating plant remains with other archaeological and textual evidence. We offer an interdisciplinary theoretical and methodological framework toward broadening the interpretative scope of medieval archaeobotanical datasets, with an emphasis on humoral and spiritual ontologies.

The Sedimentary Context of Open-Air Archaeology: A Case Study in the Western Cape’s Doring River Valley, South Africa

Despite the wealth of Late Pleistocene archaeology that exists across southern Africa’s open landscape, it is routinely neglected in favour of rock shelter (re)excavation, biasing interpretation of human–environment interaction. This is compounded by the scarcity of open-air studies that use geoarchaeological methods to investigate the history and processes involved in their formation. The open-air archaeology of the Doring River Valley is an example of this, despite nearly a decade of dedicated study and publication. Consequently, there remains a limited and untested understanding of the valley’s formation history. This paper rectifies this by providing a sedimentary context for the surface archaeology exposed across one of the Doring River Valley’s artefact-baring localities, Uitspankraal 7 (UPK7). Characterisation, particle size, mineralogical, morphometric, and geophysical analysis of UPK7′s sand mantle resulted in the identification of four artefact-bearing sedimentary units, the aeolian and pedogenic processes involved in their formation, and their proposed order of deposition. This provides a stratigraphic, taphonomic, and environmental context against which chronometric dating and an analysis of the taphonomic, spatio-temporal, and technological composition of UPK7′s surface archaeology can be compared. This work is the first vital step towards understanding the depositional and behavioural history of a landscape, irrespective of context type.

Removal of Riprap within Channelized Rivers: A Solution for the Restoration of Lateral Channel Dynamics and Bedload Replenishment?

Riverbank erosion is an essential morphodynamic process for the improvement of river health and the ecohydrogeomorphological functioning of alluvial rivers. Lateral channel dynamics and sediment supply caused by bank erosion largely create and maintain heterogeneous in-channel habitats for fauna and aquatic or riparian plant species. However, humans very early started to stabilize riverbanks in order to favour navigation or to prevent valuable land and infrastructures close to the channel from eroding. During the 20th century, bank protection works such as riprap considerably increased and blocked lateral channel erosion, causing a loss of local sediment supply, which in turn resulted in a decrease in local bedload transport and channel incision. The aim of the article is to evaluate to what extent riprap removal may be an efficient restoration measure in terms of the reactivation of bank erosion and the replenishment of the local bedload in gravel-bed floodplain rivers with a sufficient amount of freedom space. An experimental in situ restoration approach was chosen. First, riprap was removed at two geomorphologically contrasting sites on the Allier River, France. Second, bank retreat was monitored, and the volumes eroded were quantified using photogrammetric and LiDAR surveys. Third, in the case of post-restoration bank erosion, grain size and morphological channel evolution analyses were carried out. Our results suggested that the removal of riprap is an effective measure for certain but not all channelized floodplain reaches. The geomorphological and sedimentary contexts are two criteria that should be considered when selecting sites for restoration. Thus, this study helps river managers to better target the criteria to be taken into account for the selection of sites with high potential for the restoration of lateral channel dynamics.

Rudist reef structure: Insights from orientation of hippuritids at l'Espà (Campanian, southern Pyrenees)

Rudist were common Mesozoic reef builders, but rare examples exist to evaluate reef structure. The l'Espà locality (southern Pyrenees) is approached to study rudist reef structure by a quantitative assessment of the individuals' position (growing vs reworked) and its sedimentary context. This late Campanian reef is exposed along some 20 × 6 m outcrop. Builders are mainly Hippurites radiosus, although other rudists, such as Hippuritella lapeirousei, Hippuritella sp. and Mitrocaprina sp. are also present together with corals. The orientation of 325 specimens of mainly H. radiosus was plotted in stereographic and cartesian projections. Orientations and microfacies permit to differentiate 5 vertically stacked intervals (settings) along the outcrop: (1) Distal reef setting (reef-talus slope), with rudists reworked as large bunches of grouped specimens, with scarce erosion and preserving both valves articulated; (2) Halfway distal-proximal reef setting (close cluster reef), with abundant reworked, isolated, and flat-lying specimens. In this zone, endo-epibiont colonization on rudist shells is common, together with the presence of large (up to 1 m) branching and massive corals; (3) Proximal reef setting (frame/close cluster reef), where specimens are in life position; (4) A proximal back reef unit (spaced cluster reef) with few highly reworked specimens; (5) Distal back reef setting (very spaced cluster reef), with hardly any rudist fragments. This succession provides a reef tract model resembling that of most coral reefs and differs from smaller rudist reefs. The structure of the studied reef is well preserved as a result of high accommodation space related to thrust emplacement.

Abrigo 1, Cerro El Sombrero: An Early Site in Eastern Argentina

ABSTRACT Late Pleistocene human occupations are well represented in the Tandilia Range, Argentine Pampas. Abrigo 1 is a small shelter in close relation to the main and better-known site on the hilltop of Cerro El Sombrero, with both sites including Fishtail points. The oldest levels at the shelter dated to 13,000–12,000 calendar years ago and yielded two Fishtail points. This paper deals with the analysis of the sedimentary context, stratigraphy, artifact distribution, and site formation processes at Abrigo 1. The sedimentary record is dominantly composed of geogenic sediments with a minor participation of anthropogenic material, mainly lithic artifacts. The geogenic input includes sediments coming from the physical and chemical weathering of the rockshelter’s quartzites and windblown sediments. Pedogenesis is the prevailing site formation process. Artifact distribution, the homogeneity of the assemblage, and refitting are considered relevant to assess site integrity. The results are compared to other early cultural contexts of the immediate vicinity.

New field observations on the Quaternary geology and vertebrate palaeontological occurrences in the Narsinghpur region of Narmada valley (central India)

Abstract Since the beginning of the nineteenth century, the Narmada River Valley has been well known for discoveries of abundant vertebrate fossil localities, a wide range of prehistoric archaeological assemblages and the first-known hominin fossil site in India at Hathnora. The fossil and archaeological remains are found in various sedimentary contexts: boulder conglomerate, pebble-rich sand, cross-bedded, coarse-to-fine sand and reddish brown clay in the Early to Late Pleistocene deposits. Our preliminary field investigations in the Narsinghpur region of the basin mark the presence of 26 individual localities within a stretch of 70 km of the Narmada River and adjoining tributaries. Each location was documented by GPS and the geological details were recorded while collecting the fossils. Past and current palaeontological research has revealed that a variety of fauna adapted to the sub-humid climate of both aquatic and terrestrial landscapes that thrived in this area during the Pleistocene period. One of our long-term goals is to understand the reasons for the high number of palaeontological occurrences compared with other parts of India and use such information to predict the locations of new occurrences, including hominin fossils. Various taphonomic processes in this region are responsible for the preservation and destruction of fossil assemblages in different geological formations: soil type, climatic conditions, rich calcium carbonate presence, encrustation, patination and modern anthropogenic activities (among others). Most of the fossil localities are found at an elevation range of 310–350 m above mean sea level (AMSL). The Narmada Basin was inhabited by prehistoric human populations and a variety of fauna, as evidenced by the ample lithic and fossil assemblages across the region. There are definitive contextual patterns of occurrences of the Quaternary vertebrate fossils and archaeological assemblages in the landscape, which require detailed investigations and mapping to understand the spatial distribution pattern and nature of associated sedimentary environments. In addition, this uniquely fossil-rich area requires proper protection and long-term preservation as it is heavily impacted by modern anthropogenic factors such as agriculture, sand mining and other activities.

Site formation processes at Cenjiawan (Nihewan Basin, North China): a case study on the structure of the Early Pleistocene archaeological record in lakeshore environments

ABSTRACTLakeshore environments offer an excellent opportunity to explore how early humans adapted to changing landscapes and environments. The Nihewan fluvio‐lacustrine sequence in North China contains one of the densest concentrations of Early Pleistocene Palaeolithic sites outside of Africa. Among these, the Cenjiawan site, dated at 1.1 Ma, draws attention due to the large number of stone tool refits. We present here Cenjiawan's sedimentary context, artefact spatial patterns, size distribution and taphonomic features, which are complemented by an experimental programme to better understand archaeological debitage size patterns, thus enabling a detailed analysis of formation processes at the site. The Cenjiawan assemblage is also interpreted in the light of its geographical and geological context, where a synsedimentary fault induced a minor topographic relief across the lacustrine lakeshore. This resulted in a shallow‐water setting in the down‐thrown hanging wall of the fault compartment, and a fluvial environment in the uplifted footwall. Our results indicate that Cenjiawan, situated in the hanging wall of the fault, underwent minimal disturbance, constituting a remarkable example of optimal preservation of archaeological assemblages in Early Pleistocene lakeshore environments.