Stratigraphic Data Research Articles

Three-dimensional gravity modelling of a Quaternary overdeepening fill in the Bern area of Switzerland discloses two stages of glacial carving

The geometry of glacial overdeepenings on the Swiss Plateau close to Bern was inferred through a combination of gravity data with a 3D gravity modelling software. The target overdeepenings have depths between 155 and > 270 m and widths between 860 and 2400 m. The models show incisions characterized by U-shaped cross-sectional geometries and steep to over-steepened lateral flanks. Existing stratigraphic data reveals that the overdeepenings were formed and then filled during at least two glacial stages, which occurred during the Last Glacial Maximum (LGM) within the Marine Isotope Stage (MIS) 2, and possibly MIS 6 or before. The U-shaped cross-sectional geometries point towards glacial erosion as the main driver for the shaping of the overdeepenings. The combination of the geometries with stratigraphic data suggests that the MIS 6 (or older) glaciers deeply carved the bedrock, whereas the LGM ice sheet only widened the existing valleys but did not further deepen them. We relate this pattern to the different ice thicknesses, where a thicker MIS 6 ice was likely more powerful for wearing down the bedrock than a thinner LGM glacier. Gravity data in combination with forward modelling thus offers robust information on the development of a landscape formed through glaciers.

Global and local drivers of the Ediacaran Shuram carbon isotope excursion

The Ediacaran Shuram carbon isotope excursion (CIE) follows the regional Gaskiers glaciation and occurs before the appearance of macroscopic animal fossils. Previous interpretations for the Shuram CIE have proposed global perturbations to Earth's carbon cycle accompanied by significant climatic and environmental change. These studies assume that carbonate carbon isotopes through the Shuram CIE record the composition of dissolved inorganic carbon in seawater. Through a compilation of new geochemical, sedimentological, and stratigraphic data from five localities on four separate paleocontinents, we find that all of the analyzed Shuram CIE successions share general similarities including a common transgressive-regressive sequence that is coincident with similar shifts in a host of geochemical proxies (δ13C, δ18O, δ44/40Ca, Sr/Ca, Mn/Sr, U/Ca). Despite these broad similarities between sections, there are important differences in the proxies between water depths that may be linked to changes in carbonate diagenesis. Specifically, we find the excursion's magnitude is largest in slope environments where diagenesis is sediment-buffered and smaller in shallow-water settings dominated by fluid-buffered diagenesis. The transgression that accompanied the Shuram CIE is consistent in amplitude (∼10-100s m) and duration (>1 My) with eustatic fluctuations driven by plate reorganization. These coupled geochemical and stratigraphic observations argue against meteoric and burial diagenesis as drivers for the excursion; instead, they are best explained by global changes to the locus and intensity of photosynthetic primary productivity in shallow-water environments and do not necessarily require large changes in global climate or marine redox.

What do ossification sequences tell us about the origin of extant amphibians?

The origin of extant amphibians has been studied using several sources of data and methods, including phylogenetic analyses of morphological data, molecular dating, stratigraphic data, and integration of ossification sequence data, but a consensus about their affinities with other Paleozoic tetrapods has failed to emerge. We have compiled five datasets to assess the relative support for six competing hypotheses about the origin of extant amphibians: a monophyletic origin among temnospondyls, a monophyletic origin among lepospondyls, a diphyletic origin among both temnospondyls and lepospondyls, a diphyletic origin among temnospondyls alone, and two variants of a triphyletic origin, in which anurans and urodeles come from different temnospondyl taxa while caecilians come from lepospondyls and are either closer to anurans and urodeles or to amniotes. Our datasets comprise ossification sequences of up to 107 terminal taxa and up to eight cranial bones, and up to 65 terminal taxa and up to seven appendicular bones, respectively. Among extinct taxa, only two or three temnospondyl can be analyzed simultaneously for cranial data, but this is not an insuperable problem because each of the six tested hypotheses implies a different position of temnospondyls and caecilians relative to other sampled taxa. For appendicular data, more extinct taxa can be analyzed, including some lepospondyls and the finned tetrapodomorph Eusthenopteron, in addition to temnospondyls. The data are analyzed through maximum likelihood, and the AICc (corrected Akaike Information Criterion) weights of the six hypotheses allow us to assess their relative support. By an unexpectedly large margin, our analyses of the cranial data support a monophyletic origin among lepospondyls; a monophyletic origin among temnospondyls, the current near-consensus, is a distant second. All other hypotheses are exceedingly unlikely according to our data. Surprisingly, analysis of the appendicular data supports triphyly of extant amphibians within a clade that unites lepospondyls and temnospondyls, contrary to all phylogenies based on molecular data and recent trees based on paleontological data, but this conclusion is not very robust.

Application of Milankovitch cycles in the restoration of high-resolution deposition velocity of Neogene strata in Kutei Basin, Indonesia

Restoring the deposition velocity during evolution in basin analysis is an important aspect. The restoration of high-resolution deposition velocity—the deposition velocity over a short geological period—can improve the precision of basin analysis and research. However, the prerequisite for the restoration is to establish an accurate chronostratigraphic framework based on precise stratigraphic dating. Conventional methods for stratigraphic dating can only be used to determine the epochs of large stratigraphic intervals rather than accurate geological time. It is also difficult to establish a fine geological time scale with dating methods requiring sample testing such as isotopic dating due to their limitations in sample collection. In contrast, the Milankovich cycle-based dating possesses the advantages of high precision and high operability and can be used to restore high-resolution deposition velocity. Based on the identification and extraction of Milankovich cycles, this study restores the high-resolution deposition velocity of the Middle Miocene and later strata in the abyssal area of the Kutei Basin in Indonesia. The results show that the restored deposition velocity coincides well with lithological sections. This indicates that the Milankovitch cycle-based dating can be used to effectively restore reliable curves of high-resolution deposition velocity. Therefore, this study provides a methodological basis and data guarantee for studying the accumulation cycles and distribution patterns of oil and gas in the abyssal area of the Kutei Basin using wave analysis technology and can also serve as a reference for similar research in other basins.

A closer look at sedimentation processes in two dam reservoirs

Dam reservoirs are complex depositional systems, which provide barriers to natural sediment transport along river courses. In addition, reservoir sedimentation causes serious problems in their operational management. Given the wide variability of reservoir bottom shapes, total volumes of stored water, river discharges, sediment loads and sediment textures, universal depositional models are difficult to achieve for dam reservoirs. This article focuses on the need to improve current understandings of sedimentation processes, and thorough spatial particle size distribution in dam reservoirs. To achieve this aim, sonar and ground penetrating radar surveys were combined with high-resolution stratigraphic data from 44 short sediment cores in two valley-type reservoirs, Seč and Křižanovice, part of a reservoir cascade in the Chrudimka River, which is a left-hand tributary of the Labe River (Czech Republic). Sonar survey was used to construct bathymetric maps and bottom reflection intensity images. The results showed topography inherited from pre-reservoir times and a good degree of correspondence between bottom reflection intensity and grain size. The sedimentation patterns exhibit distinct proximal-to-distal and transversal changes in sediment facies and grain size. Pre-reservoir and present morphologies have substantially shaped sediment accumulation. Spatial grain size sorting is a function of travel distance within reservoirs, which is conditioned by their bended and narrow geometry, as well as by reservoir management. Two stages of reservoir sedimentation are recognised. The initial stage was characterised by the filling of local depressions, which were overlain by the second stage, typified by continuous and horizontally deposited sediments. Relatively low sediment accumulation rates (from 0.2 to 1.06 cm/year) are the consequence of reservoir characteristics (capacity and associated accommodation space) and factors at a basin scale (low discharge, geology and land-use). Slow reduction of reservoir capacity was observed. The calculated trap efficiency is very high in the Seč Reservoir and much lower in the Křižanovice Reservoir. The main factor controlling trap efficiency is reservoir capacity and shape combined with low inflow. Ultimately, the trap efficiency change over time because of varying reservoir capacity due to seasonal water level fluctuation and varying hydrologic conditions. Due to the slow silting of the reservoir, the trap efficiency has decreased only slightly. Aside from general trends, some specific features exist for every reservoir based on local geometry and reservoir management strategy. This implies that an innovative approach combining map, sonar and geophysical surveys with core data is required to develop better facies models and to optimise sediment management strategies.

The influence of coastal evolution on the paleobiogeography of the bivalve Anomalocardia flexuosa (Linné, 1767) along the southwestern Atlantic Ocean

Anomalocardia flexuosa is a bivalve that inhabits shallow, low hydrodynamics coastal environments of normal to brackish salinity, currently distributed from the Caribbean up to the state of Santa Catarina (∼28°S) in southern Brazil, but its fossil record extends along the southwestern Atlantic up to ∼40°S, in Argentina. Its absence in southern coasts today is attributed to ocean water cooling as a result of Middle-Late Holocene changes in relative influence of the warm waters of the Brazil Current and the cold waters of the Malvinas/Falklands Current, but geomorphologic and stratigraphic data suggest that coastal evolution controlled mainly by glacioeustatic-driven oscillations may have also played a role on the shifts of its distribution. Here we review the past and present distribution of A. flexuosa along southern Brazil, establishing a correlation with the Holocene geological history of this area. The Holocene post glacial marine transgression (PMT) produced a large complex of interconnected coastal lagoons landward of sandy barriers stretching from southern Brazil (state of Rio Grande do Sul) to Argentina, creating a corridor that allowed for the southward dispersion of A. flexuosa. The few available numerical ages indicate that A. flexuosa was established in the northern coastal plain of Rio Grande do Sul around ∼7.1 ka BP, and by ∼5.8 ka BP it had reached the southern plain, facilitated by warmer ocean waters than today and the sea-level highstand of 6–5 ka BP. The combination of cooling, sea-level fall that reduced marine influence, and fluvial inputs of freshwater and sediments, converted most of the lagoon complex into smaller isolated freshwater lakes after ∼4 ka BP, leading to the regional extinction of that species. The fossils of A. flexuosa and other tropical mollusks in middle and late Pleistocene interglacial barrier-lagoon coastal deposits along the southwestern Atlantic suggest that their latitudinal distribution shifted cyclically, driven by glacial-interglacial oscillations of sea-level and temperatures. The understanding of the coastal processes that affected the distribution of A. flexuosa may help assessing how mollusks and other marine species respond to environmental forcings related to sea-level oscillations and climate, thus contributing from a paleobiological perspective for conservation and management efforts under present and future scenarios of changes in coastal ecosystems.

Hydrogeological modelling of Olkaria domes geothermal field to predict ground subsidence

Ground subsidence studies have been done on Olkaria geothermal field conventionally by comparing levels on benchmarks over years. Interferometric synthetic aperture radar (InSAR) systems have also been used to map surface deformation of small spatial extent. For the prediction of future dynamics of land subsidence in Olkaria due to geothermal resource exploitation, a hydrogeological conceptual model has been developed. In this model, hydrologic geothermal fluid properties are analysed and a relationship between the reservoir and geology of the wells established, subsidence is computed numerically. The model takes into account the hydrogeological condition of Olkaria geothermal field. Hydrological reservoir parameters are computed from well testing data. The study considers the Injectivity indices of the various wells under study as pre-computational indicator of the expected subsidence extents. Both two- and three-dimensional geological cross-sections are modelled with the rockworks software by inputting stratigraphic data for Olkaria domes. Geological simulations are used to study subsidence by assigning the ground formation with virtual material that deformed according to some essential relations in Rockworks computer software. Production zones are determined by a comparison between the well properties and corresponding well geology. Subsidence is then computed by the Tezarghi’s modified equation. Cumulative subsidence figures from the computation are in the range of 0.095-0.537m, without any reinjection. Computed values are then mapped in ArcGIS to develop a representative subsidence map. By application of these modelling and numerical computation methods, ground subsidence was effectively predicted using the five selected wells in Olkaria domes field. The hydrogeological model developed, and mapping is an important tool in the planning and development of a reinjection schedule and in subsidence mitigation. Subsidence prediction also is important in design of infrastructure which will be strong enough to resist the forces caused by subsidence.

Chronologie du Paléolithique supérieur dans le Nord-Est de la principale île du Japon

Palaeolithic archaeology in Tohoku region has long been discussed on constructing chronology, however it is difficult to build reliable chronological order because of poor stratigraphic excavations. In recent radiocarbon dating has advanced. In this paper I discuss the relation between chronology and radiocarbon dating in Tohoku region. At first, I categorize the Palaeolithic industries and establish the chronology by analyzing tool typology, lithic technology, and stratigraphic data. I correlate it with radiocarbon data from sites in Tohoku region. The result of analysis shows that Upper Palaeolithic industries are divided into 18 categories and 8 periods on chronology. The calibration curve IntCal 13 indicated that oldest Early Upper Palaeolithic site appeared around 37,000cal BP, and late Upper Palaeolithic started about 27,000cal BP. The pottery first appeared as far back as around 16,000cal BP. Now we do not have enough radiocarbon data, so we have to gather and examine more 14C data.

Bathymetric Signatures of Submarine Forearc Deformation: A Case Study in the Nankai Accretionary Prism

AbstractLarge earthquakes and tsunamis in subduction zone forearcs occur via slip on the shallow plate boundary and upper plate faults, but the locations, geometries, and slip histories of these faults can be difficult to constrain in regions with minimal subsurface geophysical and stratigraphic data. Here, we test a new approach to quantify the submarine seafloor geomorphic response to forearc deformation in order to identify structures that contribute to active deformation, to interpret their geometry and kinematics, and to evaluate their relative rates, magnitudes, and timing of deformation. We develop a workflow that uses filtered bathymetric digital elevation models, where long wavelength topography has been removed, to isolate the slope, relief, curvature, ridgelines, and trough lines associated with faults, fault‐related folds, and slope failures. We apply these methods to the Kumano region of the Nankai accretionary prism, southeastern Japan, where existing constraints on fault geometry, kinematics, and deformation history allow us to both evaluate the efficacy of our approach and to identify the lateral continuity of deformation processes. Our bathymetric analyses yield a high‐resolution tectono‐geomorphic map of active structures and reveal along strike variations in strain accumulation and out‐of‐sequence deformation. These metrics also demonstrate the importance of a strike‐slip fault system at the seaward edge of the Kumano Basin as a primary structure that accommodates deformation and partitions strain in the Nankai forearc. These results show the utility of using a submarine tectono‐geomorphic approach to evaluate active deformation in forearcs, particularly in regions with limited geophysical and core data.

Increased megathrust shear force drives topographic uplift in the Colombian coastal forearc

The subsidence/uplift patterns of forearc basins are controlled by subduction dynamics and are strongly dependent on the nature of the margin (erosive vs. accretionary). Here, we explore the role that increased megathrust shear force plays in triggering and sustaining the short wavelength topography of coastal forearc regions at erosive margins, where subsidence is supposed to prevail. The northern Colombian coastal forearc contains a ~ 1000 m-high mountain range (Baudó Range) that abruptly stands-up for ~300 km along the northwestern Pacific margin of South America, where the buoyant Nazca plate is subducting at a shallow angle. Field observations and stratigraphic data of Cretaceous to late Neogene volcanic and sedimentary rocks, suggest that the Baudó Range has been uplifting since the middle-late Miocene. The uplift seems to continue nowadays as evidenced by the irregular cliffed and bluffed coastline, steep slopes and high topographic ruggedness in one of the wettest regions on Earth, where weathering and landscape smoothing is expected to be intense. Earthquake focal mechanisms, together with regional-scale N-S-trending sinistral reverse fault structures, west-verging folding, and NW- and NE-oriented topographic lineaments, seems to be related to a trench-perpendicular mostly compressional stress regime. The residual topography along the coastal range of the northern Colombian forearc indicates under-compensation, which may suggest that the relatively thin (~20 km-thick) crust cannot support isostatically the observed topography. We propose that increased shear force along a wide seismogenic zone linked to the shallow subduction of the Nazca plate and a poorly lubricated interface, due to limited sediment dispersal into the trench, drive the ongoing topographic uplift of the region. In contrast, the smoother relief and lower elevations in the southern Pacific coast of Colombia could be explained by a deficit of shear force available to support higher topography.

Taxonomy, palaeoecology and palaeobiogeography of upper Cenomanian (Upper Cretaceous) oysters and plicatulids from southern Algeria

ABSTRACT Palaeontological investigation of four lithostratigraphic sections documenting the upper Cenomanian shallow marine carbonates of three palaeogeographic domains of southern Algeria (western Saharan Atlas, Guir Basin and Tinrhert Hamada) has produced a comprehensive collection of large bivalve assemblages for taxonomic purposes. A first inventory list of late Cenomanian oysters and plicatulids from southern Algeria is now available and consists of 15 taxa as follows: Lopha syphax, Ostreidae gen. et sp. indet., Curvostrea rouvillei, Flemingostreidae gen. et sp. indet., Costagyra olisiponensis, Amphidonta obliquata, Ceratostreon flabellatum, Ilymatogyra africana, Rhynchostreon suborbiculatum, Gyrostrea delettrei, Gyrostrea sp. indet., Pycnodonte (Phygraea) vesicularis vesiculosa, Plicatula (Plicatula.) auressensis, Plicatula (Plicatula) batnensis, and Chondrodonta? sp. indet. These taxa build five distinctive oyster-facies patterns, all purportedly recognisable in the field for stratigraphic assignment and regional correlation. Scarce sclerobiontic assemblage (borings: Entobia, Gastrochaenolites and Oichnus; and epibionts: juvenile oysters, serpulid tubes and Berenicean-type bryozoa) observed within these oyster shell assemblages is also identified, briefly described and adressed. This first taxonomic analysis highlights three main palaeogeographic components within these oyster- and plicatuloid-assemblages: endemic Mediterranean, Tethyan-Atlantic and cosmopolitan taxa. Moreover, the present study on these late Cenomanian oyster assemblages provides a first inventory list and stratigraphical baseline data towards further datation and correlation at the regional scale.

Andean uplift, drainage basin formation, and the evolution of plants living in fast-flowing aquatic ecosystems in northern South America.

Northern South America is a geologically dynamic and species-rich region. Fossil and stratigraphic data show that mountain uplift in the tropical Andes reconfigured river drainages. These landscape changes shaped the evolution of the flora in the region, yet the impacts on aquatic taxa have been overlooked. We explore the role of landscape change on the evolution of plants living strictly in rivers across drainage basins in northern South America by conducting population structure, phylogenetic inference, and divergence-dating analyses for two species in the genus Marathrum (Podostemaceae). Mountain uplift and drainage basin formation isolated populations of M. utile and M. foeniculaceum in northern South America and created barriers to gene flow across river drainages. Sympatric species hybridize and the hybrids show the phenotype of one parental line. We propose that the pattern of divergence of populations reflects the formation of river drainages, which was not complete until <4.1million yr ago (Ma). Our study provides a clear picture of the role of landscape change on the evolution of plants living strictly in rivers in northern South America. By shifting the focus to aquatic taxa, we provide a novel perspective on the processes shaping the evolution of the Neotropical flora.

Sedimentary graphic logs: A template for description and a toolkit for digitalization

Graphic logs are the most common way geologists characterize and communicate the composition and variability of clastic and carbonate sedimentary successions; through a simple drawing, a graphic log imparts complex geological concepts (e.g., the Bouma turbidite sequence or a shoreface parasequence). The term ‘graphic log’ originates from a geologist graphically drawing (i.e., ‘logging’) an outcrop or core; other synonymous terms include measured section and stratigraphic column. Graphic logs generally have thickness/depth on the y axis, while the x axis can represent grain size, texture, or a weathering profile; however, there is no standardized format or template. Additionally, graphic logs can be drawn at vastly different scales, from the characterization of every bed in sections 10s of meters thick to a rough description of lithology over 1000s of meters, making comprehensive, quantitative comparison difficult. Many geologists carefully hand-draw graphic logs at fine-scale in a field notebook, and then digitally retrace them in drawing software. However, this detailed data (e.g., thickness, grain size) that may have taken days or weeks to collect is often never captured in a machine-readable, tabular format. So, while tens of thousands of meters of graphic logs exist to quantify lithologic heterogeneity and stacking patterns within and between depositional environments, this data is rarely digital and available – it often remains in an analog state in a field notebook. Despite this, geologists have long been attempting to quantify graphic log data to better distinguish stacking patterns, depositional processes, and depositional environments to aid in prediction of stratigraphic architecture and earth-resource distribution. We present litholog, an open-source software package in python that stores, plots, and analyzes graphic-log data. We also include software in R and MATLAB that digitize hand-drawn graphic logs into a tabular format readable by litholog. We discuss the diversity of graphic log data, the implementation of graphic log data in a digital, structured, tabular format; finally, we recommend methods and provide a template for standardizing collection of this important type of stratigraphic data. It is our hope that these software packages, combined with advances in ‘big data’ analytics and machine-learning algorithms, will lead to new discoveries in sedimentary geology.

Automated facies identification by Direct Push‐based sensing methods (CPT, HPT) and multivariate linear discriminant analysis to decipher geomorphological changes and storm surge impact on a medieval coastal landscape

AbstractInad1362, a major storm surge drowned wide areas of cultivated medieval marshland along the north‐western coast of Germany and turned them into tidal flats. This study presents a new methodological approach for the reconstruction of changing coastal landscapes developed from a study site in the Wadden Sea of North Frisia. Initially, we deciphered long‐term as well as event‐related short‐term geomorphological changes, using a geoscientific standard approach of vibracoring, analyses of sedimentary, geochemical and microfaunal palaeoenvironmental parameters and radiocarbon dating. In a next step, Direct Push (DP)‐based Cone Penetration Testing (CPT) and the Hydraulic Profiling Tool (HPT) were applied at vibracore locations to obtainin situhigh‐resolution stratigraphic data. In a last step, multivariate linear discriminant analysis (LDA) was successfully applied to efficiently identify different sedimentary facies (e.g., fossil marsh or tidal flat deposits) from the CPT and HPT test dataset, to map the facies' lateral distribution, also in comparison to reflection seismic measurements and test their potential to interpolate the borehole and CPT/HPT data. The training dataset acquired for the key site from coring and DP sensing finally allows an automated facies classification of CPT/HPT data obtained elsewhere within the study area. The new methodological approach allowed a detailed reconstruction of the local coastal landscape development in the interplay of natural marsh formation, medieval land reclamation and storm surge‐related land losses.

Ordovician supra-subduction, oceanic and within-plate ocean island complexes in the Tekturmas ophiolite zone (Central Kazakhstan): age, geochemistry and tectonic implications

ABSTRACT The Junggar-Balkhash region in the west of the Central Asian orogenic belt comprises Palaeozoic flysch, dismembered ophiolites, chert, basalt, and olistostrome within its accretionary wedges. The Tekturmas ophiolite zone in the north of the Junggar-Balkhash region hosts Ordovician to Early Silurian complexes, mostly formed with a convergent margin in front of the Baydaulet-Akbastau magmatic arc. The northern part of the Tekturmas zone comprises Middle to Late Ordovician (465–455 Ма) Bazarbai supra-subduction (SSZ) ophiolites, which were formed in the fore-arc settings. At the south of the Tekturmas zone Early Ordovician (~470 Ма) Tortaul SSZ ophiolites, Middle Ordovician Karamurun oceanic island basalts (OIB) and Middle to Late Ordovician Tekturmas deep water cherts are present. There are also concurrent Middle Ordovician (~460 Ma) high-temperature granulites, related to a partial melting of the subducted metasedimentary complexes. Since the second half of the Late Ordovician until the Early Silurian, the stratigraphic data constrain in front of the Baydaulet-Akbastau island arc the emergence of the Nura fore-arc trough. In the north of the Tekturmas zone, it is represented by the chert-tuffaceous Bazarbai Formation; southward, the zone can be interpreted as a concurrent accretionary wedge made up by the fragments of the Bazarbai and Tortaul ophiolites, Karamurun OIB basalts, and Tekturmas deep water cherts, accompanied by chaotic olistostrome. In the Early Silurian, growth of the accretionary wedge migrated to the south into the Uspenskу zone. We propose that while subduction was steadily directed underneath the Baydaulet-Akbastau island arc, the near-surface thrusting OIB and deep water cherts was also directed northward onto the fore-arc in the Late Ordovician to the earliest Silurian, whereas from the middle Llandovery it reversed southwards. In the end of the Palaeozoic to the Mesozoic, the Tekturmas ophiolite zone was offset into a number of segments by the sinistral strike-slip faults.

Segmentation of the Apenninic Margin of the Tyrrhenian Back‐Arc Basin Forced by the Subduction of an Inherited Transform System

AbstractThe Tyrrhenian back‐arc basin developed at the rear of the E‐ward migrating Apennine fold‐and‐thrust belt, with northward decreasing rollback of the subducting Adria slab leading to northward fading of back‐arc extension. The northern portion of the Tyrrhenian basin is made of thinned continental crust, whereas in the central/southern portion extension eventually evolved to oceanic crust production. In this framework, a long‐lasting debate concerns the existence of a &gt;200 km long transform zone along the 41st parallel, which should separate the two portions of the Tyrrhenian basin. At its eastern termination, a branch of the presumed transform zone enters the Tyrrhenian margin of the Apennine belt and occurs as an accommodation zone made of a ribbon of extensional faults and related basins. This accommodation zone, which separates areas of mutually perpendicular extension directions, is here introduced, described, and named the Ponza‐Alife accommodation zone. Interpretation of seismic lines and new structural and stratigraphic data from this accommodation zone have been used to constrain the pre‐orogenic and syn‐orogenic architecture of the subducting plate and the Plio‐Quaternary back‐arc extensional stage. Our data indicate that the studied zone retraces a deep‐seated transform fault system located in the subducting plate and inherited from an Early Jurassic rifting episode, which caused the lateral juxtaposition of different rift domains in the subducting plate. We propose that during collision and trench retreat, this lateral juxtaposition has controlled differential retreat of the subducting plate across the studied zone, forcing the development of the Ponza‐Alife accommodation zone in the overlying back‐arc basin's margin.

Sedimentology, petrography, and deposition of the Upper Cretaceous Codell Sandstone in the Denver Basin

We integrate new and previous stratigraphic and petrographic data for the mid-Turonian Codell Sandstone to interpret its provenance, depositional characteristics, and environments. Our focus is on sedimentologic, X-ray diffraction, and X-ray fluorescence analyses of cores and thin sections spread throughout the Denver Basin, augmented by interpretation and correlation of well logs, isopach maps, outcrops, and provenance data. Although we treat the Codell as a single mappable unit, it actually consists of two geographically disjunct sandstone packages separated by a southwest-northeast-trending gap, the NoCoZo, short for No Codell Zone. The Codell is everywhere capped by a significant unconformity and across much of the northern Denver Basin rests unconformably on the underlying shales of the Carlile Shale. In the southern Denver Basin, the Codell commonly contains two parasequences, each of which becomes less muddy upward. Biostratigraphic and geochonologic data suggest that the unit represents deposition over a relatively brief time, spanning ~0.4 Ma from ~91.7 to ~91.3 Ma. The Codell is predominantly a thin (&lt;50 ft) sheet-like package of pervasively bioturbated coarse siltstone and very fine-grained sandstone dominated by quartz and chert grains 50 to 100 μm in diameter. The unit is more phosphatic than the underlying members of the Carlile Shale, and its grain size coarsens to medium-grained in the northern part of the basin. An unusual aspect of the Codell across our study area is the generally excellent grain sorting despite the presence of an intermixed clay matrix. This duality of well sorted grains in a detrital clay matrix is due to the bioturbation that dominates the unit. Such burrowing created a textural inversion that obscures most of the unit’s primary sedimentary structures, except for thin intervals dominated by interlaminated silty shale and very fine sandstone. A relatively widespread and unburrowed example of this bedded facies is preserved in a thin (&lt;10 ft) interval that extends across most of the northern Denver Basin where it is informally called the middle Codell bedded to laminated lithofacies. Sparse beds with hummocky or swaley cross-stratified and ripple cross-laminated fine-grained sandstone are present locally in this bedded facies. We hypothesize that Codell sediments were derived from a major deltaic source extending into the Western Interior Seaway from northwestern Wyoming, and that the Codell was deposited and reworked southward on the relatively flat floor of the Seaway by waxing and waning shelf currents as well as storms and waves. Codell sediments were spread across an area of more than 100,000 mi2 in this epeiric shelf system that spans eastern Colorado, southeastern Wyoming, western Kansas, parts of Nebraska and beyond.

Reconaissance Researches of Kemerova Village: on the Issue of the Russian Settlement Archaeology of the XVII–XIX Centuries

The subject of this research is the history, chronology and archaeological artifacts from the Kemerova village (Kemirova, Komarova, Temirova). The research is a part of a scientific topic of exploring Russian settlements in the Tom’ River region of the XVII–XIX centuries. The aim of this work is to identify the archaeological layer structure, determine the stages of Kemerovo village site development using stratigraphic data and archaeological objects, to compare the archaeological data with the results of written and cartographic sources. The archaeological research results showed two archaeological layers well stratigraphically recognizable. The lower archaeological layer contains artifacts of the middle of the XVIII century – the cusp of the XIX–XX centuries. So, it is about pre-industrial rural society’ life. The upper layer separated from the lower one by a layer containing some coal dates from the XX century. The artifacts bear witness of how the village was transforming into a industrial township. Comparison of the archaeological data and other historical sources materials highlights the need to find cultural remains of Kemerova village emerging period and a clearer differentiation of the middle of the XVIII–XIX centuries which requires further researches on the site. The area of use of the received results includes not only the history of Kemerovo but also issues of emergence and development of Russian and other ethnic groups’ settlements in the XVII–XIX centuries in the Tom’ River basin. Main conclusions: the received results allow us to determine two periods (pre-industrial and early industrial) in the history of Kemerova village before its inclusion into the territory of Shcheglovsk town (Kemerovo since 27 March 1932). It can be suggested that Kemerova village with the other Kemerovo rural settlements (Krasnaia, Shcheglova-Ust’- Iskitim, Kuchukovy Yurty / Ulus-Mozzhukha, Evseeva, Borovaia and others) formed the urban territory. In this context, the role of Kemerova village is not only in using its name for the mine, the train station and, finally, for the city but the early idea of connection of this rural settlement with the «burnt hill», coal deposits (1721) which defined the further industrial potential of Kemerovo

Holocene Sea-Level Changes in Southern Brazil Based on High-Resolution Radar Stratigraphy

This paper focuses on high-resolution coastal stratigraphy data, which were revealed by the Ground Penetrating Radar (GPR) system. Surveys performed with GPR on the surface of prograded barriers reveal patterns of reflections that allow the interpretation of the geometry and stratigraphy of coastal deposits in a continuous mode. At the Curumim prograded barrier in southern Brazil (29°30′ S–49°53′ W), a two-dimensional transverse GPR survey revealed, with high precision, a serial of contacts between aeolian deposits of relict foredunes and relict beach deposits that have a strong correlation with sea level. In a 4 km GPR profile, a total of 24 of these contacts were identified. The high accurate spatial positioning of the contacts combined with Optical Stimulated Luminescence dating resulted in the first confident sea-level curve that tells the history of sea-level changes during the last 7 ka on the southernmost sector of the Brazilian coast. The curve shows that sea-level was still rising before 6 ka BP, with a maximum level of 1.9 m reached close to 5 ka BP; after that, sea-level started to falling slowly until around 4 ka BP when fall accelerated.

Statistical analysis of structures commonly used to determine palaeoslopes from within mass transport deposits

Mass transport deposits (MTDs) contain deformation structures often that are used to determine the kinematics of palaeo-mass flows and hence the orientation of the original slope or gradient upon which the mass flow developed. When integrated with stratigraphic data, the azimuth of the palaeoslope can help elucidate the depositional evolution and palaeogeography of a region. However, most studies have defined palaeoslopes from well-exposed MTDs, which raises some questions regarding the validity of establishing palaeoslope definition where MTDs are poorly exposed. We examine MTDs of the Itararé Group (Paraná Basin), in southern Brazil, that are only partially exposed, but widely distributed both vertically and horizontally. Datasets and transport direction (palaeoflow) obtained from different structures, variable methods and multiple stratigraphic levels and geographic localities were statistically evaluated to verify the robustness of the methodology. This allow the orientation of local palaeoslope to be established for different time intervals, even from disconnected outcrops. Faults and folds, that are the main structures used to define palaeoslopes, display the greatest potential to accurately determine palaeoflow in the examined MTDs. The use of other structures such as asymmetric boudins, quarter structures and injectites, helped to clarify flow kinematics. The integration of palaeoflow data with palaeocurrent data from associated deposits give additional support for determining the orientation of the palaeoslope.