Non-marine Sediments Research Articles

Review on geology and mineralization of North Korea (II: Phanerozoic)

AbstractIn this review, we attempted to summarize and interpret the Phanerozoic geology and mineralization following the article (vol. 71 in Resource Geology) which reviewed the Precambrian geology and mineralization of North Korea. The basement of the Korean peninsula was built during the Precambrian and gradually became more evolved and complex during the Phanerozoic. The northern part of the peninsula was in the active and passive continental margins of the Korea–China platform during the Phanerozoic. In the tectonic environments of the Phanerozoic, the tectonic provinces of North Korea comprise several Paleozoic–Mesozoic intracontinental and rift basins as well as Cenozoic ocean border and rift basins. During the Paleozoic, the sedimentary strata were formed within the marine‐to‐nonmarine intracontinental basins, such as the largest Pyeongnam and Hyesan–Iwon basin, Imjingang rift basin, and several small structural basins, and the sedimentary type of limestone, dolomite, and coal deposits were formed. Mesozoic orogenic events in the peninsula were the most overwhelming geologic event causing block movements through collision and subduction of the paleo‐Pacific plate. Songrim orogeny (late Permian to early Triassic) might be caused by continental collision associated with strong deformation, metamorphism, and granite intrusion. Daebo orogeny (Jurassic) resumed the crustal deformation under a contractional setting during the subduction and caused dextral ductile shearing, magmatism, and metamorphism in the entire peninsula. Amnokgang orogeny, corresponding to Bulguksa orogeny in South Korea, during the Cretaceous formed several pull‐apart or transtensional basins probably because of oblique subduction of the Izanagi plate, and nonmarine sedimentary and pyroclastic sequences were deposited in the basin. The mineralization related to the Mesozoic plutonism was the most dominant in the peninsula. The considerable mineral deposits are ultramafic related magmatic Ni deposits owing to rift magmatism and granite related hydrothermal Au–Ag, Cu, Pb–Zn, Fe, W, and Mo deposits caused by the subduction of paleo‐Pacific plate. During the Tertiary, several structural basins under the extensional regime were overprinted on the Mesozoic basins in the northern part of the peninsula. They contain marine and nonmarine sedimentary rocks and felsic–mafic extrusives. Some sedimentary deposits, such as coal, kaolin, bentonite, diatomite, and zeolite, were formed. The Tertiary Pohang basin in South Korea shows basin geology, magmatism, and mineralization similar to those of North Korea. The Phanerozoic geotectonics of the peninsula are characterized by the evolution of the structural basins and violent magmatism. The peninsula is located on the Amur plate, bounded by the Philippine plate, Pacific plate, and Eurasian plate. Since Phanerozoic, the peninsula's geographic position created an important tectonic link between northeastern China and the Japanese Islands throughout geotectonic evolution.

Central East and NE Greenland Composite Tectono-Sedimentary Element, East Greenland Rifted Margin, Greenland Sea

Abstract The Devonian–lower Eocene Central East and NE Greenland Composite Tectono-Sedimentary Element (CTSE) is a part of the NE Atlantic rift system. The East and NE Greenland geology is therefore analogous to that of the prolific basins on the conjugate Atlantic margin and in the North Sea in many respects. Nonetheless, hydrocarbon discoveries remain. The presence of world-class source rocks, reservoirs and seals, together with large structures, may suggest an East and NE Greenland petroleum potential, however. The CTSE was established through Devonian–Carboniferous, Permian–Triassic and Jurassic–Cretaceous rifting interspersed by periods of uplift and post-rift sagging. Subsequently, Paleocene–Eocene magma-rich rifting accompanied the NE Atlantic break-up. Depositional environments through time varied in response to the changing tectonism and climate. Non-marine deposition dominated until the end of the Triassic, only interrupted by marine sedimentation during Late Permian–Early Triassic times. Subsequently, marine conditions prevailed during the Jurassic and Cretaceous. A volumetric series of basalt erupted over most of the CTSE during the latest Paleocene–early Eocene following a significant latest Cretaceous–Paleocene regression, uplift and erosion event. Since the Eocene, denudation pulses have removed much of these basalts and uniquely exposed the up to 17 km-thick strata of the CTSE.

A radiocarbon chronology of Holocene climate change and sea-level rise at the Delmarva Peninsula, US Mid-Atlantic Coast

Radiocarbon dates from 176 sites along the Delmarva Peninsula record the timing of deposition and sea-level rise, and non-marine wetland deposition. The dates provide confirmation of the boundaries of the Holocene subepochs (e.g. “early-middle-late” of Walker et al.) in the mid-Atlantic of eastern North America. These data record initial sea-level rise in the early Holocene, followed by a high rate of rise at the transition to the middle Holocene at 8.2 ka, and a leveling off and decrease in the late-Holocene. The dates, coupled to local and regional climate (pollen) records and fluvial activity, allow regional subdivision of the Holocene into six depositional and climate phases. Phase A (>10 ka) is the end of periglacial activity and transition of cold/cool climate to a warmer early Holocene. Phase B (10.2–8.2 ka) records rise of sea level in the region, a transition to Pinus-dominated forest, and decreased non-marine deposition on the uplands. Phase C (8.2–5.6 ka) shows rapid rates of sea-level rise, expansion of estuaries, and a decrease in non-marine deposition with cool and dry climate. Phase D (5.6–4.2 ka) is a time of high rates of sea-level rise, expanding estuaries, and dry and cool climate; the Atlantic shoreline transgressed rapidly and there was little to no deposition on the uplands. Phase E (4.2–1.1 ka) is a time of lowering sea-level rise rates, Atlantic shorelines nearing their present position, and marine shoal deposition; widespread non-marine deposition resumed with a wetter and warmer climate. Phase F (1.1 ka-present) incorporates the Medieval Climate Anomaly and European settlement on the Delmarva Peninsula. Chronology of depositional phases and coastal changes related to sea-level rise is useful for archeological studies of human occupation in relation to climate change in eastern North America, and provides an important dataset for future regional and global sea-level reconstructions.

Late Devonian non-marine Naiadites devonicus nov. sp. (Bivalvia: Pteriomorphia) from the Waterloo Farm Lagerstätte in South Africa

This study defines a new bivalve species, Naiadites devonicus nov. sp., of Famennian (Late Devonian) age. The material was excavated from the non-marine deposits of the Waterloo Farm Lagerstätte in South Africa, which form part of the Witpoort Formation (Witteberg Group, Cape Supergroup) of the Cape Fold Belt region. The type material of Naiadites devonicus nov. sp. is preserved in metamorphosed, clayey to silty mudstones of a coastal estuarine to lagoonal facies, deposited along the shoreline of the Agulhas Sea, in a high-palaeolatitude Gondwanan setting. The new bivalve species is the stratigraphically oldest representative of the genus Naiadites Dawson. It is a faunal element of a high-latitude palaeoecosystem, immediately preceding the Hangenberg extinction event at the end of the Late Devonian.

Closure of the Paleo‐Asian Ocean in the Middle‐Late Triassic (Ladinian‐Carnian): Evidence From Provenance Analysis of Retroarc Sediments

AbstractA major current debate in Asian tectonics concerns the time of closure of the Paleo‐Asian Ocean (PAO) and the collision between the Central Asian arcs and the Tarim and North China cratons (NCC). This has led to much uncertainty about the reconstruction of proto‐Asia and tectonic configuration of northeast Pangea. Here we report Triassic provenance change in the foreland of the Alxa Block by field‐based zircon U‐Pb and Hf isotopic analysis. Nonmarine sediments, unconformable on or in fault contact, with the Alxa basement yield Precambrian and Paleozoic–Triassic detrital zircon ages with maximum depositional ages of Middle‐Late Triassic (∼244–224 Ma). Hf isotopic data indicate that Middle Triassic sandstones were sourced from the NCC basement and a continental arc, whereas Late Triassic sediments received an additional input from a juvenile arc. This provenance change in the foreland sedimentation indicates that the final closure of the PAO was in the Middle‐Late Triassic.

Environmental DNA signatures distinguish between tsunami and storm deposition in overwash sand

Sandy onshore deposits from tsunamis are difficult to distinguish from storm deposits, which makes it difficult to assess coastal hazards from the geological record. Here we analyse environmental DNA from microbial communities preserved in known tsunami and storm-deposited sediments and intercalating soils and non-marine sediments near Cuddalore, India, and Phra Thong Island, Thailand. Both sites were impacted by the 2004 Indian Ocean Tsunami and a subsequent storm flooding event (2011 Cyclone Thane at Cuddalore and a 2007 storm at Phra Thong Island). We show that the microbial communities in the overwash deposits are significantly different from soil and sediments that are not derived by overwash processes at both locations. Our method also successfully discriminates between modern tsunami deposits and storm deposits. We suggest molecular techniques have the potential to accurately discriminate overwash deposits from catastrophic natural events.

Upper Mesozoic stratigraphy of Sikhote-Alin (Russian Far East) and northeastern China: Non-marine and marine correlations. Part 2: Barremian–Albian

The present paper is the second article in a series of publications dedicated to the upper Mesozoic stratigraphy of Sikhote-Alin (Russian Far East) and northeastern China. The Barremian–Albian stratigraphy of Sikhote-Alin and northeastern China is reviewed and a correlation scheme between these regions is proposed. Barremian–Albian rocks in Sikhote-Alin are mainly represented by marine deposits. Non-marine deposits occur in the south of Sikhote-Alin in the Partizansk and Razdolny basins. In northeastern China, in contrast, the Barremian–Albian rocks are mainly non-marine often intercalated with volcanic rocks. Non-marine deposits alternating with marine ones occur in northeastern Heilongjiang near the border with Russia. They fill a system of sedimentary basins restricted to the Dunhua-Mishan Fault Zone and linked in the east with the Alchan Basin of Sikhote-Alin. The deposits of these basins, represented by the Jixi, Longzhaogou, Dajiashan and Huashan groups, and the Assikaevka and Alchan formations, are of high importance for non-marine and marine correlation because they contain non-marine fauna and flora assemblages together with marine molluscs. The range of the Jixi and Longzhaogou groups is clarified based on the correlation with the Assikaevka Formation containing marine index fossils and is considered here as Barremian (possibly extending to Hauterivian)–middle Albian. The Jixi Group yielding elements of the Jehol Biota corresponds to the Jehol Group, and, therefore, the range of the Jehol Group is also considered as Barremian–middle Albian.

Upper Mesozoic stratigraphy of Sikhote-Alin (Russian Far East) and northeastern China: Non-marine and marine correlations. Part 1: Upper Jurassic–Hauterivian

Upper Mesozoic (Upper Jurassic and Cretaceous) rocks are widely distributed in Sikhote-Alin (Russian Far East) and northeastern China. In Sikhote-Alin, the Upper Jurassic and Lower Cretaceous rocks are represented mainly by marine deposits, whereas the Upper Cretaceous rocks are mainly volcanic and non-marine sedimentary-volcanic. In northeastern China, the upper Mesozoic rocks are, on the contrary, mainly non-marine. Fully marine Upper Jurassic–Valanginian deposits are restricted to the northeastern Heilongjiang Province near the border with Russia. Barremian–Albian non-marine deposits alternating with marine ones also occur in this region. They contain marine and non-marine fauna and, therefore, represent an important object for non-marine and marine correlation. On the rest of the territory of northeastern China, upper Mesozoic rocks are represented by non-marine sedimentary and volcanogenic deposits. The complex geological structure of the region as well as different types of sedimentary basins cause difficulties in correlation between the upper Mesozoic rocks of Sikhote-Alin and northeastern China. Despite the long history of investigations, their correlation schemes are still rare. Creation of a correlation scheme between Sikhote-Alin and northeastern China should be based on revision of published stratigraphic data on both regions. This article is the first in a series of articles devoted to the upper Mesozoic stratigraphy of Sikhote-Alin and northeastern China. In the present article the Upper Jurassic–Hauterivian stratigraphy of Sikhote-Alin and northeastern China is reviewed. The Upper Jurassic–Hauterivian deposits of Sikhote-Alin and northeastern China contain abundant Buchia and rarer ammonites. Based on stratigraphic distribution of buchiid assemblages, the correlation scheme for Kimmeridgian–Valanginian (possibly lowermost Hauterivian) strata of northeastern China and Sikhote-Alin is proposed. The succession of Jurassic–Cretaceous buchiid assemblages of Sikhote-Alin and northeastern China is similar to those of the other regions, e.g., Northern Siberia (Arctic Realm) and California (North Pacific Realm).

Mechanisms of sedimentation in lacustrine environment of Babouri-Figuil and Mayo Oulo-Lere basins deposits (North Cameroon) during the Southern Atlantic opening: sedimentary structures and geochemistry constraints

Sedimentary structures are very useful to characterize sedimentation environments. In this study, sedimentary structures are documented in the Lower Cretaceous Babouri-Figuil and Mayo Oulo-Lere intracontinental Basins whose genesis is linked to the opening of the Southern Atlantic Ocean. Geochemical data is also presented with the aim to discriminate the paleoenvironment. Field investigations and facies analyses revealed synsedimentary and postsedimentary structures related or not to tectonic. Synsedimentary structures not affected by tectonic are lamination or bedding (rhythmic), graded bedding, cross-stratification, loads casts, channels, and ripple marks. Those affected by tectonic are convolute bedding, slump (Slump sensus stricto and olistolith). Desiccation cracks and print marks are postsedimentary structures not related to tectonic; others are stratigraphic unconformity, oblique bedding, clastic injection, and volcanic veins. The bottom of the sequence in the two basins is fluvio-lacustrine deposits with oblique stratification and global positive graded bedding; sometimes there is alternation of positive and negative graded beddings related to progressive variation of energy of sedimentation from high to low and low to high. The intermediate level is lacustrine dominated by lamination or bedding that characterizes a calm sedimentation environment marked by regular seasonal fluctuation. The ripple marks, desiccation cracks, and dinosaur footprints indicate the emersion period, and their fossilization indicates slow phases of sedimentation. Channels and load casts correspond to a rapid sedimentation phase. Seismic shocks at time break the fragile stability of deposited materials causing gravitational flows of the sublacustrine avalanche type and give olistolith and convolute bedding to slumps. The clastic or chemical injections and volcanic veins are related to brittle tectonic that affects consolidated deposits. From the geochemical data, the high accumulation of LREE (average: 142.93 ppm) over HREE (average: 13.10 ppm); La/La* generally 2) and the slight to very slight negative Ce/Ce* (0.87–0.99) suggest the nonmarine deposition, and the Y/Ho ratios (< 45) and ratios indicate river condition or transportation. The Sr/Ba ratios, ranging from 0.55 to 6.41, suggest a freshwater environment with fluctuant salinity and sometimes hypersaline (Hypersaline Lake). Thus the synsedimentary structures were essentially formed in lacustrine milieu, and some structures such as graded bedding and cross-stratification affecting the basal deposit indicate a fluviatile to fluvio-lacustrine environment.

A new elasmosaurid (Sauropterygia: Plesiosauria) from the non-marine to paralic Dinosaur Park Formation of southern Alberta, Canada.

Elasmosaurid plesiosaurian remains have been documented from non-marine to paralic (fluvial to estuarine) sediments of the upper Campanian Dinosaur Park Formation (DPF) of southern Alberta since 1898. Despite this long collection history, this material has received relatively little research attention, largely due to the highly fragmentary nature of most recovered specimens. However, this assemblage is significant, as it constitutes a rare occurrence of plesiosaurian remains in a non-marine depositional environment. This study reports on a recently collected and prepared specimen, which represents the most complete elasmosaurid yet collected from the DPF. This specimen preserves the trunk region, the base of the neck and tail, a partial fore and hind limb, and tooth, and is sufficiently complete to be assigned as the holotype of a new genus and species. This new taxon is diagnosed by a distinctive character state combination including a boomerang-shaped clavicular arch with acute anterior process, convex anterolateral margin, deeply embayed posterior margin, and pronounced ventral keel, together with the presence of 22 dorsal vertebrae, and the anterior dorsal centra bearing a ventral notch. The DPF plesiosaurian fossils were recovered from both estuarine/bay and fluvial palaeochannel sediments. The holotype skeleton represents an osteologically mature individual with an estimated body length of around 5 m, although the largest referred DPF elasmosaurid might have been closer to 7 m, which is considerably larger than other plesiosaurians reported from non-marine deposits. This suggests small-body lengths relative to typical elasmosaurids from marine settings, but is consistent with other plesiosaurians recovered from non-marine sediments. The identification of a distinct elasmosaurid taxon in the DPF might be evidence of niche-partitioning among the predominantly oceanic members of the ubiquitous plesiosaurian clade.

Age of the Post-rift Sequence I from the Araripe Basin, Lower Cretaceous, NE Brazil: implications for spatio-temporal correlation

A robust biostratigraphic zonation based on microfossils supports the stratigraphic framework and correlation of the interior basins of the Lower Cretaceous of NE Brazil. This zonation has also allowed correlations with coeval sections in the Brazilian marginal basins and in the Gabon and Congo basins (central-west Africa). These records, consisting mainly of non-marine sediments, were a great challenge with regard to the correlation with the International Chronostratigraphic Chart. Therefore, local stages were used, the most recent being the Alagoas local Brazilian Stage, with which the Post-rift Sequence I of the Araripe Basin is related. Regarding lithostratigraphy, this sequence includes the Rio da Batateira (Barbalha for some authors) and Santana formations, the last one with the famous Crato, Ipubi, and Romualdo members, from the base to the top. Although currently there is a consensus on the age of the Alagoas local Brazilian Stage in the Araripe Basin, recently a new age for at least part of the Post-rift Sequence I was proposed. This new proposal, based on isotopic analysis of Re-Os, arose as a panacea to correlate the Rio da Batateira Formation and the Crato and Ipubi members with the international stages. Surprisingly, their authors, although on the one hand, they seem to underestimate biostratigraphic results, on the other they seek to support their proposal from microfossils studied by previous authors, but they do so in an inappropriate way, leading readers to misinterpret their results. Therefore, this paper presents a critical review on the age of the Alagoas local Brazilian Stage in the Araripe Basin and nearby basins, refuting a Barremian age for part of the Post-rift Sequence I. Keywords: Alagoas local Brazilian Stage, biostratigraphy, ostracods, palynomorphs, radiometric ages.

Reevaluation of the holotypes of Koskinonodon princeps Branson and Mehl, 1929, and Borborophagus wyomingensis Branson and Mehl, 1929 (Temnospondyli, Metoposauridae)

ABSTRACT Metoposaurids are some of the most commonly occurring tetrapods in non-marine Upper Triassic sediments in the northern hemisphere of Pangea. Since the first description of a metoposaurid in 1842, nearly two dozen species have been named, but many of these have been regarded with increasing skepticism by modern workers because of minor differences used to validate novel species and sometimes novel genera. More recent comprehensive descriptions and evaluations of intraspecific variation from several presumed monospecific bonebeds of metoposaurids have prompted reevaluation of holotypes due to variation in proposed apomorphies. Four metoposaurid species were named from the Popo Agie Formation exposures of Wyoming, U.S.A., but at present, only a single species, Anaschisma browni, is considered valid following a recent redescription of two of these taxa (An. browni and An. brachygnatha). The other two taxa, Borborophagus wyomingensis and Koskinonodon princeps, have not been redescribed since their original description in 1929. A redescription of the holotypes of these two taxa is presented here to assess their historic synonymy with An. browni and to provide a detailed, updated record of the Popo Agie Formation metoposaurids in light of a historic relative lack of attention compared with other North American deposits. Our confirmation of the conspecificity of all four Popo Agie Formation metoposaurids permits a detailed discussion of potential ontogenetic variation in the Popo Agie Formation metoposaurids and latitudinal variability in An. browni.

High-Resolution Seismic Stratigraphy Offshore Haeundae Beach in Busan, South Korea

Choi, D.-L.; Shin, D.-H.; Jin, J.-Y.; Lee. Y.-K., and Kum, B.-C., 2020. High-resolution seismic stratigraphy offshore Haeundae beach in Busan, South Korea. In: Jung, H.-S.; Lee, S.; Ryu, J.-H., and Cui, T. (eds.), Advances in Geospatial Research of Coastal Environments. Journal of Coastal Research, Special Issue No. 102, pp. 187-193. Coconut Creek (Florida), ISSN 0749-0208.The stratigraphic architecture of the Haeundae shallow sea was evaluated using numerous high-resolution single-channel seismic profiles and drilled cores. Two major seismic units over the basement, the lower Unit II and upper Unit I, as well as two subunits (Units Ia and Ib) in the upper Unit I were identified in the study area. Unit II shows numerous chaotic diffraction hyperbolic seismic reflection patterns overlying high amplitude, and irregular reflection of the bedrock surface, corresponding well with the gravel-dominated deposits. Unit II is interpreted as nonmarine alluvial deposits in the Quaternary glaciations. Unit I is present over Unit II with two distinct subunits at different locations: Unit Ia, distributed inshore within ∼10 m depth, and Unit Ib, offshore beyond ∼13 m depth. Unit Ia, which is accumulated more in the western inshore section, exhibits an acoustically semi-transparent and sigmoidal clinoform wedge and is well correlated with sand-dominated deposits from core data. Unit Ib, which pinches out landward but gradually thickens seaward, is generally characterized by transparent seismic facies, likely made up of very fine sandy to muddy sediments from surface sediments. The depositional environments of Units Ia and Ib are categorized as shoreface settings and the landward innermost part of the Nakdong distal delta system during late Holocene sea-level highstand, respectively. Due to severe weather conditions associated with winter storms and summer typhoons as well as human interventions, the sediment morphology and its distribution are thought to have constantly been reactivated and modified.

Aptian Flysch in Central Tibet: Constraints on the Timing of Closure of the Bangong‐Nujiang Tethyan Ocean

AbstractThe timing of the closure of the Bangong‐Nujiang Tethyan Ocean is highly controversial. An important reason for this is that the sedimentological work within the Bangong‐Nujiang suture zone is not sufficient. In this study, based on the U‐Pb zircon dating of turbiditic sandstone and tuff interlayers, we determine the existence of Aptian flysch (ca. 126–113 Ma) in the middle and western segments of the Bangong‐Nujiang suture zone. Further analysis shows that the Aptian flysch was deposited in a trench environment. In space, from the Mabujia Co area in the western segment to the Kama area in the middle segment, the outcrop extent of the Aptian flysch spans nearly 300 km from east to west. These results indicate that the Bangong‐Nujiang Tethyan Ocean had not fully closed by the end of Aptian time, and its oceanic slab was still subducting. Based on this new discovery, and the results of previous studies, we believe that the middle and western segments of the Bangong‐Nujiang Tethyan Ocean closed between 113 and ca. 92 Ma nonmarine deposition of the Jingzhushan Formation, which lies in angular unconformity above the flysch.

New charophyte flora from the Pine Hollow and Claron formations (southwestern Utah). Taxonomic, biostratigraphic, and paleobiogeographic implications

Paleogene non-marine deposits of the Pine Hollow and Claron formations (southwestern Utah, USA) provided a rich microfossil assemblage composed of charophytes, freshwater gastropods and ostracods. Charophytes were extracted from a ca. 450-m-thick section, especially from floodplain deposits belonging to the Claron and the Pine Hollow formations. The samples from the Pine Hollow Formation includes small and recrystallized populations of Psilochara sp., Peckichara sp. and Harrisichara sp. The occurrence of these genera suggests that this unit is Paleogene in age. The richer charophyte assemblage was recovered from the Claron Formation and is dominated by Microchara cristata, Microchara cf. punctata and Peckichara torulosa (here synonymized with the well-known Eurasian species Peckichara varians), along with Lychnothamnus sp. and Dughiella sp. Based solely upon charophyte Euroasiatic biostratigraphic ranges of M. cristata, M. punctata and P. torulosa, the basal/middle part of the Claron Formation is probably Danian in age. However, recent biostratigraphic studies based on mammals indicate that the middle part of the Claron Formation (unit 7) is early Eocene in age. The correlation of charophytes with mammals and the lack of significant unconformities in this formation suggest that these species could live longer in North America than Eurasia. The lack of North American charophyte studies, along with the long biostratigraphic ranges of the dominant taxa, M. cristata and P. torulosa, makes precise relative dating, solely on the basis of charophytes, difficult. This study also provides valuable data about Eurasian charophyte species and genera discovered for the first time in North America.

Topsoe reports record results for 2019

This paper presents an integrated study aiming to assess the stratigraphy, sedimentology and paleogeography of the marine and non-marine Tellian, Bejaoua and Fortuna Oligo-Miocene deposits of northern Tunisia. The fossiliferous strata, particularly the glauconite-rich facies, bounded by major unconformities, refine the stratigraphic framework and address the spatio-temporal relationship between marine and non-marine deposits. Three new updated paleogeographic maps for the Oligocene (30-27 Ma) and the Miocene (21-20 Ma and 15 Ma) epochs, outlining the major transgressive and regressive events and the relationships between the Tellian and Atlasic basins have been produced. The genesis and evolution of the Oligo-Miocene foreland sub-basins of the Tellian, the salt domes zone and the northern Atlas are reconstructed considering the geodynamic events that accompanied the African-Eurasian convergence, besides eustasy and climate.

The Oligo-Miocene siliciclastic foreland basin deposits of northern Tunisia:Stratigraphy, sedimentology and paleogeography

This paper presents an integrated study aiming to assess the stratigraphy, sedimentology and paleogeography of the marine and non-marine Tellian, Bejaoua and Fortuna Oligo-Miocene deposits of northern Tunisia. The fossiliferous strata, particularly the glauconite-rich facies, bounded by major unconformities, refine the stratigraphic framework and address the spatio-temporal relationship between marine and non-marine deposits. Three new updated paleogeographic maps for the Oligocene (30-27 Ma) and the Miocene (21-20 Ma and 15 Ma) epochs, outlining the major transgressive and regressive events and the relationships between the Tellian and Atlasic basins have been produced. The genesis and evolution of the Oligo-Miocene foreland sub-basins of the Tellian, the salt domes zone and the northern Atlas are reconstructed considering the geodynamic events that accompanied the African-Eurasian convergence, besides eustasy and climate.

Ostracods from the Upper Cretaceous–Paleocene Jiaozhou Formation of Jiaozhou, Shandong, China and their biostratigraphic significance

Late Mesozoic–Cenozoic non-marine deposits are well developed in the Jiaolai Basin, eastern Shandong Province, China, yielding abundant fossils including ostracods. In order to further understand the geological settings of the basin during the Late Cretaceous–Paleogene, three boreholes (JK-1, JZK-01 and JZK-02) were drilled in the city of Jiaozhou. Nine genera and sixteen species (including six indeterminate species) of ostracods are described from the Jiaozhou Formation in the three boreholes, including Cypridea, Mongolocypris, Talicypridea, Candona, Eucypris, Cyprois, Porpocypris, Sinocypris and Timiriasevia. Of these, Porpocypris sphaeroidalis Guan, 1978 is reported from northern China for the first time, indicating that this species has great potential to be an indicator of the K/Pg boundary. Correlation of these species with the known Cretaceous–Paleogene ostracod assemblages suggests that the age of the Jiaozhou Formation could be latest Cretaceous–Paleocene in borehole JK-1, Campanian–Maastrichtian in borehole JZK-01, and Maastrichtian–Danian in borehole JZK-02. The exact position of K/Pg boundary, however, is unavailable for the present in the Jiaozhou Formation from boreholes JK-1 and JZK-01.

Fluvial deposits of the Diamante Formation as a record of the Late Cretaceous tectonic activity in the Southern Central Andes, Mendoza, Argentina

The Upper Cretaceous nonmarine deposits of the Neuquén Basin have an important regional exposure. These deposits are included in the Neuquén Group, a well-studied unit in both the south and central part of the basin. However, the northernmost exposed between the Laguna del Diamante and the Atuel River-assigned to the Diamante Formation-have not been studied in detail. In the studied area, the Diamante Formation corresponds to a braided fluvial system with moderate sinuosity evolving through time towards an anastomosing fluvial system. Petrographic analyses indicate that sandstones belong to feldspatic litharenites and litharenites, while the source area indicates provenance from both a recycled orogen and a transitional arc. The latter could be linked to the exhumation of the Andean orogen located to the west and to the input from the north-eastern border of the Neuquén Basin, represented by the rocks currently exposed in the San Rafael Block. On a macroscopic scale, the presence of calcareous lithic fragments in the mid and upper part of the surveyed stratigraphic section, strongly suggest an input from the west. This indicates an important change in the polarity of the basin and the presence of a deformation front located to the west of the study area in accordance to previous proposals in equivalent deposits to the south of study area.

The Tumblagooda Sandstone revisited: exceptionally abundant trace fossils and geological outcrop provide a window onto Palaeozoic littoral habitats before invertebrate terrestrialization

AbstractThe establishment of permanent animal communities on land was a defining event in the history of evolution, and one for which the ichnofauna and facies of the Tumblagooda Sandstone of Western Australia have been considered an archetypal case study. However, terrestrialization can only be understood from the rock record with conclusive sedimentological evidence for non-marine deposition, and original fieldwork on the formation shows that a marine influence was pervasive throughout all trace fossil-bearing strata. Four distinct facies associations are described, deposited in fluvial, tidal and estuarine settings. Here we explain the controversies surrounding the age and depositional environment of the Tumblagooda Sandstone, many of which have arisen due to the challenges in distinguishing marine from non-marine depositional settings in lower Palaeozoic successions. We clarify the terminological inconsistency that has hindered such determination, and demonstrate how palaeoenvironmental explanations can be expanded out from unambiguously indicative sedimentary structures. The Tumblagooda Sandstone provides a unique insight into an early Palaeozoic ichnofauna that was strongly partitioned by patchy resource distribution in a littoral setting. The influence of outcrop style and quality is accounted for to contextualize this ichnofauna, revealing six distinct low-disparity groups of trace fossil associations, each related to a different sub-environment within the high-ichnodisparity broad depositional setting. The formation is compared with contemporaneous ichnofaunas to examine its continued significance to understanding the terrestrialization process. Despite not recording permanent non-marine communities, the Tumblagooda Sandstone provides a detailed picture of the realm left behind by the first invertebrate pioneers of terrestrialization.