Local Tectonic Activity Research Articles

Genetic mechanism and petroleum geological significance of calcite veins in organic-rich shales of lacustrine basin: A case study of Cretaceous Qingshankou Formation in Songliao Basin, China

Based on the observation and analysis of cores and thin sections, and combined with cathodoluminescence, laser Raman, fluid inclusions, and in-situ LA-ICP-MS U-Pb dating, the genetic mechanism and petroleum geological significance of calcite veins in shales of the Cretaceous Qingshankou Formation in the Songliao Basin were investigated. Macroscopically, the calcite veins are bedding parallel, and show lenticular, S-shaped, cone-in-cone and pinnate structures. Microscopically, they can be divided into syntaxial blocky or columnar calcite veins and antitaxial fibrous calcite veins. The aqueous fluid inclusions in blocky calcite veins have a homogenization temperature of 132.5–145.1 °C, the in-situ U-Pb dating age of blocky calcite veins is (69.9±5.2) Ma, suggesting that the middle maturity period of source rocks and the conventional oil formation period in the Qingshankou Formation are the sedimentary period of Mingshui Formation in Late Cretaceous. The aqueous fluid inclusions in fibrous calcite veins with the homogenization temperature of 141.2–157.4 °C, yields the U-Pb age of (44.7±6.9) Ma, indicating that the middle-high maturity period of source rocks and the Gulong shale oil formation period in the Qingshankou Formation are the sedimentary period of Paleocene Yi'an Formaiton. The syntaxial blocky or columnar calcite veins were formed sensitively to the diagenetic evolution and hydrocarbon generation, mainly in three stages (fracture opening, vein-forming fluid filling, and vein growth). Tectonic extrusion activities and fluid overpressure are induction factors for the formation of fractures, and vein-forming fluid flows mainly as diffusion in a short distance. These veins generally follow a competitive growth mode. The antitaxial fibrous calcite veins were formed under the driving of the force of crystallization in a non-competitive growth environment. It is considered that the calcite veins in organic-rich shale of the Qingshankou Formation in the study area has important implications for local tectonic activities, fluid overpressure, hydrocarbon generation and expulsion, and diagenesis-hydrocarbon accumulation dating of the Songliao Basin.

Structural geology and tectonic influence on lineament density and slope variation in Southern Ebonyi, Nigeria: An ArcGIS Approach

This study investigates the structural geology and tectonic influences on lineament density and slope variation in Southern Ebonyi, Nigeria, using ArcGIS. The research aims to analyze the spatial distribution and density of lineaments and their correlation with slope variations to understand the region's geomorphology. Slope data was categorized into five classes, revealing that the majority of the area exhibits gentle slopes, indicative of tectonic stability. Conversely, regions with steeper slopes suggest localized tectonic activity. The analysis of lineament density identified areas with varying tectonic influences, with most of the study area showing low-density lineaments, suggesting relative tectonic stability. High-density lineament zones correspond to regions of significant tectonic deformation, often aligning with steeper slopes. The study concludes that the geomorphology of Southern Ebonyi is predominantly shaped by long-term erosional processes and localized tectonic activities. The novelty of this research lies in its comprehensive spatial analysis of both slope variation and lineament density, providing new insights into the tectonic and structural dynamics of the region.

Groundwater and Dissolved Gases Geochemistry in the Pesaro-Urbino Province (Northern Marche, Central Italy) as a Tool for Seismic Surveillance and Sustainability

The Pesaro-Urbino province (PUP) (northern Marche, central Italy) is one of the most seismically active areas in Italy, with the most recent earthquakes (5.2 and 5.5 Mw) having occurred on 9 November 2022 with an epicenter located in the Adriatic Sea. A detailed geochemical and isotopic characterization of 87 groundwaters (and dissolved gases) circulating in the PUP was carried out to (i) unravel the geochemical processes controlling the water circulation, (ii) investigate the interplay between deep originated fluids and shallow aquifers, (iii) evaluate the reliability of specific geochemical parameters as tracers for seismic activity, and (iv) select the most suitable sampling sites to deploy a monitoring network to highlight possible compositional changes related to the regional and local tectonic activity. The geochemical dataset includes waters showing five different hydrochemical compositional facies: (i) calcium bicarbonate with low Total Dissolved Solids (TDS); (ii) calcium bicarbonate with relatively high concentrations of sulfate (>200 mg/L); (iii) sodium bicarbonate with pH > 8.8; (iv) calcium sulfate; (v) sodium chlorine. Two distinct groups of dissolved gases can be recognized: (a) N2-dominated gases with N2/Ar ratios similar to those of Air-Saturated Water (ASW); (b) CO2- and CH4-rich gases associated with high TDS and springs rich in S-bearing reduced species. The isotopic values of δ13C-CO2 and δ13C-CH4 suggest a predominant biogenic origin for both species with a negligible contribution from deep-seated fluids. The Ca-HCO3(SO4), Ca(Na)-SO4(Cl), and Na-HCO3 waters, being likely related to deep hydrological pathways, are the best candidates to be included in the monitoring network in the Pesaro-Urbino province. This will be of paramount importance in addressing the challenge of unravelling fluid geochemical precursors of earthquakes, thus increasing and improving seismic surveillance practices and hazard mitigation.

Seismic sequence stratigraphy of Late Albian-Early Turonian successions in SW Iran: Implication for reservoir characterizations and potential for improved reservoir quality prediction

The Late Albian-Early Turonian succession on the Arabian Platform stands out as one of the world's richest hydrocarbon provinces. This study delves into the Seismic Sequence Stratigraphy (SSS) of these successions to unravel reservoir characterization and characterized potential hydrocarbon plays. Utilizing data from five exploration wells, including well logs, selected core data, biostratigraphical information, and chemostratigraphy analysis, alongside a comprehensive 3D seismic volume, enabled the identification of four 3rd-order sequences and multiple 4th-order sequences within the studied successions. Sequence-1 (DS-I), dating back to the Late Albian age, features mudstone and bioclast wackestone in an open marine environment. DS-I is a key sequence, notably witnessing the disappearance of siliciclastic input from west to east in the study area. DS-II (Early Cenomanian) and DS-III (Mid-Cenomanian) were deposited on carbonate platforms with grain-supported facies in shoal and lagoonal depositional environments.A distinct regional unconformity at the Turonian base, evident on seismic sections, aligns with depleted δ18O values on the Cenomanian-Turonian Boundary. The maximum flooding surfaces of DS-I and DS-II are characterized by continuous reflectors with negative amplitude. Furthermore, the lateral grading of reservoir facies and their intercalation with non-reservoir facies within 4th-order sequences suggest that reservoir facies heterogeneity is strongly influenced by depositional processes at this scale. Potential reservoirs, particularly in the Highstand System Tract (HST) of each 3rd sequence, are highlighted, with DC-III's HST standing out, hosting patch reef facies resulting from local tectonic activities and carbonate build-up movements.

A new sedimentary and biostratigraphic framework for the Callovian-Oxfordian transition on the Atlantic margin of Morocco

A major global marine transgression occurred during the Callovian to Early Kimmeridgian, which was interrupted locally by a hiatus during the Late Callovian to Early Oxfordian. The transgression may have been a major driver for extensive coral buildup development in the Oxfordian. The depositional hiatus may be related to a combination of eustasy, local tectonic activity and hinterland movements, highlighting the potential influence of tectonism on sedimentary evolution in sedimentary basins. Whilst a regional Late Callovian-Early Oxfordian hiatus has been recorded extensively in the Tethys realm, this study has improved the biostratigraphic and sedimentary record from Morocco, and for the first time documents the Late Callovian-Early Oxfordian depositional hiatus in the Atlantic realm. Detailed sedimentary facies analysis of Callovian to Oxfordian carbonates and siliciclastics (Ouanamane Formation) demonstrates a major transgression from continental and coastal sediments, through oolitic mid-inner ramp deposits, brachiopod-rich middle ramp deposits, and ultimately to outer ramp marls, sharply overlain by Middle Oxfordian coral buildups across the basin. Repeated hard- and firmgrounds and bioturbated bed tops highlight transgressive surfaces traceable basinwide, which suggests low sedimentation rates in the upper Ouanamane Formation. Localized siliciclastic input is evidence for episodes of erosion in the same interval. Collection of new fossil specimens (ammonites, brachiopods, echinoderms, foraminifera) and revision of existing fossil material suggest this interval corresponds to a hiatus or condensed section in the Callovian-Oxfordian transition. The uppermost part of the Ouanamane Formation is of early Middle Oxfordian age and is directly overlain by Middle Oxfordian coral buildups. Onset of buildup construction is considered synchronous based on the new biostratigraphic data. Observations in Moroco compare with the sedimentary evolution around the Tethys, and in particular with the Arabian Plate. The Callovian-Oxfordian depositional hiatus corresponds to eustatic sea level changes, which were possibly driven by global cooling, and was likely overprinted by local tectonics.

Depositional environment and sequence stratigraphy of the Qom Formation (Miocene) from the Ghalibaf section, Central Iran

The Miocene strata of the Qom Formation from the Ghalibaf section, Central Iran (NW Semnan) documented a high diversity of shallow-marine microfacies. These deposits in the Ghalibaf section, with a total thickness of 445 m, are characterized by twenty-one microfacies. The carbonate microfacies are deposited into five facies belts, including a lagoon, upper slope, lower slope, platform-margin sand shoals and margin facies. The presence of barrier reefs, intraclasts, oncoids, and grainstone aggregates, along with the absence of vast tidal flat areas, are distinguished. According to the aforementioned evidences, these sediments were deposited on a rimmed carbonate platform. In addition, the heterolithic calciturbidite deposits also show that the carbonate sequences were sedimented on a rimmed carbonate platform. Based on the available data of sequence stratigraphy analysis, seven third-order depositional sequences are bounded by type-1 and type-2 sequence boundaries. The relative sea-level changes between the upper and lower sequence boundaries in accord with the global sea-level curves reveal a reasonable correlation. However, some differences in other sequence boundaries might be due to local tectonic activities in the Qom Formation sedimentary basin, thereby leading to local sea-level changes. Moreover, biostratigraphic data based on the larger foraminifera index markers, including Praebullalveolina curdica, Borelis melo, Dendritina rangi, Meandropsina iranica, Elphidium sp. 14, Neorotalia viennoti, and Miogypsina sp. suggests the Miocene Shallow Benthic Zones, SBZ24-SBZ25 equivalent to the late Aquitanian-Burdigalian timespan.

Gas Hydrates, Subsurface Structures and Tectonic Features of the Tuaheni Landslide Complex in the Northern Hikurangi Margin, New Zealand, Revealed by Seismic Attribute Analysis

The Tuaheni Landslide Complex, located on the upper slope of the northern Hikurangi Margin in New Zealand, is a unique place to research on slow slip creep-like deformation and seabed failure, as well as their possible relationship with the presence of gas hydrates, cold seeps, and fluid migration. Based on the visual interpretation of seismic data, it is sometimes very difficult to identify various subsurface structures and tectonic features. We study certain seismic attributes, namely the reflection strength, instantaneous frequency, instantaneous phase, and the Hilbert transform, in the Tuaheni Landslide Complex and observe that these attributes play a very important role in identifying and interpreting various subsurface geological features and bed boundaries that are not clearly visible in the seismic sections. In general, these seismic attributes are studied to identify hydrocarbons such as oil and gas. However, in this present study these seismic attributes nicely illustrate the fluid migration pathways, the decollement of the sediment slide, the base of the debris flow, the base of the deformed sediment and gas migration, etc., along two perpendicular seismic profiles crossing the Site U1517 of IODP Expedition 372. The instantaneous phase and Hilbert transform attribute depict the bed boundaries and discontinuities, whereas the reflection strength and instantaneous frequency attributes characterize the various strata in terms of whether they are associated with fluid at their bases. The possible role of tectonic activity and seafloor slope failure due to gas hydrate dissociation and vice versa is clearly visible through fluid-filled weak zones in the seismic attribute volumes. Gas hydrates are dissociating and BSRs are abruptly pinching out towards the seafloor due to the movement of hot fluid and free gas, enhancing seafloor sliding and local tectonic activities together.

Seismic sequence stratigraphy and depositional modelling of the Lower Fahliyan Formation in the northwestern Persian Gulf, SW Iran

This study presents seismic stratigraphic-based sedimentary conceptual modelling through the integration of well data, seismic data, and literature in order to identify the architecture of the Berriasian-Early Valanginian Lower Fahliyan Formation in the northwestern Persian Gulf. The applied methodology is configured by interpreting seismic sections in terms of sequence stratigraphy and adapting them using well data facies associations and fossil assemblages. The time framework of these sediments is identified by their faunal/flora assemblage and extrapolated by seismic data because of their extensive coverage. Three third-order depositional sequences (DS-I, DS-II, and DS-III) were distinguished based on the facies changes, depositional geometries, and fossil assemblages. Regional and local tectonic activities and global sea-level changes controlled the sedimentation of the depositional sequences. The local tectonic activities were of higher importance as they strongly affected the thickness and facies type of the studied interval. The depositional sequences of the Lower Fahliyan Formation are deposited in the inner to outer settings of a carbonate shelf. It was concluded that DS-I and DS-II over the platform (Surmeh Platform), consisting of progradational parasequences, deposited during the highstand phase in shoal settings that due to primary texture and subsequent diagenetic imprints yield the best reservoir quality. The relationship of the parasequences with good reservoir quality was determined on seismic sections and the prepared regional correlation panel over the study area. Furthermore, the paleoenvironmentof the area was constructed and modelled for major stratal surfaces (Sequence boundaries and maximum flooding surfaces). According to the generated models, the distal setting (Garau Basin) migrated back gradually northward during the Berriasian-Early Valanginian so that it was completely replaced by a homoclinal ramp at the end of the DS-III deposition. Subsequently, the relief of Surmeh Platform was also flattened and it was recognized as the end of the first phase of the basin's activity.

Global sea level changes or local tectonics? Pliocene, Miocene and Oligocene biomarkers in cored sedimentary rocks from IODP Expedition 317, Canterbury Basin, New Zealand

The various influences of global sea level (eustasy) and local tectonic changes on sedimentation processes in continental margin deposits are important topics in sedimentary research. International Ocean Discovery Program Expedition 317 to the Canterbury Basin, on the eastern margin of the South Island of New Zealand, provided an opportunity to study sediment geochemistry in contrasting depositional settings, from mid-shelf to upper continental slope sedimentary rocks from the Eocene to the Holocene. This paper provides the first examination of the organic geochemical record from Pliocene, Miocene, and Oligocene sediment samples recovered during the expedition from the U1351, U1352, and U1353 sites, using bulk geochemistry and hydrocarbon distributions, including biomarkers. The main aim of this research was to correlate changes in organic accumulation with local tectonic activity and global climate changes that occurred in the Miocene. There is good preservation of C11 to C35n-alkanes, with varying predominance of odd-over-even chain length n-alkanes, and much variation in the terrigenous/aquatic ratio over the cores. Based on biomarker and Rock Eval parameters, thermal maturity varies from low in the Pliocene, to early oil window in the deeper Miocene and Oligocene sedimentary rocks. The pristane/phytane ratios for the three cores indicate anoxic to oxic depositional environments. Marine organic matter input is indicated by the high C30 sterane index, whilst high relative amounts of oleanane, C24 tetracyclic terpane, and C29 steranes indicates major terrigenous organic matter input. Local tectonic activity is suggested to have had a significant influence on the accumulation of the organic matter in the Canterbury Basin. The influence of eustasy and global sea temperature variations are suggested for the periods < 14 Ma, 12–7 Ma, and ∼ 6 Ma. An increase in terrigenous organic matter input during the late Miocene correlates with the uplift of the Southern Alps and an increase in the continental slope angle for the South Island of New Zealand.

WITHDRAWN: Seismic sequence stratigraphy and depositional conceptual modelling of the Beriasian- Early Valanginian lower Fahliyan Formation in the northwestern Persian Gulf, SW Iran

This study presents a seismic stratigraphic-based sedimentary conceptual modelling through integration of well data, seismic data, and literature in order to identify the architecture of the Berriasian- Early Valanginian lower Fahliyan Formation in the northwestern Persian Gulf. The applied methodology is configured by interpreting seismic sections in terms of sequence stratigraphy and adapting them using well data facies associations and fossil assemblages. The time framework of these sediments is identified by their faunal/flora assemblage and extrapolated by seismic data because of their extensive coverage. Three third order depositional sequences (DS-I, DS-II, and DS-III) were distinguished based on the facies changes, depositional geometries, and fossil assemblages. Regional and local tectonic activities and global sea-level changes controlled the sedimentation of the depositional sequences. The local tectonic activities were of higher importance as they strongly affected the thickness and facies type of the studied interval. The depositional sequences of the lower Fahliyan Formation deposited in the inner to outer settings of a carbonate shelf. It was concluded that DS-I and DS-II over platform (Surmeh platform), consisting of progradational parasequences, deposited during the high-stand phase in shoal settings that due to primary texture and subsequent diagenetic imprints yield the best reservoir quality. The relationship of the parasequences with good reservoir quality determined on seismic sections and the prepared regional correlation panel over the study area. Furthermore, geodynamic evolution of the area was constructed and modelled for major stratal surfaces (Sequence boundaries and maximum flooding surfaces). According to the generated geodynamic models, the distal setting (Garau Basin) migrated-back gradually northward during the Beriasian-Early Valanginian as a way that it was completely replaced by a homoclinal ramp by the end of the deposition of DS-III. Subsequently, Surmeh platform relief was also flattend and recognized as the end of the first phase of the basin activity.

Late Miocene to Present Paleoclimatic and Paleoenvironmental Evolution of the South China Sea Recorded in the Magneto‐Cyclostratigraphy of IODP Site U1505

AbstractThe continuous sedimentary cores recovered at the International Ocean Discovery Program (IODP) Site U1505, Expedition 368, provide an opportunity for paleoceanography and paleoclimate reconstruction in the continental margin of the northern South China Sea (SCS). In this study, we conducted detailed rock‐ and paleomagnetic studies on 420 discrete samples from the top ∼200 m of the synthetic records of Holes U1505C and U1505D. Rock magnetic analyses indicate that low‐coercivity pseudosingle domain magnetite dominates as the primary ferromagnetic mineral of Site U1505. The magnetostratigraphic age model was constructed by correlating the interpreted polarity sequence with the Geomagnetic Polarity Time Scale 2020 with the constraints of the biostratigraphic data and the distribution probability of the age of each polarity zone provided by a Dynamic Time Warping algorithm. The Milankovitch cycles of the short eccentricity, obliquity, and precession cycles were identified in the magnetic susceptibility (MS) and natural gamma radiation (NGR) series based on paleomagnetic results. We established an ∼9 Myr high‐resolution astronomical time scale by tuning the MS and NGR records to the global oxygen isotope curves, the obliquity, and the eccentricity curves of the La2004 astronomical solution. Our new age model reveals detailed sedimentation rate variations and a ∼500 kyr hiatus across the Brunhes‐Matuyama boundary related to local tectonic activity. These results lay the foundation for understanding the paleoceanography and paleoclimate evolution of the SCS.

Stratigraphy and chronology of the Cala Mosca site, SW Sardinia (Italy)

AbstractThe relict beach deposit of the Cala Mosca marine terrace is considered an important section of Marine Isotopic Stage (MIS) 5e (ca. 125 ka) sea-level highstands. Analysis of the stratigraphy and sediments of the deposit indicates the presence of a composite marine terrace comprising two superimposed marine units, luminescence dated to the MIS 5e (137 ± 7, 134 ± 7 ka) and MIS 5c (92 ± 6 ka) substages. The stratigraphic superimposition of the two highstands, both placed ~5 m above present sea level, agrees with other areas along the Sardinia coasts. The evident superimposition of two sea-level highstands and development of the composite terrace cannot be accounted solely by high-frequency sea-level oscillation that occurred within MIS 5 for the Mediterranean Sea. This suggests controversial, but significant, regional versus local tectonic activity occurred during the Late Pleistocene.

Sequence stratigraphy of the Miocene siliciclastic–carbonate sediments in Sadat Area, north‐west of Gulf of Suez: Implications for Miocene eustasy

The Miocene sequences in the north‐west of the Gulf of Suez represent transition zones between carbonate‐dominated and siliciclastic‐dominated strata. These rocks were greatly influenced by the Gulf of Suez rifting, which resulted in lateral variations of facies and hence presented a complicated stratigraphic setting. Here, we interpret the sequence stratigraphy of the Sadat Area to the north‐west of the Gulf of Suez by integrating biostratigraphic data and microfacies analysis to contribute primarily to the geology of the studied successions and incorporate the existing knowledge of syn‐rift deposition. We determined the ages of the studied formations by biostratigraphic examination of the integrated calcareous nannoplankton, planktic, and benthic foraminifera. Our results distinguish four genetic Miocene sequences. These sequences are defined by four major sequence boundaries that outline sedimentation cycles and were chiefly deposited in a lagoon to outer‐shelf settings. The proposed Miocene eustacy is well‐correlated with global curves, implying a rise in sea level in the lower parts of Zones M4, M5, and M8. In contrast, the reduction of sea‐level rise resulted in the decrease of accommodation space in the upper part of Zone M5. The studied Miocene deposits mainly formed in a shallower marine environment, as shown by a comparison between data from the eastern side of the Gulf of Suez and the data presented in this paper. Furthermore, we demonstrate that the local tectonic activity linked with the Gulf of Suez rifting and the eustatic sea‐level changes were significant factors in the deposition of the Miocene in the studied successions.

Lithofacies types, mineralogical assemblages and depositional model of the Maastrichtian–Danian successions in the Western Desert of Iraq and eastern Jordan

An integrated lithofacies and mineralogical assemblage was used to describe a depositional model and sequence stratigraphic framework of the Maastrichtian–Danian succession in the Western Desert of Iraq and eastern Jordan. Fifteen lithofacies types were grouped into three associations recognized in a distally steepened ramp characterized by an apparent, distinct increase in a gradient paleobathymetric deepening westward. The clay and nonclay minerals are dominated by smectite and palygorskite, with trace amounts of kaolinite, sepiolite, illite and chlorite. Meanwhile, quartz, calcite, dolomite, opal CT (Cristobalite - Tridymite), and apatite are the main nonclay minerals. The widely dominated smectite in the Western Phosphatic Basin of Iraq (WPB) refers to warm, subhumid climates and low topographic relief in the source area, which increased significantly with transgressive cycles. In contrast, the palygorskite was generated under seasonal semiarid/arid climates associated dominantly with regressive cycles. Five sequence boundaries are documented in the present study according to hiatus, erosional surfaces, Thalassinioides burrows, reworked fauna, and extensively bored hardground. These sequence boundaries separate the studied sequences into four third-order depositional sequences correlated to their regional and global counterparts. The combined effects of the local tectonic activity of the Rutbah High and sea-level drops are amalgamated inside the Western Desert of Iraq and eastern Jordan because of a long-time gap, particularly across the Cretaceous/Paleogene (K/Pg) and Danian/Selandian (Da/Se) transitions.

Detailed Processes and Potential Mechanisms of Pliocene Salty Lake Evolution in the Western Qaidam Basin

Hyperarid climate and salty lakes prevail in the current Qaidam Basin, but this basin was once a large paleolake until the early Quaternary. However, its evolution history and relationship with climate and tectonics are still elusive. Here we present detailed stratigraphic descriptions combined with total organic carbon content and weight ratio of organic carbon to total nitrogen records from fluvio-lacustrine sediments in the western Qaidam Basin to infer how the lake evolved during the late Pliocene-early Pleistocene. These data reveal a drying trend since 3.3 Ma, which we attribute to low latitude forcing and/or local tectonic activities. However, this trend was interrupted during 2.84–2.48 Ma, in which climate wetting was observed. We attribute the climate wetting during 2.84–2.48 Ma to intensified East Asian summer monsoon as is documented by the Chinese Loess Plateau records. Halite and gypsum content increased dramatically after 2.5 Ma, indicating the formation of salty lake in the western Qaidam Basin. These data improve our understanding of the detailed processes of Qaidam aridification and its potential forcing mechanisms.

Depositional history and sequence stratigraphy of central Tethyan from the Upper Triassic Nayband Formation, Central Iran

To progress in the knowledge of Upper Triassic evolution of the central Tethys realm, an integrated approach which includes new sedimentological and sequence stratigraphy has described in central Iran. The Nayband Formation of Late Triassic age in central Iran is composed of various rocks of siliciclastic and mixed carbonate–siliciclastic deposits and represents an example of storm-dominated shelf deposition. Based on texture and sedimentary structures of the siliciclastic deposits, 11 lithofacies were identified and classified into three categories, i.e., conglomerate (Gms, Gcm), sandstone (Sp, Se, Sm, Sr, Hcs, Scs, Sh) and mud rock (Fm, F). These mainly consist of alternations of sandstone and shale, and constitute the lower and upper units of the studied section. The mixed carbonate–siliciclastic sediments crop out in the middle unit of the section. Based on field observations and petrographic studies, 12 microfacies were recognized which can be grouped into three depositional environments: shoreface (lower, upper), offshore-transition (proximal, distal) and offshore (upper, lower) on a storm-dominated shelf. Seven 3rd-order depositional sequences have been identified in this section based on field observations, facies analysis and sequence stratigraphy studies. The lower and upper boundaries of this succession are type 1 sequence boundaries (SB1); whereas, other boundaries are type 2 sequence boundaries (SB2). Depositional sequences are composed only of TST, MFS and HST, whereby the transgressive sequences (TST) mainly consist of deeper facies, and regressive sequences (HST) consist of shallower facies. Shelf transport was driven by the available accommodation space on the shelf and therefore was a function of eustatic sea-level fluctuations, but local tectonic activity has also controlled the thickness of the deposits.

Morphological changes in the proximity of the Greek colonies founded along the western (Romanian) Black Sea coast: Orgame, Histria, Tomis, and Kallatis

This paper is a review of the up to date knowledge about the coastal environmental transformations around the Greek settlements along the present–day Romanian shoreline. The aim is to define a general pattern of the morphological configuration the Greeks were looking for when establishing their colonies. Existing quantitative and qualitative database on shoreline evolution both along the low lying deltaic sector (N) and along the soft rock cliffs along the southern sector of the present–day Romanian coast together with the present day morphological configuration analysis at each study site were used to assess large spatial (~180 km alongshore) and temporal scales (ca. 2500 yrs) of coastal behavior. The coastal dynamics during the late Holocene was controlled by the deltaic lobes development along the northern part of the present day Romanian coast which led to important shoreline progradation and subsequent isolation from the shoreline of Histria and Orgame Greek cities. The continuous sediment input depletion, sea level rise, storms set-up, longshore transport system and local tectonic activity drove the cliff line retreat along the southern sector, with important parts of the Tomis and Kallatis settlements being lost to the sea.

Chronostratigraphy of the Baringo-Tugen Hills-Barsemoi (HSPDP-BTB13-1A) core – 40Ar/39Ar dating, magnetostratigraphy, tephrostratigraphy, sequence stratigraphy and Bayesian age modeling

The Baringo-Tugen Hills-Barsemoi 2013 drillcore (BTB13), acquired as part of the Hominin Sites and Paleolakes Drilling Project, recovered 228 m of fluvio-lacustrine sedimentary rocks and tuffs spanning a ~3.29–2.56 Ma interval of the highly fossiliferous and hominin-bearing Chemeron Formation, Tugen Hills, Kenya. Here we present a Bayesian stratigraphic age model for the core employing chronostratigraphic control points derived from 40Ar/39Ar dating of tuffs from core and outcrop, 40Ar/39Ar age calibration of related outcrop diatomaceous units, and core magnetostratigraphy. The age model reveals three main intervals with distinct sediment accumulation rates: an early rapid phase from 3.2–2.9 Ma; a relatively slow phase from 2.9–2.7 Ma; and the highest rate of accumulation from 2.7–2.6 Ma. The intervals of rapid accumulation correspond to periods of high Earth orbital eccentricity, whereas the slow accumulation interval corresponds to low eccentricity at 2.9–2.7 Ma, suggesting that astronomically mediated climate processes may be responsible for the observed changes in sediment accumulation rate. Lacustrine transgression-regression events, as delineated using sequence stratigraphy, dominantly operate on precession scale, particularly within the high eccentricity periods. A set of erosively based fluvial conglomerates correspond to the 2.9–2.7 Ma interval, which could be related to either the depositional response to low eccentricity or to the development of unconformities due to local tectonic activity. Age calibration of core magnetic susceptibility and gamma density logs indicates a close temporal correspondence between a shift from high- to low-frequency signal variability at ~3 Ma, approximately coincident the end of the mid-Piacenzian Warm Period, and the beginning of the cooling of world climate leading to the initiation of Northern Hemispheric glaciation c. 2.7 Ma. BTB13 and the Baringo Basin records may thus provide evidence of a connection between high-latitude glaciation and equatorial terrestrial climate toward the end of the Pliocene.

Climatic control on stacking and connectivity of fluvial successions: Upper Cretaceous Bajo Barreal Formation of the Golfo San Jorge basin, Patagonia

Abstract Climate impact on alluvial organization owing to its control on water availability and sediment delivery within the catchment, but temporal changes in stacking patterns are often interpreted to reflect changes in subsidence and base level. To test for evidence of climatic control on the stacking pattern, we study an outcrop succession with two styles of stacking within the Upper Cretaceous Bajo Barreal Formation in the Cerro Ballena anticline, Golfo San Jorge Basin, Argentina. The 385 m thick and 2.5 km wide exposure has layer-cake geometry, lacking either large-scale erosional surfaces, fluvial terraces, or evident paleosols, dismissing either local tectonic activity or base-levels shifts. Rooted in a paleohydrological study recognizing upward increasing in both channel width and flow depth of formative rivers, we use spectral gamma-ray logs, x-ray diffraction in mudstones, and sandstone petrography to understand the controls on the stacking pattern. At the base, Section A consists of small-scale, isolated channels fills in a siliciclastic floodplain with sand:mud ratio of ~1:6, whereas the overlying Section B has a sand-mud ratio of ~1:3, with larger-scale channels and greater inter-connectivity within a volcaniclastic floodplain. Upward reduction in K percentage through Section A parallel with increasing kaolinite content, and mudstone samples from Section B contains a higher proportion of kaolinite than Section A samples, evidencing an upward increase in paleo-weathering in humid conditions. Detrital components of Section A indicate several volcanic sources (e.g., basic-intermediate components derived from the Middle Jurassic Bahia Laura Group and acidic components sourced from the Andes Cordillera), whereas Section B exclusively contains acidic clasts derived from the Andes Cordillera. Simultaneous changes in detrital constituents, suspended load type, and increasing scale of the rivers in Section B occur coeval with increases in channel inter-connectivity, here related to the increase of river discharge and sediment supply in a humid climate, favoring more frequent avulsions or higher channel migration rates in a relatively flat geomorphic scenario. The study demonstrates, combining independent lines of evidence, that climate change can impact the stacking and connectivity of potential sandstone reservoirs.

Tectonic evolution of the Qingshuihe Basin since the Late Miocene: Relationship with north‐eastward expansion of the Tibetan Plateau

Southwest Ningxia is located at the tectonic and geographical north‐eastern edge of the Tibetan Plateau and is an ideal site for studying continental dynamics and plateau building. The Southern Ningxia Arc Tectonic Belt (SNATB) formed during the Cenozoic period as a result of the collision between India and Eurasia and was affected by the Tibetan Plateau uplift. However, the upward growth and expansion processes of the SNATB remain unclear. We investigated the Qingshuihe Basin (a Late Cenozoic basin located between the Tianjingshan and Qingshuihe faults in the north‐eastern SNATB) using field geological surveys combined with borehole, high‐density resistivity, and optically stimulated luminescence dating. Four distinct stages in the tectonic evolution of the Qingshuihe Basin since the Late Miocene are identified, corresponding to four tectonic events in the local region influenced by the Tibetan Plateau expansion. First, the Late Miocene experienced several significant events, including tectonic stress field transitions, sedimentary hiatus, and sudden environmental changes, which may have been the first local tectonic activity due to the north‐eastward expansion of the Tibetan Plateau. Second, the Early–Middle Pleistocene growth strata in the Hejiakouzi valley (controlled by the Hejiakouzi anticline and Tianjingshan Fault) suggest that the basin‐range‐style tectonic features were basically formed in the SNATB. Third, geological investigations of lacustrine sedimentation reveal that two palaeolakes were present during the Late Pleistocene. Significant phase transitions and a sedimentary hiatus during the Late Pleistocene in the lake formations indicate a transformation of the sedimentary environment, which marked the beginning of the left‐lateral strike‐slip of the Tianjingshan Fault. Finally, the broad distribution of second‐level river terraces along the banks of the Qingshuihe and other seasonal rivers close to the Tianjingshan indicate the effect of the north‐eastward expansion of the Tibetan Plateau on the local tectonic evolution. We elucidate the stratigraphy, major unconformities, and river terraces formed since the Late Miocene in the Qingshuihe Basin, providing important information regarding the tectono‐topographical‐sedimentary system.