Local Basin Research Articles

Adaptive water management in the face of uncertainty: Integrating machine learning, groundwater modeling and robust decision making

This study examines climate change and water resources management challenges facing water suppliers in drought-prone regions and is particularly relevant to the American West, where agencies balance the management of imported and local water resources across multiple future uncertainties. We apply Robust Decision Making (RDM) to water management planning challenges facing the San Bernardino Valley Municipal Water District (Valley District) and investigate the performance of a machine learning-based representation of two local groundwater basins. To do so, we assess three machine learning methods--Random Forest (RF), Support Vector Machines (SVM) and Artificial Neural Networks (ANN)--and their ability to simulate the output of a high-resolution MODFLOW model. We find that RF produces the most accurate results, and thus we incorporate the RF version of the MODFLOW model into the study’s RDM approach. This constitutes an advancement to the field of decisionmaking under deep uncertainty (DMDU) through a novel application of machine learning that shortens modeling run times and allows for a greater exploration of the uncertainty space, including a broad range of future climate changes and drought conditions. This paper also constitutes an advancement to the field of empirical groundwater modeling by showing that RF is capable of simulating average basin groundwater level changes. Our results also suggest that demand management can significantly reduce vulnerabilities to drought and other climate changes, and we provide recommendations on additional adaptive management options and key signposts to track for the Valley District.

Ecological changes in geological media and Siverskyi Donets River basin under the condition of goal mines flooding

Complex economic, geological-technological state of coal mines and impact of the armed conflict factors (the breakdown of energy supply, objects of critical infrastructure, etc.) accelerated closure of coal mines by the method of “wet preservation” in particular. In most developed EU countries decommissioning of coal mines, which have great depth (up to 1,0-1,5 km) and areas of minefields, occurs according to the post-mining (PM) research and production complex, which is based on the scientific and technological activities regarding prevention of dangerous changes in the geological environment (GE) - subsidence of ground surface, lands flooding, emission of explosive and toxic gases as well as reduction of outflows of polluted water into the local river basins (RB) and the soil aquifer. Additionally, PM suggests some mining works turning into the hydraulic-filtration system of mine water retention at a depth of 250-350 m with a purpose of preventing pollution flow into the freshwater aquifers and river network, preserving regional aquitards, degassing of mountain surface. In general, the PM activities complex aims at maintaining the balance and protective potential of the GE as mineral and landscape basis of the biosphere, elimination of dangerous changes in ecological parameters of the hydrographical network. It is shown that new models of subsoil and water use, geological prospecting structure, scientific basis for permissible changes in GE and RB are required together with closure of “old” mining works (MW) and opening of new ones, improvement of the environment monitoring based on GIS technologies and Earth remote sensing.

Geochemistry of mid- upper eocene intra-continental alkaline volcanic range, south part of central alborz mountains, north of Iran.

The Ziaran volcanic Belt (ZVB), North of Iran contains a number of intra-continental alkaline volcanic range situated on South part of central Alborz Mountains, formed along the localized extensional basins developed in relation with the compressional regime of Eocene. The mid-upper Eocene volcanic suite comprises the extracted melt products of adiabatic decompression melting of the mantle that are represented by small volume intra-continental plate volcanic rocks of alkaline volcanism and their evaluated Rocks with compositions representative of mantle-derived, primary (or near-primary) melts. Trace element patterns with significant enrichment in LILE, HFSE and REEs, relative to Primitive Mantle. Chondrite-normalized of rare earth elements and enrichment in incompatible elements and their element ratios (e. g. LREE/HREE, MREE/HREE, LREE/MREE) shown these element modelling indicates that the magmas were generated by comparably variable degrees of partial melting of garnet lherzolite and a heterogeneous asthenospheric, OIB mantle sources.

Asymmetric coexisting bifurcations and multi-stability in an asymmetric memristive diode-bridge-based Jerk circuit

An asymmetric memristive diode-bridge (MDB) emulator is raised to imitate the asymmetric volt-ampere characteristic of a physical memristor. Then, an asymmetric MDB-based Jerk circuit is built and its state equation is derived, upon which the theoretical analysis, MATLAB-based numerical simulations, and hardware measurements are executed to reveal the asymmetric coexisting bifurcations and the phenomenon of multi-stability. The memristive Jerk circuit has three equilibrium points of a pair nontrivial equilibrium points of asymmetric unstable saddle-foci and a zero equilibrium point of unstable saddle-focus, which leads to the occurrence of asymmetric coexisting bifurcations and asymmetric local attraction basins. The asymmetrical bifurcations are numerically disclosed by 1-D/2-D bifurcation plots, Lyapunov spectrum, and phase plane trajectories. Multi-stability with asymmetric coexisting attractors under two sets of system parameters are demonstrated as examples by local attraction basins and phase plane trajectories. Thereafter, experimental circuit prototype employing discrete components is manually welded and hardware measurements are executed to validate the numerical simulations.

New filamentous bivalve rich event beds in the Eocene deposits from Gafsa Basin: sedimentology, sequential analysis and environmental significance in Tethyan platform

Detailed analysis of Middle Eocene deposits in the Tamerza region, located in western part of Gafsa Basin, shows the presence of several metric corrugated levels. A sedimentological study was applied to these levels showing their geodynamic characteristics, significance in energy, residence time on the sea-floor, and sequential analysis. To study these levels, detailed field work was combined with stratigraphic and sedimentological analyses, as well as systematic sampling of these levels. This facies represents shallow subtidal deposits of a moderate-energy environment. Detailed analysis of undulated facies, under petrographic microscope, reveals the stacking of micrometric sequences (400–500 μm thick) marked by an abrupt change from packstone and, sometimes, grainstone to mudstone textures. Filamentous bivalves occur in massively bedded limestones, which consist of wackestones-packstones containing planktonic foraminiferas. The filaments are smaller (200 μm in average length), isolated, and show varied orientations. In the upper part, the lamination of filament, evolution of facies texture has been a key feature in interpreting them as turbidities. The differences between the three subfacies (F1, F2 and F3) are related to the higher energy. Slope deposits include a wide variety of processes requiring detailed study to set up mechanisms involved and their geological significance. Gravitational flows seem for most, resulting from the differences in density between the fluid/sediment and the ambient fluid. Shell beds have been interpreted as hiatal shell concentrations, as transgressive system track deposits associated to special currents, or as primary biogenic concentrations, among other origins. These bio-events are the expression of communications between different local basins and can be used to establish correlations in North Africa and in other continents during the Middle Eocene interval.

The middle Cretaceous (110–94 Ma) evolution of Tangza Basin in the western Tibetan Plateau and implications for initial topographic growth of northern Lhasa

AbstractReconstruction of Cretaceous geological evolution of Tibetan Plateau growth is critical for assessing the effect of India-Asia collision on the formation of its high elevation. However, Cretaceous topographic evolution and geodynamic mechanism in northern Lhasa remain ambiguous. Here we present results from sedimentology, zircon U-Pb ages, and detrital Cr-spinel composition of the Tangza Formation in the western part of northern Lhasa. Sedimentary lithofacies document that orbitolinid foraminifera–limestone beds were deposited in a shallow-marine setting, while clastic rocks accumulated in an alluvial fan during the middle Cretaceous. Zircon U-Pb ages of interbedded volcanic rocks place a robust constraint on the initiation of clastic rock deposition at ca. 106 Ma. Sandstones are enriched lithic fragments with abundant volcanic grains. U-Pb ages of detrital zircon display a prominent age population at 101–130 Ma with a 120 Ma peak. These data indicate that the clastic rocks were mainly derived from northern Lhasa, including an Early Cretaceous magmatic arc. Sedimentary and provenance characteristics are most consistent with deposition in a local foreland basin. The activation of south-vergent local thrusting may be responsible for loading of the Tangza foreland basin. This thrust faulting may be associated with crustal shortening induced by the continuous convergence of Lhasa and Qiangtang since collision initiated during the Early Cretaceous. The initial uplift of western and central parts of northern Lhasa and eastern Gangdese arc occurred at ca. 106 Ma, while the widespread uplift of northern and central Lhasa probably initiated at ca. 92 Ma. The mid–Late Cretaceous uplift in Lhasa was significantly earlier than the early Cenozoic India-Asia collision.

Seasonal variations of groundwater recharge in a small subtropical agroforestry watershed with horizontal sedimentary bedrock

Groundwater recharge supports sustainable development for drinking water and irrigated agriculture in vast areas worldwide. Human activities and climate change (e.g., uneven precipitation) have significantly impacted groundwater dynamics. A long term monitoring and sampling campaign was conducted for the major water bodies to investigate the evolution of groundwater and its capacity to support sustainable development in a subtropical agroforestry catchment in the middle of the Sichuan Basin with horizontal sedimentary bedrock (red beds), where seasonal droughts are notable. Major hydrochemical indicators, including δD and δ18O were measured to trace the water movement. The results showed that the chemical type of shallow groundwater was Ca•Mg-HCO3 or Ca-HCO3, which was mainly controlled by the weathering and hydrolysis of rocks. The interaction processes in the rainy season were stronger than those in the dry season. The isotopic signature in rainwater showed distinct seasonal pattern was strengthened by the local basin climate. The isotopic signals of groundwater responding to rainfall showed that recharge cycles of shallow groundwater in the rainy season lasted approximately 45–75 days. The optimized estimation based on mixing model and chloride ion balance (CMB) showed that the rainfall recharge ratio to shallow groundwater averaged about 27.83% (4.3%–58.0%) at event scale and the annual rainfall recharge ratios averaged about 19.36% (12.2%–45.7%). Groundwater in this region was renewed rapidly, as its groundwater storage capacity could be low with horizontal sedimentary bedrock. By revealing the water chemistry dynamics of shallow groundwater in the study area, this work preliminarily identified the groundwater recharge sources and estimated the recharge ratios by rainfall in a typical hilly area with red beds, thus providing a scientific basis for further regional assessment of groundwater resources.

Statistics of Lifetimes for Transient Bursting States in Coupled Noisy Excitable Systems

Abstract In ensembles of oscillators, intrinsic fluctuations often enable nontrivial dynamics in seemingly simple situations. One of such effects occurs in coupled FitzHugh–Nagumo oscillators subjected to external noise. At the considered parameter values, the global deterministic attractor is the resting state. Additive noise invokes transient bursting: series of intermittent patches of spikes, followed by the abrupt decay to rest. Duration of this transient, small for weak noise, asymptotically diverges when the noise becomes stronger. Remarkably, in repeated trials at fixed parameters, the number of bursts until the ultimate decay strongly varies. Lifetime statistics for this transient in large ensembles of numerical realizations features the exponential distribution. Observations on transient bursting are confirmed by experiments with coupled analog electronic circuits, modeling the FitzHugh–Nagumo dynamics. We relate the exponential character of the distribution to the probability that the system, disturbed by noise, escapes the local attraction basin of the resting state.

Seismic and borehole-based mapping of the late Carboniferous succession in the Canonbie Coalfield, SW Scotland: evidence for a ‘broken’ Variscan foreland?

Local seismic and borehole-based mapping of the Carboniferous Pennine Coal Measures and Warwickshire Group successions in the Canonbie Coalfield (SW Scotland) provides evidence of repeated episodes of positive inversion, syn-depositional folding and unconformities. A Duckmantian (Westphalian B) episode of NE–SW transpression is recognized, based on onlapping seismic reflector geometries against NE-trending positive inversion structures and contemporaneous NNE-trending syn-depositional growth folding. The basin history thus revealed at Canonbie is at variance with generally accepted models in neighbouring northern England that imply subsidence was due to post-rift thermal subsidence during late Carboniferous times. A late Westphalian–Stephanian unconformity recognized within the Warwickshire Group succession signifies NW–SE, c . 10% local basin shortening during a time of major shortening in the late Carboniferous Variscan foreland, contradicting suggestions that maximum Variscan shortening had negligible impact on Carboniferous basins in northern Britain. Local inversion structures appear to have strongly influenced local late Westphalian–Stephanian depocentres. In this respect, the Variscan foreland at Canonbie may have resembled a ‘broken’ foreland system. Variations in crustal rheology, fault strength and orientation, and mid-crustal detachments are suggested to have played important roles in determining strain localization and the nature of Westphalian–Stephanian depocentres in the Canonbie Coalfield.

The landscape and flux of a minimum network motif, Wu Xing* *Project supported by the National Natural Science Foundation of China (Grant No. 21721003) and the Fund from the Ministry of Science and Technology of China (Grant No. 2016YFA0203200).

Wu-Xing theory is an ancient philosophy that serves as a guiding principle in the traditional Chinese medicine (TCM). It has been used to explain the unbalance among the TCM organ systems in disease states and provide treatment philosophy qualitatively. Until now, it is still a challenge to explore the Wu-Xing theory beyond its philosophical nature. In this study, we established a quantitative framework using the landscape and flux theory to characterize the nature of the Wu-Xing theory from a perspective of a minimal network motif and leave certain specific functional aspects of Wu-Xing theory for future exploration. We uncovered the irregular ring shape of projection landscape for the Wu-Xing network with several local basins and barriers. We found that the dynamics of the self-organized Wu-Xing system was determined by the underlying negative landscape gradient force and the nonequilibrium rotational flux. While the shape of the Wu-Xing landscape determines the stabilities of the states, the rotational flux guarantees the persistent periodic oscillation and the stability of the flow. This provides a physical and quantitative basis for Yin–Yang duality of the driving forces for determining the dynamics and behaviors of the living systems. Applying landscape and flux analysis, we can identify the key parameter for the dynamics/function of Wu-Xing network. These findings allow us to have a deeper understanding of the scientific merits of the ancient Wu-Xing theory from the network motif perspective.

A Detailed Assessment of Groundwater Quality in the Kabul Basin, Afghanistan, and Suitability for Future Development

Kabul is one of the most populated cities in Afghanistan and providing resources to support this population in an arid climate presents a serious environmental challenge. The current study evaluated the quality of local Kabul Basin groundwater to determine its suitability water for drinking and irrigation purposes now and into the future. This aim was aided through groundwater parameter assessment as well as determination of Water Quality Index (WQI) developed from 15 observation points near the city. The results of our physicochemical analysis illustrate that groundwater in the majority of areas of the Kabul Basin is not generally suitable for human consumption, and in some cases the concentrations of many contaminants are higher than accepted health standards or water quality benchmarks. The aquifer underlies an arid landscape, and because of this 85% of the samples tested are very hard while just over 13% are classified as hard. Groundwater in the Kabul Basin is typically high in calcium and magnesium and overall classified as a calcium bicarbonate water type. Overall, more than 60% of the analyzed samples had concentrations higher than the World Health Organization (WHO) standard of total dissolved solids (TDS), 10% in total hardness (TH), about 30% in turbidity and more than 90% in magnesium. The results show that based on WQI, without treatment, roughly 5% of groundwater in the studied area is unsuitable for human consumption, while 13.3% is very poor and 40% is poor quality water. Approximately 40% of the assessed groundwater has good quality and could be used as drinking water for future development. Groundwater in some areas shows evidence of pollution and high dissolved solids content, rendering these sources unsuitable for either drinking or irrigation purposes.

Anthropogenic Load and the Effect of Drainage Area on the Diffuse Runoff of Nutrients into a Large Water Body: Case Study of the Cheboksary Reservoir

A brief description is given for the natural conditions and economic activity on a local drainage basin of the Cheboksary Reservoir (less the Oka Basin). The main principles of a new version of landscape-hydrological method used to evaluate nutrient runoff from the drainage basin into water bodies are given. The article presents the values of the runoff of these elements into the Cheboksary Reservoir calculated taking into account the effect of the drainage basin and anthropogenic load from mineral and organic fertilizers applied on agricultural fields and the input of wastes onto the drainage basin from the population that have no access to sewage system.

Electrically assisted silver and copper coated filter papers with enhanced bactericidal effects

Increased microorganisms resistance to drugs is currently a challenging problem as more powerful drugs are necessary for successful treatments. Current research is investigating for the first time reinforced bactericidal effects in wastewater resulted by simultaneous use of metallic thin films deposited on water filter papers combined with electrical power directly applied to the coated structures. Silver and copper were deposited at room temperature onto water filter papers by using high vacuum magnetron sputtering system. The metallic coated structures efficiently eliminated common types of wastewater bacteria (e.g. Escherichia coli and other coliforms). The antibacterial effects were reinforced by using electrical power applied to the structures. Increasing the electricity levels resulted in stronger bactericidal effects and subsequently shorter exposure times were required to reduce bacteria from contaminated water. Thin films adherence to filter fibers and the morphology of the coated structures were examined using digital optical microscopy and Scanning Electron Microscopy (SEM). The method used for assessing antibacterial performance was the standardized membrane filtering technique for wastewater examination. Water was collected from local basins and the bacterial content was monitored before and after exposure to uncoated, silver and copper coated filter fibers, and electrically activated metallic coated filter fibers. The metallic thin films were retained on the fibers surface after water treatment consequently reducing the nanoparticles release to the surroundings.

Riddled Attraction Basin and Multistability in Three-Element-Based Memristive Circuit

By coupling a diode bridge-based second-order memristor and an active voltage-controlled memristor with a capacitor, a three-element-based memristive circuit is synthesized and its system model is then built. The boundedness of the three-element-based memristive circuit is theoretically proved by employing the contraction mapping principle. Besides, the stability distributions of equilibrium points are theoretically and numerically expounded in a 2D parameter plane. The results imply the memristive circuit has a zero unstable saddle focus and a pair of nonzero stable node-foci or unstable saddle-foci depending on the considered parameters. The dynamical behaviors include point attractor, period, chaos, coexisting bifurcation mode, period-doubling bifurcation route, and crisis scenarios, which are explored using some common dynamical methods. Of particular concern, riddled attraction basins and multistability are uncovered under two sets of specified model parameters nearing the tiny neighborhood of crisis scenarios by local attraction basins and phase plane plots. The riddled attraction basins with island-like structure demonstrate that their dynamical behaviors are extremely sensitive to the initial conditions, resulting in the coexistence of limit cycles with period-2 and period-6, as well as the coexistence of period-1 limit cycles and single-scroll chaotic attractors. Moreover, a feasible on-breadboard hardware circuit is manually made and the experimental measurements are executed, upon which phase plane trajectories for some discrete model parameters are captured to further confirm the numerically simulated ones.

FPGA-based Experimental Validations of Electrical Activities in Two Adjacent FitzHugh–Nagumo Neurons Coupled by Memristive Electromagnetic Induction

ABSTRACT With the consideration of electromagnetic induction generated by the difference of membrane potentials between two adjacent neurons, a five-dimensional (5-D) memristor-coupled FitzHugh–Nagumo (FHN) bi-neuron model derived from connecting two FHN neurons with the memristive electromagnetic induction is presented. Then, with the 5-D memristor-coupled FHN bi-neuron model, the equilibrium states and their stabilities are explored by theoretical and numerical analyses. It is indicated that the proposed model has two non-zero equilibrium states with the same stability of unstable saddle-focus or unstable saddle point associating to the considered model parameters. The parameter-associated electrical activities of periodic, quasi-periodic, and chaotic behaviors are disclosed by bifurcation plots, dynamical maps, phase plane plots and further confirmed by 0–1 tests. Besides, the phenomena of initial-associated bi-stability with the coexistence of chaotic and periodic behaviors, as well as the riddled attraction basin, are revealed by local attraction basins and phase plane plots. Furthermore, based on field programmable gate array (FPGA), a digitally implemented electronic circuit is made, from which the electrical activities are experimentally captured to verify the numerical ones.

Effect of water pollution control on provincial boundaries of River-Director System: based on the study of the Yangtze River valley in China.

We analyze the driving mechanism of the River-Director System reform in the article. Using the ordered probit model, the effect of the River-Director System policy was evaluated by observing the monthly water quality data of 170 water areas along the boundary of the Yangtze River system. It determines that the driving force of the local government's basin governance under the river system is mainly the top-down policy directives and that the driving path is effective synergy, rights, and diffusion in the article. We find that the upstream provinces and municipalities that implemented reforms have significantly improved the water quality of the waters in the border basin, compared with the provinces and cities that have not implemented the reform of the river system and the river basins that have implemented policy reforms but are located in the lower reaches of the rivers. At the same time, the city's reforms have significantly improved the quality of the junction basin water body. The implementation of the River-Director System has reduced the occurrences of local pollution emission and improved the water quality of the provincial boundaries through sewage treatment. We further validate the robustness of the basic conclusions by deleting special samples and changing the window type and other robust tests. Finally, through monthly examinations on the implementation of the policy, it finds that the effectiveness of the policy reform became more apparent in the eleventh month.

The 1933 Long Beach Earthquake (California, USA): Ground Motions and Rupture Scenario

We present a synoptic analysis of the ground motions from the 11 March 1933 Mw 6.4 Long Beach, California, earthquake, the largest known earthquake within the central Los Angeles Basin region. Our inferred shaking intensity pattern supports the association of the earthquake with the Newport-Inglewood fault; it further illuminates the concentration of severe damage in the town of Compton, where accounts suggest vertical ground motions exceeding 1 g. We use a broadband simulation approach to develop a rupture scenario for this earthquake, informed by the damage distribution. The predicted shaking for a 25-km-long fault matches the intensity distribution, with an indication that non-linear site response on soft sediments in some near-field regions was stronger than predicted using a simple model to account for non-linearity. Our results suggest that the concentration of damage near Compton can be explained by a combination of local site amplification, source-controlled directivity, and three-dimensional basin effects whereby energy was channeled towards the deepest part of the Los Angeles Basin.

Large Zn isotope variations in the Ni[sbnd]Mo polymetallic sulfide layer in the lower Cambrian, South China

In South China, black organic-rich shales in the lower Cambrian Niutitang Formation host a NiMo polymetallic sulfide layer that discontinuously extends over ~1600 km. Seawater and hydrothermal origins are among the many suggested hypotheses and are still under debate. In order to discriminate Zn sources, we report Zn isotopes in NiMo polymetallic sulfide layers and their host shales from the Nayong and Zunyi locations in Guizhou province and the Zhangjiajie section in Hunan province. In each section, host organic-rich shales show homogeneous Zn isotope compositions which likely resulted from quantitative scavenging of dissolved Zn from seawater under euxinic conditions. The difference in the average δ66Zn values of organic-rich shales between the two sections in Guizhou (0.76 ± 0.09‰) and one section in Hunan (0.59 ± 0.10‰) might reflect variations of Zn isotope gradient with the depth of seawater. Therefore, the organic-rich sediments need not always represent an isotopically light Zn sink, which is dependent on Zn isotope fractionation in the local basin. However, the δ66Zn values in the NiMo polymetallic sulfide layers are different from those of their host shales, indicating that these sulfide layers did not inherit the Zn isotope signal of seawater. Based on the regular increasing trend in δ66Zn values from Nayong (0.54 ± 0.06‰) to Zhangjiajie (1.34 ± 0.09‰) and the presence of PbZn mineralization in the Dengying/Doushantuo Formations, we argue that hydrothermal fluids associated with PbZn mineralization could be a major source of Zn in NiMo sulfide layers, especially in the Nayong location. A possible model is that the hydrothermal fluids related to MVT-type mineralization got overprinted on a multiple-sourced synsedimentary sulfide-rich layer. We provide additional evidence that Zn isotopes have great potential as a tracer of metal source and can be applied to similar types of mineralization as e.g., the late Devonian Ni-Zn-PGE Nick deposit (Selwyn Basin, Canada) or elsewhere.

Local Dynamics of Excitations in Glassy Liquids

In this study, we propose new elementary processes of the excitation dynamics in glassy liquids, which trigger the structural rearrangement in a local and isolated region known as the cooperative rearrangement region. We identify the existence of primary particles which facilitate local dynamics by using a machine learning technique and a time series analysis. The local soft domains are established by a few soft particles that hop between local energy basins. While particles in contact with these primary soft particles respond non-linearly, other particles not in direct contact with them respond linearly as elastic materials.

Sedimentology of Jurassic pelagic carbonate platforms in the Ankara region (Central Anatolia-Turkey)

The Jurassic–Lower Cretaceous successions cropping out in three different parts of Central Anatolia (Turkey) were deposited in local basins developed under tectonic influence from the Hettangian to the Oxfordian. Pelagic carbonate platforms (PCPs) were formed in the region during two separate phases in which synsedimentary faulting was active in the basins. Prior to the first tectonic phase, fluvial and tidal sediments, Hettangian-Sinemurian in age, were deposited unconformably on the low-grade metamorphic substrate of the Karakaya Complex (Upper Triassic), with Sinemurian crinoidal limestones above. At the end of the Sinemurian, the PCPs were developed as a result of fragmentation of shallow-marine platforms by normal faults. Across hanging-wall basins and footwall-blocks, the PCP facies: pelagic/hemipelagic nodular and marly Ammonitico Rosso facies, brachiopod-bearing limestone facies with hardgrounds, red fossiliferous mudstone, and calcareous Ammonitico Rosso facies containing blocks, were deposited with marked lateral thickness variations. The platform, which gradually became shallower in relation to the clastic sediments (180 m thick) filling the basin, was fragmented again at the end of the Bathonian. The opening of fractures in the platform is documented by neptunian dykes developed within the clastic facies, filled with Callovian ammonite-bearing mudstone. During the Callovian–Oxfordian, widespread ammonite-bearing red marl draped the clastic facies, although nodular pelagic and oolitic/ammonite limestones are locally present. Moreover, Oxfordian pelagic oolitic facies rest unconformably on Upper Triassic sandstone (Karakaya complex), which is locally intercalated between the metamorphics and the Jurassic cover, wherever these had been unroofed at the footwall of Jurassic normal faults. As a result of the tectonic activity during the Callovian–Oxfordian time, the Ankara region totally became a PCP in the Oxfordian. Condensed, nodular, pelagic oolitic–ammonitic limestones were deposited across the major uplifted blocks in an open-marine environment, previously called the Ankara seamount. These facies constitute an important key level in the Ankara region. Laterally continuous deep-marine sediments overlying the Late Oxfordian–Early Cretaceous PCP deposits indicate the rapid foundering of this sector.