Miocene Sediments Research Articles

Spectral data of paleoclimate reconstruction of Late Miocene Sediments from the Jianzha Basin in Northeastern Margin of the Tibetan Plateau [Data set

Spectral data of paleoclimate reconstruction of Late Miocene Sediments from the Jianzha Basin in Northeastern Margin of the Tibetan Plateau [Data set

A case study of paleoenvironmental interactions during the Miocene Climate Optimum in southwestern Paratethys

The marine system of the Mediterranean-Paratethys region in the Middle Miocene was influenced by the global climatic changes corresponding to the Miocene Climate Optimum. The latter was characterized by global warming of deep oceanic waters succeeded by a decrease of wind activity and ocean water circulation together with a decline in oceanic productivity. This study provides a detailed paleoenvironmental and depositional history of the Middle Miocene deposits from Mt. Požeška Gora (the east part of Croatia). Stable carbon and oxygen isotope data with foraminiferal fauna coupled together with palynological data indicate both seasonal and long-term changes in surface water temperatures, nutrient contents, and salinity. Furthermore, it was possible to determine two phases of Middle Miocene flooding in the studied marine system: (a) a shallow, high nutrient marginal sea strongly affected by freshwater inputs corresponding to the thermal maximum and periods with enhanced precipitation during the Miocene Climate Optimum, and (b) a younger deeper marginal sea with a developed seasonal stratification, rather intermediate nutrient availability and reduced fresh-water inputs. Based on the microbiostratigraphy and strontium isotope stratigraphy (87Sr/86Sr) coupled with previously published high-precision geochronology, the timing of the first and second flooding can be correlated with the Langhian age - ≤15.4 Ma and 14.6 Ma, respectively Possibly, the properties of the surficial waters that were described as a part of the flooding phases in individual time intervals can indicate changes in circulation patterns as a result of potential influence of the open-sea water masses.

Editorial Preface to Special Issue: Exploring the impact of Andean uplift and climate on life evolution and landscape modification: From Amazonia to Patagonia

• Uplift of the Northern Andes (from Peru to Colombia) took place from Late Cretaceous to Paleocene (72 and 60 Ma), and was driven by collision of the South American plate with the Caribbean Arch. This process affected drainage directions and paleogeography shaping the present Andes configuration. • Studies in the Northern Andes concur with Late Cretaceous tectonism and suggest that uplift took place in three-stages. During the final Neogene uplift stage, the Antioquia plateau (Central Cordillera, Northern Andes) is thought to have achieved altitudes higher than present. • Subsurface processes, such as slab-flattening drove uplift in Central Cordillera (Northern Andes) and caused an asymmetric topography that affected drainages and biodiversity development. • Climate as a driver of mountain uplift remains contentious, but it is clear that uplift strongly affects climate and environment, due to the orographic rain shadow effect. • Multiple studies found that Andean uplift played a key role in shaping the evolutionary history and biodiversity patterns in both plants and animals, even in mutualistic species relationships. The effect of uplift on biogeographic history is not limited to the Andes mountains, but also extends into the Amazon drainage basin with soils in the western Amazonia being most species rich. During the Neogene, eastern Amazonia gradually became species-enriched through biotic interchange. • The effects of Andean uplift on biota add to other fundamental factors, such as climate, environment and dispersal, all of which contribute to the modern biodiversity patterns in South America and their evolutionary history. • The Neotropics were hot and humid during Eocene global warming. However, paleobotanical studies in the Northern Andes suggest that during towards the end of the Eocene a shift towards arid and seasonal climatic conditions occurred. In western Amazonia the EOT is further marked by a sea level drop, and a shift from deltaic to fluvial conditions that is accompanied by a decline in species richness. • In Patagonia the Oligocene ‘icehouse’ is characterized by a species poor assemblage. Towards the MCO there is an increase in species diversity with a subsequent decline in the MMCT. The biggest paleobotanical change, however, occurs in the late Miocene and is marked by the rise in arid taxa. This coincides with the uplift of the easternmost flank of the Andes and formation of a rain shadow. Aridification and sea level drop was initiated in the MMCT and culminated in the late Miocene. In the Northern Andes this transition is recognized by a dramatic change in paleosoil profiles. • Marine incursions and fluctuating sea level played an important part in Amazonia's history and evidence of this can be found in middle and late Miocene deposits in the western Amazon. Sediment records in the large Pebas wetland system (western Amazon) indicate that orbital forcing controlled sedimentation while the towering Central and Northern Andes provided the sediment supply. • Holocene records of Amazonia suggest rainforest trees are resilient to natural drying but not to fire and deforestation. A stark warning that human influence is more devastating than climate change.

Α study on the Gas-bearing Miocene Sediments of MESSARA Basin in Crete (Greece) by Using Seismic Reflection, Geochemical and Petrophysical Data

The focus on exploiting natural gas resources has been increased in the recent years since it was characterized as the transitional fuel to a net-zero era. Consequently, a reevaluation of the gas resources under a new perspective seems to be logical. Within this context, the gas-bearing Miocene sediments of the Messara basin in Crete (Greece) are discussed in this paper. The gas shows have been first reported during the 1990’s, without being thoroughly evaluated. This paper presents the interpretation of eight legacy onshore seismic reflection lines, which led to the construction of the 3D subsurface structural model of the Neogene Messara basin. The seismic data reveals the basin depocenter which accommodates approximately 1500 m of the Miocene sediments. The relationship of the Miocene deposits with the existence of shallow gas is also examined and discussed. New organic geochemical results combined with the published geochemical data are used to discuss the gas generation potential of the Miocene sediments. The porosity and permeability measurements on surface samples are also presented to describe the reservoir characteristics. The integration of the data mentioned above suggests that the Miocene sediments of the Messara basin comprise intervals with adequate organic matter to generate the observed gasses and good reservoir sandstones to accumulate the generated gas. The gas might have been trapped by lateral and vertical facies changes which provide efficient stratigraphic trapping mechanisms.

Pollen Record Of Early/ Middle Miocene Boundary In The South Sumatra Basin

Early to Middle Miocene sediment obtained from three wells drilled in South Sumatera area has been evaluated for its micropaleontological content including foraminifera, calcareous nannoplankton and palynomorph. The boundary of Early/ Middle Miocene is clearly represented by zone N8/ N9 boundary based on foraminiferal analysis and zone NN4/ NN5 boundary on the basis of calcareous nannoplankton analysis. The rich assemblage of foraminifera and calcareous nannoplankton indicates the occurrence of marine sediment within the well sections. In addition, environmental markers of benthonic foraminifera suggest the occurrence of inner to middle neritic along the studied sections. Palynological analysis however, proves the high occurrence of pollen and spore along the marine successions situated in Early/ Middle Miocene boundary which is the first time to yield a good quality of palynological record. The Early/ Middle Miocene boundary is marked by low sea level in global sea level curve as indicated by significant decrease of foraminifera and calcareous nannoplankton. In addition, palynological record reflects climatic changes over N8/ N9 sediment marking Early/ Middle Miocene boundary with the declines of pollen assemblage suggesting seasonal/ dry climate condition. N8 sediment shows high abundance and diversity of palynomorphs including those of wet climate markers. Palynological assemblage drops gradually approaching foram zone N9/ N8 boundary, whilst seasonal climate indicators increase. On the other hand, palynological record recovers its assemblage over N9 sediment.

Revised Zonal Subdivision Of The Late Miocene Nannoplankton Biostratigraphy For Kutei Basin

Lithological complexity and intense hydrocarbon exploration with the objective of Late Miocene sediments in Kutei Basin has provided the impetus for more refined Late Miocene nannoplankton zonation than the standard global schemes of Martini (1971). Investigation to the quantitative nannoplankton analysis results in Kutei Basin has been done, and there is evident that the deltaic sediments of this basin give an excellent nannoplankton assemblage dataset to refine the Late Miocene biostratigraphy. Biostratigraphically, Late Miocene ranges from the middle part of zone NN9 to the middle part of zone NN12 of Martini zonation (1971). Zone NN11 is the most crucial zone to be refined since this zone has long time interval (more than 2m.a.). In this paper, this zone can be subdivided into 7 subzones (NN11a-NN11g) based on relatively permanent occurrences of 6 biomarkers. They are from the base to the top, as follow: FO Discoaster quinqueramus, LO. Minilitha convalis, LO Discoaster bergenii, FO Amaurolithus primus, FO Reticulofenestra rotaria, LO, Discoaster berggrenii, LO. Reticulofenestra rotaria and LO Discoaster quinqueramus. In spite of zone NN9, NN10 and NN12 which have relatively short stratigraphic ranges, each zone can also be subdivided into 2 subzones. The base and the top of zone NN9 is indicated respectively by the FO and LO Discoaster hamatus. It can be subdivided by the FO Discoaster prepentaradiatus into subzone NN9a and NN9b. Zone NN10 is marked by the LO Discoaster hamatus at the base and FO Discoaster quinqueramus at the top. It can be subdivided into subzones NN10a and NN10b by the LO Discoaster bollii. Zone NN12 is characterized by the LO Discoaster quinqueramus at the base and the FO Ceratolithus rugosus at the top. This zone can be subdivided into subzone NN12a and NN12b by the LO Helicosphaera intermedia.

Ground motions induced by pore pressure changes at the Szentes geothermal area, SE Hungary

Excessive thermal water volumes have been extracted from porous sedimentary rocks in the Hungarian part of the Pannonian Basin. Thermal water production in Hungary increased significantly from the early 1970s. Regional-scale exploitation of geothermal reservoirs without re-injection resulted in basin-scale pressure drop in the Upper Pannonian (Upper Miocene) sediments, leading to compaction. This compaction resulted in ground subsidence primarily through poro-elastic coupling.We investigated surface deformation at the Szentes geothermal filed, SE Hungary, where the largest pressure decline occurred. Subsequently, hydraulic head recovery in the western part of the geothermal reservoir was initiated in the mid-1990s. We obtained data from the European Space Agency’s Envisat satellites to estimate the ground motions for the period of November 2002–December 2006. We applied inverse geomechanical modeling to estimate reservoir properties and processes. We constrained the model parameters using the Ensemble Smoother with Multiple Data Assimilation, which allowed us to incorporate large amounts of surface movement observations in a computationally efficient way. Ground movements together with the modeling results show that uplift of the Szentes geothermal field occurred during the observation period. Since no injection wells were operated at Szentes before 2018, and production temperatures remained relatively constant through the entire production period, we explain ground uplift with pore pressure increase due to natural recharge. The estimated decompaction coefficients of the reservoir system characterizing the elastic behavior of the Szentes geothermal reservoir varies between ~ 0.2 × 10–9 and 2 × 10–9 Pa−1. Compaction coefficients of the reservoir system corresponding to the earlier depressurization period, from ~ 1970 to the mid-1990s, may be significantly larger due to the potential inelastic behavior and permanent compaction of clay-rich aquitards. The improved parametrization enables better forecasting of the reservoir behavior and facilitates the assessment of future subsidence scenarios that are helpful for the establishment of a sustainable production scheme.

Miocene Provenance Changes in Taiwan Caused by Southward Input of Sediments From East China Sea Basin

The Cenozoic sediments in marginal basins of East Asia ultimately reflected coupling between the tectonics, landscape evolution, and drainage reorganization. Recently, the provenance of Miocene sediments in the East China Sea Basin (ECSB) and Taiwan has been in hot debate, and several models were proposed to interpret the provenance changes. Most of them are related to river reorganization in East Asia and highly relied on detrital zircon U-Pb dating. In this study, a large number of detrital zircon U-Pb ages of Miocene sediments from the ECSB, Taiwan region, and the potential source areas have been compiled for quantitative provenance analysis. The results suggested that all the early–middle Miocene sediments in Taiwan and the ECSB were closely linked to North China and the Korean Peninsula. Over 80% sediments in Taiwan were delivered from the ECSB whose sediments were predominantly contributed by North China and the Korean Peninsula (70%). However, for the late Miocene to Quaternary sediments in the ECSB, the contribution of the Yangtze River system was 72%, which indicates distinct reorganization of river networks and initial formation of the Yangtze River in the late Miocene. The quantitative provenance analysis together with southward environmental changes from dominantly fluvial sediments in the northern and middle ECSB to shallow marine sediments in Taiwan region suggested that the early–middle Miocene sediments of Taiwan were mainly sourced from the North China and the Korean Peninsula by passing the ECSB. Thus, these sediments in Taiwan region would experience the river–delta–shallow marine route from the ECSB to Taiwan region.

Basement structure investigation using 3-D forward modeling and inversion of geomagnetic data of the Zeit basin area, Gulf of Suez, Egypt

The Zeit basin is located on the western coast of the Gulf of Suez. It is a major, elongated half-graben structure with faults dipping steeply to the southwest. The Zeit basin contains the thickest Miocene sediments and evaporites in the Gulf of Suez. Many exploration activities have been conducted in and around the study area due to the known presence of hydrocarbon resources. In petroleum exploration, the estimation of basement depth (or sedimentary thickness) is a primary exploration risk parameter, in particular, for estimation of heat flow. The magnetic method is one of the few methods that can be used to study the basement structure and estimate the top basement depth. In this paper, the top basement geometry, distribution of the magnetic susceptibility and the basement depth of the Zeit basin were investigated using 3-D forward magnetic modeling and the 3-D inversion of geo-magnetic data. The 3-D forward modeling of the aeromagnetic field data from the Zeit basin area revealed a NW-SE trending half-graben structure, consistent with the known geology of the study area. Magnetic susceptibility cutoff 0.005 SI was applied to show the subsurface relationships among the basement sedimentary units. The calculated depth of the Zeit basin is around 4–5 km. The magnetic field data, calculated using the Gauss Legendre quadrature method, generally agree with the measured data as well as data calculated using the inversion process. The depth and magnetization intensity values used in the 3-D forward modeling, as well as petroleum borehole data, provide a structural basis for the 3-D inversion process.

A Technique of Hydrocarbon Potential Evaluation in Low Resistivity Gas-Saturated Mudstone Horizons in Miocene Deposits, South Poland

The petrophysical properties of Miocene mudstones and gas bearing-heteroliths were the main scope of the work performed in one of the multihorizon gas fields in the Polish Carpathian Foredeep. Ten boreholes were the subject of petrophysical interpretation. The analyzed interval covered seven gas-bearing Miocene horizons belonging to Sarmatian and Badenian deposits. The water saturation in shaly sand and mudstone intervals was calculated using the Montaron connectivity theory approach and was compared with Simandoux water saturation. Additionally, the Kohonen neural network was used for qualitative interpretation of four PSUs (petrophysically similar units), which represent the deposits of comparable petrophysical parameters. This approach allowed us to identify the sediment group with the highest probability of hydrocarbon saturation. Then, the spatial distribution of PSUs and reservoir parameters was carried out in Petrel. The resolution of the model was selected to reflect the variability of log-derived parameters. The reconstruction of the spatial distribution of shale volume, porosity, and permeability was performed with standard parametric modeling procedures using the Gaussian random function simulation stochastic algorithm, while PSU distribution and hydrocarbon saturation (SH) required a separate approach. The distribution into PSU groups was carried out by facies classification. Predefined ranges of clay volume, effective porosity, and permeability were used as discriminators to achieve spatial distribution of the PSU groups. The spatial distribution of hydrocarbon saturation was performed by creating the meta-attribute of this parameter and then reducing the derived pseudo-saturation model to physical values. Results included the creation of maps of hydrocarbon saturation that show the preferable areas with the highest hydrocarbon saturation for each gas horizon.

Facies analysis and paleoenvieonmental reconstruction of the Oligocene-Early Miocene deposits in the western Lorestan Zone (North West Zagros Basin, Iran)

Facies analysis and paleoenvieonmental reconstruction of the Oligocene-Early Miocene deposits in the western Lorestan Zone (North West Zagros Basin, Iran)

Zastosowanie metod uczenia maszynowego do charakterystyki porowatości i typu nasycenia przy użyciu atrybutów sejsmicznych

The application of machine learning (ML) tools and data-driven modeling became a standard approach for solving many problems in exploration geology and contributed to the discovery of new reservoirs. This study explores an application of machine learning ensemble methods – random forest (RF) and extreme gradient boosting (XGBoost) to derive porosity and saturation type (gas/water) in multi-horizon sandstone formations from Miocene deposits of the Carpathian Foredeep. The training of ML algorithms was divided into two stages. First, the RF algorithm was used to compute porosity based on seismic attributes and well location coordinates. The obtained results were used as an extra feature to saturation type modeling using the XGBoost algorithm. The XGBoost was run with and without well location coordinates to evaluate the influence of the spatial information for the modeling performance. The hyperparameters for each model were tuned using the Bayesian optimization algorithm. To check the training models' robustness, 10-fold cross-validation was performed. The results were evaluated using standard metrics, for regression and classification, on training and testing sets. The residual mean standard error (RMSE) for porosity prediction with RF for training and testing was close to 0.053, providing no evidence of overfitting. Feature importance analysis revealed that the most influential variables for porosity prediction were spatial coordinates and seismic attributes sweetness. The results of XGBoost modeling (variant 1) demonstrated that the algorithm could accurately predict saturation type despite the class imbalance issue. The sensitivity for XGBoost on training and testing data was high and equaled 0.862 and 0.920, respectively. The XGBoost model relied on computed porosity and spatial coordinates. The obtained sensitivity results for both training and testing sets dropped significantly by about 10% when well location coordinates were removed (variant 2). In this case, the three most influential features were computed porosity, seismic amplitude contrast, and iso-frequency component (15 Hz) attribute. The obtained results were imported to Petrel software to present the spatial distribution of porosity and saturation type. The latter parameter was given with probability distribution, which allows for identifying potential target zones enriched in gas.

Depositional Environment Assessment of the Middle Miocene Sedimentary Rocks in Thien Ung - Mang Cau Structure, Block 04 - 3, Nam Con Son Basin

Sediment depositional environments are one of the important scientific bases in evaluation the reservoir potential of sedimentary rocks. This article focuses on studying this issue for Middle Miocene sediments, Thien Ung - Mang Cau structure, Block 04 - 3, Nam Con Son basin. The article has integrated the methods of well log interpretation, thin section analysis and seismic attribute analysis, combined with the results of paleontological analysis of VPI - Labs to identify depositional environments of Middle Miocene sediments in the case study area. The results of interpreting well log data show that the Middle Miocene sediments were deposited in the following environments: shallow marine, shoreline, mouth bars, delta front, prodelta and lower deltaic plain. These findings are also consistent with the results of petrographic and paleontological analysis. The results of petrographic analysis show that in the study area, there are 2 main groups of sedimentary rocks, which are clastic and carbonate rocks. In the thin sections, the following components were detected: glauconite clay is characterized of marine environment, carbonate fission and siderite ore which are characteristic of deltaic environments. While paleontological samples detected organic materials, such as algae, bitumen; and fossils such as Foraminifera, Da Gai and Oc Gai - typical for shallow marine environments. The results of the seismic attribute analysis for the Middle Miocene carbonate sediments of the structure have clarified that the carbonate is concentrated in the central and eastern uplift area. This distribution tends to fewer in the west. This finding is consistent when the authors compared to well correlation in the area (wells: C - 1X, C - 2X, C - 3X and C - 4X) and also logically with the sedimentary principles.

Late Neogene chronostratigraphy and integrated paleoecological trends in the southwestern Caribbean Sea

Palynology of the Neogene marine stratigraphic sequences in tropical latitudes is poorly studied Most studies focus on lower to middle Miocene deposits in the Caribbean, emphasizing the biostratigraphic value of dinoflagellate cysts. The palynological and calcareous nannofossil analysis of 50 samples from DSDP Hole 502A and their integration with the paleomagnetic and planktonic foraminifera data reveal a detailed and reliable chronostratigraphic framework, and the interpretation of the paleobathymetric and paleoenvironmental evolution of the sequence. Fossil content in a continuous late Tortonian to late Gelasian (~7.56-1.80 Ma) sequence of deep-marine sediments serves to calibrate ages of dinoflagellate cysts, and comparison with high latitude records reveals synchronous (Operculodinium janduchenei, Selenopemphix dionaeacysta, Barssidinium taxandrianum, and Lejeunecysta interrupta) and asynchronous events (Quadrina? condita) with biostratigraphic potential for the southwestern Caribbean Sea. Our results highlight the importance of analyzing continental palynomorphs in deep-marine deposits to increase the temporal resolution of future palynostratigraphic schemes. Micropaleontogical data indicate a lower bathyal–abyssal environment and four paleoceanographic settings defined by changes in surface water productivity. These intervals fluctuate from mesotrophic-oligotrophic (~7.56–6.31 Ma) to eutrophic (~6.18–4.98 Ma), oligotrophic (~4.74–3.41 Ma), and mesotrophic surface water conditions (~3.26–1.80 Ma). Changes in trophic conditions are strongly related to the paleoceanographic reorganization associated with the constriction and complete closure of the Central American Seaway, seasonal upwelling episodes, and the input of terrigenous organic matter probably transported from southern Central America and northern South America by turbidity currents.

Presence of the peculiar carnivore Sivanasua in Carinthia

ABSTRACT A lophocyonid carnivore (Mammalia) is reported for the first time from Miocene (lower Badenian, ca. 16 My) deposits in Austria. A single, lower first molar from Schönweg-”Brüchl” (Lavanttal, Carinthia) is assigned to Sivanasua viverroides. The species is also recognised in Germany in few faunas of similar ages.

MIOCENE PALYNOLOGY OF THE BARITO BASIN, SOUTH KALIMANTAN PALINOLOGI UMUR MIOSEN DI CEKUNGAN BARITO, KALIMANTAN SELATAN

This study has succesfully disclosed the rich assemblage of palynomorph within the Miocene sediment ofthe Barito Basin, South Kalimantan. It is characterised by the the last occurrence of Florschuetzia trilobata(Middle/ Late Miocene boundary) and the fi rst occurrence of F. meridionalis (Early/ Middle Mioceneboundary). In addition, other Miocene markers appear to mark this age such as spores of Stenochlaeniditespapuanus (Late Miocene) and Scolocyamus magnus (Early/ Middle Miocene). Mean while, the regularoccurrence of brackish palynomorphs along the studied sections indicates marine infl uence during depositionincluding Zonocostites ramonae, Florschuetzia meridionalis (mangrove pollen), Florschuetzia levipoli andSpinizonocolpites echinatus (back-mangrove pollen). The depositional environment initially occurs in thefreshwater environment of delta plain during Early to Middle Miocene (lower well sections) as suggestedby domination of freshwater pollen in the absence of marine micro-fossils. It gradually shifts in to deepermarine setting in delta front to pro delta (with possible shallow marine environment) during Middle toLate Miocene (upper well sections) as indicated by the increase of brackish palynomorphs combined withmarine micro-fossils. This study identifi es peak of riparian pollen Myrtaceidites sp. which is potential forwell correlation. This pollen is common within the lower well sections suggesting the presence of riverdeposits. On the other hand, considerable appearance of freshwater palynomorphs may be an indication ofwell development of low land forests under wet climate condition.

Reassessing Depositional Conditions of the Pre-Apulian Zone Based on Synsedimentary Deformation Structures during Upper Paleocene to Lower Miocene Carbonate Sedimentation, from Paxoi and Anti-Paxoi Islands, Northwestern End of Greece

The studied area is situated in northwestern Greece and corresponds to the northern end of the Pre-Apulian Zone, in contact with the Apulian platform to the west and the Ionian Basin to the east. The proposed model is based on fieldwork, measured deformation structures, and age determination of the studied deposits. Until now, the known Pre-Apulian platform or Pre-Apulian zone represents the margins of the Apulian platform to the Ionian Basin and was formed due to the normal faults’ activity during the Mesozoic to Cenozoic Eras. Soft sediment deformation (SSD) structures are widespread within the upper Paleocene to lower Miocene limestones/marly limestones that are exposed in both Paxoi and Anti-Paxoi Islands, mostly along their eastern coasts, across sections of 2–3 km long and up to 60 m high. SSD structures, with a vertical thickness up to 10 m, have been observed in limestones and were formed during or immediately after deposition, during the first stage of sediment consolidation. SSD structures are cross-cut by normal faults, indicating their development during the rift stage. There are at least five different SSD horizons, and most of them present either an eastward or a westward progradation. These SSD structures are classified into four (4) different types of deformations: (1) thick synclines and anticlines, formed due to strong synsedimentary deformation; (2) strong and thick SSD structures that produced erosional contacts both with the underlying and the overlying undeformed horizons; (3) thin slumps, having sharp contacts with the underlying undeformed horizons and erosional contacts with the overlying undeformed horizons; and (4) thin slump horizons passing laterally to undeformed deposits in the same horizon. The studied SSD structures and their age of development introduce active margins between the Apulian platform and the Ionian Basin that have been influenced by normal fault activity. These normal faults have been active since the Ionian Basin changed gradually to a foreland basin, and after the tectonic regime changed from extension to compression, during the early to middle Eocene. It seems that compression in the studied Apulian platform margins arrived later and after the lower Miocene, and after the development of the SSD structures. The confinement of the lower Miocene deposits, both northwards and southwards (in Anti-Paxoi Island), indicates the presence of active transfer faults, with flower structure geometry, that were formed during sedimentation, producing highs and troughs. The present open anticline geometry of Paxoi Island indicates that the Island represents the forebulge area of the middle Miocene Ionian Foreland due to Ionian Thrust activity.

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.

Understanding the complex geomorphology of a deep sea area affected by continental tectonic indentation: The case of the Gulf of Vera (Western Mediterranean)

We present a multidisciplinary study of morphology, stratigraphy, sedimentology, tectonic structure, and physical oceanography to report that the complex geomorphology of the Palomares continental margin and adjacent Algerian abyssal plain (i.e., Gulf of Vera, Western Mediterranean), is the result of the sedimentary response to the Aguilas Arc continental tectonic indentation in the Eurasian–Africa plate collision. The indentation is imprinted on the basement of the margin with elongated metamorphic antiforms that are pierced by igneous bodies, and synforms that accommodate the deformation and create a complex physiography. The basement is partially covered by Upper Miocene deposits sealed by the regional Messinian Erosive Surface characterized by palaeocanyons that carve the modern margin. These deposits and outcropping basement highs are then covered and shaped by Plio-Quaternary contourites formed under the action of the Light Intermediate and Dense Deep Mediterranean bottom currents. Even though bottom currents are responsible for the primary sedimentation that shapes the margin, 97% of this region's seafloor is affected by mass-movements that modified contourite sediments by eroding, deforming, faulting, sliding, and depositing sediments. Mass-movement processes have resulted in the formation of recurrent mass-flow deposits, an enlargement of the submarine canyons and gully incisions, and basin-scale gravitational slides spreading above the Messinian Salinity Crisis salt layer. The Polopo, Aguilas and Gata slides are characterized by an extensional upslope domain that shapes the continental margin, and by a downslope contractional domain that shapes the abyssal plain with diapirs piercing (hemi)pelagites/sheet-like turbidites creating a seafloor dotted by numerous crests. The mass movements were mostly triggered by the interplay of the continental tectonic indentation of the Aguilas Arc with sedimentological factors over time. The indentation, which involves the progressively southeastward tectonic tilting of the whole land-sea region, likely generated a quasi-continuous oversteepening of the entire margin, thus reducing the stability of the contourites. In addition, tectonic tilting and subsidence of the abyssal plain favoured the flow of the underlying Messinian Salinity Crisis salt layer, contributing to the gravitational instability of the overlying sediments over large areas of the margin and abyssal plain.

Cenozoic reorganization of fluvial systems in eastern China: Sedimentary provenance of detrital K-feldspar in Taiwan

Cenozoic passive margin sediments in Taiwan provide an important natural archive to reconstruct drainage reorganization in eastern China. In this study, we used Pb isotope compositions of detrital K-feldspar to investigate the sedimentary provenance of Cenozoic strata in Taiwan and to constrain fluvial system evolution in eastern China. Eocene to lower Oligocene sandstones in Taiwan are characterized by radiogenic K-feldspar grains (206Pb/204Pb>18.4), indicating that the eastern Cathaysia Block served as the dominant sediment contributor. In contrast, a late Oligocene sample has a Pb isotopic character indistinguishable from that of the Gan River, a major tributary of the Yangtze River. This provenance change is interpreted as the result of headward (westward) migration of the paleo-Min River to the Wuyishan (Wuyi Mountains) during the late Oligocene. Miocene deposits are enriched in relatively unradiogenic K-feldspar (206Pb/204Pb<17.0) which can be reliably traced back to the Dabie and Sulu orogenic belts. Since the early Miocene, the paleo-Yangtze River, mainly draining the Yangtze Craton and the Dabie orogenic belt, delivered a large volume of detritus to the East China Sea Shelf Basin and also to the proto-Taiwan region.