Stratigraphic Constraints Research Articles

Evolution of the Alpine orogenic belts in the Western Mediterranean region as resolved by the kinematics of the Europe-Africa diffuse plate boundary

The West European collisional Alpine belts are the result of the inversion, initiated in the middle Cretaceous, of the complex western Neotethys and the Atlantic continental rift domains and closure of remnants of Tethys between the North Africa and European cratons. While the kinematics of Africa relative to Europe is well understood, the kinematics of microplates such as Iberia and Adria within the diffuse collisional plate boundary is still a matter of debate. We review geological and stratigraphic constraints in the peri-Iberia fold-thrust belts and basins to define the deformation history and crustal segmentation of the West European realm. These data are then implemented with other constraints from recently published kinematic and paleogeographic reconstructions to propose a new regional tectonic and kinematic model for Western Europe from the late Permian to recent times. Our model suggests that the pre-collisional extension between Europe and Africa plates was distributed and oblique, hence building discontinuous rift segments between the southern Alpine Tethys and the Central Atlantic. They were characterised by variably extended crust and narrow oceanic domains segmented across transfer structures and micro-continental blocks. The main tectonic structures inherited from the late Variscan orogeny localized deformation associated with rifting and orogenic belts. We show that continental blocks, including the Ebro-Sardinia-Corsica block, have been key in accommodating strike-slip, extension, and contraction in both Iberia and Adria. The definition of a new Ebro-Sardinia-Corsica block allows refining the tectonic relationships between Iberia, Europe and Adria in the Alps. By the Paleogene, the convergence of Africa closed the spatially distributed oceanic domains, except for the Ionian basin. From this time onwards, collision spread over the different continental blocks from Africa to Europe. The area was eventually affected by the West European Rift, in the late Eocene, which may have controlled the opening of the West Mediterranean. The low convergence associated with the collisional evolution of Western Europe permits to resolve the control of the inherited crustal architecture on the distribution of strain in the collision zone, that is otherwise lost in more mature collisional domain such as the Himalaya.

Sequence modeling in zircon double-dating of early Holocene Mt. Erciyes domes (Central Anatolia)

Abstract Mt. Erciyes (3917 m), the highest stratovolcano in Central Anatolia, Turkey, is considered active based on three recently dated early Holocene dome eruptions that were also correlated with tephras in the Mediterranean and the Black Sea. Despite the demonstrated Holocene activity of Mt. Erciyes, the eruptive chronostratigraphy of these events and their hazard potential for the nearby Kayseri metropolitan area (population ~1.4 million) remain poorly constrained. Here, we apply zircon double-dating (ZDD) based on (U–Th)/He thermochronology and U–Th–Pb crystallization ages, where intra-grain crystallization age differences were used for disequilibrium correction. Individual ZDD ages were refined via sequence modeling to reconstruct the eruption timing of four early Holocene domes peripheral to Mt. Erciyes. Sequence modeling, which incorporated petrological, volcanological, and stratigraphic constraints, yielded the following eruption ages (uncertainties stated at 1σ): 8.8 ± 0.8 ka for stratigraphically directly superimposed Perikartin and Karagullu, 8.9 ± 0.5 ka for Dikkartin, and 9.4 ± 1.3 ka for previously undated Yilanli Dag, located within the perimeter of Kayseri. A model where all four early Holocene domes are assumed to have erupted simultaneously suggests an age of 8.9 ± 0.4 ka. Earlier eruptive phases of Mt. Erciyes were identified by ZDD at ca. 85–88 ka (fall-out deposits and Carik Tepe lava) and at ca. 105 ka (xenoliths from two peripheral scoria cones). Zircon crystallization ages reveal protracted magmatic activity beneath Mt. Erciyes since ca. 800 ka, in agreement with dated volcanic activity, and preceding magmatic phases at ca. 2–3 Ma that included the eruption of the widespread Valibaba Tepe Ignimbrite with a U–Pb zircon age of 2.73 ± 0.02 Ma. A volume estimate for the Quaternary edifice of ~300 km3 translates into an integrated long-term eruptive magma flux of ~0.4 km3/ka for post-collisional Mt. Erciyes, within uncertainty of the Late Pleistocene–Holocene flux estimate of >0.1 km3/ka based on dome volumes and eruption ages. The near-synchronous eruptions of a suite of four evolved domes, in three cases with sizable early explosive venting, calls for a hazard assessment that combines the impact of multiple simultaneous eruptions.

An andesitic sill complex in the Southern Permian Basin: volcanogenetic model and stratigraphic implications

Subvolcanic intrusions are highly variable in shape and structure, and occur in nearly all parts of the upper crust, as a result of extensive volcanic activity. Processes of subvolcanics interacting with the host rock are insufficiently understood, as they are rarely exposed. In the southernmost part of the Flechtingen-Altmark Subprovince, (sub)volcanic rocks of the Flechtingen Volcanic Complex (FVC) are exposed in several quarries. It is built up of silicic tuffs, ignimbrites and lava flows, but also of intermediate lavas and extended sill sheets. Additionally, major granitic intrusions exposed by drillings are associated with the FVC. In the Mammendorf quarry, a sill intruded in between lithified turbiditic series of early Carboniferous (Visean–Serphukovian) age at the base, and widely consolidated volcanoclastic deposits of late Carboniferous (late Pennsylvanian) age at the top. Various magma-host rock interactions were found indicating brittle and ductile deformation patterns occurring at the basal contact, and secondary fluidal mixing predominantly occurring at the top contact, most probably caused by fluids accompanying the intruding magma. We present an extended volcanogenetic model for the FVC. Volcanic activity initiated at 302 ± 3 Ma with fallout deposits represented by mostly re-deposited silicic ashfall deposits of the Flechtingen Formation, and cumulated in depositing major ignimbrite series, most likely forming a caldera. Later, the sills intruded at the rheological boundary of the lithified Mississippian turbiditic series and the partly consolidated volcanoclastic series. Finally, major granitic intrusions emplaced in the basement rocks at around 298 ± 4 Ma. The study contributes to clarify stratigraphic constraints of late Carboniferous to early Permian continental deposits and sheds light on stratigraphy of significant late Paleozoic volcanic deposits of the Flechtingen-Altmark Subprovince in the Southern Permian Basin.

The evolution of Nyctereutes (Carnivora: Canidae) in the Nihewan Basin, Hebei, northern China

The occurrence of Nyctereutes during the Plio-Pleistocene has long been reported in northern China, with the highest abundance in the Nihewan Basin. However, due to site dispersal, the coexistence of different taxa, and lack of a precise stratigraphic constraint, the evolutionary process of this genus remains enigmatic. In this study, we re-examined the available Nyctereutes materials recovered from the Nihewan Basin housed in IVPP and Tianjin Natural History Museum, in addition to a newly recovered specimen from our latest excavation. Furthermore, we compared these materials with Nyctereutes fossils recovered from the Pleistocene Zhoukoudian sites near Beijing and the extant species N. procyonoides. Our analysis of the upper molar morphometry reveals the variations in size and dietary characteristics within different species of Nyctereutes during the late Plio-Pleistocene. The examination of molars indicates an increase in the size of Nyctereutes sinensis compared to early Pliocene N. tingi as well as changes in the molar teeth morphology. Subsequently, changes in diet or environmental factors possibly caused the decrease of body size in the late Pleistocene. We also estimate an age constraint for the fossils of N. sinensis from the Xiashagou section by relocating Licent's localities and referring of updated magnetostratigraphic data.

Stratigraphic constraints on the Lower Cretaceous Orallo Formation, southeastern Queensland: U–Pb dating of bentonite and palynostratigraphy of associated strata

This study presents two chemical abrasion-thermal ionisation mass spectrometry (CA-TIMS) U–Pb zircon ages from tuffs as well as palynostratigraphic results from the embracing sedimentary succession of the Orallo Formation, Surat Basin, Queensland. Samples were taken from two Geological Survey of Queensland (GSQ) stratigraphic holes, GSQ DRD 26 and GSQ Roma 2. Palynological results assign the upper part of the Orallo Formation to the lower part of the Ruffordiaspora australiensis Interval Zone rather than the upper part of this zone as previously indicated. A late Valanginian isotopic date of 134.38 ± 0.04 Ma from GSQ DRD 26 and an early Hauterivian date of ≤132.46 ± 0.36 Ma from GSQ Roma 2 give the Orallo Formation a Berriasian?/Valanginian–Hautevarian age, rather than the previously inferred Berriasian–Valanginian age determined without any geochronological control. Additionally, when combined with previously published geochronological dates from the Westbourne Formation, these ages suggest that, in the Surat Basin succession, the Jurassic–Cretaceous boundary most likely lies within the Gubberamunda Sandstone. KEY POINTS Two U–Pb CA-TIMS ages of 134.38 ± 0.04 Ma and ≤132.46 ± 0.36 Ma have been found, based on zircons extracted Orallo Formation tuffs. Sediments surrounding the two tuffs the zircons were extracted from yielded palynofloras assignable to the lower part of the Ruffordiaspora australiensis Interval Zone. These dates, combined with earlier work, show the Orallo Formation to be of Berriasian?/Valanginian–Hautevarian age.

Early Permian brachiopods from the Pebbley Beach Formation, Southern Sydney Basin, southeastern Australia

A new low-diversity and low-abundance brachiopod fauna comprising seven species in four named genera and three indeterminate genera is described for the first time from the Pebbley Beach Formation in the southern Sydney Basin, southeastern Australia. Among the brachiopods described and illustrated, one new ingelarelloidean (Family Notospiriferidae) species (Tabellina laseroni sp. nov.) and one new terebratulid (Family Gillediidae) genus and new species (Paragilledia kioloaensis gen. et sp. nov.) are proposed. In addition, the status and validity of two strophalosioidean species previously described from the Pebbley Beach Formation are also discussed and revised. The age of the Pebbley Beach Formation is discussed and, based on the brachiopod fauna documented here and other stratigraphic and geochronological constraints, is considered to be late Sakmarian to early Kungurian.G.R. Shi [guang@uow.edu.au]* and S. Lee [lsam@uow.edu.au], School of Earth, Atmospheric and Sciences, University of Wollongong, Northfields Avenue, NSW 2522 Australia; J.W. Waterhouse, Oamaru, New Zealand.

The Great Oxidation Event preceded a Paleoproterozoic “snowball Earth”

The inability to resolve the exact temporal relationship between two pivotal events in Earth history, the Paleoproterozoic Great Oxidation Event (GOE) and the first "snowball Earth" global glaciation, has precluded assessing causality between changing atmospheric composition and ancient climate change. Here we present temporally resolved quadruple sulfur isotope measurements (δ34S, ∆33S, and ∆36S) from the Paleoproterozoic Seidorechka and Polisarka Sedimentary Formations on the Fennoscandian Shield, northwest Russia, that address this issue. Sulfides in the former preserve evidence of mass-independent fractionation of sulfur isotopes (S-MIF) falling within uncertainty of the Archean reference array with a ∆36S/∆33S slope of -1.8 and have small negative ∆33S values, whereas in the latter mass-dependent fractionation of sulfur isotopes (S-MDF) is evident, with a ∆36S/∆33S slope of -8.8. These trends, combined with geochronological constraints, place the S-MIF/S-MDF transition, the key indicator of the GOE, between 2,501.5 ± 1.7 Ma and 2,434 ± 6.6 Ma. These are the tightest temporal and stratigraphic constraints yet for the S-MIF/S-MDF transition and show that its timing in Fennoscandia is consistent with the S-MIF/S-MDF transition in North America and South Africa. Further, the glacigenic part of the Polisarka Formation occurs 60 m above the sedimentary succession containing S-MDF signals. Hence, our findings confirm unambiguously that the S-MIF/S-MDF transition preceded the Paleoproterozoic snowball Earth. Resolution of this temporal relationship constrains cause-and-effect drivers of Earth's oxygenation, specifically ruling out conceptual models in which global glaciation precedes or causes the evolution of oxygenic photosynthesis.

Analyzing Statistical Age Models to Determine the Equivalent Dose and Burial Age Using a Markov Chain Monte Carlo Method

In optically stimulated luminescence (OSL) dating, statistical age models for equivalent dose (D<sub>e</sub>) distributions are routinely estimated using the maximum likelihood estimation (MLE) method. In this study, a Markov chain Monte Carlo (MCMC) method was used to analyze statistical age models, including the central age model (CAM), the minimum age model (MAM), the maximum age model (MXAM), <i>etc.</i> This method was first used to obtain sampling distributions on parameters of interest in an age model using D<sub>e</sub> distributions from individual sedimentary samples and subsequently extended to simultaneously extract age estimates from multiple samples with stratigraphic constraints. The MCMC method allows for the use of Bayesian inference to refine chronological sequences from multiple samples, including both fully and partially bleached OSL dates. This study designed easily implemented open-source numeric programs to perform MCMC sampling. Measured and simulated D<sub>e</sub> distributions are used to validate the reliability of dose (age) estimates obtained by this method. Findings from this study demonstrate that estimates obtained by the MCMC method can be used to informatively compare results obtained by the MLE method. The application of statistical age models to multiple OSL dates with stratigraphic orders using the MCMC method may significantly improve both the precision and accuracy of burial ages.

Middle to Late Pleistocene Evolution of the Bengal Fan: Integrating Core and Seismic Observations for Chronostratigraphic Modeling of the IODP Expedition 354 8° North Transect

AbstractWe investigate chronology and age uncertainty for the middle to upper Pleistocene lower Bengal Fan using a novel age‐depth modeling approach that factors lithostratigraphic, magnetostratigraphic, biostratigraphic, cyclostratigraphic, and seismic stratigraphic constraints, based on results from the International Ocean Discovery Program Expedition 354 Bengal Fan and analysis of the GeoB97‐020/027 seismic line. The initial chronostratigraphic framework is established using regionally extensive hemipelagic sediment units, and only age‐depth models of fan deposits that respect the superposition of channel‐levee systems between sites are accepted. In doing so, we reconstruct signals of regional sediment accumulation rate and lithogenic sediment input through the perspective of a two‐dimensional ~320 km transect at 8°N that are consistent with more distal and more ambiguous regional records. This chronology allows us to discuss the depositional history of the middle to upper Pleistocene lower Bengal Fan within the context of sea level, climate, and tectonic controls. We hypothesize, based on the timing of accumulation rate changes, that progradation and intensification of the Bengal Fan's channel‐levee system at 8°N was largely driven by increases in sea level amplitude during this time. However, it is also possible this progradation was influenced by changes in Pleistocene climate and increased Himalayan erosion rates, driving greater sediment flux to the fan.

Enigmatic earthquake-generated large-scale clastic dyke in the Biberach area (SW Germany)

We discovered and describe a large-scale (exposed dimensions ~17 m in lateral and ~15 m in vertical extension, and up to 10 cm in width) clastic dyke in the Middle Miocene (between ~17.1 and ~14.5 Ma) sandy deposits (‘Fluviatile Untere Serie’) of the North Alpine Foreland Basin, close to Biberach an der Riß in SW Germany. The dyke appears to be of sedimentary–tectonic origin. It formed by liquefaction and injection of clastic material that occurred simultaneously with fracture opening and propagation in sandy deposits, presumably as a result of strong seismic shaking triggered by an intense earthquake. We, therefore, interpret the dyke as a seismite and a useful palaeoseismic indicator. The clastic dyke cuts through a layer of distal Ries ejecta (‘Brockhorizont’) and, thus, postdates the Ries impact. The age of the Ries event, in combination with other stratigraphic constraints, defines a relatively narrow time frame of ~14.8 to 14.5 Ma for the formation of the clastic dyke. The source of the strong earthquake responsible for dyke formation might be seismicity related to the Alpine orogeny and tectonism, seismic activity in one of the volcanic fields of the Paleogene to Quaternary European Volcanic Province, or seismicity induced by a Miocene impact event in southern Germany. We suggest the relatively strong earthquake in question may have been triggered by a large phreatomagmatic explosion in the Urach-Kirchheim volcanic field or, perhaps more likely, the Steinheim impact event on the eastern Swabian Alb plateau.

Archaeomagnetic knowledge of the Neolithic in Bulgaria with emphasis on intensity changes

Abstract Several archaeological baked clay structures from Bulgarian Neolithic sites were archaeomagnetically studied. According to the ancient firing conditions, the collected materials are dwelling remains and ovens with different heating histories. The variability of magnetic properties is greater in the burnt dwelling remains compared to the ovens. The prevailing magnetic minerals are magnetite/titanomagnetite and epsilon iron oxide. Less often, the presence of hematite is suggested. For one of the ovens, a well-pronounced evolution in magnetic properties was observed between its successive levels. The collected materials possess stable magnetic mineralogy and the success rate of archaeointensity determination experiment is 84%. The experiment completely failed only for the structure where epsilon iron oxide is not identified and where the lowest median destructive fields are determined. The obtained archaeomagnetic results are summarized as 10 new reference points. The structures subjected to the same firing event are combined as one feature. Their dating is based on well-established relative Neolithic chronology and stratigraphic constraints. The new data coincide fairly well with the Bulgarian dataset and with the data available for the neighbouring countries, confirming an intensity maximum around 5550 BC and a minimum around 5400 BC. No indications of geomagnetic ‘spikes’ or ‘jerks’ are detected.

Middle to Late Pleistocene Arctic paleoceanographic changes based on sedimentary records from Mendeleev Ridge and Makarov Basin

Three sediment cores from the Makarov Basin and Mendeleev Ridge off the Siberian margin were analyzed for a number of litho-, bio- and magnetostratigraphic proxies. Correlation to previously studied Arctic records from Mendeleev to Lomonosov ridges enables paleoceanographic reconstructions for the Middle to Late Pleistocene (estimated ∼0.8 Ma) on orbital time scales. Cyclic changes in lithology corroborated by multiple stratigraphic constraints were tuned to global climate variations based on the manganese content that increases during interglacials, while calcium and zircon were used as proxies for the Laurentide and Eurasian ice sheet inputs. The combined evaluation of glacial and interglacial proxy variabilities provides a coherent picture of the western Arctic Ocean development in the Pleistocene. We suggest that major cyclic changes were driven by summer processes, such as sea-ice retreat and enhanced biological production vs. suppressed ice melt in warmer and colder summers, respectively. A potential link to low latitudes via atmospheric moisture and heat transport is indicated by similarities in the western Arctic Ocean and East Asian monsoon records. Long-term cooling is signified by biogenic proxies related to sea-ice expansion over the western Arctic Ocean with step changes at MIS 11 and 7 (∼0.4 and 0.2–0.3 Ma). This transition also features better fossil preservation indicating less corrosive/oxidative bottom waters, probably resulting from a decrease in organic export production and/or weakening of bottom water ventilation under perennial sea ice. The latter was possibly enhanced by atmospheric cooling and increased meltwater fluxes with the growth of circum-Arctic ice sheets.

New stratigraphic constraints for the Quaternary source‐to‐sink history of the Amatrice Basin (central Apennines, Italy)

New stratigraphic constraints have been detailed for the Amatrice Basin, an intermountain morpho‐structural depression of the central Apennines (Italy) hosting up to 60‐m‐thick Quaternary continental deposits. Through the results coming from a 1:5,000 scale field survey and from facies analyses, we documented the geometry, thickness, and extent of the post‐orogenic continental deposits filling this basin. The Quaternary deposits form a complex architecture of purely aggradational and aggradational/degradational terraces with a dominant component of conglomerates and gravels, at the bottom, and subordinate sands, at the top. The Quaternary deposits overlie an up to 1‐km‐thick succession of flysch sediments that accumulated in the western Laga Basin during the Miocene syn‐orogenic phases in central Apennines. The collected data are used to constrain the style and mechanisms of both syn‐orogenic (i.e., subsidence and terrigenous sedimentation in foredeep environment) and post‐orogenic (i.e., uplift, erosion, and continental sedimentation) phases documented for the central Apennines. In particular, the post‐orogenic history of the Amatrice Basin, if compared with those of surrounding intermountain basins of the central Apennines, includes limited basin subsidence, reduced thickness of the post‐orogenic covers and progressive deepening of the drainage network during the Quaternary. The results shed light on the source‐to‐sink history of the Amatrice Basin, which results from a long‐lived interaction between regional‐scale factors (climate changes, chain uplift, and extensional tectonic regime) that influenced the activity of the hydrodynamic pattern and the amount of intrabasinal sedimentation during the Quaternary.

Zircon U‐Pb Chronostratigraphy and Provenance of the Cycladic Blueschist Unit and the Nature of the Contact With the Cycladic Basement on Sikinos and Ios Islands, Greece

AbstractSikinos and Ios Islands, located in the Southern Cyclades, represent part of a Cenozoic metamorphic core complex system that exposes subduction‐related metamorphic rocks in the highly extended back‐arc region of the Hellenic subduction zone. These exhumed HP‐LT metamorphic units are composed of Mesozoic metasedimentary rocks of the Cycladic Blueschist Unit (CBU) and the Paleozoic Cycladic Basement (CB). The magmatic and stratigraphic evolution of these units, as well as the nature of the contact between the CBU and CB, have remained poorly understood. We used zircon U‐Pb dating to determine crystallization ages of the CB on Sikinos and the maximum deposition ages and detrital provenance of the metasedimentary units to reconstruct the Mesozoic to early Cenozoic stratigraphic and tectonic evolution of the CBU on both islands. The results reveal that the CB in Sikinos is composed of Cambrian‐Silurian metasedimentary rocks intruded by Carboniferous granites and is overlain by metasedimentary rocks of the CBU with depositional ages spanning from Permo‐Triassic to Late Cretaceous. The provenance data from the CBU records a long‐lived tectonic evolution from Paleo‐Tethys subduction and rifting, to passive margin formation, and to subduction of the Neo‐Tethyan Pindos basin. The continuous stratigraphic record and provenance evolution from the CB into the CBU imply a para‐autochthonous relationship. On NE Sikinos and Ios, stratigraphic constraints suggest older‐over‐younger relationships along cryptic‐thrusts, supporting premetamorphic or synmetamorphic structural repetition of the CBU by imbrication, likely during subduction underplating.

Spatial pattern of accumulation at Taylor Dome during Marine Isotope Stage 4: stratigraphic constraints from Taylor Glacier

Abstract. New ice cores retrieved from the Taylor Glacier (Antarctica) blue ice area contain ice and air spanning the Marine Isotope Stage (MIS) 5–4 transition, a period of global cooling and ice sheet expansion. We determine chronologies for the ice and air bubbles in the new ice cores by visually matching variations in gas- and ice-phase tracers to preexisting ice core records. The chronologies reveal an ice age–gas age difference (Δage) approaching 10 ka during MIS 4, implying very low snow accumulation in the Taylor Glacier accumulation zone. A revised chronology for the analogous section of the Taylor Dome ice core (84 to 55 ka), located to the south of the Taylor Glacier accumulation zone, shows that Δage did not exceed 3 ka. The difference in Δage between the two records during MIS 4 is similar in magnitude but opposite in direction to what is observed at the Last Glacial Maximum. This relationship implies that a spatial gradient in snow accumulation existed across the Taylor Dome region during MIS 4 that was oriented in the opposite direction of the accumulation gradient during the Last Glacial Maximum.

Between plate and salt tectonics—New stratigraphic constraints on the architecture and timing of the Dead Sea basin during the Late Quaternary

AbstractThe Dead Sea is an extensional basin developing along a transform fault plate boundary. It is also a terminal salt basin. Without knowledge of precise stratigraphy, it is difficult to differentiate between the role of plate and salt tectonics on sedimentary accumulation and deformation patterns. While the environmental conditions responsible for sediment supply are reasonably constrained by previous studies on the lake margins, the current study focuses on deciphering the detailed stratigraphy across the entire northern Dead Sea basin as well as syn and post‐depositional processes. The sedimentary architecture of the late Quaternary lacustrine succession was examined by integrating 851 km of seismic reflection data from three surveys with gamma ray and velocity logs and the stratigraphic division from an ICDP borehole cored in 2010. This allowed seismic interpretation to be anchored in time across the entire basin. Key surfaces were mapped based on borehole lithology and a newly constructed synthetic seismogram. Average interval velocities were used to calculate isopach maps and spatial and temporal sedimentation rates. Results show that the Amora Formation was deposited in a pre‐existing graben bounded by two N‐S trending longitudinal faults. Both faults remained active during deposition of the late Pleistocene Samra and Lisan Formations—the eastern fault continued to bound the basin while the western fault remained blind. On‐going plate motion introduced a third longitudinal fault, increasing accommodation space westwards from the onset of deposition of the Samra Formation. During accumulation of these two formations, sedimentation rates were uniform over the lake and similar. High lake levels caused an increase in hydrostatic pressure. This led to salt withdrawal, which flowed to the south and southwest causing increased uplift of the Lisan and En Gedi diapirs and the formation of localized salt rim synclines. This induced local seismicity and slumping, resulting in an increased thickness of the Lisan succession within the lake relative to its margins. Sedimentation rates of the Holocene Ze'elim Fm were 4–5 times higher than before. The analysis presented here resolves central questions of spatial extent and timing of lithology, deposition rates and their variability across the basin, timing of faulting at and below the lake floor, and timing and extent of salt and plate tectonic phases and their effect on syn and post‐depositional processes. Plate tectonics dictated the structure of the basin, while salt tectonics and sediment accumulation were primarily responsible for its fill architecture during the timeframe examined here.

Sedimentologic and stratigraphic constraints on the orientation of the Late Triassic northern Indian passive continental margin

The orientation and distribution of the northern Indian passive continental margin basin during different epochs constrained the geometric characteristics of the hyperextended northern Indian edge (“Greater India”). Traditional paleogeographic reconstructions envisage the Late Triassic northern Indian passive continental margin as E/W-trending, whereas paleomagnetic data support an ~55° counterclockwise rotation during northward drifting. This case study of Upper Triassic units from the northern Indian margin, based on facies analysis, sandstone petrography, heavy mineral assemblages, U-Pb detrital zircon geochronology, and stratigraphic correlation from the Zanskar Range to southern Tibet, provides new constraints and suggests that the northern Indian passive continental margin might have been N/S-trending in the Late Triassic. Given the dominance of quartz sandstones with zircon, tourmaline and rutile—indicating a provenance from continental blocks and the recycling of older quartz-rich sandstones—and detrital zircon age spectra characterized by a Neoproterozoic detrital zircon U-Pb age peak (921 ± 13 Ma), the Upper Triassic sandstones widespread along the Tethyan Himalayas may have been partly derived from the Eastern Ghats Mobile Belt in eastern India and the Rayner Orogen in eastern Antarctica. The Upper Triassic Quartzite Series comprises feldspatho-quartzose to pure quartzose sandstones with intercalated bioclastic oosparites deposited in backshore, foreshore and shoreface coastal environments. Without considering the subsequent counterclockwise rotation of India, the consistent pattern of the Upper Triassic bidirectional E-W paleocurrent observed throughout the Himalaya suggests that the paleoshoreline was striking near N-S, approximately perpendicular to the regional orientation of the northern Indian margin. Progressive eastward thickening of the sandstone layers and eastward younging of the Quartzite Series suggest diachronous sedimentation. Such stratal patterns and the strike of the Late Triassic paleoshoreline were attributed to the Neo-Tethys transgression from the Zanskar Range to southern Tibet.

A middle Miocene post‐rift stress regime revealed by dikes and mesoscale faults in the Kakunodate area, NE Japan

AbstractSignificant advances were made in the last century in the investigations of the Neogene stress history of the NE Japan arc. However, previous studies have failed to fully resolve middle Miocene post‐rift stress conditions owing to their assumption of Andersonian faulting and an inability to determine maximum and intermediate stress axes from dike orientations. We applied the latest methods of paleostress analysis in this study to igneous dikes and mesoscale faults in the Kakunodate area of the NE Japan arc to elucidate post‐rift stress conditions. Stratigraphic constraints and U–Pb dating indicate that the doleritic and dacitic dikes were formed at 16–12 Ma and 15–12 Ma, respectively. Dolerite and dacite dikes yielded NW–SE extensional stresses with intermediate and low stress ratios, respectively. Mesoscale faults in the middle Miocene formations of the studied area indicated similar stresses. We suggest the sluggish deformations resulting in the dike intrusion and faulting in the normal‐faulting stress regime after the termination of intra‐arc rifting at ca. 15 Ma.

Origins of obsidian at the “Pompeii of the Syrian Desert:” Sourcing lithic artifacts from the Yale-French excavations at Dura-Europos

The Hellenistic, Parthian, and Roman site of Dura–Europos (or simply “Dura”), dubbed the “Pompeii of the Syrian Desert” by Yale historian and archaeologist Michael Rostovtzeff, was jointly excavated by Yale University and the French Academy of Inscriptions and Letters from 1928 to 1937. Given the outstanding preservation of art and architecture at Dura, it is not surprising that four obsidian artifacts have escaped attention, despite evidence that stone tools – including obsidian ones – continued to be used into and after the Iron Age in the Eastern Mediterranean. After more than eight decades, the character of Dura's connections to the Classical world remains a matter of debate. Pottery includes not only local ceramic wares but also North African and Aegean ones. Our nondestructive pXRF testing establish that the Dura artifacts match the three most widely used Eastern Anatolian obsidian sources: Nemrut Dağ volcano as well as the Bingöl A and B sources. If indeed obsidian arrived at Dura via long-standing mechanisms of Mesopotamian exchange, these Eastern Anatolian obsidians would be expected. Unfortunately, the artifacts' precise locations at Dura are unclear, the excavations lacked stratigraphic constraints, and Near Eastern obsidian distribution patterns have been rarely studied beyond the Early Bronze Age. Keeping in mind these limitations, our findings are most consistent with past suggestions regarding the importance of local Mesopotamian influences and resources at the site.

Paleogeographic implications of the Permian shallow marine carbonates in the eastern Lake Van region (eastern Turkey): Foraminiferal biostratigraphic and sequence stratigraphic constraints

The study focuses on the Middle Permian recrystallized limestone succession, previously considered as Triassic, at the eastern parts of Lake Van (eastern Turkey) representing the northern margin of Gondwana. The Middle Permian successions in the region are mainly composed of slightly metamorphosed, recrystallized limestones. The shallow‐water depositional settings of the studied units are characterized by the relative dominance of smaller foraminifers and rare occurrence of fusulinids. Middle Permian foraminifers recorded from eastern Anatolia are typically Tethyan assemblages for the Capitanian (Guadalupian) age. Detailed microfacies analysis by textural analysis and faunal assemblages have been undertaken throughout the studied sections. The Capitanian carbonates of the region are mainly characterized by six major microfacies types representing shallow marine environments, ranging from foreshoal environment to shoal and backshoal environments. Within the scope of sequence stratigraphic interpretations, vertical stacking patterns of these microfacies types reflecting different depositional environments reveal the presence of two third‐order depositional sequences, each of which consists of a transgressive systems tract and a highstand systems tract. Within the context of sequence stratigraphy, the microfacies changes point out the relative sea‐level fall towards the upper part of the sections, coinciding with the onset of a regression recorded worldwide in the Capitanian.