Biostratigraphic Evidence Research Articles

U‐Pb carbonate dating reveals long‐lived activity of proximal margin extensional faults during the Alpine Tethys rifting

AbstractSyn‐rift extensional faults play a significant role during the early stage of rifting. Constraining the age of faulting, and how and when deformation shifts from the proximal to the distal margin areas, is crucial for the reconstruction of the rifting process. Previous assessments of the structural and temporal evolution of rift‐related faults of the Adria proximal margin have primarily relied on indirect biostratigraphic evidence. Additionally, the majority of rift‐related faults underwent tectonic inversion during the Alpine orogeny. In this study, in‐situ U‐Pb geochronology was applied on syn‐kinematic calcites to unravel the activity of the Amora Fault, a remarkable example of a Jurassic growth fault unaffected by the Alpine orogeny. The obtained ages, spanning from Hettangian to Callovian, extend the AF activity beyond the previously established Early Jurassic time. This chrono‐structural model has significant implications on the role of major extensional faults in focusing deformation throughout the rift system's evolution.

Insights into glendonite formation from the upper Oligocene Sagavanirktok Formation, North Slope, Alaska, U.S.A.

Abstract The type locality for the upper Oligocene Nuwok Member of the Sagavanirktok Formation (Carter Creek, North Slope, Alaska, USA) contains an abundant occurrence of glendonite, a pseudomorph after the calcium-carbonate mineral ikaite, which typically forms in the shallow subsurface of cold marine sediments. The region during the time of Nuwok Member deposition was located at a high latitude, similar to today, and the study site is characterized by sands and silty muds interpreted here to have been deposited in coastal and shelfal marine environments. Isotopic (Sr) and biostratigraphic (foraminifera) evidence presented here refine the depositional age of the outcrop to approximately 24 Ma. Glendonites occur in two basic forms: radial clusters, commonly centered around a single larger primary crystal (∼ 10 cm, Type A) and larger single blades generally without accessory crystals (∼ 15–25 cm, Type B). Microscopic examination reveals a sequence of multiple types of replacive calcite that formed as a direct result of ikaite transformation: Type 1 rhombohedral crystals characterized by microporous and inclusion-rich cores and concentric zones, Type 2A, composed of clear calcite that overgrew and augmented Type 1 crystals, and inclusion-rich, microcrystalline Type 2B, which formed a matrix surrounding the rhombs and commonly dominates the outer rims of glendonite specimens. Type 3 calcite precipitated as fibrous, botryoidal epitaxial cement atop previous phases and is not ikaite-derived. These phases are distributed in similar ways in all examined specimens and are consistent with several previously described glendonite occurrences around the world, despite differing diagenetic and geologic histories. Stable-isotope evidence (δ13C and δ18O) suggests sourcing of glendonite carbon from both organic and methanogenic sources. Glendonites of the Nuwok Member can therefore assist in the determination of a more comprehensive ikaite transformation model, improving our understanding of glendonite formation and the sedimentological and environmental context of their occurrence. Oligocene glendonites are uncommon globally; the well-preserved occurrence described here can allow future studies to better reconstruct Arctic environmental conditions and paleoclimates during this time.

The Barremian–lower Aptian of NE Arabia: The Kharaib and Shu'aiba formations in Wadi Rahabah and Wadi Kebdah, Ras Al Khaimah, U.A.E.

We present a high-resolution record of carbonate depositional facies, biostratigraphy, stable-isotope and elemental geochemistry of the Kharaib and Shu'aiba formations exposed in Ras Al Khaimah, northern UAE. This is the first comprehensive study of these deposits in the northeastern Arabian Peninsula, which have previously been studied extensively in Abu Dhabi, Oman, NE Saudi Arabia, and southwestern Iran, and represents the most detailed biostratigraphic and chemostratigraphic record currently available from a continuous outcrop section of the Arabian Plate. The Barremian–Aptian boundary was approximated based on orbitolinid biostratigraphy, while a subdivision of the Barremain was not possible. There is no biostratigraphic evidence that the Shu'aiba Formation in the section studied ranges into the upper Aptian. Previously well-established depositional sequences of the Barremian–lower Aptian of the Arabian Plate are discussed in the context of carbonate textures, siliciclastic influx, and biotic assemblages. There is a general trend of decreasing siliciclastic components during the Barremian and earliest Aptian, and peaks in siliciclastic influx indicate episodes of maximum accommodation. Palaeogeographic implications of our data for the distribution of intrashelf basins and their connection to Neotethys are discussed. The negative carbon-isotope excursion that globally marks the onset of OAE1a is not evident in our dataset, while the positive excursion at the end of OAE1a is present in the late early Aptian. A comparison of carbon-isotope records across the early Aptian of the Arabian Plate highlights issues of correlations that are predominantly based on chemostratography in diagenetically altered platform carbonates.

A new clam shrimp (Branchiopoda: Diplostraca: Spinicaudata) from the Upper Jurassic in the Jiyuan Basin, China and its biostratigraphic significance.

A new spinicaudatan species Triglypta jiyuanensis Liao & Huang sp. nov. is described from the Upper Jurassic Maao Formation in the Jiyuan Basin, northwestern Henan Province, China. The carapace of the new species is ornamented with punctae, linear arrangements of punctae, and radial lirae. The new species differs from those of the early Triglypta forms from the Middle Jurassic but closely resembles T. jianchangensis Wang, 2014 from the Upper Jurassic Tiaojishan Formation of western Liaoning Province. Our study provides new biostratigraphic evidence supporting that the Maao and Tiaojishan formations can be correlated. Moreover, we suggest that the Yangshuzhuang Formation in the Jiyuan Basin could correlate to the Haifanggou and the Longmen formations in the Yanliao area.

Age of the basal ‘Lower Old Red Sandstone’ Stonehaven Group of Scotland: the oldest reported air-breathing land animal is Silurian (late Wenlock) in age

The basal upper Silurian–Lower Devonian ‘Lower Old Red Sandstone’ deposits of the Midland Valley of Scotland contain several important fossil biotas, including that from the Cowie Harbour Fish Bed. This biota is of great significance because it represents one of the oldest known examples of a fossilized terrestrial ecosystem and includes the oldest reported air-breathing land animal (the myriapod Pneumodesmus newmani Wilson and Anderson, 2004 ). Based on biostratigraphical evidence from dispersed spores this biota is dated as late Wenlock (late Silurian) in age. Recently, however, this age constraint was challenged, based on 238 U– 206 Pb radiometric analysis of zircons, and it was proposed that these deposits are much younger (Early Devonian: Lochkovian). This proposal has serious implications regarding (1) the composition and nature of early terrestrial ecosystems and (2) the geological setting with respect to the timing of terrane accretion and the onset of ‘Lower Old Red Sandstone’ sedimentation. We report on newly discovered dispersed spore assemblages and additional zircon data that confirm a late Wenlock (late Silurian) age. This age designation establishes the importance of the biota of the Cowie Harbour Fish Bed and is more compatible with both its biotic composition and the regional geological setting.

A new species of Lorrettina (dokimocephalid trilobite) from the Iverian (Cambrian, Jiangshanian) of the Amadeus Basin, Northern Territory, Australia

A previously unreported dokimocephalid trilobite, Lorrettina waterhousei sp. nov., is described herein from the Iverian (Jiangshanian, Cambrian) upper Goyder Formation, Amadeus Basin, central Australia. This is the first definitive biostratigraphic evidence for rocks of an Iverian (Jiangshanian) age in the Amadeus Basin. Correlation is made with the Chatsworth Limestone (=Gola beds) of the neighbouring Georgina Basin in Australia, as well as internationally to China, based on the generic occurrence. The biostratigraphic age of the unit is also supported by previous carbon isotope chemostratigraphy, further strengthening the interpretation. Patrick M. Smith [Patrick.Smith@austmus.gov.au], Palaeontology Department, Australian Museum Research Institute, Sydney, New South Wales, 2010, Australia and, Department of Biological Sciences, Macquarie University, Sydney, New South Wales, 2109, Australia.

Middle Triassic (Muschelkalk) transgression in the West Tethys: biostratigraphic evidence from Sardinia (Italy)

Stratigraphic and palaeontological analyses of the Middle Triassic (latest Anisian–Ladinian) in Muschelkalk facies are performed here to further unravel the palaeogeographic evolution of Sardinia in this time-frame. These shallow marine successions reveal a significant palaeontological record comprising facies and marker fossils (ammonoids, bivalves, conodonts, foraminifera etc.) reflecting a regional transgressive episode recorded throughout the West Mediterranean, after the Permian–Triassic biotic crisis. Particularly rich in the Nurra and Sarcidano-Gerrei areas, the facies/fossil record indicates the progressive westward settling of carbonate platforms, and consequently the development of new migration and irradiation routes for Sephardic faunas from the southeast (Palaeotethys) and Alpine faunas (Neotethys) from the northeast. Based on new findings and the revision of palaeontological associations previously reported, comparisons were made with associations of adjacent domains (Balearic Islands, Levantine area), thus refining their palaeoecological distribution and better framing Sardinia as a key area in the palaeogeographic evolution of the West Tethys during the Ladinian.

New biostratigraphic evidence of Upper Devonian deposits by metamorphosed conodonts from Sidi Bou Othmane area of central Jebilet, Morocco and their paleogeographic implications

This report is dedicated to the Sidi Bou Othmane limestones outcrops, which are exposed in the Central Jebilet. This area experienced strong Hercynian metamorphism and deformation. Strongly metamorphosed and recrystallized conodonts point to Frasnian-Famennian ages, which are reported from this region for the first time. Based on conodont data, we thus revise the age of the Sidi Bou Othmane limestones, which are definitely Late Devonian in age instead of Mississippian (late Viséan) as reported in previous publications. Six stratigraphic intervals from the Middle falsiovalis to marginifera utahensis Zones are identified. The colour alteration index of conodonts (CAI) is very high and varies from CAI 6 to CAI 8, indicating a thermal gradient from 360 °C to over 600 °C for the conodont bearing strata, which is consistent with the isograds obtained in previous publications. Transgressive Upper Devonian limestones discontinuously overlie Ordovician psammites, beginning with a variably thick polymict conglomerate. This unconformity provides evidence of a regional exhumation and erosional event of the Ordovician strata in the Central Jebilet, prior to Upper Devonian transgression. Together with the Koudiat Laabid limestones at Jebel Gueliz in the south, these Upper Devonian outcrops, locally covered by upper Viséan Sarhlef Schists, suggest that the upper Viséan basin of Central Jebilet was divided in a N–S elongated paleogeographical highland formed by the Ordovician and Devonian bedrock. The proposed paleogeographic configuration could explain the lithological differences between the slate deposits to the west and the flysch-like deposits to the east. The exhumation/erosion of Ordovician strata in the Sidi Bou Othmane area may be related to the Eovariscan block faulting and the preorogenic extension of the Meseta domain.

Triassic-Early Jurassic evaporites of the Saharan Platform, Algeria: Astronomical and geodynamic constraints on stratigraphy and sedimentation

The sequence stratigraphy of the Late Triassic - Early Jurassic evaporites of the Berkine Basin is described. Disconformities occur between all the major evaporitic units but lack of biostratigraphy (or other) chronostratigraphic control precludes their precise dating. The S4 and S3 Halites are predominantly non-marine halites deposited in low-lying salinas with a barrier to the north. The top of the S4 depositional sequence is marked by the D2, usually regarded as the Tr-J boundary in the Berkine Basin. Both the S3 and S4 salt deposits thin rapidly to the south-east and are thicker in the basin centre coincident with a subcrop of Carnian? aged volcanics. A combination of thermal cooling, rifting and reactivation of N–S lineaments parallel to the Hassi Messaoud-El Biod Arch controlled the (∼1500 m thick) depocenter.Time series analysis shows that astronomical forcing played a key role in the deposition of the S3 and S4 bedded halites. The prevailing climate was monsoonal with major replenishment of the basin indicated by long eccentricity cycles (405 kyr). Sedimentation rates were estimated using eCOCO analysis with average rates of 15 cm/kyr. Well to well comparisons shows that in marginal areas thinner sedimentary sequences relate to slower accumulation rates and periods of non-deposition or deflation. The pattern is similar in the S4 and S3 halite, but the reduced mud content and amalgamation of halite beds suggests a more arid climate in S3 times.The S1+S2 unit marks the first widespread deposition of sulphate in the basin. The lowermost anhydrite beds of the S1 + S2 rest unconformably on the underlying S3 and overstep the basin margins in the south-east; the sequence is capped by the B Horizon a basin-wide carbonate shelf deposit about 25 m thick indicating increased marine influence. Above there is a rapid return to thinly bedded mudstone-halite dominated sedimentation (Lias Salifère) which is overlain by the Lias Anhydritique an alternating sequence of halite and anhydrite deposits. Astronomical parameters of the whole sequence indicate an average sedimentation rate of ∼10 cm/kyr in this marine-influenced section, slower than the halite units. Although the time series analysis cannot provide precision dating of the evaporitic sequences the results indicate that there are important breaks in the depositional record. The combined S4 and S3 halites account for 4.75 Ma and the rest of the Liassic 9.4 Ma. It seems clear that much of the depositional record is missing.These Saharan Platform basins bear much in common with other western Mediterranean evaporite basins. Many show the same overall pattern of sedimentation with increased sulphate deposition above the Tr-J boundary. In late Triassic time they formed a contiguous low-lying zone flanked by cratonic highlands. This zone spanned the Gondwana-Laurussia boundary immediately prior to its break-up and Greater Adria formed a barrier between these basins and the developing Neotethys to the east. The major changes seen in the Saharan Platform are mirrored by the break-up of Adria and the separation of Gondwana and Laurasia and the ultimate connection of the western Mediterranean and the central Atlantic.Although the cyclostratigraphy can tell us much about the absolute duration of sedimentation, the lack of significant anchor points forbids the construction of a detailed chronostratigraphic framework. In particular, the precise location of the Tr-J boundary remains unclear. Although it is usually placed at the base of the D2 Horizon, biostratigraphical evidence from Southern Tunisia places the S3 in the Norian. The sharp contrast between the S4 and S3 halites with the later evaporite sequence suggests that positioning the boundary between the S3 halite and the S1 + S2 unconformity should be given consideration.

Late Cretaceous and Paleocene radiolarians from the San Jacinto Fold Belt, northeast Colombia: Biostratigraphic and paleoenvironmental implications

The Cansona and San Cayetano formations are the oldest sedimentary units of northwestern Colombia and record the beginning of the convergence between the proto-Caribbean and South American plates. Previous micropaleontological studies on these units indicate the presence of planktonic foraminifera, calcareous nannofossils, and pollen, with limited biostratigraphic resolution. This study challenges this issue by reporting for the first time a late Cretaceous and early Paleocene radiolarian inventory from several silicified siltstones and cherts of the Cansona and San Cayetano formations. Although radiolarian occurrences are rare, we report 21 species that characterize the Late Cretaceous radiolarian assembly and belong to the genera Alievium, Amphipyndax, Archaeodictyomitra, Archaeospongoprunum, Calocyclas, Cornutella, Dictyomitra, Dictyoprora, Foremanina, Mita, Pseudoaulophacus, Pseudotheocampe, Siphocampe, Stichomitra, Theocapsomma, Criptamphorella, Crucella, Patellula, and Triactoma. Equally rare occurrences of radiolarians are found in the Paleocene, were Early Paleocene-restricted Amphisphaera aotea Hollis, together with other spumellarians, notably Amphisphaera cf. A. kina Hollis, Artostrobus pusillum (Ehrenberg), Lithostrobus longus Grigorjeva and the nassellarian Buryella granulata (Petrushevskaya) considerably shortened the Cretaceous-Paleogene boundary hiatus. The present work concludes that the Late Cretaceous radiolarian dating reinforces the present state of knowledge on the Cansona Formation and reveals new biostratigraphic evidence regarding the presence of earliest Paleocene sequences in the San Cayetano Formation. This is an important result for understanding the geological evolution of the Cretaceous proto-Caribbean margin.

Carbon isotope and biostratigraphic evidence for an expanded Paleocene–Eocene Thermal Maximum sedimentary record in the deep Gulf of Mexico

AbstractIn this study, we present evidence of a Paleocene–Eocene Thermal Maximum (PETM) record within a 543-m-thick (1780 ft) deep-marine section in the Gulf of Mexico (GoM) using organic carbon stable isotopes and biostratigraphic constraints. We suggest that climate and tectonic perturbations in the upstream North American catchments can induce a substantial response in the downstream sectors of the Gulf Coastal Plain and ultimately in the GoM. This relationship is illustrated in the deep-water basin by (1) a high accommodation and deposition of a shale interval when coarse-grained terrigenous material was trapped upstream at the onset of the PETM, and (2) a considerable increase in sediment supply during the PETM, which is archived as a particularly thick sedimentary section in the deep-sea fans of the GoM basin. Despite other thick PETM sections being observed elsewhere in the world, the one described in this study links with a continental-scale paleo-drainage, which makes it of particular interest for paleoclimate and source-to-sink reconstructions.

Early Jurassic Flood Basalt Volcanism on the Franz Josef Land Archipelago: Geological and Palynostratigraphical Data

Biostratigraphic evidence of the presence of Early Jurassic flood basalts on the Franz Josef Land archipelago is presented. The flood basalts form layered section with two units, which is not discovered for Early Cretaceous basalts. The lower unit is composed by large-columnar basalts (colonnade), and the upper unit by small-columnar (entablature) chaotic-fan basalts. On the Hooker Island, the basalt flow is exposed on the Sedov Plateau, on the Lunacharsky Rock Cape and, possibly, on Al’banov Cape. On the southern slope of the Sedov Plateau, the basalt flow overlaps sands and sandstones, which contain palynoassemblage of the lower Toarcian. In the Lunacharsky Rock Cape outcrop, the underlying basalt sands are of the Pliensbachian to Early Toarcian chronostratigraphic interval. Apart from the Hooker Island, we observed basalts with the “colonnade/entablature” on three other islands: Scott Keltie, May and Leigh-Smith. The most complete section was found in the western part of the Leigh-Smith Island, where basalts are underlain and overlapped by sand units. The underlying sands in contact with basalts have a quenching zone. There is no quenching zone at the contact with the overlapping sands. A palynocomplex from the lower sand unit is early Toarcian in age. The palynocomplex found in the upper sand unit indicates its accumulation in the interval from the lower part of the late Toarcian to the early Aalenian. A palynological study of the underlying and overlying deposits of the basalt flow has shown that the flow is underlain by continental and coastal-marine sediments of the Pliensbachian to the upper part of the early Toarcian age interval. Basalt flow is overlain by the earliest late Toarcian–early Aalenian marine sediments. According to the modern chronostratigraphic scale, the age of the basalt flow can be estimated as approximately 180 million years, which is quite consistent with the earlier obtained 40Ar/39Ar data of 189.1 ± 11.4 million years. These data indicate that the basalt flow was formed during a narrow stratigraphic interval of the uppermost lower–earliest upper Toarcian.

Event- and biostratigraphic evidence for two independent Ries and Steinheim asteroid impacts in the Middle Miocene

For decades, the Nördlinger Ries and Steinheim Basin in southern Germany have been regarded as a textbook example of a terrestrial impact crater doublet, although the oldest crater lake deposits in both craters suggest a biostratigraphic age difference of ~ 0.5 to 1 Myr. We previously presented stratigraphic arguments that challenged the double impact scenario and favoured a model of two temporally independent impact events in the Mid-Miocene. We here present, for the first time, four localities within a distance of ~ 50–100 km from the Ries and ~ 50–70 km from the Steinheim crater that expose two independent seismite horizons, together unique within the Upper Freshwater Molasse of the North Alpine Foreland Basin, each one featuring impressive water escape structures. The seismite horizons are separated by ~ 10 to 15 m of undisturbed Molasse deposits and, biostratigraphically, by an entire European Land Mammal Zone, thus providing evidence for two independent major seismic events within a time span of ~ 0.5–1 Myr. Both the lower and the upper seismite horizons can be correlated litho- and biostratigraphically with the basal crater lake sediments at the Ries and Steinheim craters, respectively, deposited immediately after the impacts. From a biostratigraphic point of view, the impact event that formed the Steinheim Basin probably occured around 14 Ma, some 0.8 Myr after the ~ 14.81 Ma Ries impact event.

Carbon Isotope Stratigraphy of the Cambrian System in the Eastern Tarim Basin, China

AbstractThe ultra‐deep Cambrian System in the Tarim Basin is an important field for petroleum exploration, while fine division of the Cambrian strata remains controversial. In recent years, carbon isotope stratigraphy of the Cambrian System has been established and widely used. Here, we report an integrated profile of carbonate and organic carbon isotopic values (δ13Ccarb and δ13Corg) from cuttings of the Tadong2 Well in the eastern Tarim Basin. Three carbon isotope anomalies of BACE, ROECE and SPICE were recognized on the δ13Ccarb profile. Three apogees and a nadir on the δ13Corg profile and the onset of ROECE on the δ13Ccarb profile were suggested as boundaries of the present four series of the Cambrian System. Suggested boundaries are easily identifiable on the gamma logging profile and is consistent with the previous division scheme, based on biostratigraphic evidence in outcrop sections. Abnormal carbon cycle perturbations and organic carbon burials during the BACE and SPICE events might be related to the reduction and expansion of a huge dissolved organic carbon reservoir in the deep ocean of the ancient Tarim Basin.

Evidence of a Continuous Continental Permian-Triassic Boundary Section in western Equatorial Pangea, Palo Duro Basin, Northwest Texas, U.S.A.

The Whitehorse Group and Quartermaster Formation are extensive red-bed terrestrial sequences representing the final episode of sedimentation in the Palo Duro Basin in north-central Texas, U.S.A. Regionally, these strata record the culmination of a long-term regression sequence beginning in the middle to late Permian. The Whitehorse Group includes beds of abundant laminated to massive red quartz siltstone to fine sandstone and rare dolomite, laminated to massive gypsum, and claystones, as well as diagenetic gypsum. The Quartermaster Formation exhibits a change from nearly equal amounts of thin planar and lenticular fine sandstone and laminated to massive mudstone in its lower half to overlying strata with coarser-grained, cross-bedded sandstones indicative of meandering channels up to 7 m deep and rare overbank mudstones. Paleosols are absent in the Upper Whitehorse Group and only poorly developed in the Quartermaster Formation. Volcanic ash-fall deposits (tuffs) present in uppermost Whitehorse Group and lower Quartermaster Formation strata permit correlation among five stratigraphic sections distributed over ∼150 km and provide geochronologic age information for these rocks. Both the Whitehorse Group and Quartermaster Formation have traditionally been assigned to the late Permian Ochoan (Changhsingian) stage, and workers assumed that the Permian-Triassic boundary is characterized by a regionally significant unconformity. Chemostratigraphic or biostratigraphic evidence for this age assignment, however, have been lacking to date. Single zircon U-Pb CA-TIMS analyses from at least two distinct volcanic ash fall layers in the lower Quartermaster Formation, which were identified and collected from five different localities across the Palo Duro Basin, yield interpreted depositional ages ranging from 252.19 ± 0.30 to 251.74 ± 0.28 Ma. Single zircon U-Pb CA-TIMS analyses of detrital zircons from sandstones located only a few meters beneath the top of the Quartermaster Formation yield a range of dates from Mesoproterozoic (1418 Ma) to Middle Triassic (244.5 Ma; Anisian), the latter of which is interpreted as a maximum depositional age, which is no older than Anisian, thus indicating the Permian-Triassic boundary to lie somewhere within the lower Quartermaster Formation/upper Whitehorse Group succession. Stable carbon isotope data from 180 samples of early-burial dolomicrite cements preserve a chemostratigraphic signal that is similar among sections, with a large ∼−8‰ negative isotope excursion ∼20 m beneath the Whitehorse Group-Quartermaster Formation boundary. This large negative carbon isotope excursion is interpreted to be the same excursion associated with the end-Permian extinction and this is in concert with the new high precision radioisotopic age data presented and the fact that the excursion lies within a normal polarity stratigraphic magnetozone. Dolomite cement δ13C values remain less negative (between about −5 and −8 permil) into the lower part of the Quartermaster Formation before becoming more positive toward the top of the section. This long interval of negative δ13C values in the Quartermaster Formation is interpreted to represent the earliest Triassic (Induan) inception of biotic and ecosystem “recovery.” Oxygen isotope values of dolomicrite cements show a progressive trend toward more positive values through the boundary interval, suggesting substantially warmer conditions around the end-Permian extinction event and a trend toward cooler conditions after the earliest Triassic. Our observations on these strata show that the paleoenvironment and paleoclimate across the Permian-Triassic boundary in western, sub-equatorial Pangea was characterized by depositional systems that were not conducive to plant preservation.

New ornithomimosaurian (Dinosauria: Theropoda) pelvis from the Upper Cretaceous Erlian Formation of Nei Mongol, North China

A newly identified ornithomimosaurian pelvis and sacrum from the Upper Cretaceous Erlian Formation of Nei Mongol, China is described in detail in this paper. This specimen is distinguished from previously described taxa by the presence of a combination of features that is unique among Ornithomimosauria: sacrum comprising five vertebrae with neural spines fused into a continuous plate, iliac posterior end rectangular, pubic shaft distally straight, ischial boot not broadened transversely, and ischial shaft proximally straight, distally curved, and 80 percent as long as the pubis. This specimen differs from at least some material assigned to the sympatric Archaeornithomimus asiaticus, showing that two distinct ornithomimosaurian taxa are present in this Upper Cretaceous fossiliferous rock unit. A phylogenetic analysis places LH-02-01 in a relatively early-diverging position within Ornithomimosauria, outside the two major clades Deinocheiridae and Ornithomimidae, but its relationships with other early-diverging ornithomimosaurs remain unresolved. The primitive nature of LH-02-01 adds to the evidence from fossil vertebrates that the Erlian Formation correlates with the Turonian Bissekty Formation of Uzebekistan, while the biostratigraphic evidence from non-vertebrates instead indicates a Campanian to Maastrichtian assignment for the Erlian Formation. This apparent contradiction remains unresolved, pending future research aimed at reconciling the seemingly incompatible lines of evidence.

Quibas-Sima: A unique 1 ma-old vertebrate succession in southern Iberian Peninsula

With the identification of the Jaramillo geomagnetic subchron, the late Early Pleistocene vertebrate succession of the Quibas-Sima section (Quibas karstic complex, southern Spain) represents a time span scarcely recorded in Europe. To complete the existing chronostratigraphic framework published earlier by Piñero et al. (2020), we provide here additional new information about the lithostratigraphy and micromammal succession along the sedimentary sequence. Seven lithostratigraphic units have been differentiated (QS-1 to QS-7) at Quibas-Sima, documenting an almost continuous small mammal record, including representatives of the families Soricidae, Erinaceidae, Rhinolophidae, Vespertilionidae, Arvicolidae, Muridae, Gliridae, Sciuridae, Leporidae and Ochotonidae. The small mammal association indicates that units QS-1 to QS-4 have an intermediate biostratigraphic position between the sites of Fuente Nueva 3 (ca. 1.2 Ma) and Cueva Victoria (ca. 0.9 Ma). New numerical age result from the combined U-series/ESR dating of one equid tooth from QS-3 consistently support the general chronostratigraphic framework based on magnetostratigraphy and biostratigraphic inferences by confirming a post-Olduvai age. Based on an estimation of the sedimentation rate during the Jaramillo subchron, these broad chronological constraints may be confidently refined to approx. 1.1–0.9 Ma for the whole sequence. While we acknowledge the existing uncertainty associated to this age range, it is nevertheless consistent with biostratigraphic evidence indicating that all stratigraphic units most likely do not significantly differ from a chronological point of view. Both independent proxies (biostratigraphy and the sedimentation rate) strongly suggest that the sedimentary sequence covers a relatively short time interval (<200 kyr). These results place the Quibas-Sima sequence as one of the longest and most complete pre-Jaramillo (QS-1) to Jaramillo (QS-2 to QS-5) continental vertebrate succession in Europe.

Biostratigraphic evidence for incremental tectonic development of early Cambrian deep-water environments in the Misty Creek embayment (Selwyn basin, Northwest Territories, Canada)

The early evolution of the Misty Creek embayment (MCE), a prominent, northwest-trending sub-basin of the economically important Selwyn basin, is poorly understood. The abrupt contact between Cambrian Stage 4 (traditional lower Cambrian) carbonate ramp strata of the Sekwi Formation and overlying Miaolingian (traditional middle Cambrian) deep-water, calciturbiditic strata of the Hess River Formation has been regarded as diachronous. This important transition, which marks the onset of long-lived, deep-water conditions in the MCE, remains unexplained. This study uses biostratigraphic data from a previously undescribed location in the MCE, existing biostratigraphic and lithostratigraphic data from the 1970s, and regional thickness patterns to characterise the sharp yet diachronous transition from lithofacies typical of the Sekwi Formation to those typical of the Hess River Formation. The dramatic change in depositional environments was diachronous yet non-gradational, precluding a eustatic cause. The change was geologically abrupt, probably through two extension-related subsidence events, with different geographic extents, which heralded the MCE’s long life as a deep-water basin. The onset of deep-water conditions in the MCE occurred semi-contemporaneously with other extension-related events that are recorded in the northern Canadian Cordillera, demonstrating that Cambrian Series 2 – Miaolingian was a time of widespread extension and subsidence along the western margin of Laurentia.

Stratigraphic correlation of the Givetian (late Middle Devonian) deposits in Qujing,Yunnan, southwestern China and the paleogeographic implications

Detailed description of spatio-temporal framework of fossil-bearing strata is of fundamental significance for understanding the evolution of organisms and regional tectonics. The Qujing and Haikou formations are two lithological units exposed in eastern Yunnan, southwestern China, and both bear rich fossils indicative of a Middle Devonian age, while their relationship or lateral correlation remains unclear. Based on detailed observations of outcrops of these two formations in Qujing, eastern Yunnan, and as well as their typical rock characteristics and fossil contents, we propose that the two formations are basically contemporaneous heterotopic facies. From north to south of the Qujing area, the transition from the Haikou Formation to the Qujing Formation is gradual and shows an increase of carbonate component (in terms of the cumulative thickness of carbonate rocks) and as offset, a decrease of the siliciclastic component. The distribution of the Haikou/Qujing Formation indicates the development of a marine environment in the Qujing area during the Givetian, as a part of the South China Sea connected to the Paleo-Tethys Ocean, and supports that the transgression might have peaked in southwestern China during the late Middle Devonian. The available biostratigraphic evidence favors an expansion of the Paleo-Tethys Ocean prior to or during the Middle Devonian.

Stratigraphic correlation of the Givetian (late Middle Devonian) deposits in Qujing,Yunnan, southwestern China and the paleogeographic implications

Detailed description of spatio-temporal framework of fossil-bearing strata is of fundamental significance for understanding the evolution of organisms and regional tectonics. The Qujing and Haikou formations are two lithological units exposed in eastern Yunnan, southwestern China, and both bear rich fossils indicative of a Middle Devonian age, while their relationship or lateral correlation remains unclear. Based on detailed observations of outcrops of these two formations in Qujing, eastern Yunnan, and as well as their typical rock characteristics and fossil contents, we propose that the two formations are basically contemporaneous heterotopic facies. From north to south of the Qujing area, the transition from the Haikou Formation to the Qujing Formation is gradual and shows an increase of carbonate component (in terms of the cumulative thickness of carbonate rocks) and as offset, a decrease of the siliciclastic component. The distribution of the Haikou/Qujing Formation indicates the development of a marine environment in the Qujing area during the Givetian, as a part of the South China Sea connected to the Paleo-Tethys Ocean, and supports that the transgression might have peaked in southwestern China during the late Middle Devonian. The available biostratigraphic evidence favors an expansion of the Paleo-Tethys Ocean prior to or during the Middle Devonian.