Late Jurassic Early Research Articles

The first tyrannosauroid tooth from Korea

A tyrannosauroid premaxillary tooth has been discovered for the first time in the Hasandong Formation (Lower Cretaceous) in South Korea. Carinae on the tooth form both the mesial and distal edges of the lingual face, producing a “D-shaped” cross section typical of tyrannosauroids. The Korean premaxillary tooth is different from those of other known Early Cretaceous tyrannosauroids (Dilong, Eotyrannus, and a Japanese tooth) in having a distinct lingual ridge on the lingual surface. This discovery probably indicates a subsequent Asian diversification of this group (Korea, China and Japan) after the origination of tyrannosauroids in the early Late Jurassic (e.g., Guanlong) in China.

Taphonomy of fossil macro-invertebrate assemblages as a tool for ecostratigraphic interpretation in Upper Jurassic shelf deposits (Prebetic Zone, southern Spain)

Composition and taphonomy of macro-invertebrate fossil assemblages, together with facies analysis, have been approached in order to interpret shifting paleoenvironmental conditions in the External Prebetic (S-SE Spain) during the early Late Jurassic (Middle Oxfordian). In oolitic and spongiolitic limestones, the size of fossil remains, mode of preservation, within-bed position, corrasion, fragmentation, epibiont and biogenic encrustation, disarticulation and uncoupling, allow recognition of two taphofacies, respectively. Identified ecostratigraphic events and trends accord with rapid flooding under high-energy conditions related to ecospace enlargement for cephalopods and then the persistence of lower energy, long-lasting exposure of skeletals and higher sedimentary rates. The paleoenvironmental interpretation is consistent with neritic environments shifting from shallow carbonate to hemipelagic sedimentation and enlarging of shelf ecospace for marine invertebrates.

Paleomagnetism of Upper Jurassic basalts from Transbaikalia: new data on the time of closure of the Mongol-Okhotsk Ocean and Mesozoic intraplate tectonics of Central Asia

The Upper Jurassic basalts (150–160 Ma) described as the Ichetui Formation over the territory of the Tugnui, Margintui, and Maly Khamar-Daban volcanic structures have been studied paleomagnetically. It is shown that natural remanent magnetization still contains a component which may reflect the geomagnetic field direction at the beginning of the Late Jurassic. This is supported by reversal and conglomerate tests. Calculation of mean paleopole gives: Plat = 63.6°, Plong = 166.8°, α 95 = 8.5°. These values well coincide with the data for the Badin Formation from Mogzon depression, which lies east of the study area and approximately dates from the Kimmeridgian-Oxfordian interval of the Late Jurassic. At the same time, those poles statistically differ from the European and Southeast Asian poles of the same age. The available paleomagnetic data suggest that at the beginning of the Late Jurassic the Mongol-Okhotsk Ocean was probably still open. Since the early Late Jurassic the continental blocks of Southeastern Asia and Siberian part of the Eurasian plate had been approaching, with the Siberian domain rotating clockwise. Analysis of the total of data shows that sinistral strike-slip deformations were present not only in southern Siberia but also between the Siberian and European Platforms. Thus, the deformations of the Central Asian crust in the early Late Jurassic reflect the intraplate strike-slip motions coeval with the closure of the Mongol-Okhotsk Ocean and are governed by the clockwise rotation of the Siberian part of the Eurasian plate relative to its European part.

Horizontal movements in the eastern Barents Sea constrained by numerical models and plate reconstructions

SUMMARY The eastern Barents Sea basins, west of Novaya Zemlya, were mildly inverted between Late Permian and Early Jurassic times, as indicated by mild folds in the basin sediments. Previous studies have suggested that the crustal part of Novaya Zemlya was thrust westward, but the magnitude of this compressive movement is not well known. Our aim is to provide an order-of-magnitude constraint on the amount of shortening associated with the displacement of Novaya Zemlya and inversion of the eastern Barents Sea basins by combining numerical models and plate reconstructions in an iterative process. We use a 2-D finite-element method to model inversion of a pre-defined basin. The total amount of shortening imposed on the models is first constrained by plate reconstructions for the Barents Sea region for the Late Palaeozoic to Early Mesozoic. We assume that the shortening is caused by westward movement of the Siberian plate, but the magnitude of this westward displacement in plate reconstructions is highly uncertain due to the allochthonous nature of the rocks of Novaya Zemlya and the scarcity of palaeomagnetic data in the region. Our models show that shortening localizes in the model basin and at Novaya Zemlya and that westward propagation of deformation is more efficient when the strength of the lower crust is reduced. Part of the movement of the Siberian plate could be accommodated by thrusts at Novaya Zemlya and perhaps in the domain of the Kara Sea at the western margin of the Siberian plate. By comparing the inversion obtained in the numerical models to the inferred inversion structures in the eastern Barents Sea basins we further constrain the amount of shortening that caused the inversion and therewith improve the plate reconstructions for the region. Our models indicate that the westward movement of Novaya Zemlya occurred in the Late Triassic–Early Jurassic (220–190 Ma) and was limited in magnitude to 100–200 km, which is considerably less than previous estimates (500–700 km).

Perspectives on the Evolution and Diversification of the Diatoms

The understanding of diatom evolution has progressed greatly over the last two decades. Existing data sets have been reanalyzed, new data sets have been generated, and new tools have been employed. Hindering progress is the seemingly endless number of diatom species remaining to be described and relative small number of investigators active in the field. This problem is further confounded by the dramatic reorganization of generic level classification in the group. Despite these problems, many conclusions can be made about prior hypotheses concerning the group's development. Most notably, the origin of the diatoms can be bracketed between the Late Triassic and Early Jurassic using fossil record and molecular clock estimates. This combination of techniques has also provided consensus and clarification to the origin and duration of specific lineages enhancing our understanding of the group's diversification, early ecology, and evolutionary relationships.

Late Mesozoic tectonic structure and evolution along the present-day northeastern South China Sea continental margin

The northeastern South China Sea continental margin holds the key to understanding Late Mesozoic tectonics and evaluating hydrocarbon potentials in Mesozoic tectonic and stratigraphic structures offshore southeast China. With newly obtained and processed seismic data, and new drilling and logging data, we correlate regional Mesozoic stratigraphy and analyze major Mesozoic tectonic events and structures. In particular, we focus our study on the three major tectonic units in the area, the Chaoshan Depression, the Tainan Basin, and the Dongsha–Penghu Uplift, which are separated by basement high, thrust fold, and (or) faults. Stratigraphic correlations suggest a major phase of southeastward regression, spanning in time from the late Early Jurassic (∼180 Ma) to the Early Cretaceous (∼120 Ma). Seismic data reveal two major tectonic events, with the first one in the Late Jurassic to the Early Cretaceous, contemporary with the regression, and the second one in the Late Cretaceous. Regional magnetic anomaly map after the reduction to the pole clearly reveals the boundary between the Dongsha–Penghu Uplift and the Chaoshan–Tainan depositional system. The seismic and magnetic data also suggest that, while the Dongsha–Penghu Uplift has highly magnetized sources buried mostly in the upper crust at depths from about 2 km to about 20 km, the Chaoshan–Tainan depositional system has thick Mesozoic sediments of low magnetization.

A coniferous tree stump of late Early Jurassic age from the Ferrar Basalt, Coombs Hills, southern Victoria Land, Antarctica

An upright, partly rooted tree stump preserved within a late Early Jurassic basalt flow of the Ferrar Group, Coombs Hills, is described from southern Victoria Land, Antarctica. The wood structure allows the tree to be identified as a conifer (possibly Podocarpaceae) that from the stump diameter of 35–40 cm was c. 24 m tall. The possibly transported tree may have survived the lava flow because the stump was waterlogged or already mineralised. Conifers of similar age (early Middle Jurassic) are known from fossil forests at Curio Bay and Kawhia Harbour in New Zealand, and this discovery extends the known distribution of forests living in moderately warm, humid climates at very high southern latitudes during the late Early Jurassic.

Elemental composition and diagenetic alteration of dinosaur bone: Distinguishing micron-scale spatial and compositional heterogeneity using PIXE

Proton Induced X-ray Emission (PIXE) analysis of thirteen Late Cretaceous (hadrosaurid, tyrannosaurid, and Tyrannosaurus) and Early Jurassic ( Dilophosaurus) dinosaur bones, two Late Cretaceous crocodylians, one plesiosaur, and three modern archosaurs ( Rhea and Caiman), documents micron-scale diagenetic patterns of elemental uptake and loss. PIXE detected Al, Si, P, S, Cl, K, Ca, Ba, Mn, Fe, Sr, Y, and Nd at levels > 1000 ppm; and Ti, Cr, Ni, Zn, As, Zr, and U at trace amounts < 1000 ppm. PIXE interrogation with a 1.5 μm diameter beam revealed a diagenetic pattern of significant Fe (180,000 ppm) and Mn (13,000 ppm) enrichment, with a corresponding loss of Ca and to a lesser degree P, within micron-scale regions in the Haversian system of compact dinosaur bone. Elemental composition of bone mineral immediately adjacent to the annuli surrounding a Haversian canal was depleted by approximately 90% in Fe and Mn, but showed a 50% increase in Ca ppm. Calcium levels in the fossils vary from 57% to 95% concentration of modern bone. Phosphorous levels in some dinosaur bone bioapatite are > 100% of modern. This enrichment may reflect the migration of Ca and P between the hydroxylapatite matrix and the surrounding sediment after death, resulting in early diagenetic loss followed by uptake and recrystallization on crystallite surfaces. The elemental composition of fossil bone from the Early Jurassic dinosaur Dilophosaurus is distinguished by elevated As ppm, generally not present in the Late Cretaceous dinosaurs. We suggest that As is adsorbed from the reductive dissolution of As-rich iron oxyhydroxides in the local aquifer and is not reflective of Mesozoic atmospheric conditions or arsenic toxicosis in dinosaurs. PIXE allows us to reaffirm that the histological structure, tissue density, and high surface area of the vascular canals of dinosaur Haversian bone affect postmortem elemental enrichment and depletion and to quantify these differences at scales as small as 1.5 μm.

Rock magnetic evidence for inclination shallowing in the Passaic Formation red beds from the Newark basin and a systematic bias of the Late Triassic apparent polar wander path for North America

The latest Triassic and earliest Jurassic red beds from the Newark basin possess paleomagnetic inclinations that are ∼ 10° shallower than the inclinations carried by coeval volcanic rocks. It has been suggested that the difference might be due either to inclination shallowing of the sediments or to remagnetization of the volcanic rocks during a Middle Jurassic hydrothermal event. Either explanation would in turn yield significantly different apparent polar wander paths (APWPs) for the Late Triassic and Early Jurassic of North America. Here we present paleomagnetic and magnetic anisotropy data for the latest Triassic Passaic Formation red beds, which reveal deposition and/or compaction fabrics with 10% anisotropy of the high unblocking temperature, reversed polarity remanent magnetization. Inclination correction for the red beds yields similar directions to that carried by the earliest Jurassic volcanic rocks, indicating that inclination shallowing is the major cause for the difference in paleomagnetic pole position between the red beds and the volcanic rocks. Comparison of the inclination corrected data with the Late Triassic North American APWP shows a systematic error in the APWP, likely due to inclination shallowing. In turn, this error may be even more significant for much of the Paleozoic part of the North American APWP.

Small Theropod Track Assemblages from Middle Jurassic Eolianites of Eastern Utah: Paleoecological Insights from Dune Ichnofacies in a Transgressive Sequence

New discoveries show that very small theropod tracks (cf. Wildeichnus) are abundant in the upper part of the Moab Member, recently assigned to the Curtis Formation (formerly considered part of the Entrada Formation) in the Mid-?Late Jurassic of eastern Utah. The tracks represent a distinct small-theropod ichnofacies associated with eolian dune deposits that is easily differentiated from the water-lain beds of the overlying Megalosauripus-Therangospodus ichnofacies, which comprises the single-surface Moab megatracksite. Pterosaur track assemblages, representing the Pteriachnus ichnofacies, are found a few meters above the megatracksite surface in the upper tongue of the Summerville Formation. The small theropod ichnofacies is reminiscent of other early Mesozoic dune facies ichnofaunas from the Wingate and Navajo formations (Late Triassic and Early Jurassic) where small theropod tracks occur in association with other small tetrapod footprints. All such examples evidently represent a recurrent dune facies ecosystem dominated by diminutive vertebrates. Because the small theropod ichnofacies is one of three ichnofacies found in a thin stratigraphic sequence (<20 m) that contains no body fossils, it is clear that vertebrate tracks play an important role in providing insight into the paleoecology of units previously considered devoid of any useful fossil evidence. The three successive ichnofacies represent a transgressive transition from sand dunes, through sandy shoreline to shallow marine environments, each with its quite distinct vertebrate fauna.

Evolución geológica del sureste mexicano desde el Mesozoico al presente en el contexto regional del Golfo de México

The geologic evolution of southeastern Mexico is analyzed in the regional context of the Gulf of Mexico, which starts it opening with the fragmentation and spreading of Pangea. The sedimentary record in this depression begins with the deposit of continental red beds during the Late Triassic and Early Jurassic, after which, during the Callovian, sea-waters from the Pacifi c invaded an extense area; low circulation and high evaporation of these waters allowed the deposition of large volumes of salt in the central part of the basin. From Late Jurassic to Late Cretaceous, carbonate deposition prevailed, changing to clastic at the beginning of the Paleogene, when the Laramide Orogeny formed the folds and faults of the Sierra Madre Oriental. During the rest of the Paleogene clastic sedimentation was deposited in large depocenters generated in the foreland of the Sierra Madre Oriental, and in the southern and southwestern parts of the Golf of Mexico, where the Chiapas Massif produced large volumes of sediments, whereas in the Yucatan Block the deposition of shallow water carbonates continued. In the Middle Miocene, during the Serravalian, compressive stresses resulting from the lateral movement of the Chortis Block and the subduction of the Cocos Plate, against the southern end of the North American Plate, formed the folds and faults of the Chiapas-Reforma-Akal belt over a decollement at the level of the Callovian salt; later, these structures were

An abelisauroid (Dinosauria: Theropoda) from the Early Jurassic of the High Atlas Mountains, Morocco, and the radiation of ceratosaurs

ABSTRACT The fossil record of abelisauroid carnivorous dinosaurs was previously restricted to Cretaceous sediments of Gondwana and probably Europe. The discovery of an incomplete specimen of a new basal abelisauroid, Berberosaurus liassicus, gen. et sp. nov., is reported from the late Early Jurassic of Moroccan High Atlas Mountains. Phylogenetic analysis recovers Ceratosauroidea and Coelophysoidea as sister lineages within Ceratosauria, and Berberosaurus as a basal abelisauroid. Berberosaurus is the oldest known abelisauroid and extends the first appearance datum of this lineage by about 50 million years. The taxon bridges temporal, morphological, and phylogenetic gaps that have hitherto separated Triassic to Early Jurassic coelophysoids from Late Jurassic through Cretaceous ceratosauroids. The discovery of an African abelisauroid in the Early Jurassic confirms at least a Gondwanan distribution of this group long before the Cretaceous.

U-Pb zircon age for the Daohugou Biota at Ningcheng of Inner Mongolia and comments on related issues

SHRIMP U-Pb zircon dating was carried out for the Daohugou Biota near Ningcheng of Inner Mongolia and for lavas overlying or underlying salamander-bearing strata at Reshuitang in Lingyuan of West Liaoning. The results suggest that the Daohugou Biota occurred at an interval from 168 Ma to 164–152 Ma. Both the Daohugou Biota and the salamander-bearing fossil assemblage are the same biota and thus developed from 168 to 152 Ma, i.e. from late Middle Jurassic to the early Late Jurassic. The Daohugou Biota-bearing rocks, resting on the Jiulongshan Formation in disconformity and being overlain in unconformity by Late Jurassic Tuchengzi Formation and Early Cretaceous rocks containing the Jehol Biota, are mainly composed of volcanic-sedimentary rocks in a normal sequence. It is recommended that the Daohugou Biota and the related stratigraphy should be correlated with the Tiaojishan Formation (Lanqi Formation in West Liaoning) or its synchronous rocks. It is suggested that the Daohugou Biota and the Jehol Biota would be neither taken into one biota nor considered as the earliest elements of the Jehol Biota. The Daohugou Biota and the related rocks and the Yixian Formation were respectively formed in different periods of volcanic-sedimentary tectonics.

Late Triassic and Early Jurassic palaeogeography of the world

A new version of global and regional palaeogeographic maps is presented for two time intervals. These maps depict the plate tectonic configuration, palaeoenvironment and lithofacies during the Late Triassic (Carnian–Norian) and Early Jurassic (Hettangian–Toarcian) time. The individual maps illustrate the general conditions present during the maximum marine transgressions of higher frequency cyclicity within the Absaroka sequence of Sloss. During Triassic time Pangaea began to stretch, initiating the rifting and future break-up of the supercontinent. The continued northward drift of the Cimmerian continent corresponded with the progressive closure and consumption of Palaeotethys oceanic crust, and the opening of the Neotethys Ocean. The most significant Late Triassic convergent event was the Indosinian orogeny, occurring as a result of the consolidation of South China and North China blocks. Also, Indochina and Indonesia were sutured to South China. At the same time the Qiangtang block approached the Eurasian margin. The consolidation of the North Chinese and Amurian blocks left open a large embayment of Panthalassa, between Amuria and Laurasia, the so-called Mongol-Okhotsk Ocean. Active subduction existed along the margin of this ocean, dipping cratonwards towards East Siberia. The last collisional events of the Uralian orogeny took place during the Triassic and Early Jurassic time. The conclusion of the Uralian orogeny was accompanied by uplift of the adjacent areas of Eastern Europe and Western Siberia. During the Early Jurassic the Palaeotethys Ocean was finally closed and the Cimmerian continent collided with Asia causing the Cimmerian orogeny. The time around the Triassic–Jurassic boundary marked an important biotic extinction event. Plate tectonic activity caused palaeogeographic and palaeoclimatic change, which may have contributed to the mass extinction. From the plate tectonic and palaeogeographic point of view the following events could have influenced the extinction: 1) the closure of Palaeotethys and assembly of the Asian part of Pangaea; 2) the break-up of Pangaea in the future Central Atlantic area and transition from rifting to drifting; and 3) the very extensive basaltic volcanism of the Central Atlantic Magmatic Province.

Regional and global changes around the Triassic–Jurassic boundary reflected in the late Norian–Hettangian history of the Apennine basins

Palaeogeographic restorations for the Late Triassic and Early Jurassic of the west-Mediterranean area show that significant facies changes occurred in this period. The study of three basinal successions in the Northern, Central and Southern Apennines indicates that changes in ecological conditions occurred at the same time in different palaeogeographic and geodynamic domains. The early Mesozoic evolution of the Apennines is controlled by the opening of two oceans: the Ionian/East-Mediterranean Tethys to the south-east and the Alpine Ocean to the north-west. The Lagonegro basin, in the Southern Apennines, was the northern continental margin of the Ionian Tethys from the Triassic, while the La Spezia basin, in the Northern Apennines, became part of the south-eastern continental margin of the Alpine Ocean in the Middle-Late Jurassic. The third studied basin (Mt. Camicia basin, in the Gran Sasso, Central Apennines) was an intra-platform basin from the early Norian up to the late Hettangian–early Sinemurian. During the Norian–Hettangian period these basins were not directly connected to each other, being separated by wide carbonate platforms, and show different evolutionary trends. Stratigraphic studies in these successions place the Triassic–Jurassic boundary in 6–8 m thick intervals with anoxic facies in the three basins. Relevant facies changes are also recorded in the late Norian: in the Northern Apennines the sedimentation of sulphate evaporites ended, being replaced by the Rhaetavicula contorta facies; whilst in the Southern Apennines (Lagonegro basin) the deposition of radiolarites began. The end of evaporite accumulation can be explained by a climate change from arid to humid conditions, and it is also probably linked to an extensional phase preceding the Jurassic rifting of the Alpine Ocean, and may therefore have a regional significance. Nevertheless, it corresponds to the spread of the R. contorta facies into other parts of southern Europe, from France to Germany and Austria. The beginning of radiolaritic sedimentation in the Lagonegro basin could be related to the rise of atmospheric CO 2 content, linked to volcanic activity in the Ionian ridge. These facies changes reflect changes of environmental conditions, that caused the decline of some fossil associations favoring the development of opportunistic forms, e.g. Triasina hantkeni. The end-Triassic extinction, coupled with an anoxic episode in all the examined basins, immediately preceded a new environmental change, documented by the recovery of the carbonate platforms with oolitic facies and different associations. The evolution of all these basins suggests that geodynamics were probably responsible for regional events and that, at certain moments, development reflected global effects as a response to new connections between formerly different domains. The Central Atlantic Magmatic Province (CAMP) volcanism, considered as one of the possible causes for the end Triassic mass extinction, would have had even greater importance if coupled with the volcanism linked to the rifting of the Ionian Tethys.

SHRIMP U–Pb zircon ages of pyroclastic rocks in the Bansong Group, Taebaeksan Basin, South Korea and their implication for the Mesozoic tectonics

The Bansong Group (Daedong Supergroup) in the Korean peninsula has long been considered to be an important time marker for two well-known orogenies, in that it was deposited after the Songnim orogeny (Permian–Triassic collision of the North and South China blocks) but was deformed during the Early to Middle Jurassic Daebo tectonic event. Here we present a new interpretation on the origin of the Bansong Group and associated faults on the basis of structural and geochronological data. SHRIMP (Sensitive High-Resolution Ion MicroProbe) U–Pb zircon age determination of two felsic pyroclastic rocks from the Bansong Group formed in the foreland basin of the Gongsuweon thrust in the Taebaeksan Basin yielded ages of 186.3 ± 1.5 and 187.2 ± 1.5 Ma, respectively, indicating the deposition of the Bansong Group during the late Early Jurassic. Inherited zircon component indicates ca. 1.9 Ga source material for the volcanic rocks, agreeing with known basement ages. The Bansong Group represents syntectonic sedimentation during the late Early Jurassic in a compressional regime. During the Daebo tectonic event, the northeast-trending regional folds and thrusts including the Deokpori (Gakdong) and Gongsuweon thrusts with a southeast vergence developed in the Taebaeksan Basin. This is ascribed to deformation in a continental-arc setting due to the northwesterly orthogonal convergence of the Izanagi plate on the Asiatic margin, which occurred immediately after the juxtaposition of the Taebaeksan Basin against the Okcheon Basin in the late stage of the Songnim orogeny. Thus, the Deokpori thrust is not a continental transform fault between the North and South China blocks, but an “intracontinental” thrust that developed after their juxtaposition.

New winter crane flies (Insecta: Diptera: Trichoceridae) from the Jurassic Daohugou Formation (Inner Mongolia, China) and their associated biota

Four extinct new species referable, respectively, to three extinct new genera within Trichoceridae have been recovered from the Jurassic Daohugou Formation in Ningcheng, Chifeng, Inner Mongolia, China: Archaeotrichocera ephemera gen. et sp. nov., Tanyochoreta integera gen. et sp. nov., Tanyochoreta chifengica sp. nov., and Sinotrichocera parva gen. et sp. nov. The specimen described earlier as trichocerids from China, Mesotrichocera laiyangensis Hong and Wang 1990, does not belong to this family. The Daohugou biota comprises a wide range of vertebrate and invertebrate organisms that inhabited, a small lake, luxurious everglade, streams, and forest with volcanoes nearby. The Daohugou Formation can be compared to the Karabastau and Haifanggou formations based on biostratigraphic correlation. The geological age for trichocerid-bearing nonmarine volcano-sedimentary rocks may be latest Middle Jurassic (Callovian) or earliest Late Jurassic (Oxfordian) rather than early–middle Middle Jurassic or Early Cretaceous.

Organic geochemistry, depositional history and hydrocarbon generation modelling of the Upper Permian Kupferschiefer and Zechstein Limestone strata in south–west Poland

The upper Permian Zechstein Limestone carbonates in the south-western part of the Polish Zechstein basin contain small quantities of organic matter (usually less than 0.1 wt% TOC) and have poor hydrocarbon potential. In contrast, the Kupferschiefer shales have excellent hydrocarbon potential with TOC as high as 10.8 wt%, predominantly algal type II kerogen. Generally, thermal maturity of the organic matter is 0.6–0.9% vitrinite reflectance, while locally, is as high as 1.45%. The Kimmerian and Laramian tectonic events significantly influenced the regional burial and thermal history. The main subsidence of the Kupferschiefer–Zechstein Limestone complex took place during the Late Permian–Late Triassic period, with additional burial during the Jurassic and Late Cretaceous. Hydrocarbon generation from the Kupferschiefer source rocks occurred from Middle Triassic to Late Jurassic times, reaching maximum rates during the Jurassic. The Cretaceous subsidence had only a minor influence on the maturity and transformation of organic matter. Expulsion started between Late Triassic (in the western part of the study area) and Early Jurassic (in the eastern part), then ceased by the Late Jurassic–Early Cretaceous erosion. The total amount of generated and expelled hydrocarbons from source rocks was small because their thickness was limited. Therefore, Kupferschiefer shales cannot be considered as source rocks for liquid hydrocarbons, but may be a potential source for gas accumulated in the Zechstein Limestone and Rotliegend reservoirs.

Carbon isotope evidence for CAM photosynthesis in the Mesozoic

AbstractCrassulacean acid metabolism (CAM) photosynthesis, a flexible adaptation to water‐stress, has not been shown to occur before the Pleistocene, despite suggestions that CAM first evolved in the Mesozoic or earlier. Here we report on multiple (≥7) positive organic carbon isotope excursions (δ13Corg &gt; −20‰) in Late Triassic and Early Jurassic (c. 200 Ma) sedimentary rocks from an arid terrestrial ecosystem in South Africa. These excursions are interpreted as evidence of the episodic dominance of CAM plants in response to heightened aridity in the heartland of Gondwana, and hint at climatic instability in a greenhouse world.

Composition and age of the Daohugou hymenopteran (Insecta, Hymenoptera = Vespida) assemblage from Inner Mongolia, China

Hymenopteran fossils from Daohugou, Inner Mongolia, China are assigned to 17 families. These include, in decreasing order of importance, Ephialtitidae, Xyelidae, Siricidae, Xyelydidae, Anaxyelidae, Karatavitidae s.l., Mesoserphidae, Megalyridae and Praeaulacidae. Analysis of the taxonomic composition suggests that the assemblage is of Mid Jurassic age. The rather low abundance of Xyelidae suggests that the climate in Daohugou during the Mid Jurassic might have been thermally intermediate between that of peri‐Baikal Siberia during the Early/Mid Jurassic transition and southern Kazakhstan during the early Late Jurassic. A new family, Protosiricidae fam. nov., is established herein and the family Gigasiricidae is reduced in rank to Gigasiricinae and referred to the Siricidae.