Journal of Palaeogeography最新文献

Detailed sedimentological analysis of the Pokaran Boulder Bed, representing the most basal unit of the Neoproterozoic-Lower Cambrian Marwar Supergroup, clearly indicates its glacial origin. The glacial sediments are interpreted as an ice-contact submarine fan deposit. Based on the detrital and inherited zircon population of the Marwar Supergroup sediments and interlayered pyroclastic deposits, a Marinoan cryochron of the Cryogenian Period is envisaged for the Pokaran Boulder Bed. The well-preserved Ediacaran elements in the post-glacial sedimentary succession also support a Cryogenian to Early Cambrian age of the Marwar Supergroup. The glacial deposition at the base of the Marwar Supergroup strengthens the regional correlation between the studied sediments with the Lesser Himalayan Blaini-Krol-Tal sediments and the Haqf Supergroup of Oman. The available zircon ages and paleomagnetic data of the Malani Igneous suite, along with the Marinoan glacial deposits, detrital zircon ages, and Ediacaran fossil elements of the Marwar Supergroup add significant information to the Neoproterozoic Earth history.

The late Maastrichtian witnessed substantial surges in Deccan volcanism, prompting the hypothesis that these voluminous pulses may have instigated repeated episodes of ocean acidification during this period. The Cretaceous-Palaeogene (K/Pg) boundary at Bidart (France) is preceded by a ∼0.5 m thick interval with geochemical and taphonomic vestiges of an ocean acidification event linked with Deccan volcanism. New planktic foraminifera census and morphometric data now confirm biotic stress conditions related to acidification in the Deccan benchmark interval. The absolute abundance data of larger (>150 μm) heavily calcified planktic morphogroups show fluctuating populations throughout zone CF1 (spanning the final ∼225 ky), lowest peaks within the Deccan benchmark, and a demographic collapse (>90%) at the K/Pg boundary. The analyzed species are generally reduced in size, with thinner test walls in this ∼0.5 m interval, indicating the likelihood of calcification stress as a contributor to the overall biotic stress. At the K/Pg boundary, maximum biotic stress is recorded in all the tested faunal proxies. A preliminary graphic correlation of zone CF1 at Bidart with the auxiliary GSSP at Elles (Tunisia) constrains the Deccan benchmark interval of high biotic stress to the final ∼58 ky of the late Maastrichtian, culminating in the K/Pg mass extinction. The volcanogenic Hg peaks coincident with faunal and taphonomic evidence of ocean acidification strengthen the Deccan-related ocean acidification hypothesis.

Coniopteris simplex is a common component in many Jurassic floras. However, due to morphological variations in sterile fronds and incomplete preservation of reproductive organs, its classification has been controversial for a long time. Here, we present new material collected from the Middle Jurassic Yan'an Formation in the Ordos Basin, Inner Mongolia. The new material reveals important morphological characters, including hemi-dimorphic fronds, two forms of sterile pinnae, short-stalked sori and sporangia on fertile fronds, annulus of sporangium composed of about 30 cells, in situ rounded triangular spores with protruded suture, and the lips of trilete laesura encircled by one or two rows of small ostioles. Based on these observations, we emended the diagnosis of this common species. The spatio-temporal distribution of Coniopteris simplex shows that the iconic species was restricted to the paleolatitudes ranging from 19.5°N to 48.9°N in the Northern Hemisphere during the Early–Late Jurassic, mainly distributed in the tropical to paratropical zones, and the paleolongitude ranging from 9.6°E to 129.3°E, which may be limited by the opening of the Viking Corridor and the splitting of the Central Atlantic Ocean.

It is reported a multi-proxy palaeoclimatic study conducted on a MIS 5e calcarenite from the Mar Piccolo Basin (MP), Gulf of Taranto (GT) (Central Mediterranean). The calcarenite returned a rich malacofauna consisting of 120 extant species, including four of the tropical Senegalese Fauna, today absent in the Mediterranean. The biogeographic-climatic affinity of the assemblage shows, compared to today, a double percentage of warm affinity species, while the cold affinity species are nearly equally represented, indicating a warmer but not strictly tropical SST. This is confirmed by the most recurring preferred SST ranges of the assemblage, indicating an average of 20 °C. The skeletal compositions of five well-preserved molluscan and coral specimens were analyzed for trace elements and stable isotopes for further mean SST estimations. From the comparison of the results of several equations available in literature, it appears that only some SST estimations are realistic, converging into similar values of, on average, 20.8 ± 0.9 °C. Considering all the used proxies, the MIS 5e SST difference compared to today falls in the range 1.2–2.0 °C for the GT (being a more reasonable scenario) and 2.0–2.8 °C for the MP. This is not a firmly tropical-like SST setting as suggested by the sole Senegalese fauna, indicating at least 2.7 °C–3.5 °C more than today's GT and MP, respectively. The approximations and assumptions made for obtaining SST values with any single proxy indicate the need of a multi-proxy approach to define the best SST estimation.

Tracks registration is influenced by the dynamic interplay between the pedal anatomy of the trackmaker, its behaviour, and the substrate conditions it interacts with. Differences in substrate conditions, especially those linked to grain size and moisture content, often result in the most dramatic variations in track morphology. In the upper Stormberg Group, main Karoo Basin of southern Africa, diverse trace fossils, primarily comprising Late Triassic–Early Jurassic dinosaur tracks, are preserved. Numerous studies have extensively documented individual ichnosites, investigating variations between sites over time, with recent studies suggesting that track abundance and anatomical fidelity increase up-stratigraphy. Despite the well-established link between substrate and track morphology, past studies have not specifically focused on substrate conditions, often emphasizing macro-sedimentary features instead. Here, we examine the micro-sedimentary features of track-bearing units in the upper Stormberg Group using petrographic techniques to better understand the palaeosubstrate and its effect on fossil track registration and preservation. The analysis revealed that very fine-grained sandstones and substrates modified by microbial activity tend to preserve tracks with greater abundance and/or higher anatomical fidelity. Furthermore, the prevalence of very fine-grained and microbially modified strata, and their associated track trends increases in younger stratigraphic units. Across the Triassic – Jurassic boundary in southern Africa, a boom in dinosaur track abundances is observed and credited to the proliferation of dinosaur populations during the Early Jurassic. Our findings, however, suggest that the observed local increase in track abundance (and anatomical fidelity) up-stratigraphy may be linked to substrate composition differences, which were ultimately controlled by large-scale changes in the palaeoenvironment from high-energy meandering fluvial to lower-energy aeolian-lacustrine settings in the Late Triassic and Early Jurassic, respectively. These findings have implications for global macroevolutionary patterns, palaeo-geographical reconstructions, and biostratigraphic correlations in the early Mesozoic.

The thiolliericrinids (Thiolliericrinidae) are comatulids (Comatulida), which retained their stalks as adults. Here, we report a centrodorsal from the Bajocian strata (Middle Jurassic) of the Djebel Kérdacha area, northwestern Algeria (Africa). It is the first thiolliericrinid report from outside of Europe and also the oldest representative of the Thiolliericrinidae whose first occurrence is from the Oxfordian. The crinoid is assigned to Copernicrinus zamorae gen. et sp. nov. The reported new taxon shows strong similarities with the stemless ‘true’ comatulids, Solanocrinites; the only difference is the presence of a facet to the stem in Copernicrinus. The closest comparable thiolliericrinid to Copernicrinus is the Oxfordian Thiolliericrinus, interpreted as a descendant of the latter. The origin and overview of all thiolliericrinid representatives are also discussed herein.

Two rectangular-shaped lakes, Lake Hulun and Lake Buir, located at the boundary between China and Mongolia, only c. 75 km apart and therefore experiencing similar wind fields, have been studied based on satellite images and field surveys in order to compare their geomorphological and sedimentological characteristics. The wind-driven hydrodynamics, which have a significant effect on the development of littoral landforms and on sediment distribution, have been discussed for the two similar lakes that experienced a prevailing wind perpendicular to their long axis. A conceptual model related to wind-driven water bodies and sediment distribution is proposed. Wave-influenced to wave-dominated deltas, beaches, spits, and eolian dune deposits develop around these two lakes, with a strikingly similar distribution pattern. These features locally inform the longshore drift and help reconstruct the water circulation induced by wind forcing. Under the NW prevailing wind regime, the spits developed on the SW coast with a NW–SE extension, which was influenced by the NW–SE longshore currents. The same influence was observed in the delta extension in the NE area. The differences lie in the presence of fan deltas in the NW region of Lake Hulun, but not in Lake Buir. Additionally, the width of the beach and eolian deposits on the downwind coast of Lake Hulun is three times greater than that of Lake Buir which were caused by the differences in sediment supply and wind fetch between the two lakes. Lake Hulun and Lake Buir provide two reliable examples to understand the relationship among the wind field, provenance, hydrodynamics, landforms, and asymmetrical distribution of clastics in elongated lakes. They also represent relevant modern analogs, which may also be of guiding significance to wind-driven sand body prediction in lacustrine basins.