Proceedings of the Geologists Association最新文献

The Inferior Oolite Formation, 'Wild Bed' of Quarr Hill, Chideock, Dorset is described in terms of ammonite biostratigraphy down to the resolution of biohorizons for a segment of the Aalenian Stage of the Middle Jurassic. A section is presented and descriptions of the ammonites of the families Graphoceratidae, Erycitidae, Hammatoceratidae and Lytoceratidae are made in conjunction with an assessment of available types along with new illustrations of specimens collected in-situ. Examples of other molluscs are cited and imaged. Lectotypes are designated for some of the species erected by S. S. Buckman from Chideock. Comparisons are made with successions in other areas of North-West Europe thus providing an improved correlation and relationships between different ammonite morpho-taxa.

An isolated jaw fragment from the Late Cretaceous (Cenomanian) Cambridge Greensand Member of the West Melbury Marly Chalk Formation previously identified as a cestraciontid shark fin spine is referred to the pterosaur clade Azhdarchoidea on account of its lateral and occlusal foramina and edentuly. The specimen differs from the azhdarchoid Ornithostoma sedgwicki from the same deposit in having flat lateral surfaces and an acute dorsal/ventral apex. The specimen is similar in overall morphology to CAMSM B40085 from the same horizon and probably represents the corresponding jaw but from a different individual. Likely these specimens represent a new taxon but are considered too fragmentary to diagnose at present. A remarkably similar and distinctive morphology is found in unnamed pterosaur jaws from the Kem Kem Group (?Albian-Cenomanian) of Morocco, supporting the idea of faunal similarity between these two distant localities.

Spyway Quarry in Dorset contains >100 tracks made by large sauropod dinosaurs walking across what was a shelly beach in the Early Cretaceous. It is the largest in situ easily accessible UK dinosaur tracksite, a unique location for the public to directly engage with dinosaurs. Following consultation on how best to open and manage the site considering its 'value', longevity, and resources available, it was left unstaffed with the track surface directly accessible. The site has been open to the elements since 2013 and to the public since 2016. We created a new photogrammetric model of the site in 2021, for comparison with an existing 2014 model to identify any changes in the trackway surface and to assess the sustainability of direct public access and weathering to the surface. To understand public use of the site, we installed a visitor counter, compiled social media reviews, and analysed photographs of visitor's movement on the quarry surface. We provide quantitative evidence for exfoliation of the track surface and reduction in the prominence of individual tracks over time primarily due to natural processes. Visitor data suggest ~10,000 people visit annually, and feedback suggests potential improvements to visitor directions and information. We do not recommend substantial changes to the site management plan given resource constraints. Our work highlights the importance of using 3D imaging techniques to document sites upon discovery and thereafter and making these data openly available to all for conservation monitoring, communication and to preserve sites' legacies.

Ammonites of the family Lytoceratidae from the Middle Jurassic Inferior Oolite Formation, Aalenian to lowermost Bathonian, of Dorset are rarely described, perhaps because the macroconchs are often very large and difficult to collect intact and the microconchs are very small and easily overlooked. Detailed stratigraphical collecting over several years has shown them to be a minor part of the ammonite fauna but more common at certain horizons. Four genera, Lytoceras, Megalytoceras Nannolytoceras and Pleurolytoceras have been shown to have different stratigraphical ranges and abundances in the Aalenian and Bajocian but they have not been found in the Lower Bathonian of Dorset. The taxonomic basis of several of the well-known species is poorly described in the literature and is remedied here.

Trace fossils are described from the Eocene Bembridge Limestone Formation from the Isle of Wight and used to constrain the paleoenvironmental interpretation. The lacustrine–palustrine succession contains three limestone beds, which are separated by clay and marl. The middle and upper limestone beds reveal complex burrow systems developed at their top. Based on their characteristics, these burrow systems are assigned to the ichnotaxon Balanoglossites triadicus Mägdefrau, which is associated with the shallow superficial grooves Sulcolithos variabilis Knaust. B. triadicus is a common marine trace fossil mainly known from shallow-marine carbonate successions throughout the Phanerozoic. It is accompanied by other marine ichnotaxa such as Arachnostega gastrochaenae Bertling, Gastrochaenolites isp. aff. G. ornatus Kelly and Bromley, Spongeliomorpha iberica Saporta and Thalassinoides suevicus (Rieth). This ichnological evidence confirms the occurrence of short-term marginal-marine incursions in a predominantly lacustrine to palustrine environment.

In the northern Aurès Range near Batna, Algeria, the Cenomanian Smail Marls Formation consists of fossiliferous deposits rich in diverse benthic macrofauna, mostly dominated by bivalves, among them the carditid Maghrebella forgemoli (Coquand, 1862). Almost exclusively Cenomanian, the abundance zone of Maghrebella forgemoli is in the higher levels of Lower Cenomanian, extending from the Sharpeiceras schlueteri zone to the Mantelliceras dixoni zone and corresponds to a limited circalittoral interval with relatively low energy, soft substrata, and relatively cold temperatures. The distribution of Maghrebella forgemoli in Mountains of Batna evidences bathymetric variation controlled by the tectonic activity affecting the ante-Triassic and the Upper Cretaceous substrata and generating a system of tilted blocks, at the beginning of the uppermost Albian-Cenomanian and Turonian, in the eastern Atlasic domain that extends to central Tunisia.