A new ammonite faunal horizon in the Ovale Zone (Middle Jurassic,Lower Bajocian) and observations on the ammonite genus Sonninia at Coombe Quarry,Mapperton, near Beaminster,Dorset

Biostratigraphy is presented for horizons in the Discites to Sauzei zones at Coombe Quarry and Top Field at Mapperton, Dorset. The significance of these horizons is highlighted. Part of a chronocline is described in the Sonniniidae of the Discites Zone. A new ammonite faunal horizon, Docidoceras higginsi sp. nov. is erected as the oldest of the Ovale Zone. A revised subdivision of the zone is presented and the implications for the taxonomy and biogeography of the Stephanoceratidae is discussed. The distribution of Docidoceras may imply entry to western Tethys via a Hispanic Corridor. A method is presented for the allocation of generic names constituting segments of lineages.     

Two new stephanoceratid ammonites from the Aalenian-Lower Bajocian (Middle Jurassic,Dorset, UK) and their phylogenetic significance

Two new species of stephanoceratid ammonites are erected: Stephanoceras (Riccardiceras) eoeteosum sp. nov. and Stephanoceras (Skirroceras) englandi sp. nov. from the Inferior Oolite Formation of Dorset, UK. They represent the first and last members of a chronocline of serpenticonic morphospecies. The stratigraphical position of Rhytostephanus rhytus Buckman is reviewed, necessitating a change in the faunal horizon scheme. The term mesoconch is proposed for use in describing microsomic macroconchs, the function of which is considered. Names applied to morphospecies and their uses are reviewed. The role of conservation is discussed in respect of preserving Dorset Inferior Oolite exposures.     

劣质宝石的人工处理

本文简介劣质宝石的人工处理方法,有染色法、漂白法、加热法,涂层法和辐射法等方法,而且尚附有主要宝石常用的处理方法一览表。     

Sedimentary architecture of an ancient linear megadune (Barremian,Neuquén Basin): Insights into the long‐term development and evolution of aeolian linear bedforms

Linear aeolian bedforms are the most abundant bedform type in Earth's dune fields, and are very common in the Solar System. Despite their abundance, the long‐term development of these bedforms and its impact upon the resulting sedimentary architecture in the geological record is still poorly understood. The aim of this paper is to study the exposed record of an ancient linear megadune in order to discuss its development and the factors that impact the sedimentary architecture of aeolian linear bedforms. The outcrops of the ancient Troncoso Sand Sea (Barremian, Neuquén Basin, Argentina) provide a unique opportunity to study a preserved megadune record with an external body geometry that confirms its linear morphology. Architectural analysis reveals significant differences in cross‐stratified set bodies and bounding surfaces’ features and allows for the identification of three architectural complexes within the bedform's record. Analysis of deterministic models, sedimentary body relative chronology and distribution suggest that these architectural complexes result from distinctive phases in bedform development. It also clearly shows that construction of the megadune was achieved by expansion from a core, and that its development was characterized by sustained growth and strong longitudinal dynamics, without net accumulation. This study indicates how sustained bedform growth, rather than accretion, can be a critical factor conditioning linear bedform architecture towards a more ‘classic’ (bimodal bounding surface and cross‐bedding dip directions) concentric sedimentary architecture style. Furthermore, this research reveals how this style of architecture could only be relatively common in the geological record when related to bedform topography preservation.