Cretaceous Of Southern England Research Articles

The first orthophlebiid scorpionfly (Insecta: Mecoptera) from the Wealden (Lower Cretaceous) of southern England

ABSTRACTThe Family Orthophlebiidae ranges from the Middle Triassic to the Early Cretaceous. The Wealden Mecoptera have added to our knowledge of the Mecoptera from the Early Cretaceous of southern England, but have been comparatively little studied. Here we present the description of the first orthophlebiid from the Wealden of England. Mesopanorpa brooksorum sp. nov. from England is the earliest Cretaceous representative of this genus.

A new species of Vectiselachos (Chondrichthyes, Selachii) from the Early Cretaceous of southern England

Abstract Teeth of a new species of hybodont shark Vectiselachos (Chondrichthyes: Lonchidiidae) are described from the late Aptian (Early Cretaceous) of southern England. Vectiselachos gosslingi sp. nov. has very distinctive coarse striations that form raised ridges over the occlusal surfaces of the crown.

Palaeoclimate analysis using spectral gamma-ray data from the Aptian (Cretaceous) of southern England and southern France

The abundance and half-lives of potassium (K), uranium (U) and thorium (Th) make these three elements the dominant sources of gamma-rays detected in rocks both at outcrop and in the subsurface. With the advent of the spectral gamma-ray tool (SGR), the variation shown by these three elements in rocks has been considered to reflect sorting at flooding surfaces and changes in the weathering regime of sediment source-lands. K and U are considered to be more soluble than Th, thus elevated Th to K or U ratios in soils and eroded clays can reflect hot, humid climates and palaeoclimates. This study makes an assessment of the usefulness of SGR data to palaeoclimate studies by comparing changing Th/K and Th/U ratios from a known period of palaeoclimate change to extensive published and new data from other analytical methods. New SGR data from the Cretaceous of southern England and southern France compare favourably to outcrop sedimentological facies interpretations and laboratory geochemical data. Palaeoclimate data from two other sections (northern Germany, northern Italy) are compared as controls to the study. Together these analyses suggest that there was a gradual change from semi-arid climate in the Barremian and early Aptian, to a semi-humid climate in the mid-Aptian. Superimposed on this long-term rise in humidity were a number of short-term (ammonite zone-length) changes in Th/K and Th/U ratios and the abundance of climate-sensitive materials. This study shows that SGR data are more useful than originally thought. When problems of overprinting from heavy minerals and diagenesis are overcome, outcrop and borehole spectral gamma-ray logs from mudstones or the clay-rich beds of mixed successions may be used to interpret past patterns of hinterland weathering.

Volcanic clays in the Cretaceous of southern England and Northern Ireland

AbstractThe mineralogy, petrology and trace element geochemistry of volcanogenic glauconites and smectite-rich clays are described and related to clay assemblages in Lower and Upper Cretaceous sediments of southern England and Northern Ireland. Volcanogenic glauconite grains represent argillized lava particles of predominantly mafic composition and may have been derived from submarine basaltic magmatism; they occur in all the sediments examined (Aptian-Senonian), and are particularly abundant in the Cenomanian-Campanian Hibernian Greensand of Antrim. The smectite-rich clays in southern England have developed by the argillization of predominantly acid or alkaline ash during early diagenesis. Three types of volcanogenic deposit are recognized. Primary bentonites are thin ash-falls deposited in quiet, brackish and marine waters (Speeton Clay, Ryazanian; Weald Clay, Barremian). Secondary bentonites are local accumulations of ash transported into the Cretaceous seas by rivers draining ash-blanketed, local land areas (London Platform, Portsdown Axis). These deposits are well-developed in the Sandgate Beds, Folkestone Beds and their contiguous deposits, and the lower part of the Gault (Upper Aptian-Middle Albian). The ash originated from penecontemporaneous, subaerial vulcanism located in the southern part of the North Sea. The most conspicuous phase of activity occurred during late Aptian times and has been dated by 40Ar/39Ar isotope analysis at 112 m.y. Bentonitic clays and marls are widespread accumulations of argillized ash that occur as a fine-grained fringing facies to glauconitic quartz sand facies. They make up the upper part of the Atherfleld Clay (Aptian) and the upper part of the Gault (Upper Albian), and they are associated respectively with the Hythe Beds (Aptian) and the Upper Greensand (Upper Albian). They may also occur in the lower part of the Lower Chalk (Cenomanian). The distribution pattern of these smectite-rich clays in southern England is related to the changing palaeogeography of the area in Cretaceous times, and the general coincidence of extensive glaueonite deposits and smectite-rich clays in the Middle and Upper Cretaceous of western Europe and along the eastern seaboard of North America is briefly discussed.