No abstract

No abstract

The Solan Basin lies in a part of the West Shetland continental margin that has had a complex tectonic history, dominated by extension but punctuated by several episodes of inversion, transpression and extensive erosion. The oldest sedimentary sequence, identified on seismic but not yet penetrated by drilling, may comprise Devono–Carboniferous clastics. In the Permo-Triassic a large system of half-grabens was filled with a thick succession of coarse, continental clastics. These appear to have entered the basin system in two discrete pulses and it is speculated that a third pulse, representing a transition to marginal and fully marine environments, occurred in the Early Jurassic. The area was effectively peneplaned in the late Middle to early Late Jurassic, with the removal of up to 1.5 km of section. Overlying this unconformity is a thin sequence of marginal marine sandstones and organic-rich marine shales, deposited in the latest Jurassic to earliest Cretaceous. Although parts of the region received a major influx of sand derived from the West Shetland Platform in the Early Cretaceous, the equivalent strata throughout most of the Solan Basin are a thin succession of pelagic shales and carbonates. In the early Turonian the basin was inverted. During the Late Cretaceous, extension, related to rifting along the line of the Faeroe–Shetland Trough, resulted in the development of large normal fault systems, providing the space in which a thick sequence of deep marine shales was deposited. In the earliest Paleocene, transpressional reactivation of some faults produced intense, but localized, inversion structures. Generally, however, sedimentation continued uninterrupted through the Paleocene, with the accumulation of deep marine sandstones in the east of the basin. The culmination of Thulean volcanism in the earliest Eocene was marked by the deposition of tuffaceous mudstones, which are overlain by thin coal-bearing, paralic to continental sediments. Regional thermal subsidence began in the early Eocene and continued into the Oligocene with the deposition of a thick sequence of marine clastics. In the Miocene, erosion removed up to 1.2 km of sediment from parts of the Rona Ridge and produced a basin-wide unconformity. This is overlain by Pliocene to Recent glacio-marine sands and gravels.

No abstract

The biostratigraphical criteria for the recognition of Coniacian to Maastrichtian stage boundaries in the English Chalk, published in the Abstracts to the Copenhagen Symposium on Cretaceous Stage Boundari­es 1983, are reviewed in the light of the discussion at the Symposium and the final recommendations. Particular attention is given to problems relating to the base of the Coniacian and Santonian Stages. A critical assessment is made of criteria used by French workers for recognising the base of the Senonian Stage in the Anglo-Paris Basin. Benthonic Foraminifera used to identify the base of the Senonian are shown to have discrepant ranges in Kent compared with Sussex and Senonian stratotype. The nannofossil Marthasterites furcatus first appears below the level of acme-occurrence of ammonites of the Late Turonian Subprionocyclus neptuni Zone in southern England, and cannot therefore be used as a marker to identify the base of the Coniacian in the Anglo-Paris Basin. Extended comment is made on the bio­stratigraphy of the successions in southern England and northern Germany across the Coniacian - Santonian boundary, and it is suggested that the Upper Coniacian Micraster bucaillei/Gonioteuthis praewestfalica Zone of the German Lligerdorf standard section should be re-assigned to the basal part of the Santonian. The base of the Campanian Stage in southern England is arbitrarily taken at the evolution­ary first appearance of Bolivinoides culverensis, a level coincident with the top of the local Uintacrinus anglicus Zone, rather than at the extinction-level of Marsupites and/or entry of Gonioteuthis granulata­quadrata lower in the succession. The entry of the nannofossil Broinsonia parca, widely taken as a criterion for recognising the base of the Campanian Stage, is shown to occur at an horizon well above the entry-level of B. culverensis.