Marine palynomorphs from the Staffin Bay and Staffin Shale formations (Middle-Upper Jurassic) of the Trotternish Peninsula, NW Skye

Abstract

Synopsis The Staffin Bay and Staffin Shale formations of Trotternish, Skye represent an important Middle–Upper Jurassic (Callovian–Kimmeridgian) reference section. The succession is 133 m thick, mudstone-dominated, and the Staffin Shale Formation is rich in zonal ammonite faunas. Both formations have yielded abundant palynofloras rich in marine microplankton. The Staffin Bay Formation is lowermost Callovian on both dinoflagellate cyst and regional evidence. Only one ammonite has been recorded from its uppermost division, the Belemnite Sands Member. Miospores dominate the Staffin Bay Formation and the relatively low diversity dinoflagellate cyst floras are consistent with a palaeoenvironmental interpretation of restricted, nearshore marine conditions. Dinoflagellate cysts and other marine microplankton are relatively abundant and diverse throughout the Middle Callovian to Lower Kimmeridgian Staffin Shale Formation, thereby indicating an open marine depositional setting. The stratigraphical distributions and relative proportions of the dinoflagellate cysts are largely consistent with those observed in England and elsewhere in northern Europe. Established dinoflagellate cyst zonal schemes can be applied to both formations. Certain species, however, exhibit minor stratigraphical differences in overall ranges. Wanaea acollaris Dodekova 1975, for example, is recorded in the Lower Oxfordian Dunans Clay Member (Staffin Shale Formation); the range top of this species was previously thought to be within the Upper Callovian. Certain species recorded in the Staffin Shale Formation are interpreted as being of Boreal affinity; these include Ambonosphaera? staffinensis ( Gitmez 1970 ) Poulsen & Riding 1992 , Paragonyaulacysta spp. and Gonyaulacysta dentata ( Raynaud 1978 ) Lentin & Vozzhenikova 1990.

Isotopic signals from Callovian–Kimmeridgian (Middle–Upper Jurassic) belemnites and bulk organic carbon, Staffin Bay, Isle of Skye, Scotland

“…5), which identify only Type III kerogen during this interval. This is in accord with published palynological data for Staffin Bay, which record abundant palynomorphs that are dominated by gymnospermous pollen grains and associated with pteridophytic spores (Riding & Thomas 1997). More specifically, the conifer pollen Classopollis and the wood genus Cupressinoxylon (Pearce et al 2005) have been recognized.…”

“…It should be noted, however, that the Rock-Eval pyrolysis did identify several samples with relatively high Hydrogen Indices, which would suggest that a marine component is occasionally incorporated within the organic matter. Marine microplankton, most notably dinoflagellate cysts, have been recorded from the Staffin Bay section (Riding & Thomas 1997). The samples with high Hydrogen Indices do not consistently correspond to heavier carbon isotope ratios, and it is therefore argued that the organic matter source has not significantly influenced the carbon isotope trend recorded here.…”

“…The upper Ostrea Member is composed of dark grey shales with shell beds dominated by bivalves (Anderson & Cox 1948;Morton & Hudson 1995). Palynological evidence is consistent with a restricted, inshore and brackish depositional environment (Riding & Thomas 1997). The Belemnite Sands Member is made up principally of siltstones and sandstones with a more varied marine fauna of bivalves and belemnites (Anderson & Cox 1948;Anderson & Dunham 1966;Morton & Hudson 1995;Riding & Thomas 1997).…”

“…The Belemnite Sands Member is made up principally of siltstones and sandstones with a more varied marine fauna of bivalves and belemnites (Anderson & Cox 1948;Anderson & Dunham 1966;Morton & Hudson 1995;Riding & Thomas 1997). Belemnites are particularly common in the glauconitic beds towards the top of the member (Riding & Thomas 1997).…”

The palynology of the Pabay Shale Formation (Lower Jurassic) of SW Raasay, northern Scotland

“…Previous studies on the Jurassic palynology of the Hebrides Basin include Bradshaw and Fenton (1982), Riding (1984Riding ( , 1992a, Riding et al (1991) and Riding and Thomas (1997). This report represents the first palynological evidence for Upper Sinemurian strata in the Hebrides Basin.…”