Conodont biostratigraphy of the Crawford Group, Southern Uplands, Scotland

Abstract

Synopsis Extensive new conodont collections from the Crawford Group, the oldest succession in the Southern Uplands of Scotland, support the previously documented biostratigraphical ages for the included formations. The Raven Gill Formation is lower Whitlandian, Arenig (comparable in age to the Dounans Limestone in the Highland Border Complex) and the Kirkton Formation is latest Llandeilian-Aurelucian, Llanvirn to Caradoc in age. It is concluded that there is a significant stratigraphical gap within the Crawford Group. The restricted and probably fault-bounded nature of the Raven Gill outcrops suggests that these may represent olistoliths within a mélange of Llandeilian-Aurelucian age. The chert-bearing succession of the Northern Belt of the Southern Uplands thus represents the juxtaposed sedimentary records of two entirely separate basins – the oldest pre-dates the Grampian assembly of the Laurentian margin, and the younger, the Northern Belt Basin sensu stricto, entirely post-dates this event.

Middle Ordovician (Darriwilian) radiolarians from the Crawford Group, Scotland

“…In addition, based on a poorly preserved, less diverse radiolarian assemblage, Danelian (1999) tentatively correlated the same chert sequences with the Haplentactinia juncta -Inanigutta unica zone which was described from eastern Kazakhstan. The assemblage reported here can be placed within the P. anserinus conodont zone with confidence, as the fauna described comes from strata in the same area that were previously described by Armstrong et al (1990Armstrong et al ( , 2002 and Danelian (1999) (Fig. 2a).…”

“…The conodonts Pygodus anserinus and Periodon aculeatus constrain the age of the chert sequences in the Hawkwood Burn in the Kirkton Formation to the latest Darriwilianearliest Sandbian (late Llanvirnianearly Caradoc in terms of British series) (Armstrong et al 1990(Armstrong et al , 2002Danelian & Floyd, 2001). In addition, based on a poorly preserved, less diverse radiolarian assemblage, Danelian (1999) tentatively correlated the same chert sequences with the Haplentactinia juncta -Inanigutta unica zone which was described from eastern Kazakhstan.…”

Conodonts from the Margie Limestone in the Highland Border Complex, River North Esk

“…It is a common component in collections from the Baltic region (Lindstrom 1955;Van Wamel 1974;Lofgren 1978;Tolmacheva & Lofgren 2000), and is known from Kazakhstan (Dubinina 1991;2000). Occurrences in Britain include the Crawford Group at Ravengill Burn in the Southern Uplands (Lamont & Lindstrom 1957;Armstrong et al 2002) and the North Esk locality as reported here. It has been described from many localities around the margins of Laurentia, for example Cow Head Group, western Newfoundland (Fahraeus & Nowlan 1978;Stouge & Bagnoli 1988;Pohler 1994;Williams et al 1994;Johnston & Barnes 1999;2000), Deep Kill Shale, eastern New York (Landing 1976), Jutland Klippe in northern New Jersey (Repetski et al 1995), Hamburg Klippe, central Pennsylvania Repetski 1984), Mazarn Shale, Ouachita Mountains, central Arkansas (Chludzinski 1993), Ninemile Formation, Antelope Range, Eureka County, Nevada (Ethington 1972) and Kechika Formation, northeastern British Columbia (Pyle & Barnes 2002).…”

An expanded Smithian–Spathian (Lower Triassic) boundary from a reefal build‐up record in Oman: implications for conodont taxonomy, high‐resolution biochronology and the carbon isotope record

“…2009; Sheridan & Bickford 2011), and offshore migration of conodonts during their development (e.g. Armstrong & Dean 1996; Dingle & Drake 2007).…”