Late Vendian-?Cambrian glacially influenced deep-water sedimentation, Macduff Slate Formation (Dalradian), NE Scotland

Abstract

The deep-water metasedimentary rocks of the late Dalradian Macduff Slate Formation preserve a record of distal glaciomarine sedimentation in the form of ice-rafted dropstones and related bedding-deformation structures, glaciogenic debris-flow diamictites and an allochthonous slump unit. The input of ice-rafted debris was cyclical and probably related to periodic disintegration of the marine margin of an ice sheet. Downslope resedimentation processes, typical of glaciated continental margins, were responsible for the diamictites and slump deposits which were probably derived from the adjacent outer shelf and upper slope, in common with Pleistocene analogues off NW Britain. The uppermost diamictite bed is an integral part of the deep-marine succession, in contrast to the previously proposed lodgement-till hypothesis.

A composite C-isotope profile for the Neoproterozoic Dalradian Supergroup of Scotland and Ireland

“…For many years, the Port Askaig Formation, recognised in discontinuous outcrop across mainland Scotland and Ireland, was the only glacial deposit identified within the Dalradian (Spencer 1971;Eyles & Eyles 1983;Arnaud & Eyles 2006;Benn & Prave 2006 Boulder Beds in SW and NE Scotland, respectively (Sutton & Watson 1954;Stoker et al 1999;Condon et al 2000Condon et al , 2002. Thomas et al (2004) have shown that diagenetic effects on 13 C in most Dalradian limestones were likely minor.…”

The Dalradian rocks of the north-east Grampian Highlands of Scotland

“…These beds were interpreted as glaciomarine deposits by Sutton and Watson (1954). Stoker et al (1999) have documented the sequence in detail and confirmed that at least some of the larger boulders are probable dropstones from floating ice (Figure 30).…”

“…These deposits have been interpreted as the products of ice-rafting or as debris flows linked to marine tills (Sutton and Watson, 1954;Hambrey and Waddams, 1981;Stoker et al, 1999).…”

“…The presence of glacigenic boulder beds at two separate stratigraphical levels has generated much interest and discussion on the age of the succession (Sutton and Watson, 1954;Spencer and Pitcher, 1968;Hambrey and Waddams, 1981;Stoker et al, 1999) but the palaeontological studies of the higher parts of the succession are now viewed as inconclusive (Skevington, 1971;Downie et al, 1971;Bliss, 1977;Downie, 1984;Molyneux, 1998). The area has been remapped by the British Geological Survey, resulting in the publication of two 1:50 000 sheets, 96W (Portsoy, 2002) and 96E (Banff, 2002).…”

Geochemical evolution of Dalradian metavolcanic rocks: implications for the break-up of the Rodinia supercontinent

“…These are, from youngest to oldest, as follows. 1) Leslie et al (2008) and Prave et al (2009b) correlated the Loch na Cille Boulder Bed (Elles 1934;Prave 1999), which marks the top of the Tayvallich Volcanic Formation in SW Scotland (Pickett, in press), with the Inishowen glacial beds in Donegal (Condon & Prave 2000) and the Macduff Boulder Bed in NE Scotland (Stoker et al 1999). They suggested that these units represent the Gaskier global glacial event (c. 580 Ma).…”