Pseudomorphs after ikaite in a glaciomarine sequence in the Dalradian of Donegal, Ireland

Saved in:
Online Access: Get full text
doi: 10.1144/sjg31010003
Authors:Johnston, J. D.
Author Affiliations:Primary:
Trinity College, Department of Geology, Dublin, Ireland
Volume Title:Scottish Journal of Geology
Source:Scottish Journal of Geology, Vol.31(Part 1), p.3-9. Publisher: Scottish Academic Press, Edinburgh, United Kingdom. ISSN: 0036-9276
Publication Date:1995
Note:In English. 24 refs.; illus., incl. sects., 2 plates, geol. sketch map
Summary:Ikaite, calcium carbonate hexahydrate (CaCO3·6H2O) has been reported from several localities world-wide in periglacial and glaciomarine settings. The mineral has been documented forming in seawater and lakewater at temperatures close to 0°C, but inverts to calcite at higher temperatures. Widespread occurrences of pseudomorphs after ikaite have been described from the geological record in glacial sequences. An isolated occurrence of similar pseudomorphs in Precambrian Dalradian rocks on the Garvellach Islands has been noted. A newly discovered occurrence in the Skelpoonagh Bay Limestone of the Appin Group Dalradian in south Donegal is reported here. This is in exactly the same part of the stratigraphy as the Garvellach example, suggesting that there may have been widespread development of pseudomorphs after ikaite within the Dalradian basin. The Donegal examples are preserved as slightly ferroan dolomite pseudomorphs up to 40 mm in length in a matrix of calcite. The occurrence of these structures immediately beneath the Dalradian Boulder Bed is consistent with its widely accepted glacial origin.
Subjects:Calcite; Carbonates; Dalradian; Dolomite; Glacial environment; High temperature; Ikaite; Lithofacies; Petrography; Precambrian; Pseudomorphism; Temperature; Donegal Ireland; Europe; Ireland; Western Europe; Appin Group
Coordinates:N543000 N550000 W0080000 W0085000
Abstract Numbers:95M/4705
Record ID:1995047169
Copyright Information:GeoRef, Copyright 2019 American Geosciences Institute.
Tags: Add Tag
No Tags, Be the first to tag this record!