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Ice-rafting in lakes in the early Neoproterozoic; dropstones in the Diabaig Formation, Torridon Group, NW Scotland

Adrian Hartley, Bartosz Kurjanski, Jessica Pugsley and Joseph G. T. Armstrong
Ice-rafting in lakes in the early Neoproterozoic; dropstones in the Diabaig Formation, Torridon Group, NW Scotland
Scottish Journal of Geology (December 2019) Pre-Issue Publication

Abstract

A dropstone horizon is described from lake deposits in a paleo-valley from the c. 1000 Ma Diabaig Formation, Torridon Group, NW Scotland. Dropstones occur in wave-rippled, fine grained sandstones and siltstones that contain desiccation and syneresis cracks indicative of fluctuating lake levels. Five locally-derived dropstones occur at the same horizon over lateral distance of 250 m and display clear evidence of deflection and penetration of laminae at the base, with thinning, onlap and draping of laminae onto clast margins and tops. Mechanisms of dropstone formation are discussed with ice-rafting considered the most likely explanation. It is suggested that rafting was promoted by cold winters at 35 degrees S in the early Neoproterozoic, possibly in an upland setting. Interpretation of the dropstones as ice-rafted debris provides the first physical record of evidence for ice at the Earth's surface during the late Mesoproterozoic to early Neoproterozoic.


ISSN: 0036-9276
EISSN: 2041-4951
Coden: SJGEAX
Serial Title: Scottish Journal of Geology
Serial Volume: Pre-Issue Publication
Title: Ice-rafting in lakes in the early Neoproterozoic; dropstones in the Diabaig Formation, Torridon Group, NW Scotland
Affiliation: University of Aberdeen, Department of Geology & Geophysics, Aberdeen, United Kingdom
Published: 20191218
Text Language: English
Publisher: Geological Society Publishing House for the Geological Societies of Edinburgh and Glasgow, Bath, United Kingdom
References: 35
Accession Number: 2020-006851
Categories: Stratigraphy
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. strat. cols., geol. sketch map
N57°30'00" - N57°40'00", W05°40'00" - W05°19'60"
Country of Publication: United Kingdom
Secondary Affiliation: GeoRef, Copyright 2020, American Geosciences Institute. Reference includes data from The Geological Society, London, London, United Kingdom
Update Code: 202006
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