T55 Earth History in the Broadest Context—Tectonics, Impacts, Mass Extinctions, and Big History: Celebrating the Contributions of Walter Alvarez

Sunday, 25 September 2016
1:30 PM - 5:30 PM
Mile High Ballroom 3B

THE OLD RED SANDSTONE OF SCOTLAND: EVIDENCE FOR A GANGES-SIZED RIVER DRAINING THE CALEDONIAN HIGHLANDS OF NORWAY

Paper number: T55-11
Program: Technical Sessions
Time: 4:15 PM – 4:30 PM

Authors

Abstract

The Old Red Sandstone is one of the world’s most famous formations as it lies atop James Hutton’s unconformity at Siccar Point. Provenance studies of the conglomeritic sedimentary rocks in the Old Red Sandstone of Scotland’s Midland Valley point to mostly local sediment sources. However, the presence of large-scale cross-stratification, and at one locality a fossil bar over 10 m thick, suggests deposition in a large river system originating from a distant but unknown source. Stream flow indicators point to sources in or beyond what is now the North Sea and the North Atlantic Ocean. Using zircon U/Pb and white mica 40Ar/39Ar ages we established a provenance profile for these river sediments. We then compared this provenance profile to units throughout Scotland as well as from northern England to test for potential local sourcing. We found no appropriate source for the zircons in northern England. However, detrital zircon age spectra contain a number of overlapping populations, many of which correlate with ages found in the basement rocks of the Scottish Highland terranes, including a key 1.65 Ga signal. Preliminary white mica 40Ar/39Ar ages of ~410 Ma in the Old Red are too young to be sourced from these Scottish terranes. Taken together, our data are compatible with data obtained from coeval sedimentary basins in Norway where they too exhibit a pronounced U/Pb peak at 1.65 Ga and a 40Ar/39Ar peak of ~ 410 Ma, matching what we found in the Old Red Sandstone. The deposits are taken to represent a Ganges-sized river system (>20 m water depth) that drained the Norwegian Caledonian highlands, and carried sediment across what would eventually become the North Sea to Scotland.

Geological Society of America Abstracts with Programs. Vol. 48, No. 7

doi: 10.1130/abs/2016AM-282537

© Copyright 2016 The Geological Society of America (GSA), all rights reserved. Permission is hereby granted to the author(s) of this abstract to reproduce and distribute it freely, for noncommercial purposes. Permission is hereby granted to any individual scientist to download a single copy of this electronic file and reproduce up to 20 paper copies for noncommercial purposes advancing science and education, including classroom use, providing all reproductions include the complete content shown here, including the author information. All other forms of reproduction and/or transmittal are prohibited without written permission from GSA Copyright Permissions.