Reconstructing regional geological histories is challenging where basins have limited and/or fragmentary preservation. Several isolated outlier basins of Lower Old Red Sandstone (LORS) occur on the Scottish Grampian terrane; however, their sedimentology and relationship to other similar-aged LORS deposits has been poorly constrained, as has their significance in the wider Caledonian orogenic framework. Here we present a combination of new sedimentological and multidisciplinary provenance analyses for the LORS outliers at Aberdeen, Cabrach, New Aberdour, Rhynie and Tomintoul. Three facies associations are identified, the deposits of locally derived conglomeratic alluvial fans, which pass upward into fluvial channel and floodplain facies associations. Provenance data from conglomerate clast populations, sandstone petrography, heavy mineral assemblages, and U-Pb detrital zircon geochronology indicate derivation from the surrounding Dalradian Supergroup, with local influence from contemporaneous volcanic or plutonic lithologies. These data suggest a similar provenance to that of the northern Midland Valley Basin LORS, and a direct relationship between the LORS north and south of the Highland Boundary Fault. This indicates that the preserved outliers represent fragments of wider, unpreserved LORS cover that accumulated between the late phases of the Caledonian Orogeny and onset of post-orogenic collapse in the Mid-Devonian.
Bibliographical noteAcknowledgements: We thank Steven Andrews for providing additional field photographs for Tomintoul. We also thank Rufus Brunt, Linda Kirstein, Nigel Mountney and an anonymous reviewer for their insightful comments, which helped to improve the manuscript.
Funding: This research received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors.
Author contributions: ZM: conceptualization (lead), data curation (lead), formal analysis (lead), investigation (lead), methodology (lead), project administration (lead), visualization (lead), writing – original draft (lead), writing – review & editing (lead); AJH: conceptualization (supporting), methodology (supporting), project administration (supporting), resources (lead), supervision (lead), visualization (supporting), writing – review & editing (supporting); DIMM: supervision (supporting), writing – review & editing (supporting); AM: formal analysis (supporting), methodology (supporting), writing – review & editing (supporting); DF: formal analysis (supporting).
Data Availability StatementData availability: All data generated or analysed during this study are included in this published article (and its supplementary information files).
- HIGHLAND BOUNDARY FAULT
- U-PB AGE
- DETRITAL ZIRCON
- SCOTLAND IMPLICATIONS
- MOINE SUPERGROUP