Geology topics

Research about Scotland

Source-linked reports with geographic coverage including Scotland.

3 recordsLinked to original sources

USGS2022

Age and significance of former low-altitude corrie glaciers on Hoy, Orkney Islands

Geomorphological mapping provides evidence for two former low-level corrie glaciers on Hoy, both defined by end moraines. Five 10Be exposure ages obtained from sandstone boulders on moraine crests fall within the range 12.4 ± 1.5 ka to 10.4 ± 1.7 ka (weighted mean 11.7 ± 0.6 ka), confirming that these glaciers developed during the Loch Lomond (Younger Dryas) Stade (LLS) of 12.9-11.5 cal. ka BP, and demonstrate the feasibility of using this approach to establish the age of LLS glacier limits. The equilibrium line altitude (ELA) of one of the glaciers (99 m) is the lowest recorded for any LLS glacier, and the area-weighted mean ELA for both (141 m) is consistent with a general northward ELA decrease along the west coast of Britain. The size of moraines fronting these small ( ≤ 0.75 km2) glaciers implies that glacier termini remained at or close to their limits for a prolonged period. The apparent restriction of LLS glaciers to only two sites on Hoy probably reflects topographic favourability, and particularly the extent of snow-contributing areas.

Hoy, Orkney Islands↗

USGS1988

Granulite fades Nd-isotopic homogenization in the Lewisian complex of northwest Scotland

A published Sm–Nd whole-rock isochron of 2,920 ± 50 Myr, obtained from a wide range of lithologies in the Lewisian complex of north-west Scotland, was interpreted 1 as the time of protolith formation. This date is ∼ 260 Myr older than estimates for the timing of high-grade metamorphism in the complex at ∼ 2,660 Myr 2'3 , and this period is considered to represent the duration of the Lewisian crustal accretion-differentiation superevent (CADS) 4 . Here we give new Sm-Nd data, obtained specifically from granulite facies tonalitic gneisses, that yield a date of 2,600 ±155 Myr. Although depleted-mantle model ages ( t DM suggest >200 Myr of premetamorphic crustal residence, the regression date and its associated initial Nd-isotopic parameters demonstrate Nd-isotopic homogenization during the high-grade event, as well as the probability of general rare-earth-element (REE) mobility. Models for selective element depletion in the complex have previously assumed REE immobility since 2,920 Myr, but the data presented here suggest that a reappraisal of the depletion mechanism is required.

Nature↗

USGS1966

Large-scale basin-and-dome pattern resulting from the interference of major folds

The geometry of individual major folds from the Glen Cannich area in the Northern Highlands of Scotland is described. The major folds are isoclinal, and their axial planes and fold limbs strike north or northeast and dip steeply; the fold axes plunge steeply toward the south or southeast. If pairs of individual folds are joined along a common axial-plane trace they form basins, domes, or other unusual culmination structures which resemble intensely flattened cylinders. As a group, the basins and domes form a continuous pattern , which covers an area of approximately 27 square miles, with possible extension into surrounding areas. This pattern has resulted from the interference of two sets of major folds , whereby the movement direction of the second fold set lay close to the axial plane of the first fold set. The geometrical conditions and /or intensity of the second folds that obtained during the second folding have rendered the first fold set unmappable, because the basins and domes are elongated entirely in the direction of the second fold set. The probable orientation of the first- fold axial plane is suggested by joining the culminations or depressions of the basm- and - dome pattern . Subsequent deformations have substantially altered the basin - and - dome pattern from its probable original form.

Scotland↗