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Title: The geology of the Highland border from Tayside to Noranside
Author: Allan, Douglas Alexander
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 1927
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Abstract:
1. The Highland Border Series: The rocks previously mapped as Margie Grits have been examined microscopically and are shown to resemble very closely those from other localities. In the R. Prosen there has been found a new group of fine grits, black shales, and chert,which are devoid of fossils but probably belong to the older Black Shale- Jasper Series. 2. The Lower Old Red Sandstone: A petrological examination of the lava - -form rocks has shown them to belong to various sub- -divisions of the andesite and basalt families. The well- known "Lintrathen porphyry" is found to be a dacite and also a lava flow with a wide - spread occur- -ranee at one stratigraphical horizon. An investigation of the conglomerates has shown their reliability as stratigraphical indices, and a definite rhythmic variation in their composition has been demonstrated, upon which an interpretation of the conditions of their accumulation can be based. The tuffs and sandstones show a closely similar varia- -tion in composition. 3. The Upper Old Red Sandstone: What may be a remnant of Upper Old Red Sandstone sediments has been found among the Margie Grits near Auchnacree. 4. The Serpentine Belt: The rocks of the belt contain the remains of three types of ultrabasic igneous rock, HARZEURGITE, SERPENTINE-PEGMATITE, and 1)UNITE, and probably represent one plutonic intrusion; together with a smaller quantit of highly decomposed tuffs resembling schalsteins. 5. Intrusions: Most of the intrusive igneous rocks are N.E. - -S.W. dykes of tholeiitic character, identical with the Salen type tholeiite from Mull. One sill near Bridge of Cally is probably associated with these rocks, re- -presenting a slightly-different phase of the vulcanic- - ity which may be of Carboniferous age. The dyke at Auchnacree is a pyroxene -basalt and may be connected with the igneous activity of Old Red Sandstone times. 6. Sequence: A stratigraphic,al sequence of the Lower Old Red Sandstone rocks has been worked out on the field evidence evidence, and it has been found that the order and grouping is similar to that derived from the Kincar- dineshire rocks by R. Campbell. The nomenclature of that author is therefore employed. 7. Tectonics: The investigation has revealed the existence' of a major Highland thrust with a minor one to the north, both of them being steeply inclined upthrusts from the north -west. Estimates of their magnitude are given. Beyond is a normal fault with its downthrow to the south -east. The rocks of the serpentine belt are bounded both to the south -east and to the north- west by planes of dislocation, evidence of contact metamorphism by the serpentine on the country rock being absent. The serpentine- schalstein complex is therefore thought to be older than the Lower Old Red Sandstone. There is a second group of dislocations - dip faults - cutting the Highland Boundary area in a direction N.N.E. - S.S.W. The Old Red Sandstone rocks lie in synclines elongated approximately parallel to the major thrust and fault lines, and in the north-westerly area overlie/ 163 . overlie immediately a denuded halradian schist floor. In the middle and more easterly areas anticlinal folds occur in close proximity to the main Highland Boundary Thrust. 8. The glaciation of the region has left extensive relics: New striae and roches moutonn?es are recorded and various kames are noted. A series of marginal drainage channels has been mapped along the fringes of the Grampians, parallel to the main valley of Strathmore, and the possibility of their inter- communication in some cases discussed. Associated with these are certain lakes, but there are many others,at intervals along the course of the present river systems,of probably later date, when the melting snows followed the shortest route to Strathmore and cut deep gorges through the conglomerate ridges.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID: uk.bl.ethos.735208  DOI: Not available
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