Bornhardts, Boulders and Inselbergs

• Autores: C. R. Twidale
• Localización: Cadernos do Laboratorio Xeolóxico de Laxe: Revista de xeoloxía galega e do hercínico peninsular, ISSN 0213-4497, Nº 20, 1995, págs. 347-380
• Idioma: inglés
• Títulos paralelos:
  • Bornhardts, Bloques e Inselbergs
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• Resumen

  • Bornhardts are steep-sided domical hills. The profiles are associated with sheet fractures, and their plan form with steeply dipping fractures of orthogonal or rhomboidal systems. They are well developed in massive rocks, especially, but not only, in granite, and they occur in various climatic settings. They are found in multicyclic landscapes. They occur in massifs as well as in isolation, as inselbergs; in either setting they meet the adjacent plain or valley floor in a piedmont angle or nick. They may be the basic form from which are derived nubbins and castle koppies. Bornhardts are upstanding for various reasons. For example, sorne are tectonic forms, while others are exposed stocks. Such causations have only local validity. Two competing hypotheses find favour as general explanations. Sorne workers conclude that bornhardts are remnants of circumdenudation, monadnocks de position or Fernlinge, residuals shaped by and remaining after scarp retreat. Others consider that bornhardts are structural forms, Härtlinge, or monadnocks de dureté, which have evolved in two stages and are etch forms. The rock compartments on which they are based resisted subsurface weathering either because of their composition or because of their low fracture density. They are comparable to corestone boulders, with the important difference that whereas corestones are detached, bornhardts remain in physical continuity with the main mass of country rock.