Geologische Rundschau

, Volume 77, Issue 1, pp 183–190

Stratigraphic framework of the geometry of the basal decollement of the Appalachian-Ouachita fold-thrust belt

  • William A. Thomas
Article

Abstract

The geometry of the basal decollement of the Appalachian-Ouachita fold-thrust belt is related to lateral and vertical variations in stratigraphic facies. Successive lithotectonic units reflecting evolution of the tectonic framework include pre-Appalachian crystalline basement, rift-fill sedimentary and volcanic rocks, passive-margin shelf and off-shelf facies, and synorogenic clastic wedges. Five distinct configurations of the basal decollement are systematically distributed with respect to pre-thrust tectonic elements and sedimentary facies. The relationship between sedimentary facies distribution and decollement geometry is useful in describing and predicting along-strike and across-strike variations in decollement level. The geometry of the basal decollement reflects the shapes of promontories and embayments along the rifted continental margin.

Zusammenfassung

Die Geometrie der basalen Abscherung im Appalachen-Ouachita Faltungs- und Überschiebungsgürtel ist eng verknüpft mit lateralen und vertikalen Faziesänderungen. Aufeinanderfolgende lithotektonische Einheiten wie das kristalline Basement der Prä-Appalachen, die Grabensedimente und Vulkanite des Riftstadiums, der Schelf und Vorschelf des passiven Randes und die synorogenen klastischen Keile spiegeln die Evolution des tektonischen Gerüstes wider. Es lassen sich fünf unterschiedliche Formen basaler Abscherung in Beziehung zur sedimentären Fazies sowie zu den tektonischen Elementen vor der Überschiebung aufgliedern. Die Relationen zwischen sedimentärer Faziesverteilung und Abscherungsgeometrie sind für die Beschreibung und Vorhersage von parallel zum Streichen und senkrecht dazu verlaufenden Variationen des Abscherungsniveaus nützlich. Die Geometrie der basalen Abscherung reflektiert so ehemalige Vorsprünge und Einbuchtungen des auseinandergedrifteten Kontinentalrandes.

Résumé

Le décollement qui se trouve à la base de la ceinture plissée et charriée Appalachian-Ouachita présente une géométrie en relation avec les variations verticales et latérales du faciés stratigraphique. L'évolution du cadre tectonique se reflète dans des unités lithotectoniques successives telles que: le socle cristallin pré-appalachien, les sédiments et les volcanites de graben de marge passive déposés sur la plate-forme continentale et au large de celle-ci et les prismes clastiques synorogéniques. On peut distinguer cinq configurations du décollement basal, qui se répartissent en fonction des facies sédimentaires et des structures tectoniques antérieures aux charriages. Les relations entre la distribution des facies sédimentaires et la géométrie du décollement sont d'un grand intérêt dans l'analyse et la prédiction des variations longitudinales et transversales du niveau de décollement. La géométrie du décollement basal traduit la présence de baies et de promontoires de long des marges continentales qui se sont écartées par «rifting».

Краткое содержание

Геометрия базальног о срыва в поясе складкообразования и надвигов Аппалачи-К вачита связана с боко выми и вертикальными изме нениями фация. Следую щие друг за другом литоте ктонические структу рные единицы, как-то криста ллиновое основание пре-Аппалачей, седиме нты грабена и вулкани ты стадии рифта, шельф пассивно го края и фаций, отложи вшийся пред шельфом, и синоро генные кластические клинья, полностью ото бражают эволюцию тектонического карк аса. Базальное отслаи вание можно подразделить п о осадочным фациям и тектоническим элеме нтам на 5 различных фор м. Соотношения между ра спределением осадоч ных фаций и геометрией ск ола важны для описани я и предсказания различ ий уровней скола, прох одящих параллельно, или перп ендикулярно к прости ранию. В геометрии базально го скола отражаются в ыступы и прогибы материково го края, умевшиеся до столкновения дрейфующих материко в.

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Copyright information

© Ferdinand Enke Verlag Stuttgart 1988

Authors and Affiliations

  • William A. Thomas
    • 1
  1. 1.Department of GeologyThe University of AlabamaTuscaloosaUSA

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