About This Item
- Full TextFull Text(subscription required)
- Pay-Per-View PurchasePay-Per-View
Purchase Options Explain
Share This Item
Paleogeographic evidence suggests the presence of five major tectonic elements in the Circum-Mediterranean region. Starting from either the Afro-Arabian or Eurasian continental masses these tectonic units are: (1) shield or craton areas bounded by (2) marginal troughs of relatively low mobility, uniformly filled with normal sediments; (3) geanticlines or upwarps with a thin sequence of sediments, which generally separate the marginal trough from (4) internal troughs filled with a variable thickness of highly plastic sediments and zones of initial ultrabasic activity which were arcuate to (5) nuclei or minor cratons which furnished plastic sediments to the internal troughs.
Nuclear areas in the Turko-Balkan region and in the western Mediterranean grew progressively outward by incorporating the folds which developed from a series of internal troughs bordering the nuclei. The high mobility of the internal troughs--displayed in parts of the Taurus, Olnos-Pindos, southern Alps, northern and southern Apennines, Tellian Atlas, and Pyrenean foothills--has resulted in a variety of surficial gravity slides caused by the initial plasticity of the sediments rather than intense crustal shortening or buckling. The shield areas of Afro-Arabia and Fennoscandia have enlarged their cratonic dimensions by the "welding" and incorporation of successive marginal troughs. The relatively competent sediments of the uniform marginal troughs, when orogenically deformed and later xposed by epeirogenic uplift, as in the Saharan, High and Middle Atlas, and the Iberian Range, produce normal structural types oriented parallel with the configuration of preceding trough trends. In the marginal troughs both deformational intensity and local structural trends seem to be related to the original thickness of sediments and trough orientation, whereas in the internal troughs these features are in many places unpredictable.
Outward growth of the continental areas and the arcuate expansion of the nuclei have shifted the two trough types toward each other. This convergence has tended ultimately to fill in the thin crust of the Tethyan area creating a cratonic-like aspect. When the pattern of this postulated tectonic framework is related to current concepts of earth deformation, conclusions drawn from the Circum-Mediterranean region seem to be contrary to the majority of the theories, although at various stages of the orogenic cycle there are analogies to all the proposed concepts.
Pay-Per-View Purchase Options
The article is available through a document delivery service. Explain these Purchase Options.
|Watermarked PDF Document: $14
|Open PDF Document: $24
Members of AAPG receive access to the full AAPG Bulletin Archives as part of their membership. For more information, contact the AAPG Membership Department at [email protected].