Tectonics of the circum-Troodos sedimentary cover of Cyprus, from rock magnetic and structural observations

The calcareous sedimentary cover of the Troodos Ophiolite Complex dips gent ly away from the Troodos Complex. It has rare, usually open folds and, loca lly, stylolitic cleavage (S-1). Stylolitic cleavage is similar to 50% more effective than primary bedding-stylolites in removing matrix and the variat ion in the SI vergence directions are compatible with gravitational sliding radially away from the Troodos range and into sedimentary basins. Two diff erent types of magnetic fabric, anisotropy of magnetic susceptibility (AMS) and anisotropy anhysteretic remanence (AARM), reveal the sequence of prefe rred orientations of different minerals, and the vergence of their magnetic foliations with respect to bedding reveals the sense of over-shearing of t he stratigraphic sequence. AMS defines crystallographic alignments of clay minerals and dimensional alignments of magnetite in the limestones. AARM is olates the preferred dimensional orientation of magnetite. Although traces of magnetite dominate the bulk susceptibility, its anisotropy is low in com parison with phyllosilicates so that AMS essentially records the clay-fabri c. Throughout the study area, AMS foliation indicates S-vergence and AMS li neation indicates N-S extension. AMS foliation-vergence indicates shearing of the entire sedimentary cover southward from Troodos. This motion is attr ibuted to gravity sliding controlled by regional uplift to the north. In co ntrast, AARM foliation indicates a subsequent ESE vergence due to later WNW -ESE extension. The NNE, AARM lineation is a composite of bedding and tecto nic fabric contributions that do not directly yield a faithful extension di rection. The shapes of the magnetic fabrics indicate that AMS (clay) fabric s have a broad range of shapes about the neutral ellipsoid shape, whereas A ARM (magnetite) fabrics are bimodal, with equally developed bedding-oblate and tectonic linear-planar (L = S) components. Hysteresis properties, plott ed on a new three-dimensional diagram, show clearly that the magnetite has a pseudosingle domain response, so there is no reason to expect complicatio ns from inverse fabrics due to single-domain magnetite. Moreover it shows t hat hysteresis properties vary systematically with depositional depth, refl ecting systematic changes in magnetite granulometry with sedimentary enviro nment. (C) 2000 Elsevier Science Ltd. All rights reserved.