TSK 11 Göttingen 2006 Burchardt et al. Regional fold structure anal- ysis in the Eastern Alpi Apuane, Northern Apennine Poster Steffi Burchardt1 Tobias Kracke1 Gi- ancarlo Molli2 Bernd Leiss1 The Alpi Apuane represent a large tectonic window within the Northern Apennine in Italy. In this area, not only a complete succession of the tec- tonic units of the Northern Apennine can be studied, but also the structures that result from at least two Alpine de- formational events. The rocks of the Alpi Apuane have been deposited from Triassic to Ter- tiary times on the Hercynian basement of the passive continental margin of the Apulian plate. The sedimentary succes- sion included meta-dolostones, marbles, metacherts, schists, and turbiditic aren- ites. During late Oligocene more inter- nal units (the Tuscan Nappe together with the overlying Ligurides and Sub- Ligurides) were thrusted over the Exter- nal Tuscan Domain (Alpi Apuane). The Alpi Apuane stratigraphic sequence was subject to greenschist facies metamor- phosis and severe deformation within a crustal scale shear zone. Kilometre- scale tight recumbent folds developed during a first deformation event (D1). The successive crustal shortening re- sulted in a further tightening of folds and the formation of an antiformal stack geometry with a central culmination. This late phase of D1 produced a curv- ing of N–S (Apenninic) trending folds towards an E–W (anti-Apenninic) trend (Fig. 1a). During Miocene the over- 1 Geowissenschaftliches Zentrum Göttin- gen, Goldschmidtstraße 3, 37077 Göttingen, Deutschland 2 Dipartimento di Scienze della Terre, Universität Pisa, Italien thickened antiform underwent gravita- tional collapse resulting in the refolding of D1 structures producing D2 open and back folds. The studied field area is located in the Eastern Alpi Apuane between Arni and Isola Santa in an area of anti-Apenninic trending D1 folds. The purpose of this study is to contribute to an understand- ing of 1. how the anti-Apenninic fold trend is developed in the Eastern Alpi Apuane, 2. how the D2 deformational event in- fluenced the D1 folds in the area, and 3. how the anti-Apenninic fold trend developed. Hence, field work focussed on the struc- tural analysis of folds at all scales (from kilometre-scale to micro-scale). In the field area, D1 folds are commonly highly non-cylindrical and sometimes even sheathfold-like. This fold geome- try can be found in thin sections, hand specimen, to outcrop-and /cartographic scale. The development of D2 struc- tures showing sub-horizontal axial pla- nar crenulation cleavage is to a great ex- tend dependent on the lithology and on the orientation and the intensity of the development of D1 structures. The re- sults of our studies suggest that the anti- Apenninic is due to a complex interfer- ence pattern between two generations of isoclinal sheath-like folds (D1 and Late D1) refolded by later collapse folds as- sociated to a sub-horizontal crenulation cleavage (regional D2). References Burchardt S (2005) Report of the structural geology map of the Eastern Monte Fred- done area, Alpi Apuane, Northern Apennine, 1 Burchardt et al. TSK 11 Göttingen 2006 Figure 1: a) Geological setting of the Alpi Apuane region. Apuane Unit: Pz//Tr = Paleozoic to Triassic metavolcanics, phyllites, quartzites and metaconglomerates, Tr/J = Upper Triassic to Liassic carbonate platform deposits, K/T = Cretaceous to Tertiary phyllites and metasandstones. The axial surfaces of D1 folds show two different trends: Apenninic and anti-Apenninic. Map by courtesey of G. Molli (modified after Carmignani & Kligfield 1990). b) Structural geology map of the area between Arni and Isola Santa in the Eastern Alpi Apuane. The main fold trend of D1 folds is anti-Apenninic. Modified from Burchardt (2005).) Italy. University of Göttingen, unpublished Diplom mapping thesis, pp 168 Carmignani & Kligfield (1990) Crustal exten- sion in the Northern Apennines: the tran- sition from compression to extension in the Alpi Apuane core complex. Tectonics, 9, 1275–1303 2