Extension and Exhumation of the Hellenic Forearc Ridge in Kythera

• Published in: The Journal of geology 2008-11, Vol.116 (6), p.640-651
• Main Authors: Marsellos, A. E., Kidd, W. S. F.
• Format: Article
• Language: English
• Subjects: Atmosphere; Exhumation; Forearcs; Geological time; Mapping; Outcrops; Plate tectonics; Quartzite; Ridges; Rollbacks; Sediments; Seismology; Shear zones; Subduction
• ISSN: 0022-1376; 1537-5269
• DOI: 10.1086/591995

Detailed mapping and new structural observations on Kythera demonstrate that there is a major detachment fault, here termed the Potamos detachment fault (PDF), exposed on the northern part of the island and bordering the domed structure of a metamorphic core complex. The detachment forms the contact of contrasting metamorphic and nonmetamorphic units, and both ductile and brittle structures are found, related to its extensional development. The earliest Potamos mylonites, as well as some other early ductile structures near the mapped detachment fault, indicate initiation of the PDF under NE-trending extension, in mid- to late Miocene time. Later ductile, ductile-brittle, and some brittle structures in the metamorphic unit near the detachment indicate (in contrast) a significant NW-SE extension along the forearc ridge. The younger brittle structures indicate return to NE-SW extension. Late Miocene–Pliocene strata cover the detachment unconformably and are affected only by the late faults. Trench rollback and slab retreat of the subducting African lithosphere in the late Miocene requires expansion and increased curvature of the Hellenic (Crete-Peloponnese) forearc ridge. Differential movement between and vertical axis rotation of segments of the forearc ridge may have localized along-arc stretching. Cross-ridge strike-slip faults may be linked to the later parts of this process. Evidence of young E-W dextral faulting is seen in northern Kythera outcrops, related to a significant submarine fault of this type located between Kythera and the Peloponnese.