Some geomorphological features of the Orhaneli Pluton: Implications for denudation history

Year 2008, Volume: 137 Issue: 137, 61 - 72, 01.06.2008

Ahmet Evren Erginal , Ahmet Ertek

Abstract

The granitic intrusions of the variable age of cooling, size and mineral composition are widely exposed in the northwest Anatolia, Turkey. The nearly circular Orhaneli Pluton emplaced during the Early Eocene with some 15 km in diameter, is one of such plutonic bodies. Geomorphological features of the pluton are discussed here with special emphasis given on the denudation history. To this end, evidence from two isolated Inselberglike hills as remnants of roof rocks in the centre of the pluton and episodically emergence of granite landforms of etch origin after unroofing process were investigated. Field data reveal the absence of granodiorite clasts within Early to Middle Miocene lacustrine deposits in the north of the pluton, implying that the pluton might not have been exposure prior to Upper Miocene as a whole. After the first exposure, the granite landforms, such as boulders, corestones and tors constituting sound evidence of an etch origin, became exposure by continual removing of regolith cover by surficial runoff. These forms of various scale were formed at first by subsurface weathering and shaped by surficial weathering processes after any stages of removal of the regolith cover. Drainage segments accounted for removal of regolith is mostly structurally controlled defined by NW-SE, NE-SW and N-S-aligned fracture systems.

Keywords

Differential weathering, Weathering front, Regolith, Orhaneli Pluton, NW Turkey

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