--> Evolution of a Fluvial System During the Rift Initiation, Central Corinth Rift (Greece)
[First Hit]

AAPG Annual Convention and Exhibition

Datapages, Inc.Print this page

Evolution of a Fluvial System During the Rift Initiation, Central Corinth Rift (Greece)

Abstract

Standard models for initiation of continental rifting show normal faults nucleating and growing to form isolated hangingwall depocentres that enlarge and merge due to lateral fault propagation and linkage. Sedimentation rates are usually higher or equal to accommodation during the early, pre-linkage phase with footwall-derived consequent drainage systems supplying fluvial to lacustrine sediments. However, these models do not consider the impact of antecedent river systems on facies and thickness distribution in early rifts. Stratigraphic and sedimentological analysis of the Pliocene-Recent Corinth rift are here used to understand the architecture of early rift alluvial/fluvial systems from source to sink. In the northern Peloponnese, these are preserved in a series of uplifted E-W normal fault blocks incised by present-day north-flowing rivers. By correlation of fluvial successions across normal fault blocks, we propose a new sedimentary model for early rifting. The use of magnetostratigraphy and the determination of burial age using cosmonuclides 26Al/10Be give temporal constraints along four logs. The early rift fining-upward succession thickens and fines from west to east across normal fault blocks. A basal conglomeratic unit infilled an inherited paleotopography. Palaeocurrent and sedimentological data indicate that an antecedent drainage system provided high sediment supply since the onset of rifting. Fluvial sediments were deposited by a NE-flowing low sinuosity gravel-braided river system. Earliest normal faults are sealed by syn-rift sediments as displacement became focused on larger normal faults (15–20 km long, across-strike spacing of >4 km). Little or no consequent sediment supply has been detected and therefore significant footwall relief was not created during early rifting. Spatial variability of facies records displacement gradients along faults. For example, coarse alluvial conglomerates tend to occur in the centre of hangingwall depocentres while finer floodplain deposits accumulated along strike. At the rift scale, however, normal fault distribution and activity do not solely control facies distribution, being overwhelmed by high sediment discharge of the antecedent river. We develop a tectono-sedimentary model of normal fault growth and potential fluvial-lacustine reservoir distribution in early rifts with high S:A ratios that involve antecedent drainage systems and distributed normal faulting.