Sg. Stromberg et B. Bluck, TURBIDITE FACIES, FLUID-ESCAPE STRUCTURES AND MECHANISMS OF EMPLACEMENT OF THE OLIGOMIOCENE ALJIBE FLYSCH, GIBRALTAR ARC, BETICS, SOUTHERN SPAIN, Sedimentary geology, 115(1-4), 1998, pp. 267-288
The Aljibe Flysch, the largest tectono-sedimentary unit in the Gibralt
ar Are, provides a record of Oligo-Miocene sedimentation in the Betic
Orogen, southern Spain. The Aljibe Flysch can be subdivided into two s
ub-units, the Beneiza Flysch (Late Oligocene) and the Aljibe Arenites
(Early Miocene), which have very different depositional histories and
mechanisms of emplacement. The Beneiza Flysch is characterised by late
rally continuous and thin-bedded lithic arenites, siltstones and mudst
ones which contain complete and partial Bouma sequences. These are int
erpreted to have been deposited in a sheet-turbidite system which may
have formed part of the North African Flysch Trough. By contrast, the
Aljibe Arenites comprise of thick-bedded super-mature quartz arenites
which are dominated by fluid-escape structures. These sandstones are s
imilar to Facies Group B1-B2 disorganised sands of Pickering et al. (1
989), which are interpreted to be the product of deposition from high-
density turbidity currents. Fluid-escape structures have been classifi
ed according to the scheme of Lowe (1975) and their vertical arrangeme
nt indicates that a large volume of sediment was deposited extremely r
apidly during frequent remobilisation events. Consideration of the ori
gin of the fluid-escape structures and their vertical arrangement has
identified problems in their interpretation, and identified key areas
for future research. The boundary between the Beneiza Flysch and Aljib
e Arenites is interpreted to be a significant stratigraphic boundary a
cross which there is a major change in sediment source and mechanism o
f sediment emplacement. Several models can be put forward for the gene
ration of this stratigraphic break, and these serve to set the agenda
for future research into the emplacement of other similar flysch seque
nces and the origin of the Gibraltar Are Flysch. (C) 1998 Elsevier Sci
ence B.V. All rights reserved.