GeoSed - Associazione Italiana per la Geologia del Sedimentario
Dipartimento di Scienze della Terra dell'Università di Siena
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Table of Contents


Vol. 9 - 2010

Vol. 8 - 2009

Vol. 7 - 2008
SP 1 - 2008

Vol. 6 - 2007
Vol. 5 - 2006
Vol. 4 - 2005
Vol. 3 - 2004
Vol. 2 - 2003
Vol. 1 - 2001-2002

Notes for Authors
(PDF - 80 kb)



GeoActa Special Publication 1 2008


Acquisto online

GeoActa
an international Journal of Earth Sciences


Massimo Zecchin
Istituto Nazionale di Oceanografia e di Geofisica Sperimentale - OGS, Borgo Grotta Gigante 42/c, 34010 Sgonico (TS), Italy. E-mail address: mzecchin@ogs.trieste.it

The 'aggradational highstand systems tract' (AHST): a peculiar feature of highly-supplied growth fault-bounded basin fills


Volume 6, 2007, pages 83-89

PDF (204 KB)
Abstract

Normal fault-bounded basins commonly show a sequence-stratigraphic architecture that is deviated from classic models derived from passive margins. In particular, depositional sequences containing well developed shallow-marine, mostly aggradational intervals resting on back-barrier to shallow-marine transgressive intervals are common in highly-supplied growth fault-bounded basins. These aggradational intervals have been called 'aggradational highstand systems tract' (AHST), and result from the balance between the rate of sediment supply and the rate of creation of accommodation following a transgression. A distinct maximum flooding surface is not recognizable at the base of the AHST, which can be considered as an extremely expanded maximum flooding zone.
The development of this type of sequence is favoured in contexts characterized by a relatively rapid and constant fault-controlled subsidence and a high rate of sediment supply that just compensates the rate of creation of accommodation. A rapid change in the tectonic regime may lead to abrupt interruption of sedimentation and to the formation of main unconformities. For the observed linkage between depositional sequence architecture and changes in the tectonic regime, AHST recognition may be useful to discriminate between a dominant tectonic or eustatic control in sequence development.

Keywords: Aggradational highstand systems tract, Zinga-type sequence, Sequence stratigraphy, Growth fault-bounded basins, Tectonic control