We present and use the chronostratigraphy of 13 field logs and detailed mapping to constrain the evolution of the early Zagros foreland basin, in NW Iran. Large foraminifera, calcareous nannofossil, palynological and
87
Sr/
86
Sr analysis supplied ages indicating a Campanian–early Eocene age of the basin infill, which is characterizd by a diachronous, southwestward migrating, shallowing upwards, mixed clastic–carbonate succession. Growth synclines and local palaeoslope variations indicate syndepositional folding from Maastrichtian to Eocene time and suggest forelandward migration of the deformation front. We also illustrate the basin architecture with a synthetic stratigraphic transect. From internal to external areas, time lines cross the formation boundaries from continental Kashkan red beds to Taleh Zang mixed clastic–carbonate platforms, Amiran slope deposits and basinal Gurpi–Pabdeh shales and marls. The foreland basin depocentres show a progressive migration from the Campanian to Eocene (
c
. 83–52.7 Ma), with rates of
c
. 2.4 mm a
−1
during the early–middle Palaeocene (
c
. 65.5–58.7 Ma) increasing to
c
. 6 mm a
−1
during the late Palaeocene–earliest Eocene (
c
. 58.7–52.8 Ma). Coeval subsidence remained at
c
. 0.27 mm a
−1
during the first 12.7 Ma and decreased to
c
. 0.16 mm a
−1
during the last 4.2 Ma of basin filling. Finally, we integrate our results with published large-scale maps and discuss their implications in the context of the Zagros orogeny.
Supplementary material:
Tables with dating results are available at
http://www.geolsoc.org.uk/SUP18439
.
Anticlines of the Lurestan Province in the Zagros fold–thrust belt have been studied by integrating field-based analysis with the use of high-resolution satellite images and data available from the literature. The distribution of folds in the southeastern Lurestan Province, expressed in terms of axial length and wavelength distribution, shows a direct link with the characteristics of the sedimentary multilayer in which the folds developed. Within the carbonate deposits of the Late Cretaceous Bangestan Group the transition from pelagic to neritic facies determines a threefold increase in anticline spacing and promotes the development of thrust structures in the forelimb of anticlines. The Oligocene–Miocene Shahbazan–Asmari unit folds harmonically with the Bangestan Group, except in the areas where the Palaeogene deposits interposed between the two units exceed 1300 m of thickness. In these areas the Shahbazan–Asmari carbonates display short-wavelength folds indicating a complete decoupling from the underlying folds of the Bangestan Group. It is suggested that this decoupling occurs because the summed thickness of the incompetent units separating the two carbonate units exceeds the extension of the zone of effective contact strain of the Bangestan Group folds.
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