Fluvial architecture as a response to two-layer lithospheric subsidence during the Permian and Triassic in the Iberian Basin, eastern Spain



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López Gómez, José and Arche, Alfredo and Vargas Hernández, Henar María and Marzo Carpio, Mariano (2010) Fluvial architecture as a response to two-layer lithospheric subsidence during the Permian and Triassic in the Iberian Basin, eastern Spain. Sedimentary Geology, 223 . pp. 320-333. ISSN 0037-0738

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The stratigraphy of a sedimentary basin is mainly the result of the long-term response of a depositional
surface to prolonged subsidence. However, the real nature of interrelations between fluvial architecture and
subsidence is still unknown. Herein, we present new data on these relationships by combining the results of
detailed sedimentological field work with data acquired through automated forward modelling and
backstripping for the alluvial Permian and Triassic sediments of the SE Iberian Ranges. Using this
methodology, we determined tectonic subsidence of the basin by means of backstripping analysis and crust
and lithospheric mantle stretching factors (δ and β, respectively) using forward modelling technique. Results
indicated that a configuration of two individual and independent layers during lithospheric subsidence for
each tectonic phase fit better for this time of the studied basin evolution than the assumption of subsidence
due to a single layer spanning the whole lithosphere.
For this study, we simplified fluvial geometries as two main types: isolated (I) and amalgamated (A), with
subtypes in each case. Different order bounding surfaces (b.s.) were distinguished in the field, although we
only selected those affecting the whole basin under study. These included those b.s. of clear tectonic origin,
ranging from individual basin boundary-fault pulses produced over periods of approximately 1 My to those
arising from major tectonic events, such as the beginning of extension in the basin, causing major changes in
basin geometry over periods of 3–5 My.
The comparison of δ and β values and fluvial geometries for each identified tectonic phase in the basin
evolution, revealed some possible relationship between subsidence and fluvial geometry: Sections showing
the most varied fluvial architectural geometries, including ribbon and nested forms, were related to higher
β and δ stretching factors values indicating tectonic phases of greater stretching and subsidence. When both
stretching factors were similar and close to 1, fluvial geometry was basically reduced to amalgamated
geometry type. Wider ranging of fluvial geometries was associated with stages of basin development in
which crust and upper mantle activities differed, that is, showing larger differences of β and δ stretching
factors values. The related slope changes are proposed as the main surface control of fluvial styles.
Combination of subsidence with other possible controlling factors such as avulsion rate, climate or budget of
sediments, gives rise to the definitive alluvial architecture of a basin.

Item Type:Article
Uncontrolled Keywords:Fluvial architecture; Subsidence; Stretching factor; Permian Triassic; Tectonic controls
Subjects:Sciences > Geology > Stratigraphic geology
Sciences > Geology > Geodynamics
ID Code:17644
Deposited On:14 Jan 2013 11:42
Last Modified:11 Dec 2018 08:42

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