Texture and mineralogy as proxies of late Holocene tsunami deposits from the Doñana National Park (SW Spain)

Francisco Ruiz (1,8), María Isabel Carretero (2), Manuel Pozo (3), María luz González-Regalado (1), Guadalupe Monge (2), Joaquín Rodríguez Vidal (1,8), Luis Miguel Cáceres (1,8), Manuel Abad (4), Josep Tosquella (1), Tatiana Izquierdo (4,5), Juan Manuel Muñoz (6), María Isabel Prudencio (7), María Isabel Dias (7), Rosa Marques (7), Paula Gómez (1), Antonio Toscano (1), Verónica Romero (1) & Marta Arroyo (1)
(1) Departamento de Ciencias de la Tierra, Universidad de Huel- va, Avda. Tres de Marzo, s/n, 21071-Huelva, Spain. (2) Departamento de Cristalografía, Mineralogía y Química Agrícola, Universidad de Sevilla, C/Profesor García González 1, 41012, Spain. (3)Departamento de Geología y Geoquímica, Universidad Autónoma de Madrid, Avda. Francisco Tomas y Valiente 7, 28049-Ma- drid, Spain . (4) Departamento de Biología y Geología, Física y Química In- orgánica, ESCET, Universidad Rey Juan Carlos, 28933-Móstoles, Spain. (5) Universidad de Atacama, Avda. Copayapu 485, Copiapó, Chile. (6) Departamento de Estadística e Investigación Operativa, Uni- versidad de Sevilla, C/Profesor García González 1, 41012, Spain. (7) Centro de Ciências e Tecnologias Nucleares (C2TN), Institu- to Superior Técnico, Universidade de Lisboa, Estrada Nacional 10 (k 139.7), 2695-066-Bobadela LRS, Portugal. (8) Centro de Investigación en Patrimonio Histórico, Cultural y Natural (CIPHCN), Universidad de Huelva, 21071-Huelva, Spain. Corresponding author e-mail: ruizmu@uhu.es

Transitional flow deposits (TFDs) and hybrid event beds (HEBs) form part of the high-density sediment gravity flow spectrum. They record flow characteristics intermediate between fully turbulent and laminar flow states. The transformation from initially frictional into transitional or quasi-laminar cohesive flow behaviour results from enhanced detrital clay concentrations that dampen flow turbulence, triggering the development of an argillaceous sandstone interval that displays characteristics of a cohesive debris flow deposit. Since excess detrital clay proportions reduce primary porosity and permeability, the presence of TFDs and HEBs hinders turbidite sandstone reservoir properties. In applied scenarios, understanding their spatial distribution is crucial for avoiding well misplacement. Spatial distribution models for TFDs and HEBs largely document them as a characteristic feature of distal and lateral outer fan environments. These models are compared with results from facies analysis conducted on a dataset derived from the detailed investigation of three stratigraphic sections, acquired along a cross-current transect of the distal depositional domain of the Bordighera Sandstone (BGS). In its distal domain, the sand-rich Bordighera turbidite system is characterized by direct interbedding with calcareous fine-grained turbidites of the Sanremo Helminthoid Flysch, and features high proportions of HEBs and TFDs. Analysis of spatial trends in facies distribution allows the detailed allocation of intra- bed- to sandbody-scale heterogeneity to different axial and off-axis lobe sub-environments which are determined through quantitative sedimentological parameters. Results reveal that in the Bordighera turbidite system argillaceous sandstone bed types are not limited to lobe-fringe environments, but instead are primarily occurring in more proximal high net-to-gross zones of the largely unconfined terminal lobe domain. They account for more than 60% of stratigraphic thickness in axial zones (net-to-gross ratio = 0.87), whereas their proportions decrease towards off-axis lobe (36%; net-to-gross = 0.58) and marginal lobe to lobe fringe domains (23%; net-to-gross = 0.49).

Sedimentology, Mineralogy, Lagoon, Tsunamis, SW Iberian Peninsula.