Geologia Marina

Marine Geology 291-294 (2012) 63–72

Contents lists available at SciVerse ScienceDirect

Marine Geology
journal homepage: www.elsevier.com/locate/margeo

Geochemical and mineralogical characterization of surficial sediments from the Northern Rias: Implications for sediment provenance and impact of the source rocks
Patricia Bernárdez a,⁎, Ricardo Prego a, Santiago Giralt b, Jaume Esteve c,Miguel Caetano d, Santiago Parra e, Guillermo Francés f
a

Marine Biogeochemistry Research Group, Marine Research Institute (CSIC), C/Eduardo Cabello 6, 36208 Vigo, Spain Institute of Earth Sciences Jaume Almera (CSIC), Lluís Solé i Sabarís s/n, E-08028 Barcelona, Spain Departamento de Geoquímica, Petrología y Prospección Geológica, Facultad de Geología, Universidad de Barcelona, Martí iFranquès s/n, E-08028 Barcelona, Spain d Instituto de Investigação das Pescas e do Mar IPIMAR, Av. de Brasília, 1449-006 Lisboa, Portugal e Instituto Español de Oceanografía (IEO), Centro Costero de A Coruña, Paseo Marítimo Alcalde Francisco Vázquez 10, 15001 A Coruña, Spain f Departamento de Geociencias Marinas y Ordenación del Territorio, Edificio de Ciencias Experimentais, Campus Lagoas-Marcosende s/n.Universidad de Vigo, 36310 Vigo, Spain
b c

a r t i c l e

i n f o

a b s t r a c t
A multidisciplinary study of the elemental geochemistry and mineralogical characteristics of the marine surficial sediment in the Northern Rias (NW Iberian Peninsula) has been carried out. The linkages between the marine sediment composition and their potential sources were examined. The influence of theriver-borne sediments is only detected in the innermost part of the three Rias. Regional variations of the mineral assemblages are governed by the source-rock composition of the different geological complexes and the relative source-rock contribution controlled by the continental hydrology. Mineralogical composition of the Ortigueira Ria and adjacent shelf surficial sediments are mainly made up ofmafic and ultramafic rocks of the Cape Ortegal complex indicated by the high content of Mg, Mn and chrysotile and riebeckite minerals. In areas nearby Ortegal complex the imprint of heavy minerals present in the surrounding rocks has also been recorded. Barqueiro and Viveiro Rias bed-sediments are influenced by granitic and metamorphic rocks from the Ollo de Sapo complex as revealed by the highcontribution of muscovite and quartz. Mining activities in the continental domain left strong imprints on marine surficial sediments. Pyrite content is high in the innermost areas of the Ortigueira Ria since this mineral is exploited in the Mera River basin, whereas high muscovite percentages characterize the Viveiro Ria owing to the abundance of granitic rocks and its exploitation in the Landro River basin.Quartz content is high nearby Cape Estaca de Bares, induced by the presence of an important excavation of this material. © 2011 Elsevier B.V. All rights reserved.

Article history: Received 9 December 2010 Received in revised form 15 September 2011 Accepted 9 November 2011 Available online 29 November 2011 Keywords: surficial sediment elemental geochemistry mineralogy Ria land–sea exchange NWIberian Peninsula

1. Background and objectives The chemical composition of marine surficial sediments is determined by the composition of river-derived material, that is dependant of the catchment petrology (Cho et al., 1999) as well as the biogenic contribution (Lackschewitz et al., 1994). Variations in minerals, lithogenic components, organic material and trace elements abundance, therefore, area tool for deciphering possible sediment sources and for discriminating physico-chemical processes affecting the geological record. The characteristics of sediments deposited on coastal areas and continental shelves largely reflect the prevailing geology of e.g. the continental source area, oceanographic and climatic conditions and hydrography. Mineral distributions, especially clay minerals,...