Sediment supply from the Betic–Rif orogen to basins through Neogene

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<ul><li><p>n, CSIInn</p><p>Received 12 March 2008Received in revised form 22 October 2008Accepted 25 November 2008Available online 6 December 2008</p><p>Keywords:Sedimentary volumesSedimentation ratesSedimentary contributionsIberiaAfrica plate boundaryErosion and vertical movements</p><p>Tectonophysics 475 (2009) 6884</p><p>Contents lists available at ScienceDirect</p><p>Tectonop</p><p>.e lQuantifying tectonic and sedimentary processes is a signicantchallenge in contemporary geology and sometimes the only way toconstrain the evolution of regions with complex geodynamic evolu-tions. For long periods of time, the volumes of sedimentary uxesfrom growing mountains to basins and their rates are closely relatedto the intensity and duration of tectonic events rather than to climate.Therefore, accurate quantication of sediment transfer within tec-</p><p>mostly developed during the Alpine orogeny. The orogenic systemencompasses the BeticRif chain, the inner extensional Alboran Basin,the outer Guadalquivir and Rharb foreland basins, the Gulf of Cadizregion, and various small intramontane basins (Fig. 1). So far, there isno general consensus on the Neogene evolution of the BeticRiforogen and different and competing models have been proposed.These models include convective mantle removal and orogeniccollapse (e.g., Dewey, 1988; Platt and Vissers, 1989; Vissers et al.,tonically active areas is essential for understatectonic evolution of orogenic systems.</p><p>The development of the BeticRif orogeIberia plate boundary across the transition zo</p><p> Corresponding author. Fax: +34 934110012.E-mail addresses: (L. Iribarre</p><p>(J. Vergs), (M. Fernndez).</p><p>0040-1951/$ see front matter 2008 Elsevier B.V. Aldoi:10.1016/j.tecto.2008.11.029Ocean and the Mediterranean Sea resulted in a complex scenario1. IntroductionWe present a quantication of total and partial (divided by time slices) sedimentary volumes in the Neogenebasins of the BeticRif orogen. These basins include the Alboran Sea, the intramontane basins, theGuadalquivir and Rharb foreland basins and the Atlantic Margin of the Gibraltar Arc. The total volume ofNeogene sediments deposited in these basins is ~209,000 km3 and is equally distributed between theinternal (Alboran Basin and intramontane basins) and the external basins (foreland basins and AtlanticMargin). The largest volumes are recorded by the Alboran Basin (89,600 km3) and the Atlantic Margin(81,600 km3). The Guadalquivir and Rharb basins amount 14,000 km3 and 14,550 km3, respectively whereasthe intramontane basins record 9235 km3. Calculated mean sediment accumulation rates for the earlymiddle Miocene show an outstanding asymmetry between the Alboran basin (0.24 mm/yr) and the forelandbasins (0.060.07 mm/yr) and the Atlantic Margin (0.03 mm/yr). During the late Miocene, sedimentationrates range between 0.17 and 0.18 mm/yr recorded in the Alboran Basin and 0.04 mm/yr in the intramontanebasins. In the PlioceneQuaternary, the highest sedimentation rates are recorded in the Atlantic Marginreaching 0.22 mm/yr. Sedimentary contribution shows similar values for the inner and outer basins with ageneralized increase from late Miocene to present (from 3500 to 6500 km3/My). Interestingly, the AlboranBasin records the maximum sedimentary contribution during the late Miocene (5500 km3/My), whereas theAtlantic Margin does during the PlioceneQuaternary (6600 km3/My). The spatial and time variability of thesediment supply from the BeticRif orogen to basins is closely related to the morphotectonic evolution of theregion. The high sedimentation rates obtained in the Alboran Basin during the earlymiddle Miocene arerelated to active extensional tectonics, which produced narrow and deep basins in its western domain. Thehighest sedimentary contribution in this basin, as well as in the foreland and intramontane basins, isrecorded during the late Miocene due to the uplift of wide areas of the Betics and Rif chains. The analysis ofthe sedimentary supply also evidences strong relationships with the post-Tortonian crustal thickening andcoeval topographic amplication that occurred in the central Betics and Rif with the concomitant evolution ofthe drainage network showing the uvial capture of some internal basins by rivers draining to the AtlanticOcean (the ancestral Guadalquivir).</p><p> 2008 Elsevier B.V. All rights reserved.Article history:a b s t r a c ta r t i c l e i n f oSediment supply from the BeticRif oroge</p><p>L. Iribarren a,b, J. Vergs a,, M. Fernndez a</p><p>a Group of Dynamics of the Lithosphere (GDL), Institute of Earth Sciences Jaume Almerab Department of Marine Geology, INETI-National Institute for Engineering, Technology and</p><p>j ourna l homepage: wwwnding and modelling the</p><p>n on top of the Africane between the Atlantic</p><p>n),</p><p>l rights basins through Neogene</p><p>C, Llus Sol i Sabars s/n, 08028 Barcelona, Spainovation, Estrada da Portela, Zambujal, 2721-866 Amadora, Portugal</p><p>hysics</p><p>sev ie locate / tecto1995; Platt et al., 2003a,b); mantle delamination (e.g., Garca-Dueaset al., 1992; Docherty and Banda, 1995; Seber et al., 1996; Mezcua andRueda, 1997; Calvert et al., 2000); slab roll-back (e.g., Frizon deLamotte et al., 1991; Lonergan and White, 1997); active subduction(Gutscher et al., 2002; Duggen et al., 2004; Faccenna et al., 2004); slabbreak-off (Zeck, 1996; Wortel and Spakman, 2000); and slab roll-backcombined with lithosphere tearing (Spakman and Wortel, 2004;Faccenna et al., 2004; Govers andWortel, 2005). Most of thesemodels,</p></li><li><p>69L. Iribarren et al. / Tectonophysics 475 (2009) 6884however, are based on the tectonic style of the orogenic system, and/or on deeper signatures such as hypocenter location and regional orglobal tomography, but they lack incorporating surfacemass transportstudies.</p><p>Studies related to the Neogene sedimentary inlling and itstectonic signicance are restricted to few basins within the BeticRiforogen. Various works used the stratigraphic record at a regional scalein order to attain the paleogeographic and the tectonic evolution ofthe Betic Chain (Sanz de Galdeano, 1990; Sanz de Galdeano and Vera,1992; Sanz de Galdeano et al., 1993; Sanz de Galdeano and Rodrguez-Fernndez,1996; Vera, 2000; Andeweg, 2002; Hanne et al., 2003). TheNeogene sedimentary record of the Alboran Basin has been widelyanalysed by the integration of well data and multichannel seismicproles. Studies based on the age of the sedimentary sequences, theirstratigraphic relations, the basin architecture and the relationshipwith onshore sediments, have permitted to establish the timing andtectonic regime of different events controlling the evolution of thebasin (Comas et al., 1992; Soto et al., 1996; Comas et al., 1999;Rodrguez-Fernndez et al., 1999). In the Gulf of Cadiz the interactionof sedimentation and the successive deformation phases has been alsostudied (Maldonado and Nelson, 1999; Maldonado et al., 1999; Grciaet al., 2003a; Medialdea et al., 2004). Other recent works deal with theregional distribution of sedimentary markers such as coastal andmarine shallow deposits in order to obtain the late orogenic uplifthistory (Weijermars et al., 1985; Sanz de Galdeano and Alfaro, 2004;Braga et al., 2003). Recently, Iribarren et al. (2007) presented thestructure of the Gulf of Cadiz with especial emphasis on the geometryof the Miocene chaotic units with the Gulf of Cadiz Imbricate Wedgeand the Horseshoe Gravitational Unit. One limitation with previousstudies is that they focussed on the mountain chains or the inner/outer basins lacking of regional sedimentary studies that integrate theentire BeticRif orogenic system. In this context, the main objective of</p><p>Fig. 1. Tectonic map showing principal structural units of ththis work is to provide a quantitative analysis of sedimentary volumesfor all the sedimentary basins that developed during the BeticRiforogenic evolution since earlymiddle Miocene to Present. Thisquantication involves volumes of sediment (km3), rates of sedimentaccumulation (mm/yr) and sedimentary contribution (km3/My).</p><p>To this end, we have integrated available geological and geophy-sical data including well data, stratigraphic columns, cross-sections,seismic proles, geologic maps and isopach maps. The time intervalsto calculate the sedimentary contribution and the sedimentation ratesthrough time have been chosen according to their widespreadrecognition in the study region. The distribution, volume quantica-tion and rates of sedimentation of the BeticRif Neogene sedimentaryproducts and their time evolution add new quantitative constraints tothe tectonic evolution models and contribute to better understand themorphotectonic evolution of this region. We nally discuss the im-plications of these results during the BeticRif orogenic buildingthrough middlelate Miocene, Pliocene and Quaternary periods.</p><p>2. Geological setting</p><p>The BeticRif orogen occupies the Southern IberianMargin and theNorthern Moroccan Margin and is classically divided in the InternalZones, the External Zones, the Flysch Units, and the Neogene basins(Fig. 1). The Internal Zones, which constitute the so-called AlboranCrustal Domain, include Late Paleozoic to Triassic different grademetamorphic complexes. These units were affected by a Tertiarycompression, followed by a pervasive extensional event that started inthe early Miocene (e.g., Garca-Dueas et al., 1992; Crespo-Blanc et al.,1994). The External zones correspond to an imbricate system thatdeforms the cover sequences of the south-west Iberian and north-westMaghrebian paleomargins (e.g., Crespo-Blanc and Campos, 2001;Platt et al., 2003a,b). The compression in the External Zones was</p><p>e BeticRif Orogen and the associated Neogene basins.</p></li><li><p>contemporary to the extension in the Internal Zones. The Flysch Unitscomprise deep marine turbidites that were transported westwards inan imbricate system of thrusts that crop out mainly in the western-most part of the orogen (e.g., Crespo-Blanc and Campos, 2001;Michard et al., 2002) (Fig. 1). The Internal and External zones, as wellas the Flysch Units, are roughly continuous from the Betics to the Rifchains. In the Atlantic margin, the direction of the structure swingsfrom the Betics Cordillera to the Rif, west of the Gibraltar Strait(Iribarren et al., 2007). This swing in the structure produces an arcuateshape that has led different authors to refer this orogenic system asthe Gibraltar Arc System.</p><p>According to their position in the orogen and their genetic origin,the Neogene basins are here divided in some internal basins thatinclude the Alboran Basin and the intramontane basins, and theexternal basins that correspond to the Guadalquivir and Rharbforeland basins, related to the Betics and Rif chains, respectively,and the Gulf of Cadiz basin including the South Iberian and NorthwestMoroccan Atlantic Margins.</p><p>The Alboran Basin is situated in the westernmost Mediterraneanbetween Iberia and Africa and represents the innermarine basin of theBeticRif orogen. Its basement ismade ofmetamorphic complexes thatform the Internal Zones of the Betics and the Rif, and by Neogenevolcanic rocks. This basin evolved in an ENEWSWextensional regimefrom the late Oligocene or early Miocene to the Tortonian (at approx-imately 9 Ma) (Comas et al., 1992; Rodrguez-Fernndez et al., 1999).FromTortonian to Present theAlboran Basin records folding and strike-slip faulting associated to a roughly NNWSSE compressive tectonicregime (Comas et al., 1999).</p><p>Other sedimentary basins that formed and evolved during theNeogene in the BeticRif orogen are represented by the intramontanebasins. These basins were under sea level during Tortonian times,when they were individualized, and uplifted above the sea level in</p><p>Vera,1992). Currently they constitute small nonmarine basins most ofthem situated over the contact between the Internal and the Externalzones (Fig. 1).</p><p>The external basins were already marine sedimentary basins whencompression started to affect these areas. The Guadalquivir and Rharbbasins evolved from foredeep to foreland basins during theMiocene bydownward exure of the basement in response to the loading of thethrusted and imbricated External Units (Sanz de Galdeano and Vera,1992; Berstegui et al., 1998; Garca-Castellanos et al., 2002). To thewest, the successive imbricate units of the BeticRif orogen emplacedwestwards from early to late Miocene invading the Atlantic Marginregion that includes the Gulf of Cadiz and the NW Moroccan marginforming the so-called Gulf of Cadiz ImbricateWedge (Maldonado et al.,1999; Grcia et al., 2003a; Gutscher et al., 2002; Iribarren et al., 2007).</p><p>3. Sedimentary volumes</p><p>A rst objective of this work is to quantify the total sedimentaryvolume that is related to the building-up of the BeticRif orogenthrough the Neogene. To this end we have used different methodol-ogies according to the available data for each analyzed tectonicdomain. Depending on the basin these data have consisted of isopachmaps in which case the volume can be directly calculated, deep wellsreaching the basement, seismic proles and geological cross-sections.</p><p>In addition to the total volume, we calculated the partial sedimentarysupplycorresponding to several predened time intervals. These intervalshave been chosen according to theirwide-spread recognition in the studyarea corresponding to: i) early to middle Miocene (c.a. 24 to 11.6 Ma);ii) late Miocene (c.a. 11.6 to 5.3 Ma), and iii) PlioceneQuaternary (5.3 to0 Ma). In the Alboran Basin, however, the rst time period spans from20.4 to 9Ma. Similarly, in other basins the time spanmay vary slightly. Inthis section we present the data and the different methods used in each</p><p>). The f</p><p>70 L. Iribarren et al. / Tectonophysics 475 (2009) 6884different ages from late Tortonian onwards (Sanz de Galdeano and</p><p>Fig. 2. Isopach map of Neogene sediments in the Alboran Basin from Torne et al. (2000volume derived from the Betics and the Rif. To the East of this line, sediments likely com</p><p>Alboran Basin, SAB: South Alboran Basin, YB: Yusuf Basin.basin, together with the results derived from the calculations.</p><p>e dashed line indicates the limit established in this study to calculate the sedimentaryrom the Atlas Mountains or are mainly pelagic. WAB: West Alboran Basin, NAB: North</p></li><li><p>3.1. The Alboran Basin</p><p>The data used to calculate the Neogene sedimentary volume in theAlboran Basin come from the gridded maps elaborated by Soto et al.(1996) and Torne et al. (2000), who constructed a sediment isopachmap based on the interpolation of 9000 km of multichannel seismicproles (Fig. 2). The isopach map shows an irregular inll, with aprominent depocentre in the West Alboran Basin where sedimentsreach a thickness of more than 8 km. The depocentre is elongated andarcuated matching the shape of the BeticGibraltarRif. The northernbranch of the basin continues into the North Alboran Basin (NAB in Fig.2). The sedimentary thickness is reduced in the centre of the basinwhere it has a mean value of about 500 m.</p><p>The Alboran Basi...</p></li></ul>