PLEISTOCENE LACUSTRINE BASIN OF THE EASTDOMAIN OF GUADIX-BAZA BASIN

(GRANADA, SPAIN): SEDIMENTOLOGY,CHRONOSTRATIGRAPHY, AND

PALAEOENVIRONMENT

TRINIDAD TORRES 1, JOSÉ EUGENIO ORTIZ', VICENTE SOLER2, E. REYES) ,

ANTONIO DELGAD03, MARUJA VALLE4

, JUAN FRANCISCO LLAMAS1, RAFAEL

COBOs, RAMÓN JULLA/', ERNESTINA BADAL7

, MIGUEL ÁNGEL GARCÍA DE LA

MORENA', MARÍA JESÚS GARCÍA-MARTÍNEZ 1, JORGE FERNÁNDEZ-GIANOTTI

s,JOSÉ PEDRO CALV09

, ANTONIO CORTÉS 10

, Laboratorio de Estratigrafía Biomolecular. E.T.S.1. Minas, Madrid2 Instituto de Agrobiología y Productos Naturales (CSlC), La Laguna (Tenerife).

3 Estación Experimental del Zaidín (CSIC), Granada4 Opto de Paleontología, Universidad de Salamanca

5 CEOEX, Madrid.6 Instituto de Ciencias de la Tierra Jaume Almera (CSIC), Barcelona.

7 Opto. de Prehistoria y Arqueología. Universidad de Valencia8 Instituto Geológico y Minero de España, Madrid

9 Opto. de Petrología y Geoquímica, Universidad Complutense de Madrid10 Empresa Nacional de Residuos Radiactivos, Madrid.

ABSTRACT

We present the study of the lacustrine deposits of the eastern part of the GuadixBaza basin (GBE), an intramontanous basin which remained isolated from erosiveconditions until upper Middle Pleistocene times. The facies distribution shows a clearcentripetal pattern, with alluvial fan systems reaching the GBE through still visiblegorges, all of them which were fed by run-off as well as groundwater from karst withdissolved sulphates from marine Miocene and Upper Triassic age evaporites. A complexsystem of sandy beaches, mud flat playa and marginal lacustrine sands connccted centrallacustrine environments and marginal alluvial fans (sheet flow deposits). After fíeldmeasurements, paleomagnetism determinations and amino acid racemisation, a"composite-stratotype-section" was established that provided a time-and-spaceframework for the GBE lacustrine deposits. Unfortunately, all fossils in the centrallacustrine facies were destroyed by gypsum diagenesis.

In the "composite-stratotype-section" (average sedimentation rate of 22 cm/ka)samples were collected at 50 cm intervals. After sample washing, sieving, and ostracoderecovery, an almost continuous ostracode species lag was obtained. The ostracode recordshow abrupt and frequent changes in lake water salinity occurred during the LowerPleistocene, and high salinity during the upper part of the Lower Pleistocene and the first

152 T. Torres el al.

half million years of the Middle Pleistocene prevailed (Cyprideis torosa (Jones)dominance). The uppermost part ofthe section, characterized by highly saline conditions,is located in the Orce Corridor, where geological data indicate restricted basin geometryand local hydrological input from saline groundwater. Further studies are needed toinvestigate the role ofthese conditions in the origin ofthese high salinity values.

Keywords: Guadix-Baza basin, palaeosalinity, Pleistocene, magnetostratigraphy,aminostratigraphy, limnogeology, Spain

RESUMEN

Se presenta el estudio de los depósitos lacustres de la parte este de la Cuenca deGuadíx Baza (GBE), una cuenca intramontañosa que permaneció preservada de laerosión hasta la parte superior del Pleistoceno medio. La distribución de facies muestrauna clara distribución centrípeta con sistemas de abanicos aluviales que alcanzaron laGBE a través de cañones todavía hoy visibles, aunque también se produjeron aportes deexutorios kársticos con sulfatos disueltos de las evaporitas del Mioceno y Triásicosuperior. Un sistema complejo de playas arenosas, llanuras fangosas y arenas lacustresmarginales conectaba los ambientes lacustres centrales y los depósitos de manto dearroyada de los abanicos aluviales. A partir de trabajo de campo, paleomagnetismo yracemización de aminoácidos en moluscos y, principalmente, en ostrácodos se haestablecido una sección estratigráfica tipo compuesta. El principal objetivo de este trabajoes establecer las relaciones espacio-temporales de los depósitos lacustres de la GBEaunque se evitó trabajar en las facies lacustres centrales, ya que en ellas todos los restosfósiles habían sido destruidos por la yesificación.

En la seccion estratigráfica tipo (con una velocidad media de sedimentación de22 cm/ka) se tomó una muestra cada 50 cm. Se obtuvo la curva de variación de especies yse han documentado cambios de salinidad muy frecuentes durante el Pleistoceno inferior,mientras que en la parte superior del Pleistoceno inferior y en el primer medio millón deaños del Pleistoceno medio predominaron condiciones de alta salinidad (dominancia deCyprideis torosa (Jones). El predominio de esta especie en la parte superior del registronecesitará análisis posteriores, isotópicos, ya que en el área de Orce las condicioneslocales como la restricción geométrica del Corredor de Orce y la presencia d~ fuentessalinas podría haber condicionado este hecho.

Palabras clave: cuenca de Guadix-Baza, paleosalinidad, Pleistoceno, magnetoestrati­grafia, aminoestratigrafia, limnogeología, Spain

1. INTRODUCTION

Among all the Alpine basins located on the lberian Peninsula, theGuadix-Baza basin appears to be a very singular realm where almost"continuous" continental sedimentation took place from the Pliocene until ca.300 ka BP, a period commonly characterised in Europe by erosive processes. Theaim of this paper is to describe the stratigraphy and sedimentology of the eastem

Pleistocene lacustrine basin ofthe east domain ofGuadiz-Baza basin 153

part of the Guadix-Baza basin (GBE), where a large number of palaeontologicallocalities, some with abundant lithic tools, have been studied. Achronostratigraphic framework is also established based on palaeomagnetism,amino-acid racemization, and paleoenvironmental evolution of ostracode speciesassemblages.

2. GEOGRAPHICAL AND GEOLOGICAL SETTING

The Guadix-Baza basin (Fig.l) is a long and narrow basin (4,500 km2)

with its majar axis oriented NE-SW within the Betic Range. Accarding to Pous etal. (1995), the Guadix-Baza basin is nested between the Internal and ExternalZone of the Betic Range.

j

(;U3<!,a¿~~I:'~~R__I'~/

"

IOkm

\[EDITERRA........ EA...'\ SEA

Figure 1. Geographical overview of the Guadix-Baza basin and other Iberian Cainozoicbasins. 1: Guadix-Baza basin. 2: Guadalquivir basin. 3: Guadiana basin. 4: Tajo basin.5: Duero basin. 6: Ebro basin. Other minor basins are not represented.

Figura l. Situación geográfica de la cuenca de Guadix-Baza y otras cuencas cenozoicas.1: cuenca de Guadix-Baza. 2: cuenca del Guadalquivir. 3: cuenca del Guadiana. 4:cuenca del Tajo. 5: cuenca del Duero. 6: cuenca del Ebro. Otras cuencas menores nose han representado.

154

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l!TM: 1211320 l'T!\I: ·UIU20

T. Tarres el al.

UTM:S75H7U

o: B~drock(Mesozoicl

1:PHocenema,ineundsandlutlUos

2:LlmnlonuoIBolardo­Galeraantlcllne

3:sandsandconglo"",ramsIG+Scb+fs)

4: Sands,lultlesandlimulonuISm+SI+Fy)

5: Sands.gYp$arenites.gypsumandc¡o,bonalesIFYl+Fm+Fl+Sy+DL+Oly+Yml

6: Limeslones.\Iypsumandsands(OL<·DLytFc.O,ceUmesloneHo,izonl

7: Conlllome'3Ies(allu"iallanpiedmontj

8:lftdhl'enc13le<lalluvlal ..ndftu"""deposils

5km

Figure 2. Simplified geological map of the east (Baza) domain of Guadix-Baza basin(GBE). LAF=Laneros AIluvial Fan, OAf= Orce AIIuvial Fan, HAF= HuéscarAIIuvial Fan, CAF= CúIlar AIIuvial Fan. CTB: Cortes de Baza; CNOR: Norte deOrce; CGAL: Cementerio de Galera; LAN: Laneros; BEN: Benamaurel; SCC: SanClemente channel; VMS: Venta Micena; ERE: East of río Baza; CBS: CúIlar-Bazastratigraphical sections

Figura 2. Mapa geológico simplificado del sector este (Baza) de la cuenca de Guadix­Baza (GBE). LAF= Abanico aluvial de Laneros, OAF= Abanico aluvial de Orce,HAF= Abanico aluvial de Huéscar, CAF= Abanico aluvial de CúIlar. CTB: Cortes deBaza; CNOR: Norte de Orce; CGAL: Cementerio de Galera; LAN: Laneros; BEN:Benamaurel; SCC: Canal de San Clemente; VMS: Venta Micena; ERB: Este de ríoBaza; CBS: CúIlar-Baza

Pleistocene lacustrine basin ofthe east domain ofGuadiz-Baza basin 155

The Internal Zone consists of four stacked nappe complexes containingrocks of Triassic age or older. The External Zone is composed of allochthonousforeland and Iberian Plate continental margin material; this zone comprises adeformed wedge of dominantly marine rocks ranging from Mesozoic to LowerMiocene age along with plastic evaporite and mudstone layers of Triassic age(Banks and Warburton, 1991).

The Guadix-Baza basin is a foreland basin formed during the AlpineOrogeny from the Upper Tortonian-Lower Pliocene (Vera, 197üb; Soria, 1996).The presence of backthrusted Triassic evaporites and mudstones in this basin wasresponsible for local rock strain during the Pliocene and Pleistocene. The basinfill contains sediments from the Pliocene until the Recent (Fig. 2). By the time ofthe Upper Tortonian, sedimentation was continental in origin with the depositionof alluvial and palustrine-lacustrine sediments in two well-marked depocentresdivided by the Jabalcón threshold: Guadix or west domain (GBW) and Baza oreast domain (GBE). During the upper Middle Pleistocene, the GBE experiencedan erosional episode documented by a general progradation of alluvial fansystems towards the central part of the basin and the erosion of all the precedingcontinental Pliocene and lower Middle Pleistocene stratigraphical sequences.Faults affecting underlying Mesozoic rocks were responsible for local tilting,which allowed for preservation of the upper Middle Pleistocene stratigraphy.These faults controlled the direction of streams and their related valleys.

The sediment fill of the GBE comprises gravels/conglomerates,sands/sandstones, lutites, carbonate rocks and gypsum. The source rocks at thenorth rim of the basin are limestones and dolostones of Mesozoic age as well asevaporites and mudstones of Triassic age while in the southern edgemetamorphic rocks (marble, schist) are also present. Recyc1ing of ancientevaporites has affected sedimentation as evidenced by the saline springs whichfeed rivers today in a way common in all Iberian cenozoic basins (Ortí et al.,1988). The detrital gypsum deposits are made of intrac1asts of intrabasinal originin the way proposed by Sanz et al. (1994).

3. SEDIMENTOLOGY

Former sedimentological and stratigraphical studies of GBE were carriedout by Vera (1969, 197üa, 197üb), Peña (1985), Vera et al. (1984), Soria et al.(1987), and Gibert et al (1992).

The sedimentary evolution of the basin was inf1uenced greatly by itsirregular shape and the unequal inputs of the catchments feeding the alluvial fanswhich display different centripetal patterns (Fig. 2) from the basin borders to thecentral portion of the basin. The different alluvial fan systems distinguishedinc1ude the most important one, the Laneros Alluvial Fan (LAF) (Fig. 2), which

156 T. Torres el al.

can be described as a high-efficiency alluvial fan or as a "humid alluvial fan" inthe sense proposed by Collinson (1996).

NEOrce

NWCortesde Baza

5 km

== Fresll\\ atcr ostracodcse BrackISIH\'aler oslrncodcs

Figure 3. Schematic fence diagram of facies distribution in GBE. 1: gravel/conglomerates(G); 2: channeled sand/sandstones and gravel/conglomerates (Scb); 3: Massivesands/sandstones (Sm); 4: Fossiliferous sands/sandstones (Sf); 5: massive lutites(Fm), laminated lutites (Fl); 6: carbonate lutites-marls (Fe), dolomitic limestones andlimestones (DL), dolomitic limestones and limestones with gypsum (DLy); 7:laminated lutites and gypsum (Fyl); 8: massive gypsum (Ym); 9: sandy/gravelIylutites (Fs); 10: lutites with displacive gypsum (Fy); 11: gypsiferous sands/sandstones(Sy).

Figura 3. Panel de correlación de facies en GBE. 1: gravas/conglomerados (G); 2:arenas/areniscas y gravas/conglomerados canalizados (Scb); 3: arenas/areniscasmasivas (Sm); 4: arenas/areniscas fosilíferas (Sf); 5: lutitas masivas (Fm), lutitaslaminadas (Fl); 6: lutitas carbonatadas-margas (Fe), calizas dolomíticas y calizas(DL), calizas dolomíticas y calizas con yeso (DLy); 7: lutitas laminadas y yeso (Fyl);8: yeso masivo (Ym); 9: lutitas arenosas/con grava (Fs); 10: lutitas con yesointrasedimentario (Fy); 11: arenas/areniscas yesíferas (Sy).

The LAF interfingers with a lacustrine system in a typical radial faciesdistribution (Fig. 3) with sorne exceptions (Fig. 4a), though a clear lacustrineexpansion is documented towards the top of LAF through the lack of marginallacustrine sand facies and a compression of fan facies. Other identified alluvialfan systems are: Huéscar Alluvial Fan (HAF), Orce Alluvial Fan (OAF) andCúllar Alluvial Fan (CAF) (Fig. 2). In these cases, the alluvial fan-lakerelationship is radially distributed but not well-commingled (Fig. 3,4b). Alluvialfan-lake deposits in the GBE differ markedly from those found in the GBW. Inthe westem part of the basin, subsidence ratios were much higher, so thatsediment thickness in the GBE on the shallow "Mesozoic bedrock" (IGME,1988) were significantly thinner.

Pleistocene lacllstrine basin o{the east domain o{Clladiz-Baza basin

3.1.Facies description

157

Due to the large number of facies which can be distinguished in the GBE,the facies, their descriptions, and interpretations are listed in Table 1.

3.2. Facies interpretation

AH the described facies can be grouped into three different depositionalsettings sensu Rodríguez-Aranda et al (1991): alluvial fan (G, Scb), transitionalenvironment (Fm, Fs, Fy) and shallow-lacustrine realm (Sm, Sf, Sy, Fc, Fy1, Fy,Ym, DL, DLy, L). Alluvial fans and shaHow lakes constitute very distinctivepaleoenvironments in the GBE -with the transitional environment laterallypassing into both alluvial fan and lacustrine environments.

3.2.1. Alluvialfan

Near the alluvial fan apex, facies G is dominant but three subfacies arepresent: (1) poorly-sorted subangular to angular limestone and dolostone pebbles(only micaschists appear near the southem fringe of the basin) in a sandy ormuddy matrix in beds of 0.S-1.0 m thickness, (2) normally graded and crudelystratified carbonate boulders and gravel stacked as up to 1 m-thick beds withnon-erosive flat bottoms with carbonate cement and (3) red-brown sandy­gravelly lutites (Fs) stacked in beds 0.1 O-O.S m in thickness containing variableamounts of scattered quartz and carbonate sand and gravel. These three subfaciesof facies G are interpreted as alluvial fan proximal facies consisting of (1) debrisflow, (2) sheetflow and (3) mud flow deposits (Bull, 1972; Miall, 1981; Alonso­Zarza et al., 1990; MacCarthy, 1990; Alonso-Zarza et al., 1993; Nemec andPostma, 1993).

In the Laneros alluvial fan (LAF), cut and fill channels with stronglyscoured bases are commonly eroding fom1er lacustrine deposits. These channelinfil1s are made of single or muItiple episodes of normal1y graded gravel sets.The total thickness of these channel infil1s is more than 3 m with a singleerosional episode ranging from 0.2 to 1.0 m.

In some cases Facies G grades downs10pe to the Scb facies consisting ofbroad sandy bodies whose width varies from l-lS m and the thickness ofindividual sets can reach 1m but the total thickness can reach Sm. Grave1 c1astsappear as lag deposits, some cm thick, or beds more that I.S m-thick. Clasts aremade of carbonate rocks with schist clasts common in the southem edge of thebasin. Cong10merates can be strong1y carbonate or rare1y gypsum-cemented andsoft pebbles of mudstone or micrite are not uncommon. Sedimentary structuresinelude massive bedding to trough cross-stratification as sets with thicknessvarying from some dm to more than 1m. This facies association can be

158 T. Torres el al.

interpreted as mid-toe alluvial fan deposits where incipient and mobile channelbelts appeared (Friend, 1983; Cabrera et al., 1985; Alonso-Zarza et al., 1993;Nemec and Postma, 1993).

Table 1. Description of the main facies differentiated in the alluvial and lacustrinedeposits ofthe GBE basin. Colors are from Goddard et al. (1984).

Tabla l. Descripción de las principales facies diferenciadas en los depósitos aluviales ylacustres de la cuenca GBE. Los colores se han tomado de Goddard et al (1984).

FaciesGravell conglomerates (G)

Cross bedded sand-gravellconglomerates (Scb)

Fossiliferoussands/sandstones (Sf)

Massive sands/sandstones(Sm)

Gypsi feroussands/sandstones (Sy)

Sandy/gravelly lutites (Fs)

Massive lutites (Fm)

Laminated lutites (Fl)

Description/lnterpretationMesozoie carbonate roeks and metamorphie (sehist, marble) elasts. Poorly towell sorted. Well or poorly (breeeia) rounded. Rarely carbonate eemented.Sandy-Iutitie matrix sometimes present. Color (5R 6/6. lO R 4/6). Thieknessbetween 0.1 m to 20m.Apex-alluvial fan

Cong10merates contain calcareous rock fragments. usually well rounded andwell sorted. Sand grains inelude carbonate rock fragmcnts with variable amountsof quartz grains (Iithic arenite). Fine-to coarse-grained. Parallel lamination.planar cross bedding. trough cross-bedding and ripple cross-Iamination arecommon. 10 YR 8/2, 10 YR 8/6 colors dominate. Cement, when present, iscalcite. Thickness between sorne decimetres to 20m.Mid-toe alluvial fan (sheet flow and channels)

Sand grains are Mesozoic carbonate rock elasts (calcarenite). Very fine to verycoarse grained. Well sorted. Can show nonnal grading as well as parallel andripplc cross-Iamination. Fossils (ostracods and foraminifera) can be dominant(bioarenite). 5 G 611, N5 colors. lO YR 5/6 color when weathered. Sometimesgypsum- andlor carbonate cemented. Thickness between sorne decimetres to20m.Lacustrine marginSand grains are Mesozoic carbonate rock elasts (ealearenite). Very fine-to verycoarse-grained. Well sorted. Azoic. Sometimes gypsum- andlor carbonate­cemented. Pedogenic-carbonate accumulations. 5YR 5/6 color. Thicknessranging from sorne decimetres to 10m.Lacustrine marginlsheet flow

Detrital gypsum of intrabasinal provenance (gypsarenite). Very fine-to medium­grained. Well sorted. Can show nonnal grading. parallel. and ripple cross­lamination. Fossils (ostracodes, gastropods) can be very abundant. Chert nodulesand opalised wood. Gypsum-cemented. 5 GY 6/1 color. From sorne centimetresto 1m.Central lacustrine.Massive to crudely parallel laminated lutites with scattered gravel and sand.Pseudoglcy and bioturbation. 5 R 4/6 and 5 YIR 5/6 colors. Thiekness betweensome deeimetres to 15 m.Transitional (sheet flow)

Massive lutites with interbedded gravellconglomerate and sand/sandstone sheets.Carbonate or gypsum eemented. Rare terrestrial and/or freshwater gastropodshells. Ostracodes are frequent. Selenite beds. Pedogenie carbonate. N9 - 10 YIR8/2 color. Thiekness from some eentimetres to 10m.Transitional.Lutites with a distinetive lamination of white-grey 1-2 mm thiek lutite laminaealtcmations. Carbonate eemented. Selenite beds. Thiekness from sornecentimctres to 17 metres.

Pleistocene /acustrine basin ofthe east domain ofGuadiz-Baza basin 159

Centrallacustrine

Carbonate lutites-marls (Fc) Massive calcareous/dolomitic lutites/marls with fossils (ostracodes, gastropods)10 YR/2 ~ N9-1 OYR 8/2. From sorne decimetres to 3 m.Lacustrine

Laminated lutites and Altemating gypsum (N 9) and lutite (5 G 611) continous laminae 1-3 mm thick.gypsum (Fyl) Ostracodes are common. rare bioturbation. Rare undulating lamination.

Maximum thickness 7 m.Lacustrine (central saline lake)

Lutites with displacive Azoic massive lutites (5 GY 411. N9 and 10 R 6/6) with variable amounts ofgypsum (Fy) randomly-oriented lenticular gypsum (10 YiR 4/2) entombing insect larvae and

ostracodes. Gypsum lenticles can reach 25 cm in diameter. From sornecentimetres to 3 m.Transitional (dry saline mudflat)

Massive gypsum (Ym) Some bioturbation (burrowing) traces still visible (5 mm in diameter). 10 YR412 -10 YR 8/2 colors. Secondary chert visible. From some centimetres to 8metres.Lacustrinc (central)

Dolomitic lil11estones and Fine-grained (mieritic) with variable amounts of terrigenous (extraclasts) lutitelimestones (DL) and sand-size carbonate clasts, grainstones. Freshwater and brackish water fossil

(gastropods) shells are locally very abundant. Black-brown chert concretionaryaggregations are frequent. Plant stems. 5 Y 6/4, 10 Y 8/2 colors. Thickness fromsomc centimetres to 5 l11etrcs.Shallow carbonate l11argin/ pondo

Dolomitic limestoncs and As DL but with variable amounts 01' displacive gypSUl11 crystals which. whenlil11estones with gypSUl11 dissolved, originate moldic porosity. Thickness from some centimetres to 5(DLy) metres.

Shallow carbonate marginl pondoLignite and peaty lutites (L) Tme lignite seams with still visible but rare (microscopic) phytoclasts; charcoal;

phoetid black lutite beds some centimetre thick with plenty 01' fossil (vertebrate.gastropods and ostracodes) are common. Thickness from sorne centimetres to 2m.Palustrine linked to alluvial fans andlor palustrine saline lake

3.2.2. Transitional

Typical alluvial fan facies (G and Scb) grade into red-coloured rnassivelutites (Frn). At the Orce and Huéscar alluvial fans (see Fig. 3), G and Scb areinterbedded with very fine sand and rnicaceous silt. These facies are not wel1developed in the Cúllar Alluvial Fan because both G and Scb facies abruptlyinterfinger with lacustrine deposits with cornmon scattered sand and gravel aswell as bioturbation (roots) traces (Fs). These facies has been described as c1ayplaya lake (Hubert and Hyde, 1982) or c1astic playa (Kendall, 1984), but a sheet­flow linked origin cannot be discarded in sorne cases.

Fy is one of the rnost cornrnon facies in the basin: grey or brown-beigelutites. Sedirnentary structures include rare parallel larnination and usuallymassive bedding with beds up to 2-3 rn in thickness. Sorne bioturbation(burrowing) is present and gypsurn occurs as cernent or as srnall-sized gypsurncrystals. We interpret these facies as representative of a transitional environrnentbetween the alluvial fan and shallow-Iacustrine realrns. In al1 cases lacustrine

162 T. Torres el al.

waters after evaporation, were settled and where drifted terrestrial plant remainsdid not arrive.

One of the best examples of palaeoenvironment (1) is the Venta Micena­1 palaeontological site (Fig 2 for location and Fig. 6 for description) where,according to Anadón et al. (1987), the palustrine sediments are dominantly madeof dolostones, dolomitic marls, and black-grey lutites. The biomarkers obtainedin a sample from this site (Table 2) indicate an extrabasin origin (predominantlong chain alkanes represent organic matter inputs from terrestrial plants),transported through the alluvial fan channels and drifted into the lacustrine realm.

Table 2. Predominant n-alkane and long chain alkanes to short chain alkanes ratio in twoGBE samples. n-C29 and n-C3) alkanes and high long chain/short chain ratiosrepresent organic matter inputs from terrestrial plants while n-C)7 and n-C 19 alkanesand short long chain/short chain ratios derive from microorganisms and/or algae.

Tabla 2. n-alcano predominante y ratio de cadenas largas de alcanos respecto a cadenascorta de alcanos en dos muestras de GBE. La predominancia de alcanos n-C29 Yn-C31y ratios altos de cadenas largas de alcanos respecto a cadenas corta de alcanos reflejaaportes de materia orgánica procedente de vegetación terrestre mientras que lapredominancia de alcanos n-C)7 y n-C)9 Y ratios bajos de cadenas largas de alcanosrespecto a cadenas corta de alcanos reflejan aportes de materia orgánica procedente demicroorganismos y/o algas.

Sample

VentaMicena-l

GBES-206

Predominant n-alkane

n-C29 and n-C31

n-C)7

L(n-C24) alkanes/L(n-C<23) alkanes

7.75

0.72

Palaeoenvironment analogs for type 2 appear scattered throughout thebasin lacustrine record, from the Pliocene-Pleistocene boundary to the topmost ofthe "composite-stratotype-section". They appear as black lutite beds, sometimesvery continous, with a thickness ranging from 20 cm to 2 m; however, theassociated faunal remains are brackish water gastropods andlor pelecypods. Inthis case organic biomarkers, as in sample GBES-206, indicate an autochthonouscharacter being tentatively interpreted as derived from microorganisms (seeTable 2).

Oolomitic limestones (OL) and dolomitic limestones with gypsum (OLy)are very common facies in the GBE basin as beds usually ranging from 2-20 cmthick with a remarkable lateral continuity. In all cases they are calcilutitesstrongly carbonate-cemented. Rarely they have a chalky aspect with bioturbation.Sorne features as karstification, brecciation, and iron and manganese stainssuggest frequent subaerial exposure events. A 2-5 m-thick carbonate bed whichextends over sorne hundreds of square kilometres in the east domain of GBE

Pleistocene lacustrine basin ofthe east domain ofGuadiz-Baza basin 163

(Orce, Galera and Cúllar localities) (Fig. 2), named the "Orce LimestoneHorizon" (OLH), constitutes a wide and distinctive mesa. It consists oflimestones to dolomitic limestones with a wide variety of local subfacies in thecentral portion of the basin. They include: i) black micritic limestones withcentimetre thick bioclastic beds (lumachelle) made of freshwater gastropodsshells, ii) gypsiferous limestone comprising dissolution cracks and mosaicbreccia, iii) porous limestone containing moldic porosity consisting of dissolvedgypsum crystal voids (0.8 mm thick), iv) lenticular tuffaceous limestones sornedecimetres thick, v) massive lutites with displacive gypsum (Fy) crystals (up to10 cm) in units of variable thickness, and vi) calcareous and dolomitic marls withthicknesses varying between sorne centimetres to sorne metres. Towards thenorthem margin of the basin, sandy limestones (OL) and carbonate-cementedmassive sandstones (Sm) appear. We interpret facies OL and OLy in the wayproposed by Anadón et al (1987) as a shallow carbonate margin or pondo

jMassive sands/sandstones (Srn)

Massive ¡utites (Frn)Laminated lutites (FI)

Gravel/ _ Channeled _ Fossiliferous Dolomitie Iimestonesl Laminated lutites andconglomerates sands/ sands/ • limestones (DL) - gypsurn (Fyl)(G) sandstones sandstones (Sf) Dolomitie Iimestones/

and gravel/ IXimestoneswith gypsurn (DLy)

lJ\l ~~~::om\erates l'~ Massive gypsum

(Yrn)Carbonate lutites-marls (Fe)Dolomitie Iimestones/limestones (DL)Dolomitie limestones/limestones with gypsurn (DLy)

Larninated lutites

ood gyPT ('y']

Massive gypsum(Yrn)

Gravel/ Channeled Sandy/gravelly Lutites with Gypsiferouseonglomeralet sands/ -¡utites (Fs) -+ displaeive - sands/sandsto~(G) sandstones ~psum(Fy) (Sy)

and gravel/ """ !eonglomerates ~ ~

[!!J (Seh) Carbonate lutites­marls (Fe)Dolomitie Iimestones/limestones (DL)Dolomitie Iimestonesllirnestones with gypsum (DLy)

Figure 4. Facies distribution (A) in the Laneros Alluvial Fan (LAF) and (B) in Orce,Huéscar and Cúllar Alluvial Fans (OAF, HAF and CAF).

Figura 4. Distribución de facies en el Abanico Aluvial de Laneros Alluvial Fan (A) ydistribución de facies en los Abanicos Aluviales de Orce, Huéscar y Cúllar (B).

164 T. Torres el al.

(AA) CTBOSES.2B ~ Grave! ~ Mari Figure 5. Cortes de Baza2S0m -l...L..l.. .... ..L. él 0° 0 °0 ..L..I....l.....L.

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Pleistocene lacustrine basin ofthe east domain ofGuadiz-Baza basin 165

insufficient water to maintain a surface brine (Rosen, 1994) and evaporativepumping processes occurred (Hsü and Siegentaler, 1969).

Laminated 1utites and gypsum (Fyl) facies occurs as altemating gypsumand grey lutite fine lamination in the central portion of GBE. Sedimentary sty1eindicates chemica1 sedimentation altemating with siliciclastic input including adetrital gypsum contribution, which has been observed as very fine, even siltsize, sand beds 1-3 mm thick. Lowenstein and Hardie (1985) interpreted similarhalite/mud altemations as a result of dry/wet periods. This is not the case in thecentral portion of GBE because hollow, still articulated ostracode shells areextremely abundant, and they indicate little or no transportation as well as nodiagenesis. Laminae show a remarkable lateral continuity, tens of metres, and arecommonly interbedded with other facies, such as Fm and Fy, as well as with 1-4cm-thick selenite layers. In sorne places laminae sets are regularly undulated dueto gypsum crystal growth. Bell (1989) describes ondu1ated laminae in a salinelake in Chile and similar altemances have been observed in the Miocene depositsof the Tajo basin (Sanz et al, 1994; Ortí and Rosell, 2000).

Massive gypsum (Ym), is not very common in the basin. A singlemassive microcrystalline buff gypsum bed (thicker than 8m) occurs in theCementerio de Galera section (Figure 6). Due to the scarcity of pure gypsumbeds in the basin, this bed has been intensively mined to obtain plaster for localbuilding purposes. Because of diagenesis processes, there is no distinctivebedding feature although sorne phantoms of bioturbation indicate burrowing. Abrown 0.8 m-thick chert "bed" is visible at its topo In other zones we havedistinguished the plaster gypsum-ki1n bed ("nivel de yeseras") which consists ofa brown 1 m-thick massive gypsum bed, deeply weathered, which can befollowed for kilometres due to the conspicuous presence of dig ho1es and bumedwood ash deposits.

4. THE GHE COMPOSITE "COMPOSITE-STRATOTVPE-SECTION"AND ASSOCIATED SECTIONS

In order to find a pristine 1acustrine "composite-stratotype-section"containing minimal diagenesis for geochemical ana1yses, including amino acidsand stable isotopes, we selected more marginal lacustrine deposits with theminimal effects of gypsum dissolution. Also, the Lower Pleistocene record fromthe Orce strait was avoided because very low sedimentation rates and 10wsubsidence can be expected to contain sections with extensive hiati development.Therefore, the best section to perform geochemical analyses for its mostcontinuous stratigraphy was the Cortes de Baza section (CTB, location shown inFig.2). With the erosion ofthe uppermost part of this section in this part of GBE,the Norte de Orce section (CNOR) to the east was used to complete the Midd1ePleistocene lacustrine "composite-stratotype section". Therefore, a 356 m-thick

166 T. Torres el al.

composite-stratotype section of the Cortes de Baza and Norte de Orce sectionswas obtained at the palaeo-margins of the GBE lacustrine environment.Correlation was created through field observations, palaeomagnetism studies, andthe use of amino acid racemisation.

The amino acid stratigraphy (aminostratigraphy) strongly supported bypaleomagnetic stratigraphy and palaeontological dates aided in establishing ageboundaries. For example, the Pliocene age deposits crop out poorly in the eastemcomer of the GBE (see Fig. 2) and consists of marls and micritic lacustrinelimestones with common lignite seams. At this place the contact with theoverlying lower Pleistocene deposits is an erosive angular unconformity which,in sorne places, appears underlain by chert nodules anci/or by a karstified surfacewith aterra rossa infill of corrosion holes. In the central part of GBE, however,there is no unconformity marking the Pliocene-Pleistocene boundary, so it hasbeen established through palaeomagnetism. The top of the GBE stratigraphicalrecord is marked by erosive surfaces carved after the basin opening towards theGuadalquivir river valley. The GBE connection to the Guadalquivir river valleyproduced a general progradation of the already existing alluvial fans which firsteroded and later covered the former lacustrine deposits, building a bajada whichwas known as "glaci" i.e. "alluvial fan piedmont" (Fig. 2).

Isotopic studies on ostracode and mollusc shells allowed Bonadonna andLeone (1989) to postulate a restricted marine origin for the sediments of thebasin. It is now interpreted as a continental realm from the Lower Pliocene times(Soria, 1996).

For the description of the GBE sections we will concentrate on thecomposite-stratotype section. Secondary sections will complete the description ofthe main sedimentological aspects of the basin.

4.1. GRE Composite-Stratotype Section

4.1.1. Cortes de Baza section: UTM"ol/ol/1:201679; UTM/op:223670 (CTB)

This section is 253 m-thick (Fig. 5), extending from the east bank of theCastril river to the highest topographical point in the area (Cañada del Fraile) andwas partially described by Oms et al. (1994) and Calvo Sorando (in press). Fordescriptive purposes we have divided this section into three different parts: 1)Lower Lutitic Part (55 m-thick), 2) Sandy Intermediate Part (75 m-thick) and 3)Upper Heterolithic Part (123 m-thick).

The most striking features of the Lutitic Lower Part are: more than 1 m­thick charcoal unit at the bottom (L), 17 m of laminated lutites (Fl) with micriticlimestone (DL) intercalations, 6 m of fine-grained sandstone-calciarenites withmassive lutitic intercalations (Sm-Fm), 4 m of lutites with a thin gravellayer anda black lutitic bed at the top (Fm, G, L), 2 m of massive well-rounded and

Pleistocene lacustrine basin olthe east domain ofGuadiz-Baza basin 167

poorly-sorted gravels with a lutitic matrix and a non-erosive base and flat top(G), and 16 m oflutites (Fm and Fs) with at least 12 thick-bedded and sorne thinor very thin-bedded calciarenites (Sm). Sorne sand beds are laminated. Thecontact between sand and overlying beds is usually horizontal.

The Sandy lntermediate Part begins with more than 17m of calciareniteswhich are stacked in beds ranging from thick to very thick (St). Towards the topthere are sorne lutitic intercalations (FI and Fm). Above this part, there is analtemation of lutites (Fm) and sands- calciarenites (St) and gypsarenites (Sy)­with sorne beds of lutites with displacive gypsum (Fy).

The carbonate deposits (OL) of the Heterolithic Upper Part consist oflutitic limestones with plant stems (metre 130), micritic limestones and lutiticlimestones with moldic porosity (metres 155, 185, 205, 215, 220, 240) and marlsand carbonate lutites, commonly containing displacive gypsum (Fy). Sands aredominantly gypsarenites (Sy) but carbonate ami/or quartz grains are also present.One of the most typical characteristics of this part of the Cortes de Baza sectionis the presence of displacive gypsum: enormous lenticular crystals, sometimeswith a diameter up to 30 cm-long, which appear concentrated in sorne beds (Fy).A carbonate intra-fonnational breccia -result of the destruction of a formercalcrete bed was also identified (metre 238).

4.1.2. Norte de Orce section: UTMbo!!o!n:423770; UTM!op:337807 (CNOR)

The Norte de Orce section (Fig. 5) begins with 13 m of reddish fine­grained carbonate cemented sandstones (Scb) and lutites with little bioturbationand no fossil remains (Fs). Sandy bodies have planar or slight1y erosive bases andripple cross-Iamination is abundant; this can be interpreted as distal alluvial fanto dry mudflat deposits. Above this there are 45 m of an altemation of gray-bufflutites (Fm-FI) and sands (St) along with vertebrate remains. 0.3-3.0 m thick sandbeds (St) are common, rarely with slightly erosive bases and with "soft pebble"lag deposits. Bed limits are underlined by lutitic laminae. Sand beds can showparallel or ripple cross-Iamination and in one case (metre 26) sigmoidal cross­bedding is clearly distinguished. In the middle part of this section (metre 52)there are two beds of sands mostly massive (Sm), sometimes with ripple cross­lamination (Scb) where an extreme abundance of mica occurs but no fossils arepresent. Close to the top, the OLH appears as a cracked mosaic breccia ofcarbonate (Laznicka, 1988).

A 1.2 m thick massive gypsum bed (Ym) named "nivel de yeseras"(gypsum kiln bed) is another characteristic stratigraphical marker. Overlying the"nivel de yeseras" bed, 12 m of lutites (Fm) with sorne interbedded 0.2-0.6 mthick sand beds (St) appear. In this lutitic bed, a displacive gypsum bed (Fy),Cerastoderma shell accumulation, and sandy (Sm) seismite beds are verydistinctive features. The remaining part of the section has a dominant1y carbonate

168 T. Torres el al.

lutitic character (Fc) although there are 0.5-2.2 m thick interbedded sand units(St), sandy lutites (Fs), massive gray lutites (Fm), and two very thin lignite seams(L). There are also two lutitic beds (Fm) with abundant terrestrial and freshwatergastropod shells.

4.2. Associate Sections

The aim of this description is to offer a framework of the succession ofthe different facies described in the "composite-stratotype-section". For thispurpose we have selected sorne sections from the central lacustrine facies(Cementerio de Galera, Benamaurel and East Río Baza sections) and the alluvialfan deposits-palustrine-Iacustrine facies (Cúllar-Baza site, Venta Micena, SanClemente Channel and Laneros sections). The section locations are shown in Fig.2.

4.2.1. Cementerio de Galera section: UTMbo//om:386776; UTMtop:356768(CGAL)

The Cementerio de Galera section (Fig.6) can be considered to berepresentative of the transition between marginal and central lacustrine facieswith sorne considerable fluvial influence. The section is very heterolithic becausechemicallacustrine deposits appear: gypsum (Ym) and chert. Micritic dolomiticlimestones (OL), silicified micrites (OL), grainstones, and gypsiferous-calcareouslutites (Fm) constitute the üLH. The main part of the section containsinterbedded gypsiferous lutites (Fy) and gypsiferous sands (Sy and Scb).

4.2.2. Benamaurel section: UTMbo//om:276620; UTM¡op:296605 (BEN)

This section (Fig.6) is representative of the lacustrine basin central facieswhere channeled sediments are not present. This section has been described inCalvo Sorando (in press). The lower part of the section consists of 12 m ofinterbedded gypsarenites (Sy) and massive lutites (Fm), in sorne cases withdisplacive gypsum (Fy). A 40 cm-thick bed of marly limestones (OL) is overlainby an altemation of gray lutites (Fm) and gypsiferous sands (Sy) with two­millimetre-thick bioclastic beds made of almost intact Cerastodermadisarticulated shells accumulation. The middle part of the section can bedescribed as an altemation of composite bed sets of gypsarenites (Scb) with thin­bedded lutite intercalations (FI-Fm). Sandy beds commonly contain horizontaland ripple-cross-Iamination and are lenticularly-shaped with flat or slightlyconcave bases and planar or convex tops. Microselenite in lutitic beds is verycommon as well as enormous crystals of displacive gypsum and gypsum crusts.

Pleistocene lacustrine basin o[the east domain ofGuadiz-Baza basin 169

rare

<=

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In the uppermost part of this section, lutites (Fm-Fl) are dominant withdisplacive gypsum and medium- to thin-bedded detrital gypsum units (Sy).

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Figure 6. Cementerio de Galera (CGAL), Laneros (LAN), Benamaurel (BEN), SanClemente channel (SCC), Venta Micena (VMS), East of río Baza (ERB) and Cúllar­Baza (CBS) stratigraphical sections. (AA): ostracode samples for aminoacidracemization dating. The legend can be seen in Fig. 5.

170 T. Torres et al.

Figura 6. Secciones estratigráficas de Cementerio de Galera (CGAL), Laneros (LAN),Benamaurel (BEN), San Clemente channel (SCC), Venta Micena (VMS), Este de ríoBaza (ERB) y Cúllar-Baza (CBS). (AA): muestras de ostrácodos para datación porracemización de aminoácidos. La leyenda se encuentra en la Fig. 5.

4.2.3. East e<!río Baza section: UTMbollolll:257527; UTMrop:278514 (ERB)

This section represents the most central lacustrine facies of the GBEbasin. The visible bottom of the section consists of 7 m of beige lutites and veryfine, even silt size, detrital gypsum (Fyl); the individual lamina are several mmthick and the bedding is undulatory. This detrital gypsum/lutites altemation isoverlain by 7.5 m of grey lutites (Fm) with sorne detrital gypsum beds (Sy) anddisplacive gypsum (Fy). The section ends with more than 25 m of sands withparallel and ripple cross-Iamination (Scb). There ostracode shells constitutebioclastic sand beds several cm or even dm thick. Several centimetre thickbioclastic beds made of almost intact Cerastoderma sp. and Corbicula sp.articulated and disarticulated shells accumulations are very common as well.

4.2.4. Cúllar-Baza palaeontological site section: UTMbollolll:387580;UTMrop:388585 (CSS)

According to Alonso-Oiago (1990), the lower part of this section (Fig.6)consists of reddened poorly-sorted gravels (G) with strongly erosive basescontaining calcium carbonate cement and coarse sand matrix. Pebbles are madeof sedimentary and metamorphic rocks (dolostone, limestone, marble and schist).There are also thick beds of red carbonate-cemented coarse-grained sand crudelystratified or massive (Sm). Pedogenic carbonate accumulations occur as welldeveloped beds or noduli. Near the top of the section there is an abrupt change insedimentation with the appearance of Fc, Scb, and OL facies. Fc facies consistsof 30 cm of gray-green lutites with oxidized pyrite and carbonate stains; 1m ofblack to light brown lutites with mammal bone remains and many freshwatergastropods and land snails intercalated with a thin-bedded white micriticlimestone (OL). Scb facies consists of 2-m-thick medium-sized bioclastic sand(ostracodes) with ripple cross-lamination (climbing ripples). OL facies dominatein the upermost part ofthe section: 2.5 m ofmarlstones, marls, brown marls (Fc),and limestones (OL) which we identify as the üLH.

4.2.5. Venta Micena palaeontological site section: UTMbottolll:527768;UTM(~:516764 (VMS)

Venta Micena-I site, one of the most important paleontological localitiesof the Iberian Peninsula (Martínez, 1991), is located at the base of the section.

Pleistocene lacustrine basin ofthe east domain o(Cuadiz-Baza basin 171

The section (Fig.6) records the uppermost part of the Orce Alluvial Fan (OAF) ofred trough cross-bedded gravels and sands (Scb) with red massive lutiteintercalations (Fs) containing pseudogley, bioturbation, and root marks.

The invertebrate remains which have been used for amino acidracemisation analysis are in a 1 m-thick marly bed (Fc) with granules (gravel),charcoal, freshwater gastropods, and ostracodes. According to Anadón et al.(1987), the mammal-bearing bed is at the top of a crudely stratified, slightlylutitic limestone bed 3 m-thick, followed by 6m of partially cover~d lutiticlimestones, marls, dolostones, and dolomitic marls (OL and Fc facies); overlainby 7 m of trough-cross-bedded gravels and sands (Scb) and 3 m of crudelystratified dolostones and limestones (OL). 17 m of the section is made ofpartially-covered marls (Fc). Near the top 4 m ofthese beige marls are extremelyabundant Ammonia sp. and Cyprideis torosa shells. At the top the OLH iscomposed by ocherous micritic limestones (OL) with freshwater gastropodshells.

4.2.6. San Clemente Channel section: UTMhoIl0l11:442833; UTM(op:455821 (SCC)

This section (Fig.6) comprises the well known and dated MiddlePleistocene Huéscar-I palaeontological locality (Mazo et aL, 1985). ThePleistocene sediments lie disconformably on very hard Pliocene micriticlimestones with vug porosity and fossil freshwater molluscs which were tilted,faulted, and folded after local diapiric doming of Triassic evaporitic rocks. Thelower third of the section is lutitic in character, where green and gray colourspredominate over brown ones (Fm). Calcium carbonate pedogeneticconcentrations form stains, small nodules, and films throughout the lutites; it isinterpreted as a calcrete (Mack and James, 1993).

Near the base of the section there is a conspicuous lignite seam (L) 20-30cm in thickness with a significant number of freshwater gastropods In this part ofthe section the Huéscar-\ paleontological site is located in channeledconglomerates (Scb and G) which are strongly carbonate cemented. At the top ofthis part of the section there is a 3 m-thick bed set of poorly-carbonate-cementedfine-grained sandstones (Sf) with sandy lutite intercalations with abundantostracode shells (Cyprideis torosa), this bed can be traced for long distances. Atits top, a 4 m-thick set of altemating yellow medium-coarse grained sandstone(Sm) and lutites (Fm) with a massive \ m-thick gravel bed (G) at their top occurs.They are followed by 4.5 m of grey lutites (Fm) with ostracodes and white fine­grained carbonate cemented sandstone intercalations (Sm).

The top of the section comprise 10.5 m of massive green lutites withsorne fine-to medium-grained sand intercalations and two medium grained sandbeds (Scb) with climbing ripple cross-Iamination, flaser bedding, and ostracodes.

172 T. Torres el al.

4.2.7. Laneros section: SCC: UTMbottom:182733; UT~op:455821 (LAN)

This section (Fig.6) is associated with the Laneros Alluvial Fan (LAF)area. Massive fine-grained material with high carbonate content are the mostcommon (Fc), but rarely laminated (Fl), which are interpreted as being lacustrinein origino LAN can be divided into two unequal parts. In the first 37 m, reducedcolours (from a geochemical point of view) are common: white, light beige, orlight green. In the remaining 90 m of the section, red or dark yellow colours aredominant with sorne carbonate beds. Hydromorphic (pseudogley) features arevery common too. In the lower part of the section there is a very conspicuouspresence of palaeochannels of (G) representing debris flow processes; eachchannel deeply erodes the lower muddy lacustrine sediments, with enormousflute marks visible at the channel base. Medium-sorted boulder-sized clasts arecommon in these channels. In the uppermost 90 m of the section, thehydrological behavior of the LAF was probably quite similar to the lowermost(reduced colour) part - perhaps only slightly different source rocks were eroded.In the uppermost third of this uppermost part of the section, very coarsecarbonate-cemented sandstones with trough cross-bedding (Scb) are cornmon,being finally overlain by an altemation of gravel (G), sand (Sm-Scb), and lutite(Fm) beds. This section has not been intensively sampled formicropaleontological analysis but the constant presence of the ostracode generaPotamocypris and Candona indicate freshwater lacustrine conditions.

5. STRATIGRAPHY

According to previously published palaeomagnetic analysis (Oms et al.,1994; Agustí et al., 1999) and our own data (Ortiz, 2000), a magnetostratigraphyof the GBE of the representative "composite-stratotype-section" (Fig. 7) has beendetermined. Likewise, with the aid of the amino acid racemisation method, wehave established the chronostratigraphy of the GBE "composite-stratotype­section" (Ortiz, 2000 slightly modified by Ortiz et al., in prep.). For the aminoacid analysis, mostly ostracodes were sampled from several horizons becausethey have sorne characteristics that make them particularly useful for amino acidracemisation dating (cf. Ortiz, 2000). Unfortunately, in the Cementerio deGalera section (CGAL), almost all the ostracode calcitic shells were totallyreplaced by gypsum and the amino acids were destroyed. In the LAN section, theamount of recovered valves were not enough to analyse in Gas-Chromatography(ca. 1500-2000 valves).

5.1 Palaeomagnetism

A total of 168 samples were taken for palaeomagnetic analysis from the

Pleistocene lacustrine basin ofthe east domain ofGuadiz-Baza basin 173

GBE "composite-stratotype-section". The samples were drilled and oriented insitu with a Pomeroy D-280 l portable drill. After removing the weathered surfacematerial, cylindrical cores were prepared and measured in the PalaeomagnetismLaboratory of the Institut de Physique du Globe de Paris (IPGP), using a verticalcryogenic 2G magnetometer. All the samples were submitted to thermaldemagnetisation to 600°C at steps of 50aC in a low thermal gradient PYROXoven. The magnetic susceptibility was measured at every stage with aKappabridge KLY-2 instrument.

Samples recovered from the bottom of GBE "composite-stratotype­section" showed a palaeomagnetic po1arity change from normal to reverse inmetre 18 (Fig. 7), which is interpreted as the top of the Olduvai chron, that is, thePlio-P1eistocene boundary at 1.77 Ma (Cande and Kent, 1995). Thisinterpretation was based on both the age of the Cortes de Baza pa1aeontologicalsite (located approximately in metre 108 of the section) which, according toAgustí (1986), belongs to the Lower P1eistocene. The paleomagnetic data of theremaining lower part of the GBE "composite-stratotype-section" (Cortes de Bazasub-section) were previously collected by Oms et al (1994) and substantiated byOrtiz (2000). They found a negative magnetic polarity, which according topalaeontological data (Agustí, 1986), can be placed in the MatuyamaMagnetozone (Lower Pleistocene).

For most of the upper part of the GBE "composite-stratotype section", anormal polarity resulted and has been interpreted as belonging to the BrunhesMagnetozone. The negative reversa1 found close to the top of the GBE section isassigned to either the reverse Emperor (419 ka) or Lake Biwa III (ca. 412 ka)palaeomagnetic events.

5.2 Aminostratigraphy and Aminochronology

Aminostratigraphy consists of "placing in a stratigraphica1 order" sornegeological, palaeontological, and archaeologica1 sites in which fossils werepreserved under similar environmental conditions, inorganic geochemistry, andthermal histories. To apply this method, because of their nearly ubiquitousoccurrences ostracodes belonging mainly to the species Cyprideis torosa (Jones)(Superfarnily Cytheracea) were picked in numerous sites. However in on1y a fewcases, such as Venta Micena-1, valves be10nging to other genus, I1yocypris(Superfami1y Cypridacea) and as well as Cyprideis torosa, had to be se1ected. Inspite of the racemisation process being genus-dependent, these two differentostracode genera were employed to calculate the cross-ca1ibration racemisationand epimerisation rates. In fact, in previous studies (McCoy, 1988; Oviatt et al.,1999; Kaufman, 2000), only slight differences between D/L ratios (less than 0.05in old sarnples) from different phylogenetic ostracode groups (SuperfamiliesCypridacea and Cytheracea) were reported.

174

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T. Torres el al.

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Figure 7. Chronostratigraphy (magnetostratigraphy, aminochronology andlithostratigraphy) of the GBE "composite-stratotype-section" coupled together fromthe CTB (Cortes de Baza section) and CNOR (Norte de Orce section). Sornepalaeomagnetical data are from Oms et al. (1994). Aminochronology dates are fromOrtiz (2000) slightly modified in Ortiz et aL (in prep). Pm: paleomagnetism; aard:amino acid racemisation method.

Figura 7. Cronoestratigrafia (magnetoestratigrafia, aminocronología y litoestratigrafia) delas sección tipo de GBE. Algunos datos paleomagnéticos se han tomado de Oms et al.(1994). Las dataciones aminocronológicas son de Ortiz (2000) ligeramentemodificadas en Ortiz et al. (in prep).

1

Pleistocene lacustrine basin 01the east domain 01 Guadiz-Baza basin 175

Once the samples were recovered, they were sieved under running water,dried at room temperature, and studied under a binocular microscope todetermine the lithology and faunal assemblages. Ostracodes were sonicated andcleaned with water to remove sediment which might have been attached to theirvalves. Afterwards, we isolated 15-20 mg of the ostracodes' shells. The samplepreparation protocol is described in Goodfriend (1991) and Goodfriend andMeyer (1991) and involves (1) hydrolysis under N2 atmosphere in HCl for 20 h at100°C and, then, desalt in HF: (2) a two step process of amino acids isolationinvolving first esterification with thionyl chloride in isopropanol, and secondacylation by reaction with trifluoroacetic acid anhydride (25% indichloromethane). Injections of 1-4 aliquots ~l into a Hewlett-Packard 5890 gaschromatograph equipped with a Chirasil-L-Val fused silica colurnn (0.39 mm x0.25 ~m x 25 m) from Chrompack and an NPD detector were made. Integrationof the peak areas was carried out using the HP PEAK96 integration programfrom Hewlett-Packard. In this work, D-aIle/L-Ileisoleucine, D/L Leucine, D/Laspartic acid and D/L glutamic acid ratios were chosen to establish theaminostratigraphy of the GBE basin because of their reliability. According toTorres et al. (2000), isoleucine and leucine are the most reliable ones. Kaufman(2000) used aspartic acid and glutamic acid for ostracode studies.

In order to improve the reliability of the results, samples were recoverednot only in the "composite-stratotype-section" and associate sections, see figs. 5and 6, but also in sorne selected sites of GBE, whose stratigraphical position wasknown throughout relative dating (field-work), (Table 3), and in which Cyprideistorosa valves were picked. For the GBE aminostratigraphy study, 112 sampleswere used to perform a cluster analysis, employing the euclidean distance andcomplete linkage (Fig. 8).

Table 3. Geographical location of ostracode samples for aminoacid racemization datingfrom GBE basin.

Tabla 3. Localización geográfica de muestras de ostrácodos para datación porracemización de aminoácidos de la cuenca GBE.

SampleCVA4LQMPASSC

PTRFN-2

CTARICTAR2CTAR3

Coordinates (UTM)449769419816278777258776227717521744303728303732297740

Elevation (m)960900865890900980765780815

176 T. Torres el al.

Five aminozones were distinguished from GBE ostracode racemisationratios, whose descriptive statistics are in Table 4. Aminozones were named fram1 to 5. These five aminozone clusters designate a "chronostratigraphical order"with the higher racemisation values at the aminozone bottom, decreasing to valuetoward the top of the aminozone. Slight deviations can be explained as sampleerror factors.1.4 14

1.2

O.K

0.6

0.4 -5 --------------- -4--------------------------------- -----------

0.2

1.2

0.8

0.6

0.4

0.2

Figure 8. Similarity clusters of isoleucine, leucine, aspartic acid, and glutamic acidracemisationlepimerisation ratios of ostracode samples from GBE stratigraphicalsections. Each cluster is interpreted as an aminozone.

Figure 8. Análisis cluster de los ratios de racemizaciónlepimerización de la isoleucina,leucina, ácido aspártico y ácido glutámico en muestras de ostrácodos de las seccionesestratigráficas de GBE. Los cinco grupos diferenciados representan aminozonas.

Table 4. Mean and standard deviation of isoleucine, leucine, aspertic acid and glutamicacid D/L ratios used for the ostracode aminozones differenciation in GBE (n: numberof samples of each cluster).

Tabla 4. Media y desviación típica de los ratios D/L de la isoleucina, leucina, ácidoaspártico y ácido glutámico D/L que caracterizan a las aminozonas de ostrácodosdiferenciadas en GBE (n: número de muestras de cada grupo).

Aminozone D-allo/L-Ile D/L Leu D/L Asp D/L Glu1 (n=ll) 0.083±0.091 0.n9±0.098 0.759±0.037 0.687±0.0862 (n=15) 0.832±0.On 0.606±0.082 0.705±0.035 0.579±0.0393 (n=25) 0.678±0.067 0.457±0.066 0.637±0.062 0.469±0.0524 (n=51) 0.504±0.046 0.380±0.057 0.549±0.049 0.382±0.0365 (n=10) 0.316±0.037 0.280±0.On 0.492±0.026 0.344±0.042

Pleistocene lacustrine basin olthe east domain o(Guadiz-Baza basin 177

According to these aminozones, the stratigraphical sections werecorrelated with the GBE "composite-stratotype-section" as proposed in Fig. 10where the OLH is used as a base lineo The continuity of this horizon was testedthrough field work and confirmed by the homogeneity of aminostratigraphicaldata obtained in many samples taken at its lower contact. The Laneros section(LAN) was only tentatively correlated.

For age calculation, see Fig. 7, where we, employed the calibrated modelsdescribed in Ortiz (2000) slightly modified by Ortiz et al. (in prep.).

6. PALAEOENVIRONMENTAL INTERPRETAnON

The palaeoenvironmental characteristics of a lake can be inferred fromthe ostracode assemblages because ostracodes have well known environmentaltolerance ranges, e.g. salinity (Anadón et al., 1994).

OrccLimC'il.llncIlllrll.lI11

..... './(,,"

;'0',", AmllllllOO~ I

Figure 9. Aminostratigraphical and Iithostratigraphical correlation of the stratigraphicalsections of GBE. Note that LAN cannot be exactly correlated due to lack of data.

Figura 9. Correlación aminoestratigráfica y litoestratigráfica de las seccionesestratigráficas de GBE.

The presence of abundant ostracode shells in the sediments of the GBE"composite-stratotype-section" indicates a dominant lacustrine environment. The

178 T. Torres el al.

most common representative is Cyprideis torosa (Jones) that colonizes waterswith a wide range of salinity which can vary fram 0.5 %0 to 140 %0 (cf. DeDeckker, 1981; Carbonel, 1983). When salinity is high, it can be the only speciesremaining, constituting monospecific bioclastic accumulations (ostracodite), or itmay appear to be associated with other high salinity biomarkers such as otherostracodes (Loxoconcha minima and Leptocythere castanea), the pelecypodCerastoderma sp, and foraminifera (Ammonia sp) (Gasse et al., 1987). In thesecases we interpret the sedimentation was produced in a high salinity lake. In fact,according to Anadón (1989), the presence of thalassic fauna, as those citedaboye, suggests the existence of oligohaline to hyperhaline waters. However, atlow or moderate salinities, Cyprideis torosa (Jones) is found together with otherostracode species, mainly representatives of the Candona, I1yocypris andPotamocypris groups, and usually constitutes less than 50% of the valvescontained in a sample. The occurence of sorne lower salinity tolerant ostracodessuggests periods of significant freshwater input.

A total of 674 samples were recovered approximately at 40-50 cmintervals along the GBE "composite-stratotype-section" in order to determine theostracode species and their percentages. We decided to take a sample each 40-50cm because of the calculated sedimentation rate, 22 cm/ka (Ortiz, 2000). Whenthe percentage of C. torosa in a sample is very high, sometimes reaching 100%,the salinity would be high, in contrast to samples with small percentagesdesignating freshwater or slightly saline waters. Thus, we have plotted thepercentage of Cyprideis torosa valves recovered in the samples in Fig. 10, whichwe relate to the salinity ofthe lacustrine environment. According to the ostracodegenera distribution, even in the selected areas of the "composite-stratotype­section" located in a marginal zone of the central saline lacustrine realm, highsalinity conditions prevailed over low salinity ones. However a noticeabledistinctive hydrological behavior can be observed between metres 75 and 175 ofthe CTB subsection where low salinity ostracodes dominated. This fact suggeststhat during most of the Lower Pleistocene, a high frequency altemation of dryand humid conditions occurred, most likely linked to the Laneros Alluvial Fan(LAF) hydrological regimes. This cannot be interpreted as a change in the sourcerock because it remained unchanged over time, and only small neotectonic eventsaffected the area during the Pleistocene. With sorne scarce exceptions (orcoincidences) high or low palaeosalinities cannot be correlated to a specificsediment grain size. Sandy or lutitic sediments may contain dominantly highsalinity biomarkers (c. torosa) or not. In sorne parts of the "composite­stratotype-section", ostracodes are lacking because of low preservation orincompatible palaeoconditions, as in red alluvial fan sediments or sandy beds atthe bottom of the CTB subsection corresponding to the Laneros Alluvial Fanchannel deposits, or sand flat areas. In sorne other cases, as ostracode barrenlutites and sands the presence of large quantities of displacive gypsum, suggest a

Pleistocene lacustrine basin ofthe east domain ofGuadiz-Baza basin 179

• % Cyprideis torosa D % other oslraeode species [I] Barren samplcs

Figure 10. Paleosalinityevolution based on thepercentages of Cyprideistorosa (black) vs. otherostracode species (white)in the GBE "composite­stratotype-section" .Figura lO. Evolución dela paleosalinidad basadaen los porcentajes deCyprideis torosa (en ne­gro) respecto a otras es­pecies de ostrácodos (enblanco) en la seccióntipo.

The high sali­nity of lacustrine waterin the CNOR stratigra­phical subsection mustbe interpreted takinginto account its singu­lar palaeogeographicalsituation: a narrow co­rridor developed bet­ween two sierras fed byan alluvial fan with

dry period which didnot allow ostracode de­velopment. The presen­ce of mummified ostra­codes or insect larvaeinside the displacivegypsum crystals whichwere lacking in themudstone matrix, indi­cates that only locali­zed micro-ponds occu­rred at these maximumdry periods.

% Cvprideis torosa (lones)O 20 40 60 80 1110

I

1'",-':"; ••_~ .. t·.··.·..... .L..L ... .1.

..... ----­------

•

".,"-.••...•...._-.':.~..•1----- ...----------- ""

..~~~:~~~};----------~

"'~ ~.~:~.... r;...:~------

~4:.:=.~~~:~

-~~.;:;~~~--- ..---~ .

" ...- .. ,

.-'.r-"":fl:,~,m

~~;?:)*::;: .. ,. ,--7;;~~,

.... ...l.. ..... .L ~~

..... ::.::.,~,,:.

-~;r~.... ~• _":ro '

200 m

Om

50m

250m

300 m

350 m

"150m - 5

ca jE-U II

~

oS

100m

c:z::OzU

180 T. Torres et al.

its catchment located on soft Cainozoic marine rocks contammg gypsum.Furthermore, in the Orce and Huéscar area, saline springs are still active and the"trail" of an ancient palaeospring at the east of Huéscar has been clearly mappedby Vera (l970a).

CONCLUSIONS

A stratigraphical "composite-stratotype-section" mainly composed bysandy and lutitic sediments has been described in the lacustrine margin of theGBE basin. According to palaeomagnetic studies and amino acid racemisationratios, the stratigraphical "composite-stratotype-section" covers a time spanbetween the Pliocene-Pleistocene boundary (1.77 Ma) and the upper part of theMiddle Pleistocene (ca. 300 ka). In this section a very important event oflacustrine expansion, the "Orce Limestone Horizon", is defined (and dated) as anisochron and allows the correlation of palaeobiological (palaeontological sites),palaeoanthropological (Lower and Middle Palaeolithic sites) and neotectonic(seismites) events. The stratigraphical "composite-stratotype-section" has beenplaced in the basin facies framework to define unconformities so as to establishpalaeogeographical realm and facies relationships. Four main alluvial fans,Laneros, Huéscar, Orce and Cúllar, and their catchments, played a decisive rolein the definition of the basin boundaries. Another important unconformity wascreated in the Venta Micena-Orce realm, where neotectonics tilted and faldedformer Pliocene lacustrine deposits, reinforcing the low sedimentation ratesduring the Lower Pleistocene times. Fossil shells of mainly ostracoderepresentatives appeared in almost all the samples taken along the stratigraphical"composite-stratotype-section". Based on Cyprideis torosa (Jones), a saline waterostracode, abundance as well as the presence of foraminifera, a lacustrine salinityvariation has been established. Because of the lack of a stratigraphical record inthe western realm of GBE due to erosion, and the possible development of hiatiin the eastern part, two subsections have been used to compose the stratigraphical"composite-stratotype-section". It is noteworthy that during the lower half of thelower part of the Lower Pleistocene, the recorded salinity variation exhibitsstrong and frequent changes while during the remaining Lower Pleistocenestratigraphical record, high salinity conditions prevailed. The Middle Pleistocenesalinity record was studied in a restricted part of the basin, the Orce strait, whichshowed a dominance of high salinity palaeoconditions stable trough-time. Thisimplies that possible climatic changes were not recorded in the ostracode recordof this part of the basin, because tectonic-linked influence (diapirism and gypsumdissolution) masked any possible paleosalinity fluctuations induced by climatevariability. On the other hand, a constant high salinity could have beenmaintained through time because of the local hydrologic conditions (Rosen,1994).

Pleistocene lacustrine basin ofthe east domain ofGuadiz-Baza basin

ACKNOWLEDGEMENTS

181

We want to thank Dr. Jorge Civis from the University of Salamanca forhis help in the determination of the ostracode species. Funding was obtainedthrough the projects "Evidency from Quatemary Infills PalaeohydrogeologyEQUIP" (European Union, FI4W/CT96/0031), "Evolución Paleoclimática de laMitad Sur de la Península Ibérica" of ENRESA (National Company forRadioactive Waste Management, 703238), and "Paleoclima" of ENRESA andCSN (Consejo de Seguridad Nuclear). We are indebted to Dr. Veronika Meyer ofthe University of Bem who aided in laboratory set-up. Dr. Glenn Goodfriendfrom the Camegie Institution in Washington sent the analysis protocol and GasChromatography programo The Biomolecular Stratigraphy Laboratory has beenpartialIy funded by ENRESA. We want to thank Prof. Gierlowski-Kordesch forreviewing the manuscript.

BIBLIOGRAPHY

Alonso Diago, M.A., 1990. El Plio-Pleistoceno de la Cuenca de Guadix-Baza (zonaoccidental y área de Cúllar-Baza): Estratigrafia, sedimentología y evoluciónpaleogeográfica, tafonomía de yacimientos de vertebrados. Ph.D.Dissertation,University of Salamanca, Spain, 561 pp.

Alonso-Zarza, A.M., Calvo, 1.P., García de Cura, M.A., Hoyos, M., 1990. Los sistemasaluviales miocenos del borde noroeste de la Cuenca de Madrid: sector Cifuentes-LasInviemas (Guadalajara). Revista de la Sociedad Geológica de España 3, 213-229.

Alonso-Zarza, A.M., Calvo, J.P., García de Cura, M.A., 1993. Palaeogeomorphologicalcontrols on the distribution and sedimentary styles of alluvial systems, Neogene of theNE of the Madrid basin (central Spain). In Marzo, M., Puigdefábregas, C. (Eds.).Alluvial Sedimentation. Intemational Association of Sedimentologists, SpecialPublication 17, pp 277-292.

Agustí, 1., 1986. Synthese biostratigraphique du Plio-Pléistocene de Guadix-Baza(Province de Granada, Sud-est de I'Espagne. Geobios 19 (4), 505-510.

Agustí, 1., Oms, O., Parés, 1.M., 1999. Calibration of the Early-Middle Pleistocenetransition in the continental beds of the Guadix-Baza Basin (SE Spain). QuatemaryScience Review 18, 1409-1417.

Anadón, P., 1989. Los lagos salinos interiores (atalásicos) con faunas de afinidad marinadel Cenozoico de la Península Ibérica. Acta Geológica Hispánica 24, 83-102.

Anadón P., Juliá R., De Dekker P., Rosso J.c., Soulié-Marsche l., 1987. Contribución ala paleolimnología del Pleistoceno inferior de la cuenca de Baza (Sector Orce-VentaMicena). In: Agustí, J. (Ed.), Geología y Paleontología del Pleistoceno inferior deVenta Micena, Instituto de Paleontología Miquel Crusafont, Memoria Especial 1, pp.35-72.

Anadón, P., Utrilla, R., Julia, R., 1994. Palaeoenvironmental reconstruction of aPleistocene lacustrine sequence from faunal assemblages and ostracode shell

182 T. Torres el al.

geochemistry, Baza Basin, SE Spain. Palaeogeography, Palaeoclimatology,Palaeoecology 111, 191-205.

Banerjee, l., Kidwell, S.M., 1991. Significance of molluscan shell beds in sequencestratigraphy: an example from the Lower Cretaceous Manville Group of Canada.Sedimentology 38 (5), 913-934.

Banks, CJ., Warburton, J., 1991. Mid-crustal detachment in the Betic system ofsoutheastSpain. Tectonophysics 191,275-289.

Bell, e.M., 1989. Saline lake carbonates within an Upper Jurassic-Lower Cretaceouscontinental red bed sequence in the Atacama region of northem Chile. Sedimentology36 (4), 651-664.

Blair, T.e., MacPherson, J.G., 1994. Alluvial fans and their natural distinction fromrivers based on morphology, hydraulic processes, sedimentary processes and faciesassemblages. Joumal of Sedimentary Research A64, 450-589.

Bonadonna, F.P., Leone, G., 1989. La Región de Guadix-Baza: datos de la composiciónisotópica del oxigeno y del carbono y reconstrucción paleoambiental. In: AlberdiM.T., Bonadonna, F.P. (Eds.), Geología y Paleontología de la cuenca de Guadix­Baza, Trabajos sobre Neógeno-Cuatemario (CSIC), 11: 79-98.

Bull, W.B., 1972. Recognition of alluvial fans deposits in the stratigraphic record. In:Rigby, K., Hambin, K. (Eds.), Recognition of ancient sedimentary environments.Society of Economy, Paleontology and Mineralalogy, Special Publication 16, pp 63­83.

Cabrera, Ll., Colombo, F., Robles, S. (1985). Sedimentation and Tectonicsinterrrelationships in the Paleogene marginal alluvial fans of the SE Ebro basin.Transition from alluvial to shallow lacustrine environments. In: Rosell, J., Milá, M.(Eds.), 6th European lAS Meeting in Lérida, Spain. Excursion guidebook lO, pp. 394­492.

Calvo Sorando, J.P., in press. Mapa geológico Magna, 1:50.000 Cúllar-Baza (972).Instituto Geológico y Minero de España. Documentación complementaria inédita (inpress).

Cande S.e., Kent, D.Y., 1995. Revised calibration ofthe geomagnetic polarity time scalefor the late Cretaceous and Cenozoico Joumal of Geophysical Research lOO, 6093­6095.

Carbonel, G., 1983. Morphométre et hypersalinité chez Cyprideis torosa (Jones)(Ostracoda, Actuel) dans les salines de Santa-Pola (Alicante, Espagne). SciencesGéologiques Bulletin 36 (4), 211-219.

Collinson, J.D., 1996. Alluvial sediments. In Reading H.G. (Ed.), SedimentaryEnvironments: Processes, Facies and Stratigraphy. Blackwell Science, Oxford, pp.37-82

De Deckker, P., 1981. Ostracods ofathalassic saline lakes. Hydrobiologia 81,131-144.Friend, P.F., 1983. Towards the field c1assification of alluvial architecture or sequence.

In: Collison, J.D., Lewin, 1.) Modem and Ancient Fluvial Systems. Special.Publications ofthe Intemational Association ofSedimentologists 6, pp 345-354.

Gasse, F., Fontes, J.e., Plaziat, J.e., Carbonel,P., Kaczmarska, l., De Deckker, P., Soulié­Marsche, 1, Callot, Y. y Dupeuble, P.A., 1987. Biological remains, geochemistry andstable isotopes for the reconstruction of environmental and hidrological changes in the

Pleistocene laclistrine basin ofthe east domain ofGuadiz-Baza basin 183

Holocene lakes from North Sahara. Paleogeography, Paleoclimatology, Paleoecology60, 1-46.

Gibert, J., Arribas, A., Martínez Navarro, B., Albadalejo, S., Gaete, R., Gibert, L., Peñas,c., Torrico, R, 1992. Síntesis cronoestratigráfica del Pleistoceno inferior de la regiónde Orce. In: Gibert, J. (Ed), Presencia humana en el Pleistoceno inferior de Granada yMurcia. Proyecto Orce-Cueva Victoria (1988-1992). Museo de Prehistoria JosepGibert, Granada, pp. 107-114.

Gierlowski-Kordesch, E.H., 1998. Carbonate deposition in an ephemeral siliciclasticalluvial system: Jurassic Shuttle Meadow Formation, Newark Supergroup, HartfordBasin, USA. Palaeogeography, Palaeoclimatology, Palaeoecology 140: 161-184.

Goddard, E.N., Trask, P.D., Fard, R.K., Rove, O.N., Singewald, J.T., Overbeck, R.M.,1984. Rock-Color Chart. Geological Society of America.

Goodfriend, G.A., 1991. Patterns of racemization and epimerization of amino acids inland snail shells over the course of the Holocene. Geochimica et Cosmochimica Acta55, 293-302.

Goodfriend, G.A., Meyer, V., 1991. A comparative study of the kinetics of amino acidracemization/epimerization in fossil and modern mollusc shells. Geochimica etCosmochimica Acta 55, 3355-3367.

Hanford, C.R., 1982. Sedimentology and evaporative genesis in a Holocene continentalsabkha playa basin, Bristol Dry Lake, California. Sedimentology 29, 239-253.

Hardie, L.A., Smoot, J.P., Eugster, H.P., 1978. Saline lakes and their deposits. In: Matter,A., Tucker, M.E. (Eds.) Modern and Ancient Lake Sediments. Special Publication ofthe International Association of Sedimentologists 2, pp 7-41.

Hubert, J.F., Hyde, M.G., 1982. Sheet-flow deposits of graded beds and mudstones on analluvial sandflat-playa system: Upper Triassic Blomidon redbeds, St Mary's Bay,Nueva Scotia. Sedimentology 29, 457-474.

Hsü, K.J., Siegentaler, c., 1969. Preliminary experiment on hydrodynamic movementsinduced by evaporation and their bearing on the dolomite problem. Sedimentology 12,11-25.

IGME, 1988. Exploración de lignitos en la cuencas terciarias del ámbito bético. InstitutoGeológico y Minero de España, Madrid (inédito), 320 p.

Kaufman, D.S., 2000. Amino acid racemization in ostracodes. In: Goodfriend, G.A.,Collins, M.J., Fogel, M.L., Macko, S.A., Wehmiller, J.F. (Eds.), Perspectives inAmino Acids and Protein Geochemistry. Oxford University Press, New York. pp.145-160.

Kendall, A.C., 1984. Evaparites. In: Walker, RG. (Ed.), Facies Model. GeoscienceCanada 1, pp 259-296.

Laznicka P., 1988. Breccias and coarse fragmentites: petrology, environments,associations, ores. Developments in Economic Geology 25. EIsevier, New York, pp832.

Lowenstein, T.K., Hardie, L.A., 1985. Criteria for the recognition of salt-pan evaporites.Sedimentology 32: 627-644.

MacCarthy, l.A.J., 1990. Alluvial sedimentation patterns in the Munster Basin, Ireland.Sedimentology 37 (4), 685-712.

Mack, G.H., James, W.c., 1993. Control of basin symmetry on fluvial lithofacies, CampRice and Palomas Forrnations (Plio-Pleistocene), southern Rio Grande Rift, USA. In:

184 T. Torres el al.

Marzo, M., Puigdefábregas, e (Eds.), Alluvial Sedimentation. IntemationalAssociation of Sedimentologists, Special Publication 17, pp. 439-450.

Martínez, B., 1991. Revisión sistemática de la fauna de macromamíferos del yacimientode Venta Micena (Orce, Granada). In: Gibert, l (Ed), Presencia humana en elPleistoceno inferior de Granada y Murcia. Proyecto Orce-Cueva Victoria (1988­1992). Museo de Prehistoria Josep Gibert, Granada, pp 21-85.

Mazo, AV., Sesé, e, Ruiz Bustos, A, Peña, J.A, 1985. Geología y paleontología de losyacimientos Plio-Pleistocenos de Huéscar (Depresión de Guadix-Baza, Granada).Estudios Geológicos 41, 467-493.

McCoy, W.D., 1988. Amino acid racemization in fossil non-marine ostracod shells: apotential tool for the study of Quatemary stratigraphy, chronology andpalaeotemperature. In De Deckker, P., Colin, J.P., Peypouquet J.P. (Eds.), Ostracodain the Earth Sciences. Elsevier, Amsterdam & New York. pp. 201-218.

Miall, A.D., 1981. Alluvial sedimentary basins: tectonic setting and basin structure. In:Miall, A.D. (Ed.), Sedimentation and tectonics in alluvial basins. GeologicalAssociation ofCanada, Special Paper 23, pp. 1-33.

Nemec, W., Postma, G., 1993. Quatemary alluvial fans in Crete. In Marzo, M.,Puigdefábregas, e (Eds.), Alluvial Sedimentation. Intemational Association ofSedimentologists, Special Publication, pp 235-276.

Oms, O., Garcés, M., Parés, lM., Agustí, l, Anadón, P., Julia, R., 1994.Magnetostratigraphic characterization of a thick Lower Pleistocene lacustrinesequence from the Baza Basin (Betic Chain, Southem Spain). Physics of the Earthand Planetary Interiors 85, 173-180.

Ortí, F., Pueyo, ].J., Geisler-Cussey, D., Dulau, N., 1984. Evaporitic sedimentation in thecoastal salinas of Santa Pola (Alicante, Spain). Revista del Instituto deInvestigaciones Geológicas. Diputación de Barcelona 38-39, 169-220.

Ortí, F., Rosell, L., Utrilla, R., Inglés, M., Pueyo, J., Pierre, e, 1988. Reciclaje deevaporitas en la Península Ibérica durante el ciclo alpino. Il Congreso Geológico deEspaña 1,421-424.

Ortí, F., Rosell, L., 2000. Evaporative systems and diagenetic patlems in the CalatayudBasin (Miocene, central Spain). Sedimentology 47 (3), 665-685.

Ortiz, lE., 2000. Evolución paleoclimática durante el Pleistoceno de la mitad sur de laPenínsula Ibérica mediante el estudio paleontológico y geoquímico de ostrácodos dela cuenca de Cúllar-Baza (Granada, España). Ph.D. Dissertation, PolitechnicalUniversity ofMadrid, Spain, 4 vol., 567 pp.

Ortiz, lE., Torres, T., Delgado, A, Julia, R., Llamas, F.J., Soler, V., in prep. Numericaldating algorithms of amino acid racemization ratios analyzed in continentalostracodes of the Iberian Peninsula (Spain). Application to Guadix-Baza basin(Andalusia, southem Spain).

Oviatt, eG., Thompson, R.S., Kaufman, D.S., Bright, J., Forester, R.M., 1999.Reinterpretation of the Burmester core, Bonneville Basin, Utah. Quatemary Research52, 180-184.

Peña, J.A., 1985. La Depresión de Guadix-Baza. Estudios Geológicos 41, 33-46.Pous, l, Queralt, P., Ledo, ].J., Roca, E., García, X., Marcuello, A., 1995. Electrical

conductive structure of the central Betics from magnetotelluric data. Revista de laSociedad Geológica de España 8 (4), 513-517.

Pleistocene lacustrine basin ofthe east domain ofGuadiz-Baza basin 185

Rodríguez-Aranda, J.1., Calvo, lP., Ordóñez, S. 1991. Transición de abanicos aluviales aevaporitas en el Mioceno del borde oriental de la cuenca de Madrid (sector Barajas deMelo-Illana). Revista de la Sociedad Geológica de España 4 (1-2), 33-50.

Rosen, M.R., 1994. The importance of groundwater in playas: a review of playac1assifications and the sedimentology and hydrology of playas. In (Rosen, M.R., Ed),Paleoc1imate and Basin Evolution of Playa Systems. Geological Society of America,Special Paper 289, pp. 1-8.

Sanz, M.E., Rodríguez-Aranda, J.P., Calvo, J.P., Ordóñez, S., 1991. Sedimentología delas facies de yesos detríticos de la Unidad Intermedia del Mioceno (sector sur de laCuenca de Madrid). Congreso Español del Terciario de Vic 1,316-319.

Sanz, M.E., Rodríguez-Aranda, lP., Calvo, J.P., Ordóñez, S., 1994. Tertiary detritalgypsum in the Madrid basin, Spain: Criteria for interpreting detrital gypsum incontinental evaporitic sequences. Sedimentology and Geochemistry of Modern andAncient Saline Lakes, SEPM Special Publication 50, 217-228.

Soria, J.M., 1996. Historia de la subsidencia y levantamiento en el margen norte de lacuenca intramontañosa de Guadix (Cordillera Bética central). Geogaceta 20 (2), 464­467.

Soria, F.J., López-Garrido, A.c., Vera, J.A., 1987. Análisis estratigráfico ysedimentológico de los depósitos neógeno-cuaternarios en el sector de Orce(depresión de Guadix-Baza). Paleontologia i Evolució. Memoria especial 1, 11-34.

Torres, T, Llamas, J., Canoira, L., CoeHo, F.1., García-Alonso, P., Ortiz, J.E., 2000.Aminostratigraphy of two Pleistocene marine sequences fram the MediterraneanCoast of Spain: Cabo de Huertas (Alicante) and Garrucha (Almería). In Goodfriend,G.A., CoHins, M.J., Fogel, M.L., Macko, S.A., Wehmiller, lF. (Eds.) Perspectives inAmino Acids and Protein Geochemistry. Oxford University Press, New York. pp.263-278.

Vera, J.A., 1969 Características estratigráficas de la serie de Baza (Depresión de Guadix­Baza). Acta Geológica Hispánica, IV (1), 14-17.

Vera, lA., 1970a. Facies del Plioceno de la Depresión de Guadix-Baza. CuadernosGeológicos de la Universidad de Granada 1, 23-25.

Vera, l.A., 1970b. Estudio estratigráfico de la Depresión de Guadix-Baza. Boletín delInstituto Geológico y Minero de España 81, 429-462.

Vera, lA., Fernández, J., López-Garrido, A.c., Rodríguez-Fernández, J., 1984. Geologíay estratigrafia de los materiales plioceno-pleistocenos del sector de Orce-VentaMicena (Prov. Granada). Paleontologia i Evolució 18,3-11.

Yagmurlu, F., Helvaci, c., 1994. Sedimentological characteristics and facies of theevaporite-bearing Kimir Forrnation (Neogene), Beypazari Basin, central Anatolia,Turkey. Sedimentology 41 (5),847-860.