Intraplate deformation and basin formation ... - Wiley Online Library

TECTONICS, VOL. 19, NO. 2, PAGES 258-289 APRIL 2000

Intraplate deformation and basin formation during the Tertiary within the northern Iberian plateOrigin and evolution of the Almazn Basin Antonio M. Casas-Sainz,Angel L. Cort6s-Gracia,and Adolfo Maestro-Gonzfilez Departamentode Geologia, Facultad de Ciencias,Universidadde Zaragoza,Zaragoza, Spain

Abstract. The Tertiary Almazfin Basin was a topographic high during the Mesozoic rifting at the northern part of the Iberian plate. It was borderedby two Mesozoic basins:(1) the Castilian Basin (with a maximum thickness of more than 2000 m) to the south and (2) the Cameros Basin (with a maximum thickness of 9000 m) to the north. To the east the

Almazfin Basin is bordered by Paleozoic rocks of the NW-SE trending Aragonian Range, which underwent little subsidence during the Mesozoic. The two Mesozoic basinsshow an E-W direction.During the Tertiary NNE-SSW compression(mainly late Eocene-early Miocene), both Mesozoic basins were inverted and uplifted, and the Almazfin Basin, with an overall synclinal geometry, was filled with syn-tectonic terrestrial sediments, reaching a maximum thickness of 3500 m. Deformation during the Tertiary was strongly controlled by preexisting structures,both Mesozoic extensional faults and reactivated Variscan folds. The depocenter of the Tertiary basin migrated southward during the Paleogene. This migration is consistent with a piggyback transport of the whole

basin northward,

due to the movement

on the

System, respectively, each show cumulate thickness over 2500 m of Tertiary deposits,with structuralreliefs of nearly 5000 m betweenthe bottom of the basinsand the tops of the neighboringmountain chains [De Vicente et al., 1996a,b]. The processesinvolved in intraplate deformation were mainly basement thrusting, strike-slip faulting and inversion of Mesozoic basins [Guimer• and Alvaro, 1990; Casas-Sainz,

1993; Van Wees and Stephenson,1995; Casas-Sainzand GilImaz, 1998]. Structuresformed during inversionwere strongly controlled by the orientation and geometry of pre-existing

extensionalfaults. Inheritedbasementstructuresalso played an importantrole in the geometryof extensionand inversion [Mu•oz, 1992; Liesa-Carrera and Casas Sainz, 1995; Alonso et al., 1996].

Continentaldeformationsometimesimplies the formation of piggyback basins, defined as intermontane basins that

formedandwerefilled while beingcarriedon movingthrust sheets[Ori and Friend, 1984]. Piggybackbasinsusually show an elongatedshape,following the trend of the thrust system. The active thrusts transportingpiggyback basins

underlying, crustal-scalenorth verging Cameros thrust. The geometry and sedimentary evolution of the Almazfin thickskinned piggyback basin was controlled by the uplift

evaporitesor shallow strengthunits [Ori and Friend, 1984; Lawton and Trexler, 1991; Gonzalez and Guimerd, 1993;

associated with the main crustal-scale thrust, which was the

Hyppolyteet al., 1994; Teixell and Garcœa-Sansegundo,

main sourcearea, and was separated from the foreland basin sincethe early stagesof filling (late Eocene).This makesthe main difference with thin-skinned piggyback basins, controlledby the foreland thrust belt and separatedfrom the forelandbasinonly at their late stages.

1995; G6mezet al., 1996; GimbnezMontsantand Salas, 1997; Mu•oz-Martfn and De Vicente, 1998], or may involve a thicknessof severalkilometersof the uppercrust[Beeret al., 1990; Babyet al., 1995;Bonini, 1999a,b].The sedimentary syntectonic evolution of piggyback basins is strongly influencedby the geometryof thrustsheets[Zoetemeijer et al., 1993; Talling et al., 1995; Pivnik and Khan, 1996; Bonini,

may be detached at shallbwcrustallevels,namely,on

1999a,b], and is recordedby the main unconformitieswithin

1. Introduction

The inner part of the Iberian plate was strongly deformed during the Tertiary by the collision between Africa, Europe, and Iberia, forming intraplate mountain chains and nonmarine basins [Sanz de Galdeano, 1996]. The greatest thickness(2500-5000 m) of syntectonicTertiary terrigenous sedimentsis found at the northernpart of the Ebro and Duero Basins (foreland to the Pyrenean margin, [Riba et al., 1983; Instituto Tecnol6gicoGeoMinero de Espana (ITGE), 1990]). Some areaswithin the plate subsidedsignificantly:the Madrid and Almazfin Basins, located south and north of the Central

the sedimentaryfilling [Beer et al., 1990;Zoetemeijerand Sassi,1992].The forelandthrustbelt usuallyprovidesone of the main controlsin basingeometryand is commonlythe sourcearea for the piggybackbasin during its first stages. Toward the middle stagesof its evolution a longitudinal drainagemay appear,and finally the leading edge of the underlying thrust may emerge [Mugnier et al., 1997], also becominga sourcearea [Puigdefdbregas, 1975; Ori and Friend, 1984; Lawton and Trexler, 1991; Turner, 1992; Pivnik and Khan, 1996].

The AlmazfinBasin,definedas a piggybackbasin[Guimerit

et al., 1995], was an area of high subsidence duringthe Tertiaryin the innerpart of the Iberianplate, with a thickness of 3500 m of Tertiary terrigenoussediments[Armenteroset

Copyright 2000by theAmerican Geophysical Union.

al., 1989;Bond,1996].It is locatedbetweenmountain ranges whereolder rocks(Paleozoicand Mesozoic)crop out: the

Papernumber1999TC900059. 0278-7407/00/1999TC900059512.00

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CASAS-SAINZ ETAL.:PIGGYBACK BASINEVOLUTION (NORTHERN SPAIN)

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CASAS-SAINZ ET AL.: PIGGYBACK BASIN EVOLUTION (NORTHERN SPAIN)

Aragonian Range of the Iberian Chain to the east, the Cameros Massif to the north and the Castilian Range to the south (Figure 1). Both the Cameros Massif and the Castilian Range were basinalareasduring the Mesozoicand underwent positive tectonic inversion during the Tertiary. The Cameros Basin shows a horizontal displacement of 25-30 km northwardon the Camerosthrust and a lower displacement(23 km) southward, toward the Almazfin Basin [Platt,

1990;

Guimer• et al., 1995]. The Castilian Range is limited by monoclines or reverse faults involving the Paleozoic basement.The Aragonian Range subsidedduring the Triassic and late Cretaceousand was a topographichigh during ail the Jurassicand the early Cretaceous.During the Tertiary it was folded with NW-SE trend, parallel to the underlyingVariscan folds. According to Guimerh and Alvaro [1991] Tertiary thrusting involving Paleozoic rocks was favored by a midcrustaldetachmentin the Iberian plate. The objectives of this work are (1) to characterize the Mesozoic-Tertiary evolution of the Almazfin Basin, (2) to determine the influence of preexisting structures (Mesozoic extensional faults and Variscan folds and thrusts) on the

developmentof compressionalstructures,(3) to determinethe history of Tertiary deformation from relationshipsbetween tectonics and sedimentation, and (4) to establish a model of

2.1.

The

Cameros

Massif

The CamerosMassif is the result of the Tertiary inversion of the Mesozoic (mainly upper Jurassic-lower Cretaceous) Cameros Basin [Casas-Sainz, 1993; Guimer& et al., 1995]. It

consistsof Mesozoicrocks, with upper Triassicevaporites, marine Jurassiclimestones(up to 800 m thick), and a series (up to 8000 thick) of terrigenousKimmeridgianto Albian deposits (sandstones, shales, and lacustrine limestones) [Guiraud and S•guret, 1984]. The basin was a half graben bounded northward by large NW-SE normal faults with downthrowto the south-westof up to 8 km [Casas-Sainzand Gil-Imaz, 1998] and boundedsouthwardby smallerfaults,with downthrowsof up to 2-3 km [Platt, 1990; Clementeand P•rezArlucea, 1993; Guimer& et al., 1995]. The normal faults at the southernmargin of the basin show two main strikes,WNWESE and NE-SW, which coincide with the late Variscan fracture

directions [Salomon, 1980, 1983; Clemente and Alonso, 1990]. Up to 1000 m of Albian-Cenomanian sandstones

(Utrillas Formation) and upper Cretaceous limestones constitutethe postriftsequence(Figure 2). The present-day structure of the Cameros Massif reflects positive inversion. To the north the Cameros Massif overthruststhe Tertiary depositsof the Ebro Basin along the E-W-striking, shallow-dipping Cameros thrust with a detachmentlevel in the upper Triassic gypsiferousbeds

basin evolution and compare it with described piggyback basins.The methodologyused involved the study of seismic [Casas-Sainz, 1993]. This thrust continues to the west in the profiles, aerial photographs,and field mappingto constrain Sierra de la Demanda (defining a continuousfront 100 km balanced cross sections and the geometrical relationships long) wherePaleozoicrocksare exposedin the hangingwall. between tectonosedimentary units. The horizontal displacementof the Camerosthrust is between 15 and 25 km

and its vertical

throw

is more

than 4 km

[Mut•oz-Jim•nez and Casas-Sainz, 1997]. The present-day

2. Main Tectonostratigraphic Domains

southern

The Tertiary Almazfin Basin is located in the northwestern sectorof the Iberian Chain, an intraplate mountainrange that occupies the central-eastern part of the Iberian peninsula [Julivert, 1978; Alvaro et al., 1979; Capote, 1983a] and which concentratedmuch of the intraplatedeformationduring the Mesozoic and the Tertiary. Variscan structures include cleavage,folds, and thrustswith N-S to NW-SE orientation [Capote, 1983b]. Late Variscan faults and fractures are arrangedin two sets:NW-SE and NE-SW [Arthaud and Matte, 1975; 1977; Alvaro et al., 1979; Capote, 1983a,b; Ziegler, 1989; Vegas et al., 1990], forming part of a system with relatively constant orientation throughout western Europe [Dikkers,

1977; Illies,

1977; Johnson and Frost,

1977;

Ramberg et al., 1977; Ziegler, 1989]. These faults were reactivated as normal faults during Mesozoic rifting and as wrenchor reversefaults duringthe Tertiary shortening[Alvaro et al., 1979; Arias et al., 1979; $alas and Casas, 1993],

controlling the location of structuresin the Mesozoic cover. In some parts of the chain Tertiary deformation is thinskinned, with a detachment level in the upper Triassic evaporites.The Almazfin Basin is surroundedby three main tectonic units within the Iberian Chain (Figure 1): the Cameros Massif to the north, the Aragonian Range to the east, and the Castilian Range to the south.

border

of the Cameros

Massif

shows folds

and

thrusts,with NE-SW and NW-SE segments(Figure 1•).They result either from the reactivation

of the Mesozoic

normal

faults limiting the Cameros Basin or from newly formed thrusts [Navarro, 1988; Platt, 1990; Clemente and P•rezArlucea, 1993; Guimer• et al., 1995]

2.2

Aragonian

Range

The Aragonian Range consistsof two NW-SE oriented antiforms of Paleozoic rocks (-150x10 km), bordered by Mesozoic sediments.The Paleozoicrocks of the Aragonian Range are included in the Western Asturian-LeoneseZone of the Iberian Massif [Lotze, 1945; Julivert et al., 1972]. In the southernmost antiform, which forms the eastern limit of the

AlmazfinBasin, the Paleozoicsequenceconsistsof Cambrian and Ordoviciansandstonesand shales,up to 7000 m thick, folded in NW-SE direction during the Variscan orogeny [Julivertet al., 1972; LendfnezGonzc•lezand Martfn Herrero, 1987; Ruiz-Fernc•ndez et al., 1987]. The Mesozoic sedimentaryseriesoutcroppingat the border with the Almazfin

Basinis -500 m thick and comprisesTriassicrocks(mainly Buntsandstein facies) [Tallos-Gonzc•lez,

1984], Albian-

Cenomaniansandstones,and upper Cretaceouslimestones (Figure 2). To the north and south the thickness of the Mesozoic series increases, as it approachesthe Cameros

CASAS-SAINZ ET AL.' PIGGYBACKBASINEVOLUTION(NORTHERNSPAIN)

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261

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CASAS-SAINZET AL.: PIGGYBACK BASIN EVOLUTION (NORTHERN SPAIN)

Basin and the Castilian Range. The Tertiary structureof the southernantiform of the Aragonian Range is defined by NWSE north plungingfolds. Several thrustsdipping between30ø and 80ø S, with displacementsbetween 100 m and 1 km, crosscutthe Mesozoic series [Maestro et al., 1997].

2.3.

Castilian

Range

The Castilian Range consists mainly of Triassic and Jurassicrocks reachinga maximum thicknessof 2000 m. The Permianseries,localized in small basinsin the westernpart of the Castilian Range, can reach thicknessesof more than 2000 m [Virgili et al., 1983]. The Triassic appears in Germanic facies: Buntsandstein (sandstones and shales), Muschelkalk

(limestones, marls, and evaporites), and Keuper (lutites and evaporites), corresponding approximately to the lower, middle, and upper Triassic, respectively[Sopehaet al., 1983]. The Jurassicconsistsmainly of marine limestones[Goy et al., 1976; Goy and Sudrez Vega, 1983]. Albian sandstonesand upper Cretaceous limestones constitute the top of the Mesozoic series[Garcœa-Hidalgoet al., 1997]. The Paleozoic rocks

below

the

Triassic

are

Ordovician

to

Devonian

sandstones, shales and limestones, more than 3 km thick

[Adell Argilds et al., 1978; Bascones-Alvira et al., 1978]. Variscan folds show a'NNW-SSE to NNE-SSW direction, with

those of the Duero Basin. The Paleogene and the lower Miocene are divided into four tectonosedimentary units separated by unconformities or sedimentary breaks [Armenteros et al., 1989; Carballeira and Pol, 1989; Bond, 1996; Mediavilla et al., 1996; Santisteban et al., 1996], while the Neogene, from the lower Miocene to the Pliocene, is divided into two units [Bond, 1996; Varas Muriel, 1997]. During the Mesozoic rifting the Almazfin Basin, together with the Aragonian Range, was a structural high [Sope•a et al., 1983; Marfil and G6mez Gras, 1992; Mu•oz et al., 1995]. borderedby subsidingbasins. In the central part of the basin the Mesozoic series below the Tertiary is less than 500 m thick, in some placesthe Albian sandstoneslie directly on the Paleozoic [Lanaja, 1987; ITGE, 1990, see Figure 2). The thickness of the Triassic and Jurassic sequence below the Tertiary basin increaseswestward,reachingmore than 1000 m in the boreholeGormaz-1 (Figure 2). East of Almazfin, the Almaz•n

Basin shows an overall

synclinal geometry, with a maximum thickness(3500 m) of preservedTertiary depositslocated along a WNW-ESE trend [ITGE, 1990; Bond, 1996]. Folds located within the basin show E-W to NW-SE trends. West of Almaz•n, the structure is

characterized by E-W folds and thrusts, with a maximum preservedthicknessof Tertiary depositsof -2000 m.

bedsdippingbetween30ø and 60ø. Sedimentation

of the lower Triassic is linked to WNW-ESE

normal faults which probably crosscutthe whole crust, since alkali basaltswith mantle affinity are presentin many partsof the Iberian chain [Lago et al., 1988; Pocovi et al., 1997]. The lower Triassic shows sharp thickness changescontrolled by these faults [Sopeha et al., 1983; Capote, 1983b]. Triassic grabens are asymmetric, with the main faults dipping northward [Mugoz et al., 1995, Figure 2]. Two WNW-ESE striking, SSW dipping normal faults are also present in the westernpart of the studiedarea (Figure 2). Normal faults were probably active during all the Mesozoic, since the Albian sandstonesand the Cenomanian are also crosscut by them [Bascones Alvira et al., 1978; Lendœnez, 1987; Lendfnez Gonzdlezand Muhoz del Real, 1988].

The Castilian Range shows fiat-lying and gently folded Mesozoic strata. The orientationof Tertiary folds is WNWESE to E-W, changingto NE-SW nearthe CentralSystem[De Vicente, 1988]. To the north and souththe CastilianRangeis in contact with Tertiary basins (the Almazfin and Madrid basins, respectively), with a structural relief of-3500 m [De Vicente et al., 1994]. 2.4.

The

Almazfin

Basin

TheAlmazfinBasinoccupies an areaof 4500km2, withan average elevation of 1100 m. The basin fill consists of

Paleogene and Neogene sediments, composed of alluvial deposits,with conglomeratesand sandstonesnear the basin borders and shales and lacustrinelimestonesand gypsum toward the basin center. At present, most of the basin is coveredby horizontal Neogene sediments,which onlap the Mesozoic rocks of the southernborder, and the Paleogene materialsonly crop out at the northeasternmargin (Figure 1). To the west the Neogene sedimentsare in continuity with

3. Structures

Within

the Almazfin

Basin

The overall geometry of the Almazfin Basin can be inferred from the contoursof the base of the Tertiary constructedfrom seismicreflection data (lines shown in Figure 2). The contour map was constructedtaking into accountthe depth of the base of the Tertiary, calculated at the common depth point reflections (CDPs) of each seismic profile, and tracing the contoursaccordingto the dominant strike of beds at surface (Figure 3a). Two sectorswere considered:an easternsector (east of the Almazfin-Soria meridian) where the dominant strike is NW-SE and a western sector (west of the Almazfin-

Sofia meridian) with dominantstrike E-W (Figure 3b). The structure of the basin is characterized by folds, with NW-SE to E-W trends, associated in some cases with north-

verging thrusts(Figures 3a and 3b). Four areaswith different structurescan be distinguishedwithin the basin: 1. In the basin center,east of Almazfin, the main structure

is a flat-bottomed E-W trendingsynclineborderedby the G6maraandAlmazfinmonoclines (Figures3a and3b). It is 8

km wide(halfwavelength), andcanbe followed25 km along trend(Figures3a, 3b, and 4, crosssection3-3'). The thickness

of preserved Paleogene deposits at the coreof the synclineis -3000 m. To theeastthissynclinebecomes a symmetric NWSE synclinorium, reachingthe AragonianRange.The western prolongationis an asymmetric syncline with a thrusted southernlimb (Figures3b and 5, crosssection4-4'). The

G6maramonoclinedips 200-30ø S, graduallydiminishing westwards [Ferreiro Pad(n, 1988]. The Almazfin monocline

changesfrom very shallowdips at the easternpart to more than 60 ø in the western sector.

2. The Almazfin monoclineis separatedfrom the Arcos

monocline(Figure3b) by a zone of shallow-dipping beds occupying andarea60x15km wide.The averagethickness of

CASAS-SAINZET AL.: PIGGYBACK BASIN EVOLUTION (NORTHERN SPAIN) ß

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Figure 3. (a) Contours showing the depth(elevation abovesealevel)of the top of the upperCretaceous, obtainedfrom the interpretation of seismicprofiles,boreholes,and surfacedata.The main structuralfeatures of the basincanbe seen.(b) Structural(subcrop)mapof the Paleogene of the Almaz•nBasin,drawnfrom the interpretation of seismicprofiles,boreholes,and surfacedata. Stereograms (Schmidtprojection,lower hemisphere) showthe attitudeof beddingat the westernand easternsectorsof the basin.

264

CASAS-SAINZ ET AL.: PIGGYBACK BASIN EVOLUTION (NORTHERN SPAIN)

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thePaleogene sequence in thissectoris 1000-1500m (Figure cross sections 3-3', 4-4', and 5-5'), probably because their 4, crosssections 2-2' and3-3').TowardthewestthePaleogene direction was nearly perpendicular to the Tertiary sequence is thicker,andfoldsbecometighter.Towardthe east

this shallow-dipping areabecomesa flat-bottomed syncline betweenthe Arcos monoclineand the AragonianRange (Figures3a, 3b, and 4, crosssection 1-1'). At the southern limb of the Arcos monocline the Mesozoic rocks of the

CastilianRangecrop out. 3.

West of Almazfin the reconstruction of the structure

below the horizontalNeogenecoveris not so accurate,since

thereare lessseismicprofiles,and they are obliqueto the mainstructures (seelocationof seismiclinesin Figure2). The structure is characterized by E-W folds,with locallythrusted northernlimbs (Figures3b and 5, crosssection5-5'). The maximumpreserved thickness of the Paleogene is - 2000 m. 4. To thenorthof the G6maramonocline (Figure3a,b)the

compression. They are overlain by non-thrusted upper Cretaceousand Tertiary strata with syncline geometry. east of Soria, at the northern limit of the Aragonian Range, the main NE-SW normal fault limiting the Cameros Basin divides into an E-W normal fault system(Figure 2). At the northernbasin border (cross section 6-6', Figure 5) the WNW-ESE-striking Mesozoic faults were inverted only where they dip northward, favoring the thrustingof the CamerosBasin over the Tertiary deposits. In the Castilian Range the basement is folded in the footwall of normal faults, without apparent reactivation or inversion of Mesozoic faults. Within the basin, small thrusts

and folds (Figure 6) are associated with mesozoic normal faults. These folds propagateupward into the Paleogenebeds. In some places along the Aragonian Range (section 2-2', preservedthicknessof the Paleogeneis about 1000 m. Together withtheAragonian Range,foldsforman arc-shaped Figure 4) the structurein detail showsTriassic normal faults that were folded, and not reactivated,during the Tertiary. bandwith E-W to NW-SE trend(Figure3b), limitingto the In cross section 5-5' (Figures 5 and 7) Mesozoic normal northwiththe southern Cameros thrustsystem. Wavelengths faults can be inferred from the changes in thickness of the are between2 and 4 kin, and their envelopingsurfaceis pre-Cretaceousseismicreflectors.The Cretaceousand Tertiary horizontal or showsa shallowdip(- 10ø)basinward (Figure5, crosssection4-4'). Someof the anticlinesare a doubley- units define asymmetric north-verging anticlines with straight southernlimbs 3-4 km long dipping 10ø-13ø S and plunging(dome)shape,with steeply-dipping thrustsat their steepernorthernlimbs, less than 1 km long dipping between northern front limbs. At the northern border of the Almazfin 28ø and 37ø The geometry of the Tertiary growth strata Basin the main structures result from the inversion of the indicates a genesis by limb rotation (Figure 7). Hinges of CamerosBasin,with shallow-dipping thrustsinvolvingthe folds involving the Cretaceous and the Tertiary are located Paleozoic[Guimer• et al., 1995]. TheseE-W thrustsshowNEover the expectedpoints of intersectionbetweenthe faults and SW and WNW-ESE segments,which correspond to the the Cretaceous (Figure 7). In this case the Tertiary orientationof Mesozoic extensionalfaults [Clemente and compressionaldeformation can be interpretedas conditioned Alonso, 1990]. and localized by the underlying normal faults [see, e.g., Huntoon, 1993], inverted or nonreactivatedaccordingto their 4. Balanced and Restored Cross Sections:Styles senseof dip (Figure 7). of deformation

Six cross sections, showing the main structuresand their relationshipswith the Tertiary sedimentary units, have been drawn (Figures 4 and 5). Cross sections 1-4 coincide with seismicprofiles along most of their length. Cross sections5 and 6 are constrainedat depthby their intersectionswith some seismic profiles. At the basin borders, the structure was determined from photogeological studies and surface mapping. At the basin center, cross sectionsare constrained only by seismic reflection profiles. The amount of Tertiary shortening(obtained from the top of the upper Cretaceous) varies between 1 km in cross section 1-1' (Figure 4) and 6-7

km in crosssections 3-3' (Figures4 and6) and4-4' (Figure5), with valuesof 4 km in crosssection5-5'(Figure 5). The amountof shorteningis relatively homogeneous, between7 and 8% in the majority of the cross sections. The main mechanismscontrolling the geometry of structuresare the

inversion of Mesozoic faults, "basement"folding and faulting, and reactivationof Variscan folds. 4.1.

Inversion

of

Mesozoic

normal

faults

The southernlimit of the CamerosMassif is formedby south-vergingfolds and thrusts,with NE-SW, NW-SE, and EW trends,controlledby the geometryof the Mesozoicbasin.

Somesegments of the Mesozoicfaults,dippingsteeplyto the north,were not reactivatedduringthe Tertiaryinversion(see

4.2.

Basement-involved

monoclines

The Almazfin monocline shows a growth geometry in the Paleogene strata (cross section 3-3', Figures 4 and 6), with maximum changes of thickness in units A2 and A3. The averagedip of the monoclinechangesfrom 15ø at the eastern part to more than 45ø in the westernsector,being substituted westward by a north verging, steeply dipping thrust. Farther west (cross sections 5-5' and 6-6', Figure 5) a series of asymmetric folds occupy the central part of the Almazfin Basin, with thinned, preservedTertiary deposits. Growth strataover the dippinglimb show rotationalofflap-

onlap syntectonic unconformities, with progressively decreasingdips from bottom to top, indicating that limb

rotationtookplaceduringthefirststagesof folding(Figure6, section A80-07, see also Figure 10.a). The limits of the dippinglimb are an anticlineand a synclinewith rounded geometry(Figure6, sectionA80-14).The singlehingesmay be substituted by two kink bands(Figure6, sectionA80-07). Within the kink band,bedsshowdipsbetween30ø and45ø. The axialsurfaces of the kink bandsconverge upwardfor the

A3 and A4 tectonosedimentary units,beingparallelin the olderunits(A2 andthe Mesozoic).

From the geometryof growthstratathe superposition of two folding mechanisms can be inferred:(1) limb rotationis

interpreted from the upwarddecreasing dip of bedstogether

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l.,•O• I •I

.

--T--

_ --

'

R7

R5

__

3000

......

2500

o

U

=

o

---

----

,oøi

soo

R3

2000

0 1500

.......

5OO

DO0

i

i

!

i

K L SCo

b

0_S

N

5km

Figure10. (a)Synthetic stratigraphic profile of thePaleogene of thenorthern border of theAlmazfin Basin

andtheRiojaTrough, showing thevertical evolution of tectonosedimentary units. Lithology includes the

following: K, lacustrine limestones; L, lutites; S, sandstones; Co,conglomerates. Micromammal fossilsites areAll, Mazater6n; AI2,Deza; A13,Cetina; A14,Ariza; andA15,Radona intheAlmazfin Basin (data arefrom Guisado etal.[1988], Armenteros etal.[1989], Armenteros [1994], Cuesta-Ruiz-Colmenares andJirnEnez-

Fuentes [1994]), andRil,Bergasa-Arnedo; Ri2,Autol-Valhondo; Ri3,Quel; Ri4,Carretil' Ri5,lslallana; Ri6, Fuenmayor; Ri7,LosAgudos; Ri8,Badarfin; Ri9,Cel16rigo (data from SantalE etal.[1982], Cuenca [1983, 1985], Daarns andMeulen [1984], Martœnez-Salanova [1987], Alvarez-Sierra [1987], Alvarez-Sierra etal. [1987], Agustœ etaL[1988], Lacomba andMartœnez-Salanova [1988], Cuenca et al. [1992] andMugoz-

Jim•nez [1992]). (b)Seismic expression andlinedrawing oftherotational syntectonic unconformity (inthe sense ofRiba[1976]) between units A2-A3 andA3-A4 attheAlmazfin monocline inseismic profile A80-07 (seelocation inFigure 2).Offlap geometries atop ofunits A2andA3andonlap geometries atthebottom of

units A3andA4canbeseen. TSU,tectonosedimentary unit;TWT,two-way time.

275

276

CASAS-SAINZ ETAL.:PIGGYBACK BASINEVOLUTION(NORTHERN SPAIN)

a A4

/

.:•. .........

A3

/

A2

/ A1 !

UpperCretaceous

•'::•::• •;-.•':.' :::::::::::::::::::::::::::::::::::: -:::?::•::. •.....•::::::::::::::::::::::•:•.:•?:•?:}•:.•::::::::•:•:•u•}}::::::.`.•:•:::::•5•::::::::>:•*;•>•C•`.`•:i:•{````•:•:.•. •...•:•::::::::::::::::•;•:•.•3•D•::::::::::::::::::•...•.•M•::::•::::::•:•:•`•::•::•::.:.•..`•:::::::::::::::::::::

b

photograph in Figure 1la

horizontal Neogene ['•

Paleogene Paleozoic andMesozoic

5 km

Figure 11. (a) Photograph showingthe borderbetweenthe Almaz•nmonocline andthe AragonianRange, with units A l, A2, and A3 and the unconformable horizontalNeogene.(b) Photogeological sketchshowing

thegeometrical relationships between Tertiaryunitsat thenorthern sectorof theAlmaz•nBasin(showsthe pointof view of the locationin Figure1l a). Seelocationof sketchin Figure1.

extension([3=1.11to [3=1.19)proposean averagevalue of 30 km at the end of the Mesozoic

at the central sector of the

depressed AlmazfinBasin.Similarkindsof inversionarefound in areasadjacentto orogenicbelts,whereblocksof basement

Chain. were individualized by normal faults during extension[De During the Tertiary, with an overall NNE-SSW shortening Gracianskyet al., 1989;Hayward and Graham, 1989]. The [Guimer• and Alvaro, 1990; Casas-Sainz and Maestro- main structuredevelopedduring this stage was the north Gonzdlez, 1996], the sedimentarypolarity reversed,and the verging Camerosthrust, its foreland, the Rioja Trough, inverted Mesozoic basins became elevated source areas for the located to the north (Figs. 15, 16). Syninversion

Iberian

CASAS-SAINZ ETAL.:PIGGYBACK BASIN EVOLUTION (NORTHERN SPAINi

277

•--.:_,:' .;•½'.iiiii•!•i•;i:E:::;.½!-:.•:•-•,•i.•.'..,,•.•?•?.•-• •i::•::•i½•,:•i:•i•:½'::" ß.

•

'.'.'•'.

...... ::::::::::::::::::::::::::::::::::::::::.:::::.::. •...... •..•,•2•.•.•: •:s½•-:•r• ßß ßß

......

•'' .

.

30 km

-...

A4+HorizontalNeogene

o-.

,

:%'

' THICKNESSOF TERTIARYUNITS

'•*""• •'-••i• ...... '•' '" •"' •'•"',• ''•'"' ' >500 rn

'!i•

>1000

rn

Figure 12. Isopachmapsof TertiaryunitsA1 to A4, obtainedfrom the seismicprofilesand outcrop observations.In the western part of the basin it is difficult to determinethe limits between tectonosedimentary units,because noprofilelinksthisareawiththeeastern sectorandtheoutcrop conditions are

worse.

sedimentation took place within the Almaz•inBasin, and large volumesof syn-tectonicsedimentswere preserved.The nature and geometry of the older basins conditionedthe Tertiary compressionalstructure:At the northernbasin margin there are thin-skinned folds and thrusts involving the Mesozoic cover and shallow-dipping thrusts, reactivating, or shortcutting,the Mesozoic normal faults. In areas near the Castilian Range the main compressional structures are monoclines, involving the rotation and reactivation of northwarddipping normal faults. The differences with the northern basin border probably lie in (1) the difficulty for reactivatingsteeplydippingnormal faults under compression nearlyperpendicularto them [Etheridge,1986; Gillcrist et al., 1987], (2) the different structural trends of the Paleozoic "basement"(NNW to NNE), with relationshipto the Tertiary structures (WNW-ESE), and (3) the very natureof the Paleozoic "basement",with an increasing incidence of igneous rocks

toward the Central System [see, e.g., Escuder Viruete et al., 1998].

In the crustal-scalecross section presented(Figure 17) we considerthe possibility that the newly formed thrust crosscuts the whole continental crust (hypothesis proposed by Salas and Casas [1993]), the Moho acting as a d6collement,as has been interpreted in mountain uplifts developed in front of orogens [Cook and Varsek, 1994]. Since no deep seismic profile existsin the studiedarea, the variationsin depth of the Moho can only be determined from gravimetric data [Salas and Casas, 1993], correlated with seismic relYaction data in the easternIberian Chain [Zeyen et al., 1985]. Midcrustallevels have been suggestedas the detachmentfor the Cameros thrust and other large structuresin the Iberian Chain [Guimer& and Alvaro, 1990; Guimerh et al., 1995]. From a geometricalpoint of view, the main differencebetween the two models

would

be the location

of the thickened

crust

278

CASAS-SAINZET AL.: PIGGYBACK BASIN EVOLUTION (NORTHERN SPA1N)

age Late

OLiGOCENE I A3

IA2 i EOCENE

' PALEOCENE?

Figure 13. Activity of the main structuresat both basin bordersobtainedfrom their relationshipswith tectono-sedimentary units.

with respect to thrusts (Figure 18a). According to thrust geometry,in the midcrustaldetachmentmodel the region of maximum crustal thickening coincides with the zone of hangingwall flat/footwall flat (duplicationof the whole upper crust involved in thrusting). If the thrust crosscutsthe whole crust, the region of crustal thickening will be located both beneath the uplift and at the hinterland of the main thrust (Figure 18a). Gravimetricdata in the sectionof the Cameros thrust and the Almazgn Basin (Figure 17), are consistentwith the secondmodel, if the actual displacementof the Cameros thrust (between 25 and 35 km [Guimer• et al., 1995; CasasSainz and Gil-lmaz, 1998]) is taken into account.

at the southern border, over the Almaz•n monocline. For units

A3 and A4 the situation is completely different, since the depocenterof both units coincide with the present-daybasin center, and proximal facies are found at the present-day northern

basin

border.

At

the northern

and southern

basin

borders both units show progressive or syntectonic unconformities, indicating that these units probably did not extend much farther north from their present-day outcrops. The southward migration of the depocenter of the basin and the

erosion

of

the

northern

sector

of

older

units

from

the

Oligocene to the Miocene agree with the hypothesis of consideringthe Almaz•n Basin as a piggyback basin of the crustal-scale Cameros thrust [Gttirner• et al., 1995]. The

6.2.

A Piggyback Basin Above a Crustal-Scale

Thrust

Facies

and

thickness

distributions

of

the

first

tectonosedimentaryunit, A1, (Figure 12a) indicate that both the basin center (marked by the occurrence of lacustrine limestonesand gypsum)and the depocenterof the basin were at the northeasternborder of the present-dayAlmaz•n Basin (or farther north). The tectonic setting of A1 is not easy to determine, since there are no progressive or syntectonic unconformities with which to define that relationship to

foldingat the basinborders.Sometilted normalfaultsat the northern border are associatedwith thicknesschangesof this unit. Normal faults at the outcropscale crosscuttingthe upper

Cretaceousand A1 are also present.Theseobservations seem to indicatean extensionalregimein the Almaz•n Basinduring

deposition of A1, probably relatedto thecrustalflexureof the Iberian lithosphereduring the emplacementof Pyrenean thrusts (-- 150 km north of the Almaz•n Basin) during the early-middleEocene. Within the second tectonosedimentary unit, A2, the

elevationof the base of the Tertiary, 1500-2500 m deeper in the Rioja Trough with respect to the Almaz•in Basin (see Figure 15), is also consistentwith this hypothesis.

Thecomparison between theage,thickness ande•olution

of tectono-sedimentary units at the Rioja Trough and the Almaz•n Basin (see Figures 10 and 15) agreeswith the coeval developmentof the foreland(Rioja Trough) and the piggyback (Almaz•n Basin) basins of the Cameros thrust. The main deformation period is constrained, in both basins, between the late Eocene and the early Miocene, and the unconformities limiting the A4-R4 units can be fairly well correlated in both basins. The main difference is the thicker Neogene (Aragonianto Turolian) seriesin the Rioja Trough, favored by the prolongation of thrusting till the Vallesian [Mtt•ozJirndnez and Casas-Sainz, 1997]. The erosion of the syntectonic unconformities between A3 and A4 at the northern

border

of the Almaz•n

Basin

can be attributed

to

these late movements.

The northward displacement (-- 25 km) of the Cameros block over the Ebro Basin (together with the shortening associatedto southward thrusting and folding at the northern outcrops at the northernbasinbordershowdistalfacies(see margin of the Almaz•n Basin) implies also a northward Figure 11), the depocenteris also found near the northern transportof the Almaz•n Basin during its development(Figure basinborder,and progressive unconformities are only found 17b). The maximum displacement took place during the

CASAS-SAINZET AL.: PIGGYBACKBASINEVOLUTION(NORTHERNSPAIN)

279

b

Figure 14. (a) Digital modelof the topographyshowingthe tributariesof the Duero river at the northern

sourceareaof the AlmazanBasin.(b) Contours of the thickness of Mesozoicsedimentary seriesmissing abovethe present-day erosionlevel. SinceQuaternary erosionis negligible,the contours indicatethe values

of Tertiaryerosion in theneighboring areasof theAlmazan Basin.Therectangle indicates theareacovered by

Figure 14a.

280

CASAS-SAINZET AL.: PIC•YBACK BASIN EVOLUTION (NORTHERNSPAIN)

3500 Santo • Domingo •-•--3000'

-4cx]0Logr

Ri•

5

Burgo de •

osma

Paleozoicand Mesozoic "%.. .........

borehole •5

30 •

"•:..... "'

I

Figure 15. Contours showing the depth to the base of the Tertiary in the Rioja Trough and the Almazfin Basin. Contoursof the Rioja Trough are after Muhoz-Jirngnezand Casas-Sainz11997].

deposition of A2 and A3, during the late Eocene-upper Oligocene(units R1-R3 at the Rioja Trough, [Muhoz-Jimdnez

17b) a midcrustal fault block should be left beneath the limit between the Almazfin Basin and the Cameros Massif. The

and

existenceof sucha block agreeswith a E-W elongated minimum (-12to -14 mGals)in theresidual gravitymapof the Cameros zone[Riveroetal., 1996](Figure17b).According to Riveroet al. [1996],the maximumdepthto the top of the

Casas-Sainz,

1997]), which is consistent with the

locationof depocentersof units A1 and A2. The displacement of unit A3 would be much lesserbut enoughto erode the basin margin with its associated syntectonic unconformity (above the present-day topography). According to our geometrical reconstruction(Figure 17b) the Tertiary piggyback basin lies 20 km above a shallowdippingramp. Variationsin the dip of the thrustcan be related to the reutilization of some segmentsof the Mesozoic normal faults. Since the paths of the Mesozoic normal fault limiting the CamerosBasin and the Tertiary thrustare different (Figure

causative bodiesfor someof the gravityanomalies foundfrom the residualgravitymap of the Cameroszonevariesbetween8 and 17 km.

Thenorthward displacement of thehanging wallalongthe Camerosthrust ramp would be the responsiblefor the migrationof depocenters within the Tertiaryseriesand the erosionof the northernmost partsof A1 and A2. Guirner• et

CASAS-SAINZ ETAL.:PIGGYBACK BASINEVOLUTION (NORTHERN SPAIN)

ß..•SEISMICPROFILETOR84-05 and TOR84-06

ß--'"•:-•; :•.: •'':"...:: ::-':: :-':,.'::t •... ::.'::':.. '. ,::::::.: .:........

SSE /

,i

...........

:'",,;' .:.: :.,.

I .............

LINE DRAW TOR 84-05 and TOR 84-06

Rioja 4

SSWo .......

LINE DRAW

NNE

R1-19

Figure16. Seismic profiles andlinedrawings showing thestructure of theCameros thrust andtheRioja

Trough.Locationof seismicprofilesis shownin Figure15.

281

282

CASAS-SAINZ ETAL.:PIGGYBACK BASINEVOLUTION (NORTHERN SPAIN)

NNW

Tertiary Mesozoic Paleozoic Figure16. (con•inued/ al. [1996] propose a model with fault bend folding at the northern part of the Almazfin Basin over a footwall ramp dipping - 25ø at 12-15 km depth. However, only a relatively small sector of the northern border of the basin (the G6mara

monocline can be followed for - 20 km) shows a geometry consistent with this possible fault bend fold, and this monoclineis probably linked to the reactivationof Variscan folds. Neoformed folds, reactivationof folds, and thrustingof the Paleozoicin the hanging wall of the Camerosthrust at the present-dayborderof the Almazfin Basin seemto have played an important role during the Tertiary compression,which is consistentwith deformationof the hanging wall and makes it difficult to apply directly the template constraint.

5 km

Hyppolyteet al., 1994; Talling et al., 1995; Teixell and Garcœa-Sansegundo, 1995; G6mezet al., 1996;Pivnik and Khan, 1996] are controlledby the forelandthrustbelt, from which most sediments filling the basin derive. The sedimentarypartitioning between the foreland and the

piggybackbasinscan be consideredas a late stageof the basinfilling (Figure 18b). The frontal structures associated to the thrust below the transportedbasin are responsiblefor modifyingthegeometryof sedimentary sequences, butthe real causes of subsidence and for basin-scale changes in

sedimentationare thrust sequencesand stacking of thrust sheets[Puigdefabregaset al., 1992; Barnolas and Teixell, 1992; Milldn et al., 1994; Tailing et al., 1995]. From the

geometricalpoint of view, this kind of piggybackbasincan 7. Discussion'

Controls on piggyback Basin Evolution Most of the piggyback basins described in the literature [Ori and Friend, 1984; Gonzdlez and Guimer•, 1993'

be considered thin-skinned, since the thrust surface below

thesepiggybackbasinsis detachedat shallowlevelswithin the crust [Ori and Friend, 1984]. The amountof transportis

relativelysmall, as comparedwith shorteningat the thrust belt.

CASAS-SAINZET AL.: PIGGYBACK BASIN EVOLUTION (NORTHERNSPAIN)

_

oo

o

oo

o

o E • •o,,n-< •'•o• •"9 E.......... I I I I I

o

o-c:Fo • , •8 •

o !

,

o ,

i

o i

!

,

! .

I .! •-+ + + +I

o• •

•-

+

+

+

+

ß

t ++ + ++ ++

ß

:, +

+

+

ß

ß

+ I

• g•1•1u•/ k • + + + + •B

•

+k. + +* ++ ++

++++• +

+

+ +

+ ++i ++ ++ • ,+ '--

o

+

[.•

1(•i*.

+•

• +

+

•

+

+

+

•

o

+

+

+++

• •+• +i +• + +

k+ ] +

+

•

•

o

+ +

+ X. + +

• + k +++

c

i + i+

ß

ti."l'4

+

+

+

+

+

+

+

+

283

c

-+

+

+

+

+ + +

+

+

B

.

+ +

+ +

+

284

CASAS-SAINZ ET AL.:PIGGYBACKBASINEVOLUTION(NORTHERN SPAIN) zone of crustal thickening

UPPER CRUST

midcrustal

d LOWER CRUST

MOHO

zone of crustalthickening

UPPER CRUST

LOWER CRUST

detachment

basement

of t•• wj•

at the base

sheets

cover

sheets

ß++++ +•.•

,.,,•11111111/•.foreland basin

+

.••.•.:•:.•.:.:.•.;.;•:•;.:.•.:.:.:•:.•.•••.:.:•:•:••.:.•.••;.•.•.;.;.;.:.•.;.•.•.:•;•;•:•;•;.•.;.••:.:.•.:.;.:.:•:.;.•.:•:.;.•.;.

+

+

+

+

+

+

+

+

+

+

+

.

+

+

+

+

+

.

+

+

+

+

+

+

+

+

+

+

+

basin feeding

+++• • +

+

+

piggyback basin foreland basinPIGGYBACK

+•

;• •:•:..",

ß

THIN-SKINNED (JACA-•PE)

,•-:•'•

........................................ ..................................

++++++++++

piggybackbasin +

b

forelandbasin

+ +••r + + , + + + + + + + + + + + + + + + + + + + , + + +_-,'•..v;':':".':';':'"":'"""':"v":'"""¾ ============================================================================== •'r -• 1 ...... ½"";"'¾'"¾"•F olA•b

+/+ /+

+

/'+'+

, +

+

•

+

+

+

+

+

+

+

+

+

+

+

+

+

+

+

+

+

+

+ •

+ .•,,,ff-

+ + + + +'+'+•'+'+'+'+

......

+

+.+•+

+ +

+

+

+

+

+

+

+

+

+

+

+

+

+

+

+

+

+

+

+

+

+

+

+

+

+

+

+ CONTINENTAL -.k

+ + + + + + + + + +GRUST

+

++•½__.z:--•--

THICK-SKINNED

(ALMAZAN-TYPE) a k

• •

piggyb c bas'n• +/•'"

+/+

• /+ ,4-

•

+

+

+ +

+

+

+

+

+

+

+ +

+

+ +

+

+ +

+

+

+

+

+

+ +

+

+ •

¾ + + + + + + + + +•,,--•+

/+

+

+

•

'

¾.. •-•-•--•+ •1•,,,•-'-'-'-'.•-•'......-'...••";;-..'..'.;.:.:-:::::-_:.:-:.:-.'.:.:.;.;.'.-.'-'..: + + + + + + + +

+

¾+ + + +

+

+

+•,t,---"•

+

+

+

?,•,,,-'+•+

+•

+

+

+

+

•-

+

+

+

+

+

PIGGYBACK

forelandbasin

+

+

+

+ +

+

+ +

+

+ +

+

+ +

+

+ +

+

+ +

-".','.'.'-'.'.'. +

+ +

+

+½,(•iNlTiiXJi=iXJTA/ • ..............

+ + + + + + + + + + + + +CRUST +

+

+

+

+

+

+

+

t

ß

ß

ß

+ + + + +

Figure18. (a) Thetwopossible solutions for intraplate thrusting. Theuppercrosssection showsmidcrustal subhorizontal detachment. The regionof maximumcrustalthickeningmustbe locatedbelow the zoneof hanging wallflat/footwall flat (duplication of thewholeuppercrustinvolvedin thrusting). The lowercross sectionshowsthethrustcrosscutting thewholecrust.The regionof crustalthickening is locatedbothbeneath

theupliftandat thehinterland of themainthrust. (b) Geometry of thetwoextreme typesof piggyback basins andtheirrelationship with sedimentation. The uppercrosssectionshowsa thin-skinned piggyback basin. The sedimentary evolutionis controlled by the forelandthrustbelt,andthe basalthrustonly displaces the wholebasinat the endof the filling stage.The lowercrosssectionshowsa thick-skinned kind of piggyback basin.The sedimentary evolutionis controlledby the mainthrustin boththe forelandand the piggyback basin.

285

CASAS-SAINZ ETAL.:PIGGYBACK BASINEVOLUTION (NORTHERN SPAIN)

From A2(early Oligocene) tothelateMiocene theAlmazfin Basin wasisolated fromitsmainforeland, theRiojaTrough,

the sedimentaryload can be done consideringthe equation derivedof isostaticcompensation [Stecklerand Watts,1978],

byatopographic high, withaminimum horizontal separation

s=(Pa-Pw)z (l)

of 60kmbetween bothbasins (widthoftheuplifted Cameros

\Pa-Pz

block). Palaeocurrents indicate a filling ofthebasin, withthe

Ps is the density mainsource arealocated atthenorthern basin border during wherePais the densityof the asthenosphere,

most ofthefillingstage, which supports theinterpretation of of sediment,Pwis the densityof water,Z is the initial depthof

itsseparation from theforeland basin. IntheRioja Trough,basin, and S is the subsidencedue to sedimentarycharge. Assuming that the initial accommodationspace was not palaeocurrents indicate a southward provenance [Muhoz- filled with water (lacustrinefacies, when existing are shallow

Jimdnez andCasas-Sainz, 1997], which implies thatboth basins shared thesame source area. Atthehinterland ofthe [Bond, 1996], that is equalingto zero the term Pw, and the piggyback nofold-and-thrust beltexists, andtherefore the valuesof pa=3300kg m-3 andPs=2300kg m-3,a valueof

tectonic control of thebasinis givenby thethrustunderlying S=3.3Z would be obtained,a higher value than the obtained

thepiggyback. Thepiggyback character oftheAlmazfin Basin

(2.3Z) in marine basins. In the case of internally drained

is defined by thenorthward movement of thewholebasin, basins, Z can be considered as the difference in elevation conditioning the geometry of thesedimentary units.The betweenthe uplifting mountainbordersand the bottom of the transport ofthepiggyback basin toward theforeland, together basin. This value can only be considered as approximate, withtheCameros crustalblock,is muchmoreimportant than in the caseof thin-skinnedpiggybackbasins.This basin

owing to the possible variations of Pa and Ps and possible conditions of nonisostaticequilibrium, but it gives an idea of configuration is morelikelyto occur when theorigin of the the subsidence created by the sedimentary load once an piggyback isa crustal-scale thrust such theCameros thrust and internal drainagewas createdby the uplifting of the mountains can be defined as thick-skinned.Other thick-skinned surroundingthe basin. All the referenced piggyback basins, thick-skinned and piggyback basins [Beer etal.,1990]show similar controls on the sedimentary evolution,but because of the different thin-skinned, are located above thrusts marginal to the configuration of thefrontalstructures associated withthe orogenic belts with the same vergence as that of the main

crustal-scale thrust underlyingthe basin, the origin of thrusts. The Cameros thrust can be considered as a basement unconformities is also relatedto episodiccommunications uplift, facing the Pyrenean orogen [Guirnerd and Alvaro, between the foreland and the piggyback. In some cases

[Bonini, 1999a,b]the geometry of the basinmaybe a

combination of thin-skinnedand thick-skinned tectonicsbut

the geometrical characteristics of this modelmustbe

1990; Casas-Sainz and Gil-Imaz, 1998]. In basementuplifts of the type of the Cameros thrust, opposite to orogenic belts as the Laramides [Brown, 1988; Erslev, 1993; Stone, 1993], no piggyback basins are described, probably owing to the

particular[Bonini,1999a,b].

nonconfluence

sequence of thrustsseparated by the piggyback basin,in

described.

of the variables

found

at the Cameros

thrust:

The overall geometryof syntectonicunits and (1) a nonrigid pre-Cambrian and Paleozoic basement, more unconformitiesat the Almazfin Basin, the migration of than 10 km thick at most part of the hanging wall, (2) depocenters duringbasintransport in theopposite sense of internally drained basins in the hanging wall, allowing the movementof the main thrust,and the erosionof the earlier accumulation of sediments and subsequent sediment load sedimentary unitsin thehanging wallof themainthrustallow subsidence, (3) irregularities at the footwall ramp due to us to relate the AlmazfinBasin to the geometricalmodels preexistingextensional structures,and (4) the asymmetry in proposed for otherthin-skinned or thick-skinned piggybackthe displacementof the thrusts limiting the basement uplift basins.The AlmazfinBasin fits with the model of an only that separatesthe foreland and the piggyback basins. In this activethrustwith slowdisplacement, allowingthe migration sense, the Almazfin Basin can be considered as a particular of depocenters [Zoetemeijer and Sassi,1992]or witha type of basin, developedabove a basementuplift, till now not whichthe faster(or the active)thrustis locatedtowardthe

foreland (types2 and4, respectively, of Bonini[1999b]). One of the main controlsin the formationof the Almazfin

8. Conclusions:Intraplate Deformation and Basin

Formation

piggyback basin wasthechange fromanexternal (tillthelate

The Almazfin Basin can be understoodwithin a strongly Eocene) to an internaldrainage pattern,whichremained till thelateMiocene. The geometry of thelaterunits(horizontal deformed zone in the central part of Iberia, between the Neogene), in continuity withthecontiguous Calatayud basin Central System and the Castilian Range to the south and the (seelocation in Figure1), indicates thatthefinalstages of Cameros Massif to the north. The structural reliefs are more fillingwereatectonic at thebasinscale,although thrusting than 5 km, since the Paleozoic mountains are between 2200

continued to occurat the Camerosthrust[Muhoz-Jim•nez and

and 2500 m above sea level, and the top of the Paleozoicis

Casas-Sainz, 1997].Depending on theamountof upliftof the more than 2500 m below sea level in the Almazfin and Ebro mountainborders,the changefrom external to internal Basins.West of the Almazfin Basin, the E-W elongatedAranda

drainagemay causethe accumulation of a significant basin,

filled with Paleogene rocks, can be inferred from subsoil exploration [ITGE, 1990] (Figure 17a). At the caseof the AlmazfinBasina completesubsidence curvecannot southernlimit of the CastilianRange the Madrid Basin is also be done,owingto thelackof precise datingduringthemain filled with Paleogene(up to 2000 m) and Neogene(up to 1200 accumulation period,an approximation to thecontribution of m) deposits[Racero Baena, 1988; Calvo Sorando et al., 1991;

thickness of sediments [Tailinget al., 1995].Althoughin the

286

CASAS-SAINZET AL.' PIGGYBACKBASIN EVOLUTION (NORTHERNSPAIN)

De Vicenteet al., 1996a,b], the thicknessof the Tertiary

et al., 1995; Casas-Sainz

and

Gil-Imaz,

1998] and the

units decreasing progressively toward the east. The

uplifting of the Castilian Branch. The change to internal northwestern border of the Madrid Basin is a NE-SW reverse drainage was also probably responsible for the amount of fault againstthe Paleozoicrocks(igneousandmetamorphic) subsidencein this area. During compressionthe continental crust thickened to more than 40 km below and north of the of the Central System [Banks and Warburton, 1991' Stinchez Serrano et al., 1993' De Vicente et al., 1994]. Both in the Almazfin Basin [Salas and Casas, 1993]. The Tertiary CastilianRangeandin the CentralSystem,Tertiarystructures evolution, recorded by deposition, indicates a coeval deformation at the western sector of the Ebro Basin, formed at high angles to the Variscan (N-S to NNE-SSW) structures. constituting the Rioja Trough [Muhoz-Jimdnez and CasasSainz, 1997] and the Almaz•n Basin, with a main deformation Intraplate deformation during the Tertiary within the Iberian plate gave rise to sedimentarybasins, subsiding periodbetweenthe late Eoceneand the late Oligocene. between2000 and 3000 m below their originalelevation(the Acknowledgments. The authorsare very grateful to Mary Ford, Franqois Roure, and Joan Guimerh for their suggestions,which improvedthe originalmanuscript, andto W. L6pez, Repsol-exploraci6n, andthe Ministry of Energyand Industryof Spainfor allowingustouse and copythe seismicreflectionprofiles.This work was supportedby project PB97-0997 of the Direcci6n General de EnsefianzaSuperior (Spain).

shallowmarineupperCretaceous limestonesmay be takenas a reference).Intraplate mountain ranges (Iberian Range and SpanishCentral System) were elevated more than 2000 m. In the Almazfin Basin the initial subsidence could be due to the

flexure of the lithospherecausedby the emplacementof the Camerosthrust sheet,60 km wide and 1-6 km high [Guimerg

References Adell Argi16s, F., F. Gonzfilez Lodeiro and M.

Tena-Dfivila,Mapa geoldgicode Espaha,scale 1:50,000, sheet 434, 45 pp. Inst. Geol. y Minero de Esp., Madrid, 1978. AgustL J., L. Cabrera, P. Anad6n, and S. Arbiol, A late Oligocene-early Miocene rodent biozonation from the SE Ebro Basin (NE

Spain): A potentialmammalstage stratotype, Newsletter Stratigr., 18, 81-97, 1988.

Alonso,

J.L.,

Estructura

y

evoluci6n

tectonoestratigrfificade la regi6n del manto

del Esla (zona Cantfibrica,NW de Espa•a), 276 pp., Diputaci6n Provincial de Le6n, Le6n, Spain, 1985.

Armenteros, I., Sintesis del pale6geno del borde oriental de la Cuenca de Almazfin (Soria):

Geologia del yacimiento de Mazater6n, Stud.Geol. SaImanticensia, 29, 145-156, 1994. Arthaud, F., and P. Matte, Les d&rochements

tardi-herciniensdu Sud-Ouest de l'Europe: Ge6metrie

et

essai

de

reconstruction

des

conditionsde la deformation,Tectonophysics, 25, 139-171, 1975. Arthaud, F. and P. Matte, Late Paleozoic strike-

slip faulting in southern Europe and north Africa: Results of a right-lateral shear zone between the Appalachiansand the Urals, Geol. Soc. Am. Bull., 88, 1305-1320, 1977.

Alonso,J.L., Fold reactivationinvolvingangular Baby, P., B. Colletta and D. Zubieta, Etude unconformablesequences:theoreticalanalysis gfiom•trique et expfirimentale d'un bassin and natural examples from the Cantabrian

Zone (Northwest Spain). Tectonophysics, 170, 57-77,

1989.

Alonso, J.L., J.A. Pulgar, J.C. Garcia-Ramos,and P. Barba, Tertiary basinsand Alpine tectonics in the CantabrianMountains(NW Spain), in

transportfi: exemple du synclinorium de l'Alto

Beni (Andes centrales), Bull.

Soc.

Ggol. Fr., 166(6), 797-811, 1995. Banks, C.J., and J. Warburton, Mid-crustal

detachmentin the Betic system of southeast Spain. Tectonophysics,191, 275-289, 1991.

Tertiary basins of Spain: The Stratigraphic Barnolas, A., and A. Teixell, La cuenca Record of Crustal Kinematics,editedby P.F. surpirenaicade Jaca como ejemplo de cuenca Friend and C.J. Dabrio, pp. 214-227, de antepais marina profunda con Cambridge Univ. Press, New York, 1996. sedimentaci6n carbonfiticaen el margendistal, Alvarez-Sierra,M. A., Estudio sistemfiticoy paper presentedat III CongresoGeo16gicode bioestratigrfificode los Eomyidae (Rodentia) Espafia, Sociedad Geo16gica de Espafia, del Oligoceno superior y Mioceno inferior Salamanca,Spain, 1992.

espafiol, Script. Geol., 86, 1-207, 1987. Alvarez-Sierra,M. A., R. Daams, J.I. Lacomba,N. L6pez-Martinez, and M.A. Sacristfin-Marffn, Succession of micromammal

faunas in

Oligocene of Spain, Munchner

the

Geowiss.

Abh. A, 10, 43-48, 1987.

Alvaro, M., R. Capore,and R. Vegas,Un modelo de evoluci6n geotect6nica para la Cadena Celtib6rica, Acta Geol. Hisp., 14, 172-177, 1979.

Arche, A., and J. L6pez-G6mez,Origin of the Permian-Triassic

Iberian

Basin,

central-

eastern Spain, Tectonophysics,266, 443-464, 1996.

Arias, C., R. Mas, A. Garcia, A. Alonso, L. Vilas, R. Rinc6n, and N. Me16ndez, Les facies

Urgoniens et leurs variations pendant la transgressionaptienne occidental de la Chatne Ib6rique (Espagne), Geobios, 3, 11-23, 1979. Armenteros, I., C. J. Dabrio, R. Guisado, and A.

Sfinchez

de

Vega,

sedimentarias del terciario

Megasecuencias del borde oriental

Bascones-Alvira, L.,

F. Gonzfilez-Lodeiro, F.

Martinez Alvarez, V. Gabald6nL6pez, and P. Ruiz Reig, Mapa geoltSgicode Espaha, scale 1:50,000, sheet 433, Inst. Geol. y Minero de Esp., Madrid, 1978.

Beer, J.A., R.W. Allmendinger, D.E. Figueroa, and T.E. Jordan, Seismic stratigraphyof a Neogene piggyback basin, Argentina, A.A.P.G.

Bull., 74, 1183-1202,

1990.

Bergamin, J.F., G. De Vicente, R. Tejero, F. Sfinchez Serrano, D. G6mez, A. Mufioz Martin, and M.A. Perucha, Cuantificaci6n del

desplazamiento dextroso Alpino en la cordillera Ibfirica a parfir de datos gravim•tricos, Geogaceta, 20(4),

917-920,

1996.

Bond, J., Tectono-sedimentaryevolution of the AlmazfinBasin,NE Spain,in Tertiary basinsof Spain: the stratigraphic record of crustal kinematics, edited by P.F. Friend and C.J. Dabrio, pp. 203-213, CambridgeUniv. Press, New York, 1996.

de la Cuenca de Almazan (Soria-Zaragoza) Bonini, M., Basement-controlled Neogene Stud. Geol. Salmanticensia,5, 107-127, 1989. polyphase cover thrusting and basin

development along the Chianti Mountains ridge (Northern Apennines, Italy), Geol. Mag., 136, 133-152, 1999a.

Bonini, M., Evolution and depocentremigration in thrust-top basins: Inferences from the Messinian Velona Basin (Northern Apennines, Italy), Tectonophysics, 304, 95108, 1999b.

Brown, W.G., Deformation style of Laramide uplifts in the Wyoming foreland, inlnteraction o.! the Rock)' Mountain )'breIand and the Cordilleran thrust belt, edited by C.J. Schmidt and W.J. Perry, Mem. Geol. Soc. Am., 171, 1-26,

1988.

Calvo Sorando, P., G. De Vicente, and A.M. Alonso Zarza, Correlaci6n entre las

deformaciones alpinas y la evoluci6n del relleno

sedimentario

de la Cuenca

de Madrid

durante el Mioceno, paper presented at I Congreso del Grupo Espafiol del Terciario, Grupo Espafiol del Terciario, Vic, Espafia, 1991.

Capote, R., La evoluci6n tardihercinica, in Geologfa de Espaha: Libro Jubilar de J.M. Rios, vol. 2, edited by J.A. Comba, pp. 17-25, Inst. Tecnol. GeoMinero de Esp., Madrid, 1983a.

Capore, R., La tect6nica de la Cordillera Ib6rica, in GeoIog[a de Espaha: Libro Jubilar de J.M. Rios, vol. 2, edited by J.A. Comba, pp. 108120, Inst. Tecnol. GeoMinero de Esp., Madrid, 1983b. Carballeira, J.,

and

C.

Pol,

lnforme

complementario sobre el Pale6geno de la Cuenca de Almazfin, in Mapa geoldgico de Espaha, scale 1:50,000, Inst. Tecnol. GeoMinero de Esp., Madrid, 1989. Casas, A.M., I.Gil, B. Lerfinoz, H. Millfin, and J.L.

Sim6n, Quaternaryreactivationof flexural slip folds by diapiric activity: example from the western Ebro Basin (Spain), Geol. Runds.,83, 853-867,

1994.

Casas-Sainz,A.M., Oblique tectonic inversion and basement thrusting in the Cameros Massif (Northern Spain), Geodin. Acta , 6(3), 202216, 1993. Casas-Sainz, A.M.,

subsidence,

and A. Gil-Imaz,

contractional

Extensional

folding

and

subsequent inversion of the Eastern Cameros Basin (NW Spain), Geol. Runds., 86, 802818, 1998. Casas Sainz, A.,

and A.

Maestro

Gonzfilez,

Deflection of a compressionalstress field by

CASAS-SAINZ ETAL.:PIGGYBACK BASINEVOLUTION(NORTHERN SPAIN) large-scale basementfaults:A casestudyfrom the Tertiary Almazfin Basin (Spain), Tectonophysics,255, 135-156, 1996. Chang, K. H., Unconformity bounded stratigraphic units, Geol. Soc. Am. Bull., 66, 1544-1552,

1975.

Clemente, P., and A. Alonso, Estratigrafia y

sedimentologia de las facies continentalesdel Cretficico inferior

en el borde meridional

de

la Cuenca de los Cameros. Estud. geol., 45, 90-109,

1990.

Clemente,

P.,

M.

P6rez-Arlucea,

Deposiuonalarchitectureof the Cuerda del Spain, J. Sediment. Petrol., 63,

437-452,

1993.

Cook, F. A., and J.L. Varsek, Orogen-scale decollements. Rev. Geophys., 32, 37-60, 1994.

Cuenca, G., Nuevo yacimiento de vertebradosdel inferior

del horde

meridional

Cuenca del Ebro, Estud. Geol., 39,

de la

217-224,

1983.

Cuenca, G., Los Roedotes (Mammalia) del Mioceno lnj•rior de Autol (La Rioja), 96 pp., Ciencias

de la Tierra,

2,

Inst.

de Estud.

Riojanos,Logrofio,Spain, 1985. Cuenca, G., J.I. Canudo, C. Laplana, and J.A. Andr6s, Bio y cronoestratigrafia con mamiferos

en la

Cuenca

Terciaria

del

Ebro:

Ensayo de sintesis, Acta Geol. Hisp., 27, 127143, 1992. Cuesta-Ruiz-Colmenares,

M.A.,

and E. Jim6nez-

Fuentes, Sintesis del Pale6geno del horde oriental de la Cuenca de Almazfin (Soria): Vertebrados

de

Mazater6n.

Stud.

Geol.

Salmanticensa, 29, 157-175, 1994. Daams, R., and A. Meulen, Paleoenvironmental

and paleoclimatic interpretation of micromammal faunal successionsin the Upper Oligocene and Miocene of north central Spain, Paleobiol.

Conti., 14(2), 241-257,

1984.

De Graciansky, P.C., G. Dardeau, M. Lemoine, and P. Tricart, The inverted margin of the French Alps and foreland basin inversion, in Inversion Tectonics, edited by M.A. Cooper and G.D. Williams, Geol. Soc. Spec. Pub., 44, 87-104,

1989.

De Vicente, G., Anfilisis poblacional de fallas: E1 sector

de

enlace

Sistema

Central-Cordillera

Ib6rica, doctoral thesis, 317 pp., Univ. Complutensede Madrid, Madrid, 1988. De Vicente, G., J.M. Gonzfilez Casado, J.P. Calvo,

A. Mufioz Martin, J. Giner, and M. Rodriguez Pascua, Evoluci6n y estructurasalpinas en la zona del centro peninsular, Cuadernos Lab. Xeohixico Laxe, 19, 175-190, 1994. De Vicente, G., J.P. Calvo, and A.Mufioz Martin,

Neogene tectono-sedimentaryreview of the Madrid basin, in Tertiary Basins 03"Spain, edited by P.F. Friend and C.J. Dabrio, pp. 267-271, Cambridge Univ. Press, New York, 1996a.

De Vicente, G., J.M. Gonzfilez Casado, A. Mufioz

Martin, J. Giner, and M.A. Rodriguez Pascua, Structureand Tertiary evolution of the Madrid basin, inTertiary Basins of Spain, edited by

P.F. Friend and C.J. Dabrio, pp. 263-267, Cambridge Univ. Press, New York, 1996b. Dikkers, A.J., Sketch of a possible lineament pattern in northwest Europe. Geol. Mijnbouwn, 56(4), 275-285, 1977. Erslev,

E.A.,

Thrusts,

back-thrusts

and

detachment of Rocky Mountain foreland arches,in Laramide BasementDejbrmation in the Rock), Mountain Foreland of the Western United States, edited by C.J. Schmidt, R.B.

in the Iberian

Massif:

Structural,

metamorphic and geochronological evidence from

the Somosierra

sector of the Sierra

del

Guadarrama (Central Iberian Zone, Spain), Tectonophysics,290, 87-109, 1998.

Etheridge, M.A., On the reactivation of extensional fault systems, Philos. Trans. R. Soc. London, Set. A, 317,

179-194, 1986.

Ferreiro Padin, E., Mapa geoldgico de Espaga, scale

and

Pozo Formation, lower Cretaceous of the extensional Cameros Basin, north-central

Mioceno

and G. Dunning, Variscan syncollisional extension

1:50,000,

sheet

379,

Inst.

Tecnol.

GeoMinero de Esp., Madrid, 1988. Garcia-Hidalgo,J.F., M. Segura , and A. Garcia, E1 Cretficico del borde septentrional de la Rama Casteliana de la Cordillera

Ib6rica, Rev.

Soc. Geol. Esp., 10(1-2), 39-54, 1997. Garrido-Megias, A., Estudio geol6gico y relaci6n entre tect6nica y sedimentaci6n del Secundario y Terciario de la vertiente meridional pirenaica en su zona central (provincias de Huesca y L6rida), doctoral thesis,395 pp., Univ. of Granada, Spain, 1973. Gillcrist, R., M. Coward, and J.L. Mugnier, Structural inversion and its controls: Examples from the Alpine foreland and the French Alps, Geodin. Acta, l(1), 5-34, 1987. Gim•nez

Montsant, J., and R. Salas, Subsidence

analysis in thrust tectonics: Application to the southeastern Pyrenean foreland, Tectonophysics,282, 331-352, 1997. G6mez, J.J., M. Diaz-Molina,

and A. Lendinez,

Tectono-sedimentary analysis of the Loranca Basin (Upper Oligocene-Miocene, Central Spain): A "non-sequenced"foreland basin. in Tertiary basins of Spain, edited by P.F. Friend and C.J. Dabrio, pp. 285-294, Cambridge Univ. Press, New York, 1996. Gonzfilez,

A.,

and J. Guimerh,

Sedimentaci6n

sintect6nica en una cuenca transportada sobre una lfimina de cabalgamiento: La cubeta terciaria de Aliaga, Rev. Soc. Geol. Esp., 6(12), 151-165, 1993. Gonzfilez, A., G. Pardo , and J. Villena, E1 anfilisis tectosedimentario

como

instrumento

de

correlaci6n entre cuencas, paper presented at II Congreso Geol6gico de Espafia, Sociedad Geo16gicade Espafia,Granada, Spain, 1988. Goy, A., and L.C. Sufirez Vega, Tect6nica y estratigrafia mesozoicas: E1 Jurfisico, in Geologfa de Espaga. Libro Jubilar J.M. Rios, vol. 2, edited by J.A. Comba, pp. 62-79, Inst. Geol. Min. de Esp., 1983. Goy, A., J.J. G6mez, and A. Y6benes, E1 Jurfisico de la Rama Casteliana

Ib6rica

(Mitad

Norte),

de la Cordillera

I,

Unidades

litoestratigrfificas, Estud. Geol., 32, 391-423, 1976.

Guimerh,

J.,

and

M.

Alvaro,

Structure

et

6volution de la compression alpine dans la Chaine Ib6rique et la Chaine Coti•re Catalane (Espagne), Bull. Soc. Gdol. France, 6(2), 339-348, 1990. Guimerh, J., A. Alonso, and J.R. Mas, Inversion

of an extensional-rampbasin by a neoformed thrust: The Cameros Basin (N Spain), in Basin Inversion, edited by J. G. Buchanan, and P. G. Buchanan, Geol. Soc. Spec. Pub., 88, 433453,

1995.

Guimerh, J., R. Salas, J. Verg6s, and A. Casas, Extensi6n mesozoica e inversi6n compresiva terciaria en la Cadena Ib6rica: Aportacionesa

partir del anfilisis de un perill gravim6trico, Geogaceta, 20 (7), 1691-1694, 1996. Guiraud, M., and M. S6guret, Releasing overstep model for the Late Jurassic-Early Cretaceous

(Wealdian) Soria strike-slip basin (North

Spain), in Strike-slip deJbrmation, basin jbrmation and sedimentation, editedby K.T.

Chaseand E.A. Erslev, Spec. Pap. Geol. Soc.

Biddle, and N. Christie-Blick, SEPM Spec.

Am., 280,

Pub., 37, 159-175, 1984.

339-358,

1993.

Escuder Viruete, J., P.P. Hernfiiz Huerta, P.

Valverde-Vaquero, R. Rodriguez Fernfindez,

Guisado, R., I. Armenteros, and C. Dabrio, Sedimentaci6n continental pale6gena entre

287

Almazul y Deza (Cuenca de Almazfin oriental, Soria), Stud. Geol. Salmanticensa, 25, 67-86, 1988.

Guti6rrez

Elorza,

M.,

and

F.J.

Gracia,

Environmental interpretation and evolution of the Tertiary erosion surfaces in the Iberian Range (Spain), in Palaeosurj'aces: Recognition, Reconstruction and Palaeoenvironmental Interpretation, edited by M. Widdowson, Geol. Soc. Spec. Pub., 120, 147-158,

1997.

Hardy, S., and J. Poblet, Geometric and numerical model of progressive limb rotation in detachment folds, Geology, 22, 371-374, 1994.

Hayward, A.B., and R.H. Graham, Some geometrical characteristics of inversion, in Inversion Tectonics, edited by M.A. Cooper and G.D. Williams, Geol. Soc. Spec. Pub., 44, 17-39,

1989.

Huntoon,

P.V.,

Precambrian

Influence basement

of

inherited

structure

on

the

localization and form of Laramide monoclines,

Grand Canyon, Arizona, in Laramide basementde.[ormationin the Rocky Mountain l'breland , t the Western United States, edited by C.J. Sc, midt, R.B. Chase, and E.A. Erslev, Spec. Pap. Geol. Soc. Am., 280, 243-256, 1993.

Hyppolyte, J.C., J. Angelier, F. Roure, and P. Casero, Piggyback basin development and thrust

belt

evolution:

Structural

and

palaeostress analysis of Plio-Quaternary basins in the Southern Appennines,J. Struct. Geol., •6(2), 159-173, 1994. Illies, J.H., Ancient and recent rifting in the

Rhinegraben.Geol. Mijnbouwn, 56(4), 329350,

1977.

Instituto Tecno16gico GeoMinero de Espafia, Documentos sobre la Geologfa del Subsuelo de Espaga, vol. 5: Duero-Almazdn., Madrid, 1990.

Johnson, M.R.W.,

and R.T.C.

Frost, Fault and

lineament patterns in the southern highlands of Scotland, Geol. Mijnbouwn, 56(4), 287294,

1977.

Julivert, M., The areas of Alpine folded cover in the

Iberian

Meseta

(Iberian

Chain,

'Catalanides, etc.), in Geological Atlas of Alpine Europe and Adjoining Alpine Areas, pp. 93-112, Elsevier Sci., New York, 1978. Julivert, M., A. Marcos, and J. Truyols, L'6volution pa16og6ographique du NW de l'Espagne pendant l'Ordovicien-Silurien, Bull. Soc. Gdol. Min. Bretagne,Ser. C, 4, 1-7, 1972.

Lacomba,

J.

I.,

and

J.

Martinez-Salanova,

Quercomys Bijami Gen. Nov. Sp. Nov. (Gliridae, Rodentia, Mammalia) del trfinsito Oligoceno-Mioceno espafiol, Estud. Geol., 44, 107-118,

1988.

Lago, M., A. Pocovi, J. Bastida, and J.M. Amig6, The alkaline magmatismin the Triassic-Liassic boundary of the Iberian Chain: geological and petrological characters, paper presented at II Congreso Geo16gico de Espafia, Sociedad Geo16gicade Espafia, Granada, Spain, 1988. Lanaja, J. M., Contribuci6n de la exploraci6n petrolifera al conocimiento de la Geologia de Espafia, 465 pp., Inst. Geol. Minero de Esp., Madrid,

1987.

Lawton, T.F., and J.H. Trexler, Piggyback basin in the Sevier orogenic belt, Utah: implications for development of the thrust wedge, Geology, 19, 827-830, 1991. Lendlnez, A., Mapa geol6gico de Espaga, scale 1:50,000, sheet 435, Inst. Tecnol. GeoMinero

de Esp., Madrid, 1987.

Lendinez Gonzfilez, A., andDi Martin Herrero, Mapa geoldgico de Espai•a, scale 1:50,000, sheet 436, Inst. Tecnol. GeoMinero de Esp., Madrid,

1987.

288

CASAS-SAINZET AL.: PIGGYBACKBASIN EVOLUTION (NORTHERNSPAIN)

Lendinez Gonzfilez, A., and J.L. Mufioz del Real,

Mapa geoldgico de Espaha, scale 1'50,000, sheet 405, Inst. Tecnol. GeoMinero de Esp., Madrid, 1988. Liesa-Carrera, C.,

and

A.M.

Casas

Sainz,

Reactivaci6n alpina de pliegues y fallas del z6calo

hercinico

de

la

Cordillera

Ib6rica:

scale

1:50,000,

sheet

380,

Inst.

Tecnol.

GeoMinero de Esp., Madrid, 1987. Ori, G.G., and P.F. Friend, Sedimentary basins formed and carried piggyback on active thrust sheets,Geology, 12, 475-478, 1984. Pardo,

G.,

J.

Villena,

and

A.

Gonzfilez,

ejemplos de la Sierra de la Demanda y la

Contribuci6na los conceptosy a la aplicaci6n del anfilisis tectosedimentario: Rupturas y

Serranla

de

unidades

Xeoldxico

Laxe, 19, 119-135,

Lotze,

F.,

Cuenca.

Einige

Cuadernos

Lab.

1995.

probleme der Iberischen

Meseta, Geotecton. Fersch., 6, 1-12, 1945. Maestro, A., A. Cort6s, and A.M. Casas,

Pliegues y cabalgamientos terciarios en el sector noroccidental de la Rama Aragonesa (Cordillera

Ib6rica),

in

A vances

en

el

Conocimientodel Terciario Ibdrico, edited by J.P. Calvo and J. Morales, pp. 113-116, Univ. Comp. de Madrid, Madrid, 1997. Marill, R., and D. G6mez Gras, Procedencia y modelo diagen6ticode las areniscasde facies Utrillas

en la Cordillera

Ib6rica

(umbral de

Ateca) y la meseta norcastellana, Rev. Soc. Geol. Esp., 5 (3-4), 101-115, 1992. Martinez-Salanova,J., Estudio PaleontoIdgico de los Micromamœferosdel Mioceno inferior de Fuenmayor (La Rioja), vol. 10, 99 pp., Ciencias de la Tierra, Inst. Estud. Riojanos, Logrofio, Spain, 1987. Mediavilla,

R., C.J. Dabrio,

A. Martin-Serrano,

and J.I. Santisteban, Lacustrine Neogene systems of the Duero Basin: evolution and controls, in Tertiary Basins of Spain: The Stratigraphic Record of Crustal Kinematics., edited by P.F. Friend and C.J. Dabrio, pp. 228-236, Cambridge Univ. Press, New York, 1996.

Mezcua, J., A. Gil,

and R. Benarroch, Estudio

gravim6trico de la Peninsula Ib6rica y Baleares, Inst. Geogr. Nac., Madrid, Spain, 1996.

Mill fin,

H.,

M.

Aurell,

and

A.

Me16ndez,

Synchronous detachment folds and coeval sedimentation in the Prepyrenean External Sierras (Spain): A case study for a tectonic origin of sequences and system tracts, Sedimentology, 41, 1001-1024, 1994. Mugnier, J.L., P. Baby, B. Colletta, P. Vinour, P. Ba16, and P. Leturmy, Thrust geometry controlled by erosion and sedimentation: A view from analogue models, Geology, 25 (5), 427-430,

1997.

Mufioz, A., A. Ramos, A. Sopefta, and Y. SfinchezMoya, Caracterizaci6nde las unidades litoestratigrfificas del Trifisico en el subsuelo del

tercio

noroccidental

de

la

Cordillera

Ib6rica y fireas adyacentes, Cuad.

Geol.

Ibdrica, 19, 129-171, 1995. Mufioz, J.A., Evolution of a continental collision belt: ECORS-Pyrenees crustal balanced cross section, in Thrust Tectonics, edited by K.R.

McClay, pp. 235-243, Chapman and Hall, New York,

1992.

Mufioz-Jim6nez, del

Terciario

A., Andlisis del

Sector

Tectosedimentario Occidental

de

la

Cuenca deI Ebro (Comunidad de La Rio.ja), vol. 15, 347 pp., Cienc. de la Tierra, Inst. Estud. Riojanos, Logrofio, Spain, 1992. Mufioz-Jim6nez,

A., and A.M.

Casas-Sainz, The

Rioja Trough (N Spain): tecto-sedimentary evolution of a symmetric foreland basin, Basin Res., 9, 65-85, 1997. Mufioz-Martin, A., and

G.

De

Vicente,

Cuantificaci6n del acortamiento alpino y estructura en profundidad del extremo suroccidental de la Cordillera Ib6rica (Sierras

de Altomira y Bascufiana), Rev. Soc. Geol. Esp., 11(3-4), 233-252, 1998. Navarro, D., Mapa geoldgico de Espaha, scale 1:50,000, sheet 350, Inst. Tecnol. GeoMinero

de Esp., Madrid, 1988.

NavarroVfizquez,D., Mapa geoldgicode Espaga,

tectosedimentarias

como

fundamento de correlaciones estratigrfificas, Rev. Soc. Geol. Esp., 2, 199-221, 1989. Pivnik,

D.A.,

and

J.

Khan,

Transition

from

foreland- to piggyback-basindeposition, PlioPleistocene Upper Siwalik Group, Shinghar Range, NW Pakistan, Sedimentology, 43, 631-646, 1996. Platt, N.H., Basin evolution and fault reactivation in the Western Cameros Basin, Northern

Spain, J. Geol. Soc. London, 147,

165-175,

1990.

Pocovi, A., A. Me16ndez, and G. Me16ndez, Los

aspectos mfis obvios del Jurfisico de los Pirineos, paper presented at IV Congreso de Jurfisicode Espafia, Universidad de Zaragoza, Alcafiiz, Spain, 1997. Puigdefhbregas, C., La sedimentaci6n molfisica en la Cuenca de Jaca, Monogr. 104, 188 pp., Inst. Estud. Pirenaicos, Jaca, Spain, 1975. Puigdefhbregas,C., J.A. Mufioz, and J. Verg6s, Thrusting and foreland basin evolution in the Southern Pyrenees, in Thrust Tectonics, edited by K.R. McClay, pp. 247-254, Chapman and Hall, New York, 1992. Racero Baena, A., Consideraciones acerca de la

evoluci6n geo16gica del margen NW de la cuenca del Tajo durante el Terciario a partir de los datos del subsuelo, paper presented at II Congreso Geo16gico de Espafia, Sociedad Geo16gicade Espafia, Granada, Spain, 1988. Ramberg, I.B., R.H. Gabrielsen, B.T. Larsen, and A. Solli, Analysis of fracture patterns in southern Norway,Geol. Mijnbouwn, 56(4), 295-310,

1977.

Riba, O., Syntectonic unconformities of the Alto Cardener, Spanish Pyrenees: A genetic interpretation, Sediment. Geol., 15, 213-233,

Presencia

del

Vallesiense

en

el

Mioceno

continentalde la Depresi6n del Ebro, Rev. R. Acad. Cienc. Exactas, F[s. Nat. Madrid, 76, 277-284,

1982.

Santisteban, J. I., R. Mediavilla, A. Mart/nSerrano, and C. J. Dabrio, The Duero Basin: a

generaloverview,in TertiaryBasinsof Spain: The Stratigraphic Record of Crustal Kinematics, edited by P.F. Friend and C.J. Dabrio, pp. 183-187, CambridgeUniv. Press, New York, 1996.

Sanz de Galdeano, C.M., Tertiary tectonic framework of the Iberian Peninsula, in

Tertiary Basins of Spain: The Stratigraphic Recordof Crustal Kinematics,editedby P.F. Friendand C.J. Dabrio,pp. 9-14, Cambridge Univ. Press, New York, 1996..

Sell, I., G. Poupeau,C. Casquet,C. Galindo,and J.M. Gonzfilez-Casado, Exhumaci6n alpinadel bloque morfotect6nico Pedriza-La Cabrera (Sierra del Guadarrama, Sistema Central Espafiol): Potencialidad de la termocronometria por trazas de fisi6n en apatitos,Geogaceta, 18, 23-26, 1995.

Sopefta,A., C. Virgili, A. Arche, A. Ramos,and

S. Hernando,E1 Trifisico,in Geologfa de Espatia:Libro Jubilar J.M. Rh•s, vol. 2, edited by J.A. Comba, pp. 47-63, Instituto Geol. Min. de Esp., Madrid, 1983. Steckler, M.S., and A.B. Watts. Subsidenceof the

Atlantictype continental marginoff New York. Earth Planet. Sci. Let., 42, 1-13, 1978.

Stone,D.S., Basement-involved thrust-generated folds as seismicallyimagedin the subsurface of the central Rocky Mountain foreland, in LaramideBasementDe./brmationin the Rocky Mountain Foreland o! the Western United States, editedby C.J. Schmidt,R.B. Chaseand E.A. Erslev, Spec. Pap. Geol. Soc. Am., 280, 271-318,

1993.

Suppe,J., Chou, G.T., and Hook, S.C., Rates of

foldingand faultingdetermined from growth strata,in Thrust Tectonics,edited by K.R. McClay,pp. 105-121.Chapmanand Hall, New York,

1992.

Suppe,J., F. Sfibat,J.A. Mufioz, J. Poblet, E. Roca,andJ. Vergfis,Bed-by-bed fold growth by kink-bandmigration:Sant Llorenq de Riba, O., S. Reguant,and J. Villena, Ensayo de Morunys,easternPyrenees,J. Struct. Geol., sintesis estratigrfifica y evolutiva de la cuenca 1976.

terciaria del Ebro, in Geolog[a de Espa•a: Libro Jubilar de J.M.Rios, vol. 1, edited by J.A. Comba, pp. 131-159, Inst. Tecnol. GeoMinero de Esp., Madrid, 1983. Rivero, L., J. Guimerh, and A. Casas, Estructura profunda de la cuenca de Cameros (Cordillera

Ib6rica) a partir de datos gravim6tricos, Geogaceta, 20(7), 1695-1697, 1996. Ruiz Fernfindez, V., A. Lendinez, and D. Martin

Herrero, Mapa geoldgico de Espa•a, scale

I9(3-4),

443-461,

1997.

Talling, P.J., T.F. Lawton, D.W. Burbank, and R.S. Hobbs, Evolution

of latest Cretaceous-

Eocene nonmarine deposystems in the Axhandle piggyback basin of central Utah, Geol. Soc. Am. Bull., 107,

297-315, 1995.

Tallos Gonzfilez, A. Distribuci6n y evoluci6n sedimentaria de las facies detriticas trifisicas de

la Rama Aragonesa de la Cordillera Ibmfica, paper presented at I Congreso Espafiol de

1:50,000, sheet 408, Inst. Tecnol. GeoMinero

Geologia, Sociedad Geo16gicade Espafia,

de Esp., Madrid, 1987.

Salamanca,Spain, 1984.

Salas, R., and A. Casas, Mesozoic extensional

tectonics, stratigraphy and crustal evolution during the Alpine cycle of the eastern Iberian basin, Tectonophysics,228, 33-35, 1993.

Teixell, A., and J. Garcia-Sansegundo,Estructura del

sector

central

de

la

Cuenca

(Pirineos meridionales), Rev. Esp., 8 (3), 215-228, 1995.

de

Soc.

Jaca

Geol.

Salomon, J., Apparition des principaux traits Turner, J.P., Evolving alluvial stratigraphy and structuraux

de

la

Sierra

de

Los

Cameros

(Cha•ne Ib6rique, Espagne du Nord) au Jurassique sup6rieur-Cr6tac6 inf6rieur, C. R.

thrust front development in the West Jaca piggyback basin, Spanish Pyrenees, J. Geol. Soc. London, 149, 51-63,

1992.

Acad. Sci. Paris, 290, 955-958, 1980.

Van Wees, J.D., and R.A. Stephenson, Salomon, J., Les phases "foss6e" dans l'histoire Quantitative modelling of basin and theological evolution of the Iberian Basin du bassin de Soria (Espagne du Nord) au (Central Spain): Implications for lithospheric Jurassique sup•rieur-Cr6tac• inf•rieur, Bull. dynamics of intraplate extension and Centr. Rech. Explor.-Prod. Elf Aquitaine, 7(2), 399-407, 1983. inversion, Tectonophysics, 252, 163-178, 1995. Sfinchez Serrano, F., G. De Vicente Mufioz, and

J.M. Gonzfilez Casado, Cortes compensados Van Wees, J.D., A. Arche, C.G. Beijdorff, J. para la deformaci6n principal alpina en el L6pez-G6mez, and S.A.P.L. Cloetingth, borde sur oriental del Sistema Central Temporal and spatial variations in tectonic espafiol(Zona de Tamaj6n, Guadalajara),Rev. subsidencein the Iberian Basin (eastern Soc. Geol. Esp., 6(1-2), 7-14, 1993. Spain): Inferences from automated forward Santaf& J. V., L. Casanovas, and E. Alf•rez,

modelling of high-resolutionstratigraphy

CASAS-SAINZET AL.: PIGGYBACK BASIN EVOLUTION (NORTHERN SPAIN) (Permian-Mesozoic), 285-310, 1998. Varas Muriel, M.J.,

Tectonophysics, 300,

Sedimentaci6n

continental

ne6gena en el SE de la Cuenca de Almaz•in. tesis de licenciatura, 77 pp., Univ. Salamanca, Salamanca, Spain, 1997. Vegas, R., J.T. V•izquez, E. Surifiach, and A. Marcos,

Model

of distributed

deformation,

block rotations and crustal thickening for the formation of the Spanish Central System, Tectonophysics, 184, 367-378, 1990. Viilena, J., G. Pardo, A. P6rez, A. Mufioz-

Jim6nez, and A. Gonzfilez, Tertiary of the Iberian

margin of

the Ebro Basin:

1)

Stratigraphicsynthesis,in Tertiary Basinsof Spain: The Stratigraphic Record of Crustal Kinematics, edited by P.F. Friend and C.J. Dabrio, pp. 77-82, Cambridge Univ. Press, New York, 1996.

Virgili, C., A. Sopefta, A. Ramos, A. Arche, and

S. Hernando, El relleno posthercfnicoy el comienzo de la sedimentaci6n mesozoica, in

Geologia de Espa•a, Libro Jubilar de J.M. Rios, vol. 1, edited by J.A. Comba, pp. 25-36, Inst. Geol. Min. de Esp., Madrid, 1983. Zeyen,

H.J.,

E.

Banda,

J. Gallart,

and E.

Ansorge, A wide angle seismic reconnaissance survey of the crust and upper mantle

in the Celtiberian

Chain

of eastern

Spain, Earth Planet. Sci. Let., 75, 393-402, 1985.

Ziegler, P.A., Evolution of the North Atlantic: An overview, in Extensional

Tectonics

289

stratigraphy: record of tectonic evolution, Tectonophvsics,226, 253-269, 1993.

Zoetemeijer,

R.,

and

W.

Sassi,

2-D

reconstruction of thrust evolutionusing the fault-bendfold method,in Thrust Tectonics, edited by K.R. McClay, pp. 133-140, Chapmanand Hall, New York, 1992.

A.M. Casas-Sainz, A.L. Cort6s-Gracia,and A.

Maestro-Gonzfilez, Departamento de Geologfa, Facultadde Ciencias,Universidad de Zaragoza,

50009 Zaragoza,Spain([email protected])

and

stratigraphy of the North Atlantic Margins, edited by A.J. Tankard and H.R. Balkwill, AAPG Mere.,46,

111-129, 1989.

Zoetemoijer,R., S. Cloetingh, W. Sassi, and F. Roure, Modelling of piggyback-basin

(Received April4, 1998;revised July27,1999;

accepted September 7, 1999.)