GEOLOGICA BALCANICA, 23, 5, Sofia, Oct. 1993, p. 23-33. Stratigraphy of the Middle Triassic in a part of the Iberian Ranges (Spain) based on foraminifera data 2 Mart a Perez-Arlucea1, Ekaterina Trifonova 1 Faculdado de Geologia, Uni Fe rsidad Complutense, 28040, Madrid Geological Institute, Bulgarian Academy of Sciences, I 113 Sofia (Receh·ed 02. 06. 1993; accepted 07. 06.1993) M. J/epec-Ap:tycea, E. TpuifjoHoiJa - Cmpamu<parfiu_q cpeOHe,•o mpuaca 11 'lacmu H6epuo ( Hcnauun), ocHoiJaH­ Han ua ifjopaMuHuffjepo'II»X oauHblX. B cpe.n;HeTpHacoaoe apeMII .n:ae rnaBHhre TpaHcrpeccHu (aHu3HitCKall H na­ ~HHCKall no B03pacTy) c TeTHCCKofi o6nacTH 3aTpoHYJJH 3ana.D;HbiH Kpati 116epHJ1CKOH nnaT!j>opMbr. Knaccuqe­ CKH 6bTJJH pa3rpaHH'IeHbl TpH xapaKTepHbie J!HTOJ!OfH'IeCKHe e.D;HHifl\bT, Tpa.n;HUHOHHO Ha3BaHHbie HIDKHKM, cpe.n;HHM If aepXHHM MyllleJJKaJJbKOM. C ueJJbfO CpaBHeHHII 3TH JKe Ha3BaHHII CoxpaHHJ!HCb H B HaCTOliU.(eii pa6o­ Te. HHlKHHfi MylllenKaJJbK npellCTaaneH !j>opMauHeil An6appacHn, a BcpxHHH MyllleJJKaJJbK- !j>opMaUHliMH Tpa­ MaKaCTHJJJJa H Poyena. B noll. CTaTbe Ylleneno BHHMaHHe rnaBHbiM !j>aUHliM :JTHX Tpex !j>opMaUHI1 H B 'laCTHO­ CTH !j>opaMHHH!j>epaM, HaHD;eHHblM B HHX BnepBbie. B pe3yJJbTaTe anaJJH1a CTpaTHrpa!j>H'!CCKOfO 3Ha'leHHll !j>o­ paMHHH!j>epOBbTX C006~eCTB Mbl OTHOCHM !j>OpMaUHIO Anb6appaCHH K neJJbCOHCKOMy llOllbllpycy aHH3HHCKO­ ro Hpyca, a !j>opMauruo TpaMaKaCTHJJJJa K noHro6ap.n;cKoMy no.n;bllpycy JJallnHcKoro llpyca. 0TJJOlKeHHll !j>opMa­ UHH Poyena co.n;epJKaT aepxnenallHHCKHe - ? KapHHtiCKHe !j>opaMHHH!j>epoBh!C accow-ral.(HH. Abstract. During Middle Triassic time two major transgressions (Anisian and Ladinian in age) took place over the Tethys domain affecting the western border of the Iberian Plate. Classically three characteri­ stic lithological units have been recognised in the Middle Triassic, traditionally named in Spain, Lower, Mid­ dle and Upper Muschelkalk. In order for comparison the same designations are kept and in the present work. Lower Muschelkalk comprises the Albarracin Formation, and Upper Muschelkalk - the Tramacastil­ la and Royuela Formations. In this paper the attention is drawn to the main facies of these three forma­ tions and especially to the foraminifers found for the first time in their sediments. As a result of the ana­ lysis of the stratigraphical significance of the foraminiferal assemblages we refer the Albarracin Formation to the Pelsonian substage of the Anisian stage, and the Tramacastilla Formation to the Longobardian sub­ stage of the Ladinian stage. The deposits of the Royuela Formation contain Upper Ladinian - ?Carnian fo­ raminiferal associations. Introduction The Triassic in the central Iberian Ranges, comprises three main lithofacies groups, as had been described in Germany: Buntsandstein, Muschelkalk and Keuper facies. These lithofacies groups are the product of the evolution of a number of sedimentary basins that formed almost at the end of the Hercynian Orogeny. The first deposits corresponding to the first rifting phase are the fluvialite facies of the Buntsandstein deposits (Late Per­ mian and Early Triassic). These facies have an arrangement that follows the ancient Her­ cynian fault trends (Sop e ii a et al. , 1988). Clastic deposits (Buntsandstein) later evolved to shallow marine carbonate deposit (Muschelkalk), when subsidence began to be thermal 23 in ongm. Eustatically controlled, sea level ri sing and failings also are possible to have a control in sedimentation during this time (Middle Triassic), allowing to the sedimentation of transgressive carbonate ramp deposits and regressive evaporites all over the Tethys domain (Z i e g I e r, 1988, see fig. 1). Some of the ancient Hercynian tectonic trends did have an influence in the Middle Triassic sedimentation when, in a distensive tectonic envi-· ronment, marine transgressions allow the formation of a carbonate ramp systems in the Tethyan domain. This tectonic control is only local in character and had the effect of con­ trolling the border deposition of the transgressive deposits and in the distribution of the different facies and depocenters. In the Iberian Peninsula, at the western border of the Tethys realm, the two main Mid­ dle Triassic transgressions, described in other Europian localities, can be recognised. The deposits of the first Middle Triassic transgression (Lower Muschelkak facies), that enter only to the most eastern part of the Iberian Ranges are Late Anisian in age (P e r e z - A r I u c e a, 1986); though in Central and Occidental Europe the same transgression is registered as Middle Anisian (Z i e g I e r, 1990). Second transgressive marine deposits (Upper Muschelkalk facies) are Early Ladinian in age and are more extensive inland in the Iberi­ an Peninsula. Between the two main transgressive events is recorded a middle regressive event that left to the sedimentation of fine clastic and evaporite deposits (Middle Muschelkalk facies). EMERGED BLOCKS r=-:1 EVAPORITES. CARBONATES r;--71 BASIN FLOORED BY D (POSITIVE AREAS) L..:...:.J AND SOME CLASTICS ~ OCEANIC CRUST MAINLY CONTINENTAL ~ CARBONATIC . SHALLOW ~ WRENCH AND NORMAL D AND SHORELINE DEPS. L_..=J MARINE DEPOSITS ...-<"' FAULTS ~ THRUST FAULTS EJ MAINLy EVAPORITES D DEEP MARINE DEPOSITS ~ SUBDUCTION ZONE FENNOSARMATIA SAHARA PLATFORM • TETHYS SEA Fig. I. Middle Triassic (Anisian-Ladinian) paleogeographic reconstruction. IB: Iberian Massif, E: Eb ro Massif, ARM: Armorican Massif, RB : Rockall-Hatton Bank, B: Bohemian Massif, and CMR: Cimmeria (after Z i e g I e r, 1988) 24 MEDITERRANEAN SEA D TERTIARY BASINS D MESOZOIC BASINS D ALPINE FOLD BELTS f'77A PRECAMBRIAN AND ~ PALAEOZOIC MASSIFS C.B. CAMEROS BASIN G.B. GUADALOUIVIR BASIN 100 Km Fig. 2. Tectono-sedimentary units of the Iberian Peninsula (after Sop e fi a et a!., 1988) Carnian clastic-evaporite Keuper facies represent the last Triassic, eustaticaly controlled reg­ ressive event, that has been recorded also in the whole Central and Occidental Europe (Ziegler, 1990). Finally Goy et al. {1990) defined the Im6n Formation that repre­ sents a third, Late Triassic (Norian-Rhaetian) transgressive event. Litho-and biostratigraphy In the Iberian Ranges (Fig. 2 and 3) Middle Triassic in Muschelkalk facies lies unconformably over Buntsandstein deposits, and show an onlap pattern (P e r e z- A r 1 u c e a & S o­ p e fi a, 1985; 1985; Sop e fia et al., 1988; Garcia G i I & Sop e fi a, 1988). Upper contact with Keuper deposits is concordant. Muschelkalk deposits in the Iberian Penin­ sula can be separated in three lithologic units, defined at first by Vi r gil i (1958) as Ml, M2 and M3 in the Catalonian Ranges (North-Eastern Spain). These three units were des­ cribed later in the Iberian Ranges (Hi n k e 1 be in, 1969; P e r e z- A r l u c e a, S o­ pe fi a, 1985; L 6 p e z, 1985). M1, M2 and M3 have been also named Lower, Middle and Upper Muschelkalk, respectively. Lower (M1) and Upper (M3) Muschelkalk are car­ bonate units, and Middle (M2) Muschelkalk, clastic and evaporitic. Main facies of M2 are very similar to Keuper facies. In the Iberian Ranges, Lower Muschelkalk deposits have been formally defined as Albarracin Formation (Perez- A r I u c e a, Sop e fi a, 1985) and the Middle Mus­ chelkalk as Torete Formation (Ram o s, 1979). Finally, the Upper Muschelkalk comp­ rises two units, the lower one, has being described as Tramacastilla Formation, and the upper one as Royuela Formation (P e r e z- A r l u c e a, S o p e fi a, 1985; see fig. 4). The Albarracin Formation is equivalent to the Landete Formation, and Tramacastilla and Royuela Formation are equivalent to the Cafiete Formation defined by L 6 p e z et al. (1988) at the southern part of the Iberian Ranges. 25 I. R • IBERIAN RANGES A.B.• ARAGONESE BRANCH C.B.• CASTIUAN BRANCH C.B.• CAMEROS BASIN EBRO BASIN D POST-TRIASSIC D PERMIAN AND TRlASSK; D TERTIARY AND QUATERNARY ~ LOWER PAL.EOZOtC D MESOZOIC ........ THRUST FAULT ~ :=USANOMETAUORPHIC _., NORMAL FAULT • LOWER PALAEOZOIC 30Km () STUDIED AREA Fig. 3. Geologic location of the studied area Lower Muschelkalk Albarracin Formation This formation has a mainly dolomitic lithology, though in the border, where the forma­ tion wedges out (fig.5) may have some clastics (quartzarenites and mudstones). The Albar­ racin Formation overlies unconformably the Buntsandstein deposits at the Castilian Branch of the Iberian Ranges, and lies conformably over Rot like deposits in the studied sections of the Aragonian Branch (fig. 2). Maximum measured thickness of the Albarracin Forma­ tion is about 60 m (Torre de las Areas section, fig. 6). Sporo-polenic ansambles indicate Early Anisian age for the formation (P e r e z- A r 1 u c e a, 1986). Foraminifera evidences for the age of the Albarracin Formation. By the investigation of a series of samples of this formation (sections Barranco del Comedor and Torre de las Areas) some important for the stratigraphy of the sediments formaniferal assemblages have been found. In the lower part of the Albarracin Formation in Barranco del Comedor section the foraminifers are represented by numerous specimens of Palaeomi/iolina judi­ cariensis (P r e m o I i - S i I v a) (figs. 7, 9). The sediments from the jounger strata of the same formation in Torre de las Areas section contain more various foraminifers: Glomo­ spira sinensis H o, Pilamminella semiplana (K o c a h n s k y - D e v i d e & P a n t i c), ~ngulodiscus pragsoides (0 be r h au s e r), Areno1•idalina amylo voluta H o, Arenovida­ lina chialingchian gensis H o, Palaeomilio/ina judicariensis (Pr e m o I i - S i I v a), Dip­ lotremina astrofimbriata K r i s t a n - T o I I m a n n, Duostomina alta K r i s t a n - T o I I m a n n, Duostomina cf.