1 Published In García-López, S. and Bastida, F. (eds). Palaeozoic conodonts from northern Spain: Eight International Conodont Symposium held in Europe. Instituto Geológico y Minero de España, Serie Cuadernos del Museo Geominero 1, (2002), pp. 419-438. Madrid (438p.). ISBN: 84-74840-446-5.
Devonian and Lower Carboniferous rocks from the Cadí nappe (eastern Pyrenees) J. Sanz-López Facultad de Ciencias de la Educación. Universidad de A Coruña. Paseo de Ronda 47, 15011 A Coruña (Spain).
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ABSTRACT The stratigraphy of the Devonian and the Lower Carboniferous rocks in the Cadí nappe is described. The stratigraphic sections from the different Variscan thrust sheets show varied lithologies and facies changes, in spite of dealing mainly with carbonate formations. Conodont studies are used for the correlation of selected beds and to recognize some Devonian boundaries. Special attention is devoted to the boundary situated between the Castanesa and Villech formations (Lower Emsian), as well as the upper Frasnian to Viséan conodont contents of mainly cephalopod limestones, including to the Frasnian/Famennian boundary. A schematic cross section of the partial basin made from the studied stratigraphic sections is explained where sedimentary bodies, condensations, discontinuities and environments are discussed. Keywords: Stratigraphy, conodonts, Devonian, Lower Carboniferous, Pyrenees.
RESUMEN Se describe la estratigrafía de las rocas del Devónico al Carbonífero inferior en el manto del Cadí. Las secciones estratigráficas realizadas en diferentes láminas cabalgantes variscas muestran una litología variada y cambios de facies, a pesar de tratarse sobre todo de formaciones carbonatadas. Los estudios sobre conodontos son utilizados para la correlación de niveles seleccionados y el reconocimiento de algunos límites del Devónico. Se tiene un especial hincapié acerca del límite entre las formaciones Castanesa y Villech (Emsiense Inferior), así como del contenido en conodontos del Frasniense al Viséense, incluido el límite
2 Frasniense/Fameniense, de las abundantes calizas de cefalópodos. Además, se explica una sección transversal esquemática de una parte de la cuenca obtenida a partir de secciones estudiadas, y en donde se discute acerca de los cuerpos sedimentarios, niveles de condensación, discontinuidades y ambientes sedimentarios. Palabras clave: Estratigrafía, conodontos, Devónico, Carbonífero Inferior, Pirineos.
INTRODUCTION The Cadí nappe (Puigdefàbregas and Soler, 1980, in Muñoz, 1985) is an Alpine tectonic unit located in the south-eastern part of the Pyrenean Axial zone (Fig. 1). It is the highest unit with Palaeozoic rocks in the antiformal stack of the eastern Axial zone (Muñoz, 1985). Below it, there are some of the so-called lower thrust sheets, which include to Palaeozoic rocks older than Silurian time. The antiformal stack is cut out to the north by pre-Devonian rocks of the alpine Canigó unit, whereas to the west it is limited by the faults of the Tertiary La Cerdanya graben. Consequently, Palaeozoic rocks from the Cadí nappe are unrooted from the Axial zone, and its pre-Alpine position is often discussed. The Palaeozoic succession of the Cadí nappe is composed of unconformable StephanianAutunian rocks above Silurian to Lower Carboniferous rocks. Pre- Stephanian-Autunian rocks are affected by Variscan thrust faults made up by a piling of units (Domingo et al., 1988; Casas et al., 1989). Fold development is local and associated to a cleavage better developed in the argillaceous beds and in the hinge zones, while carbonate beds show the usual development of stylolites. The Silurian to Lower Carboniferous rocks area is included in el Comte domain (this volume) and has been described by many authors, such as Faura i Sans (1913), Boersma (1973), Muñoz and Sábat (1981/82), Muñoz (1985), Domingo (1985), Sanz López (1986, 1995). The stratigraphic nomenclature was stable since Boersma (1974), who applied the terminology of Hartevelt (1970), proposed in the Segre valley, to several sections of the Cadí nappe. However, Sanz López (1995) has revised and defined some formations from the Cadí nappe based on 39 stratigraphic sections. He showed evidence of changes in the Devonian facies along the nappe and coinciding with the distribution of Variscan thrust sheets. The precise original position of localities depends on the restoration of the original position of the thrust sheets, changing after the chosen structural interpretation. We have proposed a correlation scheme (Fig. 2) based on the balanced and restored cross section along the western
3 thrust sheets from Domingo et al. (1988) and Casas et al. (1989). A minimum shortening is supposed for it, while the original position for the eastern sections is only approximate because there are no restored geological cross sections published. The present work summarized the stratigraphy from this area and extended data and descriptions can be found in Sanz López (1995). Some conodont faunas are indicated, particularly from the boundary among the formations.
STRATIGRAPHY Black shales with nodules are assigned to the Silurian times, although a part of these beds corresponds to the lower Lochkovian (Sanz López, 1995). An alternation of black shales and limestones crops out in Camprodon (eastern Cadi nappe), with lobolith in some beds. This succession is disturbed by frequent detachment horizons, developed in the base of the thrust sheets. In units located between the Alp and La Molina villages, the end of the Prídolí and the base of the Devonian have been recognized in a metre thick enriched cephalopod and crinoidal limestone (Anyella limestone). Conodont Oulodus elegans detortus occurs below fragments of Icriodus cf. woschmidti. A covered interval of a metre, probably of shales, is followed by the argillaceous limestones and shales from the lower member of the Rueda Formation of Mey (1967), where middle Lochkovian conodonts were found. The Rueda Formation continued on 15 to 50 m of limestones, shales and siltstones. Castanesa Formation (Mey, 1967) in the Cadí nappe shows distinct facies to those observed in the type area. Here, it can be divided in two sub-units. A lower one composed by nodular limestones, dacryconarid and bryozoan lime mud to packstone, and an upper unit with bioturbated dacryoconarid and/or crinoidal limestones (Sanz López, 1995). Lateral changes were detected from the different structural thrust sheets, together with different thickness. Effectively, the sections from the eastern thrust sheets show a thickness between 16 to 25 m (Fig. 1), while the sections from the western units reach to 70 m thick. The distribution of the platform and slope apron deposits points out to the Roca Sança thrust sheet (Fig. 2, section 5) as the inner ramp area. This ramp is deepening southward, to the Coll de Jou unit (Fig. 2, section 2) where the dacryoconarid hemipelagic facies prevail. It also takes place toward the eastern Castellar units (Fig. 2, 11-19), characterized by condensed hemipelagic facies. Lower part of the Castanesa Fm is correlated with the P. pireneae Zone while the upper part contains the entry of Icriodus curvicauda. At 6.5 m below the top, slender elements like Icriodus gracilis (Serra de Comabella, section 9) appear. The range of this species is around
4 the original Pragian/Zlichovian boundary (Chlupac et al., 1980; Carls and Valenzuela-Ríos, 1999). It occurs together with Polygnathus kitabicus and P. sokolovoi in the Lower Emsian P. kitabicus Zone of Yolkin et al. (1989) at the Coma d’Oriola section (Fig. 3). Above, Polygnathus excavatus excavatus entry indicates the Lower P. excavatus Zone of Yolkin et al. (1994). Polygnathus excavatus ssp. 114 and Icriodus n. sp. 21 (both in the sense of Carls and Valenzuela-Ríos, 1999), together with rare and broken elements of Icriodus sigmoidalis, appear near the top of the Castanesa Fm (Figs. 3 and 4). They are assigned to the Middle P. excavatus Zone of Yolkin et al. (1994). Icriodus n. sp. 21 (‘Icriodus bilatericrescens’ in Kalvoda, 1995) is proposed as indicative of the Zlichovian, although it can overlap the uppermost range of tentaculites Guerichina strangulata in the uppermost Pragian of Bohemia. The reddish marls and limestones of the Villech Formation (Hartevelt, 1970) show locally intraformational conglomerate beds (Coma d’Oriola and the Tosa d’Alp units, Fig. 2, sections 7-9) close to the base. They are indicating the drowning of the Castanesa ramp. The formation is 12 to 75 m thick. Condensed sedimentation was developed in the basal part of the eastern sections, between the Middle P. excavatus Zone and the lower part of the P. gronbergi Zone of Klapper et al. (1978). Only a shallow-water sedimentation of grey limestones continued in the Roca Sança unit (Sanz López, 1995), while hemipelagic facies with local mass flows are characteristic of the Villech Fm. The hemipelagic facies are condensing and changes to calcareous platform margin facies in the Roca Sança, northern part of the Coll de Jou unit and slides of the Molina-Alp thrust system (Fig. 2, sections 1-5). The top of the formation belongs to the upper part of the P. serotinus Zone or to the basal P. c. patulus Zone (both zones from Weddige, 1977; Upper Emsian). It coincides with the episode of maximum widespreading of the hemipelagic facies, also present in the Roca Sança unit, and with the wide presence of ammonoids of the ‘Anarcestes horizon’ (see Montesinos and Sanz López, 1998). Boersma (1973) subdivided the Compte Formation into three members. However, Sanz López (1995) proposed two formations (Comabella and La Mena) to substitute approximately the first two members. Furthermore, two defined members (Barousse and Aspe-Brousset of Perret, 1993), with formation status, were applied for the third Boerma’s member. The Comabella Fm shows great variation on thickness. It ranges from to 20 m to more than 200 m, coinciding with the changes among the carbonate facies. Hemipelagic basinal facies are located to the northeast, and replaced by slope, slope-apron and reefal platform in the western thrust sheets. Grey to white nodular limestones of the Comabella Fm are prograding above the Villech Fm, in the Upper Emsian (P. c. patulus Zone), although skeletal limestones are also found in the shallow-water setting of the Roca Sança unit (Fig. 2, section 5). A deepening
5 tendency was recognised from the P. c. costatus Zone to the P. ensensis Zone (both of Weddige, 1977) in the nodular slope limestones at the Tosa d’Alp thrust sheet (Sanz López, 1995), where Eifelian ammonoid Pinacites cf. eminens has been reported (Montesinos and Sanz López, 1999). Strong condensation is detected during upper Eifelian T. k. kockelianus Zone of Weddige (1977) and the Lower ensensis Zone. Broad bodies interpreted as slopeapron deposits are displayed in the Lower P. varcus Subzone of Ziegler et al. (1976), interbedded with hemipelagic carbonates. The supply for these bodies was originated to the south-west of the Cadí nappe, where biostrome beds are frequent in the carbonate platform (Fig. 2, sections 1 and 4, Roca Sança and Coll de Jou units). Dacryoconarid bioturbated limestones are overlying by condensed upper Givetian succession. A widely distributed drowning is recognised in the Upper Pa. rhenana Zone of Ziegler and Sandberg (1990). Finally, the top of the Comabella Fm, or the base of the la Mena Fm, are diachronous. The Mena Fm was defined at the Tosa de Das (Fig. 5), south-west slope of the Tosa d’Alp peak, in the Coma d’Oriola thrust sheet. The basal bed is located at the first white brachiopod lime grainstone included in the Grèixer Member. The member corresponds to storm-originated beds with hardground development and near-shore, sublittoral brachiopod bars are preserved (Fig. 6). The tempestite beds form a thinning-upwards sequence among red nodular cephalopod limestones. The distribution of the Grèixer Mbr shows shallow-water facies to the southern part of the Roca Sança unit and a deepening towards the north units (Tosa d’Alp unit). Conodonts at the base of the formation, are correlated with the Lower Pa. triangularis Zone of Ziegler (1962), although Frasnian conodont from the Pa. linguiformis Zone of Sandberg et al. (1988) dominates. The lower boundary is difficult to recognise in the absence of Grèixer Mbr and conodonts from the basal bed are correlated with the Upper P. crepida or the Uppermost crepida Zone (both of Ziegler, 1962) in deeper water eastern areas. It is located at grey limestones with red solution surfaces or spots under reddish limestones. Sometimes, an ochre or yellow limestone bed, with hardgrounds, is observed just above the greyish purple carbonates of the Comabella Fm. La Mena is composed of a less nodular lower part, occasionally as pseudo-brecciated limestones, under an upper part of nodular cephalopod limestones. The top of the La Mena Fm. is located at the last red carbonate bed, although a gradation with the Barousse Formation occurs. Conodonts from the uppermost bed of the La Mena are considered from the middle Famennian Lower P. marginifera Zone of Ziegler and Sanberg (1984). The Barousse Fm consists of nodular limestones with an increase in the cephalopod
6 and crinoidal contents in the upper part. The formation includes a shale bed, level B of Boyer et al. (1974), which is below the base of the Carboniferous. The top of the Barousse Fm is located in the Tournaisian, concretely in the upper part of the S. sandbergi Zone of Sandberg et al. (1978). Tournaisian Saubette Cherts (Perret, 1993) are preserved locally at the western section of Das (Fig. 2, section 3) and at the easternmost sections (Fig. 2, sections 16-19). The differentiation between the Barousse and Aspe-Brousset formations of Perret (1993) has allowed the delimitation of a local erosive gap under the second formation. This gap together with the facies distribution indicates a high sedimentary in the Roca Sança and Coma d’Oriola units (Fig. 2, sections 4 to 7) fossilized by the Aspe-Brousset sedimentation. Conodonts from the first beds are correlated with the upper Tournaisian S. anchoralis Zone of Bischoff (1957). Aspe-Brousset Fm includes to the cherts of the Louron Member (Perret, 1993), but they are replaced, in the sedimentary rise, by limestones with Viséan conodonts from the G. texanus Zone of Lane et al. (1980) to the G. bilineatus Zone of Belka (1985). The top of the formation provided conodonts assigned to the L. nodosa Zone (upper Viséan/lower Serpukhovian) in the western thrust sheets (Fig. 5), while they are considered from the G. bilineatus Zone (upper Viséan) in the eastern thrust sheets. The Bellver Fm shows different facies along the Cadí nappe, from outer to middle deep-sea fan facies, slope and delta facies. The thickness reaches to a few kilometres. The basal beds are transitional with siliceous shales and limestones of the Aspe-Brousset Fm in the eastern thrust sheets (Fig. 2), while an unconformity is often recognised over the limestones with local presence of palaeokarst deposits.
DISCUSSION AND CONCLUSION The correlation scheme (Fig. 2) shows a different thickness in the formations for the different sections of the Cadí nappe. Some double wedge geometry is brought up in the western thrust sheets, while a decrease of the thickness towards the eastern thrust sheets is patent. This decrease of thickness is poorly visible for the units located to the east of the Freser window (sections 17-19). The Lower Devonian formations show the morphology of a ramp decreasing the thickness to the northeast, in spite of some faulted sections. The Lower Emsian carbonate ramp is buried under hemipelagic deposits of the Villech Formation. A strong condensation and skeletal limestones prevails in the western thrust sheets, while condensed pelagic limestones are located
7 to the easternmost. Nodular or crinoidal limestones of the Comabella Fm move forward at the basin in the Upper Emsian, but with retrograding pulses in the Eifelian. High differences on thickness are related with the Givetian and Frasnian local coralline development, as well as deposits derived from it towards the slope. However, the geometry on double wedge, visible between the western sections 1-9 (Fig. 2), can be related with different subsidence rates and the activity of Devonian sin-sedimentary faults with an extensional component. These faults should be located towards the border of the tectonic units and probably re-moved as thrusts. This interpretation is supported on the presence of Givetian and Frasnian intraformational breccias and debrites in the slope-apron bodies. Condensation is also observed for the hemipelagic Frasnian rocks, because a strong eastward decreasing on thickness is noted over the time-line ‘a’ (Fig. 2). The tabular geometry of the overlying La Mena Fm corresponds to condensed sedimentation covering the slope to basinal facies. The brachiopod bars are developed attached to the Frasnian reefal development of the Roca Sança unit, where La Mena Fm can be found lacking (Fig. 2, sections 4-6). This unit can be interpreted as a sedimentary inherited rise, during the lower Famennian. Southwards, the La Mena and Barousse formations are found together with Saubette Mbr. Tilting movements are necessary after the sedimentation of the nodular limestones of the Barousse Formation, probably during the Tournaisian chert episode, because the sedimentary high is newly differentiated under the unconformity fossilised by the AspeBrousset Fm. In this case, the sedimentary high includes to the Tosa d’Alp thrust unit (Fig. 2, sections 8-9). The siliciclastic deposition of the Bellver Fm is developed over an unconformity in the thick western thrust sheets (Fig. 2, sections 1 to 10). Devonian-Carboniferous stratigraphy from each thrust sheet included the Alpine Cadí nappe thrust sheet and biostratigraphic determination of selected conodont samples result powerful tools for sedimentary history and basin reconstruction of an area where sedimentation was usually considered homogeneous.
SELECTED STOPS Stop 1: Intraformational conglomerates from the basal beds of the Villech Formation, Lower Emsian, Tosa d’Alp. Location: From Alp or Das localities, we take the road to La Masella, towards the hills heading south of La Cerdanya. Then, we take the secondary road to the ski resort called Toses de Das, in
8 the Coma d’Oriola. The parking is situated at the beginning of a beautiful climb to the Tosa d’Alp peak (2536.4 m). The small section at the top of the Castanesa Fm is in the east part of the Tosa d’Alp peak, just along a mining way. Stratigraphic units: Castanesa and Villech formations Age: Lower Emsian Figures: 1 and 4. What to see: Crinoidal and bioturbated limestones with carbonate conglomerates and nodular red limestones and shales. What to collect: Sample Cco2, at the top of the Castanesa Formation CAI: 5.5 to 6. The outcrop corresponds to the basal surface of the Variscan Tosa d’Alp thrust sheet (Domingo et al., 1988), where Devonian rocks are above Carboniferous shales and sandstones. We can observe some meters of grey crinoidal limestones of the Castanesa Fm, with scarce beds of nodular or argillaceous limestones with Chondrites bioturbations. One meter of nodular limestone, included in the Villech Fm, is followed by 4-5 m of crinoidal and conglomerate grain-classified beds with erosive lower surfaces and reworked corals. It is followed by dacryoconarid grey packstones under the typical part of the formation, composed of red and green marls with lime white to pink lime mudstone beds. The top of the Castanesa Fm has provided Icriodus celtibericus, I. gracilis, I. cf. sigmoidalis, I. sp. 21 Carls and Valenzuela-Ríos, Ozarkodina miae, Polygnathus excavatus excavatus and P. excavatus 114 Carls and Valenzuela-Ríos. The association is considered from the Middle P. excavatus Zone. Stop 1bis (optional): Intraformational conglomerates from the basal beds of the Villech Formation, Lower Emsian, Coma d’Oriola. Location: From Alp or Das villages, we take the road to La Masella and later a secondary road to the ski resort of Toses de Das. At the end, the parking is near the Lower Devonian rocks of the Coma d’Oriola section, on the left side of the valley. Stratigraphic units: Castanesa and Villech formations Age: Lower Emsian Figures: 1 and 3. What to see: Crinoidal limestones below carbonate conglomerates and bioturbated nodular limestones.
9 What to collect: Sample Co53 with Polygnathus sokolovi and sample Co106 from the conglomerate of the Villech Fm. CAI: 5 to 5.5. The outcrop corresponds to the lower part of the Variscan Coma d’Oriola thrust sheet, unit overthrusted by the Tosa d’Alp unit (Domingo et al., 1988). Pragian Rueda Fm is overthrusting to the Carboniferous shales where the parking place is. Limestones and shales of the Rueda Fm are below limestones of the Castanesa Fm. Dacryoconarid limestones are followed by crinoidal limestones in the formation. They show erosive surfaces, crosslaminations and some levels with reworked corals in the upper meters. At the top, two grainclassified crinoidal beds, mass flows, are succeed by an argillaceous and bioturbated nodular limestone corresponding to the base of the Villech Fm and a deeper setting. Above, 0.5 m of a fining-upwards carbonate conglomerate occurs. The next 6.5 m are composed of grey or ochre mud to dacryoconarid packstones with some crinoidal few centimetres thick beds. They have an erosive base and scarce lateral continuity and are interpreted as tempestites. Above, grey beds are followed by red lime mudstones, typical lithology in the Villech Fm, although without marl inter-beds in this section. Five meters below the top of the Castanesa Fm, Polygnathus pireneae together with P. kitabicus and P. sokolovi occur. The association is correlated with the lower part of the P. kitabicus Zone, Lower Emsian in the actual concept. Above, Icriodus gracilis and Polygnathus e. excavatus correspond to the Lower P. excavatus Zone. Polygnathus excavatus 114 Carls and Valenzuela-Ríos entries near at the top of the formation and it indicates to the Middle P. excavatus Zone. Polygnathus gronbergi appears in the lower part of the Villech Fm with Icriodus sigmoidalis. The typical red beds provided Icriodus latus, Polygnathus mashkovae and elements similar to P. dehiscens, in the lower part of the P. gronbergi Zone. Stop 2: Lower Famennian succession and the upper Tournaisian paraconformity at the Comes de Das. Location: The Toses de Das are located to the western slope of the Tosa d’Alp peak (2531 m), a high point overlooking four valleys. Rocks of the Coma d’Oriola tectonic unit form an anticline and good outcrops correspond to the hinge zone and the inverse limb. Stratigraphic units: uppermost part of the Comabella, La Mena, Barousse and Aspe-Brousset formations.
10 Age: upper Frasnian to upper Viséan Figures: 1, 5 and 6, tables 1 and 2. What to see: The Frasnian/Famennian boundary, the type section of the La Mena Formation, and Upper Tournaisian limestones above middle Famennian ones. What to collect: Brachiopod beds provide many conodonts from the P. triangularis Zone in the Grèixer Member. Samples Co33 to Co35 yielded Icriodus tumulosus. CAI: 4 to 6. The Variscan Coma d’Oriola thrust sheet is over-thrusting by the Tosa d’Alp thrust sheet (Domingo et al., 1988). The Comes de Das outcrops correspond to an anticline cut by normal faults, with small displacements. Furthermore, the stratigraphy is also disturbed by the development of manganese and iron enriched carbonates, and palaeokarst deposits. Mineralizations are noted by the holes made in mining labours during the first half of the 20th century. Some 400 tones of manganese and iron oxides were extracted. The impregnation is filling karst caves, taken advantage of the stratification and fault surfaces, in the uppermost beds of Comabella Fm. The origin of the oxides came from the La Mena Fm. Furthermore and related with the faults, there are developed dolostones and cherts, sparite filling fissures, breccias and silicified laminar claystones. Crinoidal limestones of the Comabella Fm include coral and stromatoporoid fragments, and intraformational clasts. The uppermost 2-4 m corresponds to pink to white lime mudwackestone with pellets, dacryoconarids, foraminifers, crinoid ossicles, rare rugose corals and big cephalopods. Beds are divided in centimetric layers with plane erosive surfaces, fine-grain crinoidal layers, bryozoan packstone, laminated limes, bioturbated layers and convoluted laminations. Several cement generations and limestone fragments can be filling to shells, vertical and horizontal fissures. These limestones (samples Co26 and Co103, fig. 5, Tabl. 1a) contain upper Frasnian conodonts of the MN Zone 13 of Klapper (1988), Palmatolepis bogartensis index species among them. Lowermost Famennian Palmatolepis triangularis occurs (samples Co92 and Co92A, Tabl. 1a) at the top. A discontinuity is at the base of the overlying La Mena Formation, defined in this section (Sanz López, 1995). The formation begins at the Grèixer Member, brachiopod coquinas with hardground surfaces, whose first centimetres contain an association dominated by Frasnian palmatolepid, and only an element of the Famennian P. triangularis was obtained. It can be interpreted as a paraconformity with local erosion and reworking of beds corresponding to the Frasnian linguiformis Zone. The upper
11 sample Co27 contains a fauna from the Middle to Upper triangularis Zone of (Ziegler, 1962), because several elements correspond to Pa. variabilis variabilis (Tabl. 1a). The probable location of the Frasnian/Famennian boundary can be discussed. The boundary should be recognised at the first occurrence of P. triangularis, below the uppermost centimetres of the Comabella Fm. However, this taxa has its first finding in beds considered from the Frasnian P. linguiformis Zone in some sections, and the boundary must be recognised at the massive appearance of index species after Shulke (1995, 1999). Frasnian dominating taxa of the reworked association from the basal Grèixer Mbr could be correlated with the Famennian base, because a small sedimentary gap and/or a breccia limestone bed above, are described in the stratotype stage boundary of the Coumiac quarry and in sections of the Rheinisches Schiefergebirge (Shulke, 1995, 1999). Icriodus tumulosus is a lower icriodid abundant in this section (Sanz López, 1997), and it was defined from elements obtained in the bed of sample Co35 (Tabl. 1b). Narrow and slender elements were described and named Icriodus olivierii in Sardinia (Corradini, 1988). Top of the La Mena Fm is assigned to the Lower P. marginifera Zone (sample Co36, Tabl. 1c), and so are limestones laminated and bioturbated of the Barousse Fm. The Barousse Fm is eroded and it bears to the Aspe-Brousset Fm with conodonts correlated with the Upper Tournaisian S. anchoralis Zone at the base (Fig. 5, Tabl. 2). In spite of some mineral concentrations and faults, Aspe-Brousset Fm corresponds to nodular cephalopod limestones. The top has provided L. multinodosa from the L. nodosa Zone, Upper Viséan. A sandstone bed includes angular limestone clasts in the Bellver Formation.
ACKNOWLEDGEMENTS We thank J.C. Sanz, who has greatly improved the English text. This paper has received financial support from the PB98-1558 project of the Spanish Dirección General de Enseñanza Superior. REFERENCES Belka, Z. 1985. Lower Carboniferous conodont biostratigraphy in the northeastern part of the Moravia-Silesia Basin. Acta Geologica Polonica, 35, 33-60. Bischoff, G. 1957. Die Conodonten-Stratigraphie des rheno-herzynischen Unterkarbons mit Berücksichtigung der Wocklumeria Stufe und der Devon/Karbon-Grenze. Abhandlungen des Hessischen Landesamtes für Bodenforschung zu Wiesbaden, 19, 1-64.
12 Boersma, K.Th. 1973. Devonian and Lower Carboniferous conodont biostratigraphy, Spanish Central Pyrenees. Leidse Geologische Mededelingen, 49, 303-377. Boyer, F., Krylatov, S. and Stoppel, D. 1974. Sur le problème de l'existence d'une lacune sous les lydiennes à nodules phosphatés du Dinantien des Pyrénées et de la Montagne Noire (France, Espagne). Geologie Jahrbusch B, 9, 1-60. Carls P. and Valenzuela Rios, J. I. 1999. Faunas, correlations, various boundaries, and opinions concerning the early Emsian sensu lato and a cancellata boundary. Emsian Working Party, Macquaire University, Internet electronic page, http://www.es.mq.edu.au/mucep/emsian/carls and rios.htm. Casas, J.M., Domingo, F., Poblet, J. and Soler, A. 1989. On the role of the Hercynian and Alpine thrusts in the Upper Paleozoic rocks of the Central and Eastern Pyrenees. Geodinámica Acta (Paris), 3, (2), 135-147. Chlupáč, I., Križ, J. and Schönlaub, H.P. 1980. Silurian and Devonian conodont localities of the Barrandian. Field Trip E. Abhandlngen Geologie Bundesanstalt, 35, 147-180. Corradini, C. 1998. New Devonian (Famennian) taxa of Polygnathids and Icriodids (Conodonts) from Sardinia. In: E. Serpagli (ed.), Sardinia Field-trip Guide-book, ECOS VII; Giorn. Geologia, 60, Spec. Issue, 89-92. Domingo i Rigol, F. 1985. Estructura geológica del massís de la Tossa d'Alp (BerguedàCerdanya). Tesis de Licenciatura, Dpt. Geomorfología y Tectónica, Fac. Geología, Univ. Barcelona, 123 pp. Domingo, F., Muñoz, J.A. and Santanach, P. 1988. Estructures d'encavalcament en els materials del sòcol hercinià del massís de la Tosa d'Alp (Pirineu oriental). Acta Geológica Hispánica, Barcelona, 23, 141-153. Faura i Sans, M. 1913. Sintesis estratigráfica de los terrenos primarios de Cataluña con una descripción de los yacimientos fosilíferos más principales. Memorias de la Real Sociedad Española Historia Natural, IX ( 1), 5-202. Hartevelt, J.J.A. 1970. Geology of the Upper Segre and Valira valleys, Central Pyrenees, Andorra/Spain. Sheet 10, 1: 50.000. Leidse Geologische Mededelingen, 45, 167-236. Kalvoda, J. 1995. Conodont fauna from the Pragian/Emsian boundary in the Mramorka and Stydlé vody Quarry (Barrandian, Czech Republic). Věstník Českého geologického ústavu (Bulletin Czech Geological Survey), 70 (2), 33-44.
13 Klapper, G. 1988. The Montagne Noire Frasnian (Upper Devonian) conodont succession. Canadian Society of Petroleum Geoloy, 14 (3), 449-468. Klapper, G., Ziegler, W. and Mashkova, T.V. 1978. Conodonts and correlation of LowerMiddle Devonian boundary beds in Barrandian area of Czechoslovakia. Geologica et Palaeontologica, 12, 103-116. Mey, P.H.W., 1967. The Geology of the upper Ribagorzana and Baliera valleys, Central Pyrenees, Spain. Leidse Geologische Mededelingen, Leiden, 41, 153-220. Montesinos, J.R. and Sanz-López, J. 1999. Ammonoideos del Devónico Inferior y Medio en el Pirineo Oriental y Central. Antecedentes históricos y nuevos hallazgos. Revista Española Paleontología, Madrid, Nº extr. Homenaje Prof. J.Truyols, 97-108. Muñoz, J.A. 1985. Estructura alpina i herciniana a la vora sud de la zona axial del Pirineu oriental. Tesis Doctoral, Univ. de Barcelona, 305 pp. Published in: Monografies 1. Publicació del Servei Geològic de Catalunya (1992), 227 pp. Muñoz, J.A., Vergés, J., Martínez-Ríus, A., Fleta, J., Cirés, J., Casas, .Mª and Sabat, F. 1994. Hoja geológica 1.50000 de Ripoll (n. 256) 2ª serie. Instituto Tecnológico Geominero de España, Madrid. Perret, M.F. 1993. Recherches micropaléontologiques and biostratigrafiques (conodontesforaminifères) dans le Carbonifère Pyreneen. Strata , 2 (21), 1-597. Sandberg, Ch.A., Ziegler, W., Leuteritz, K. and Brill, S.M. 1978. Phylogeny, speciation, and
zonation
of
Siphonodella
(Conodonta,
Upper
Devonian
and
Lower
Carboniferous). Newsletters on Stratigraphy, 7 (2), 102-120. Sandberg, Ch.A., Ziegler, W., Dreesen, R. and Butler, J.L. 1988. Late Frasnian Mass Extinction: Conodont Event Stratigraphy, Global Changes, and possible Causes. Courier Forschungsinstitut Senckenberg, 102, 263-307. Sanz López, J. 1986. Estratigrafía, sedimentología y bioestratigrafía (Conodonta) del Devónico-Carbonífero inferior en el área de la Tossa d'Alp. Tesis de Licenciatura Universitat de Barcelona, 274 pp. Sanz López, 1997. Nueva especie de Icriodus (Conodonta) del Fameniense inferior. In Grandal d’Anglade, A., Gutiérrez Marco, J.C. y Santos Fidalgo, L. (eds.), XIII Jornadas de Paleontología y V Reunión Internacional Proyecto 351 PICG ‘Paleozoico Inferior del Noroeste de Gondwana’, A Coruña, Comunicaciones, 232-234.
14 Sanz López, J., 1995. Estratigrafía y bioestratigrafía (Conodontos) del Silúrico superiorCarbonífero inferior del Pirineo Oriental y Central. Tesis Doctoral, Univ. Barcelona. Col.lecció de Tesis Doctorals Microfitxades 2840, 1-9 y microfilms. Publicacions de la Universitat de Barcelona (1996). Sanz-López, J., Valenzuela-Ríos, J.I., García-López, S., Gil Peña, I. and Robador, A. 1999. Nota preliminar sobre la estratigrafía y el contenido en conodontos del Prídolí-Lochkoviense inferior en la unidad de els Castells (Pirineo central). In Rábano, I. (ed.), Actas de las XV Jornadas de Paleontología y Simposios de los proyectos PICG 393, 410 y 421. Temas Geológico-Mineros ITGE, 26 (2), 638-642. Schülke, I. 1995. Evolutive Prozesse bei Palmatolepis in der frühen Famenne-Stufe (Conodonta, Ober-Devon). Göttinger Arbeiten zur Geologie und Paläontologie, 67, 1-108. Schülke, I. 1999. Conodont multielement reconstructions from the early Famennian (Late Devonian) of the Montagne Noire (Southern France). Geologica et Palaeontologica, SB3, 123 pp. Vergés, J., Martínez-Ríus, A., Domingo, F., Muñoz, J.A., Losantos, M., Fleta, J. and Gisbert, J. 1994. Hoja geológica 1.50000 de La Pobla de Lillet (n. 255) 2ª serie. Instituto Tecnológico Geominero de España, Madrid. Weddige, K. 1977. Die Conodonten der Eifel-Stufe im Typusgebiet und in benachbarten Faziesgebieten. Senckenbergiana lethaea, 58 (4/5), 271-419. Yolkin, E.A., Apekina, L.S., Erina, M.V., Izokh, N.G., Kim, A.I., Talent, J.A., Walliser, O.H., Weddige, K., Werner, R. and Ziegler, W. 1989. Polygnathid lineages across the PragianEmsian boundary, Zinzilban Gorge, Zerafshan, USSR. Courier Forschungsinstitut Senckenberg, 110, 237-246. Yolkin, E.A., Weddige, K., Izokh, N.G. and Erina, M.V. 1994. New Emsian conodont zonation (Lower Devonian). Courier Forschungsinstitut Senckenberg, 168: 139-157. Ziegler, W. 1962. Taxionomie und Phylogenie Oberdevonischer Conodonten und ihre stratigraphische Bedeutung. Abhandlungen des Hessischen Landesamtes für Bodenforshchung zu Wiesbaden, 38, 166 pp. Ziegler, W., Klapper, G. and Johnson, J.G. 1976. Redefinition and subdivision of the varcusZone (Conodonts, Middle-? Upper Devonian) in Europe and North America. Geologica et Palaeontologica, 10, 109-140.
15 Ziegler, W. and Sandberg, C.A. 1984. Palmatolepis-based revision of upper part of standard Late Devonian conodont zonation. Geological Society of America, Special Paper, 196, 179-194. Ziegler, W. and Sandberg, C.A. 1990. The Late Devonian standard conodont zonation. Courier Forschungsinstitut Senckenberg, 121, 1-115.
16
FIGURE CAPTIONS Figure 1. Geological sketch of the Cadí nappe in the south-east Pyrenees based on Hartevelt (1970), Muñoz, (1985), Casas et al. (1989), Muñoz et al. (1994) and Vergés et al. (1994). (1) Cambrian to Ordovician rocks, (2) Silurian rocks, (3) Devonian to Lower Carboniferous rocks involved in some western thrust sheets, and in other eastern thrust sheets (4), Devonian to Lower Carboniferous rocks of the Segre Variscan unit (5), uppermost Carboniferous to recent rocks (6), and Neogene rocks of the La Cerdanya basin (7). Figure 2. Correlation chart of some stratigraphic sections studied in the Cadí nappe. The chart is divided in three parts, A is continued with B; C corresponds to sections to the east of the Freser Valley. The chosen horizontal level is the base of the Barousse Fm (Lower P. marginifera Zone). Section eastwards of the Freser valley are located on the lower right of chart. The horizontal dimension is based on the restored cross-section of Domingo et al. (1988), but sections of the Alp unit are placed to the north of the Coll de Jou thrust sheet. The vertical scale is twelve and a half larger than the horizontal. Consequently, the angles of the correlation lines are exaggerated about 4.5º. The stratigraphic sections correspond to: (1-2) Coll de Jou thrust sheet, (3) Coll de Mola thrust sheet and Alp unit, (4-5), Roca sança thrust sheet, (6-7) Coma d’Oriola thrust sheet, (8-9) Tosa d’Alp thrust sheet, (10) Anyella unit (11) Puigllançada thrust sheet, (12) Rus unit, (13-14) La Creueta unit, (15-16) La Pleta Roja unit, (17) La Cubil sub-unit, (18-19) Serra Cavallera unit. The thick lines are used for the boundaries among the formations, the thin lines for lateral facies changes and the discontinuous lines for time-levels: (a) Upper M. falsiovalis Zone, (c) P. ensensis Zone, (n) P. nothoperbonus Zone, (p) P. c. partitus Zone, (s) interval between the P. serotinus and the P. c. patulus zones, (t) S. sulcata Zone, (v) Middle P. varcus Subzone. Figura 3. Conodont distribution in the section through the uppermost Castanesa Formation and the lower Villech Formation in the Toses de Das parking, Coma d’Oriola Variscan thrust sheet. See Stop 1A. Figure 4. Stratigraphic section of the boundary between the Castanesa and the Villech formations in the Tosa d’Alp peak, Tosa d’Alp Variscan thrust sheet. See Stop 1. Figura 5. Partial cross-sections and conodont distribution from the uppermost part of the Comabella Formation to the Bellver Formation at the Comes de Das.
17 Figura 6. Correlation scheme of some sections of the La Mena and Barousse formations in the Roca Sança thrust sheet: 1, Canal de la Serp, 2, riu de Grèixer, 3 and 4, north limb of the Roca Sança anticline, 5 and 6, cabanya de les vaques, 7 and 8, La Mena. The section 9 corresponds to the Tosa de Das en la Coma d’Oriola thrust sheet, while 10 is the Castellar de n’Hug section, several kilometres eastward from the others. Table 1. Conodont taxa identified from the uppermost part of the Comabella Formation, La Mena Fm and the lower part of the Barousse Fm at the Comes de Das composed section. Table 2. Conodont taxa studied from the Aspe-Brousset Formation at the Comes de Das section.
18
Figure 1
19
Figure 2
20
Figure 3
21
Figure 4
22
Figure 5
23
Figure 6
Table 1 Formations and member conodont zones samples Co kg Ancyrodella curvata An. gigas An. nodosa Ancyroides asymmetricus Belodella resima Icriodus a. alternatus Palmatolepis bogartensis Pa. boogardi Pa. hassi Pa. winchelli Polygnathus decorosus Po. webbi Ic. alternatus helmsi Palmatolepis rhenana Polygnathus lodinensis Palmatolepis d. delicatula Pa. gigas Pa. triangularis Polygnathus brevilaminus Po. imparilis Po. aequalis Mehlina sp. Ancyroides ex gr. uddeni Anc. ubiquitus Palmatolepis barba Polygnathus brevis Po. krestovnikovi Palmatolepis. variabilis variabilis Pa. protorhomboidea Pa. quadrantinodosalobata Pa. abnormis abnormis (= P. praeterita) Pa. subperlobata
Comabella Formation 13MN
linguiformis to triangular.
La Mena Formation Grèixer triangularis Low M-U 27A 27
Low 28
P. crepida Middle Upp 29 30 31
Um 32
P. rhomboidea Lower Up 33 34 35
Barousse Fm Lower P. marginifera 36 37 38
0.5
1.1
0,5
26
103
92
92A
0.4 *
1.05 *
0.52
1.01
1.06 *
0.45
1.02
1.1
0.5
0.5
* * * * *
* * *
* * *
*
* * *
*
*
*
*
*
* *
* *
* * *
*
* *
*
*
*
*
* *
* *
* *
0.91
0.99
* *
* *
* * *
* *
*
*
* * * * * *
* * *
*
* *
* *
*
*
* *
* * * * * * * * * *
* *
*
*
*
* * *
* *
* *
0.89
0.27
Formations conodont zones samples Co Palmatolepis winchelli Polygnathus ex gr. germanus Polygnathus sp. C Palmatolepis. crepida Pa. delicatula postdelicatula Pa. p. perlobata Pa. tenuipunctata Pa. variabilis glabei Pa. wolskae Ancyrognathus sinelaminus Icriodus cornutus Ic. alternatus-tumulosus Ic.tumulosus Palmatolepis sandbergeri Pa. aff. wolkajae Pa. m. minuta Pa. loba Pa. cf. P. regularis Pa. termini Polygnathus g. eoglaber Po. glaber glaber Polygnathus procerus Pa. minuta aff. gracilis Pa. m. aff. wolskajae Pa. m. subtilis Pa. aff. poolei Pa. quadrantinodosalobata M1 Pa. crepida-circulariss Pa. subgracilis Polygnathus nodocostatus ovatus Palmatolepis glabra prima Pa. prima-pectinata Pa. glabra pectinata Pa. g. pectinata-acuta Pa. klapperi Palmatolepis cf. inflexa
Comabella Formation linguiformis 13MN to triangular.
26
103
92
92A
triangularis Low M-U 27A 27
Low 28
La Mena Formation P. crepida Middle Upp Um 29 30 31 32
P. rhomboidea Lower Up 33 34 35
Barousse Lower P. marginifera 36 37 38
? * * * * * * * *
* * * *
*
* *
* *
*
?
* * * * * * * * * *
*
* * *
* *
* ?
*
*
*
*
*
* *
*
*
*
*
* * *
*
*
* *
*
*
*
*
* * *
*
*
*
*
*
* *
* * * * * * * *
*
* * * *
* *
*
*
* *
* * * * * * ?
*
* *
* *
*
*
*
Formations conodont zones samples Co Palmatolepis p. schindewolfi Pa. glabra Pa. minuta ssp. a Polygnathus bouckaerti Po. n. nodocostatus Po. nodocostatus. incurvus Po. planirostratus Po. semicostatus Palmatolepis lobicornis Pa. g. gracilis Pa. minuta Pa. glabra falcata Palmatolepis rhomboidea Polygnathus c. communis Alternognathus pseudostrigosus Palmatolepis inflexa inflexa Pa. inflexa inflexoidea Pa. stoppeli (small elements) Polygnathus ? diversus Po. glaber medius Polygnathus sp. “Spathognathodus” sp. Pa. m. minuta – shleizia Palmatolepis cf. helmsi Pa. marginifera marginifera Pa. perlobata Polygnathus sp. Po. cf. fallax Po. lauriformis Po. aff. symmetricus Palmatolepis marginifera Palm. m. scheizia Polygnathus glaber Po. glaber medius Po. glaber bilobatus
Comabella Formation linguiformis 13MN to triangular.
26
103
92
92A
triangularis Low M-U 27A 27
Low 28
La Mena Formation P. crepida Middle Upp Um 29 30 31 32
P. rhomboidea Lower Up 33 34 35 * * * ? * * * *
Barousse Lower P. marginifera 36 37 38
*
*
*
*
*
* *
*
*
*
*
cf. * * * * *
1 *
*
* * cf.
8
3
*
*
* * * * * * * *
* * * *
* *
* * * * * * * * * * * * * *
Table 2 Aspet-Brousset Formation kg
Co93
Co39
Co94
Co40
Co41
Co42
Co43
Co45
Co46
0.58
1.03
0.5
0.95
0.5
1.06
0.4
0.84
0.34
conodont zones: anch. Bispathodus stabilis Idiopriniodus sp. Polygnathus bischoffi P. inornatus ? Polygnathus pinnatus Scaliognathus anchoralis europensis Vogelgnathus campbelli early morph V. campbelli late morph Pseudognathodus symmutatus G. pseudosemiglaber Gnathodus sp. G. cuneiformis G. semiglaber G. semiglaber-typicus G. semiglaber-punctatus G. typicus Morphotype 1 G. delicatus G. praebilineatus G. ex gr. bilineatus Lochriea commutata Gnathodus bilineatus bilineatus G. cantabricus Pseudogn. homopunctatus Lochriea mononodosa L. nodosa Gnathodus girtyi G. girtyi girtyi Lochriea multinodosa
+ + + + + + +
+ +
Gn. texanus
G. praebilineatus
+
bilin.
L. nodosa
+
+
+ +
+ +
+ +
+ +
+
+
+ +
+ +
+ +
+
+ + + +
+ + +
+
+ + + + + + + + +
+
+
+
+ ?
+ + +
+ + +
+ +
