New Devonian fossil localities in Bolivia

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New Devonian fossil localities in Bolivia ‘*§A. BLIECK, **§P.-Y. GAGNIER, 3F.P BIGEY, 4G.D. EDGECOMBE, 5*P. JANVIER, ‘S. LOBOZIAK, 6P.R. RACHEBCEUF, 7T. SEMPERE and ‘P STEEMANS ‘URA 1365 du CNRS, Universite des Sciences et Technologies de Lille, Sciences de la Terre, F-59655 Villeneuve d’Ascq Cedex, France *Redpath Museum, MC Gill University, 859 Sherbrooke Street West, Montreal, QuCbec H3A 2K6, Canada 3Universite P. et M. Curie (Paris 6), Laboratoire de Micropaleontologie, 4 Place Jussieu, F-75252 Paris Cedex 05, France 4Palaeontology section, Division of Earth and Environmental Sciences, Australian Museum, 6 College Street, PO Box A285, Sydney South, NSW 2000, Australia *URA 12 du CNRS, Museum National d’Histoire Naturelle, Laboratoire de Paleontologie, 8 Rue Buffon, F-75005 Paris, France %JRA 11 du CNRS, Universitt Claude-Bernard, Centre des Sciences de la Terre, 2743 Bd du 11 Novembre, F-69622 Villeurbanne Cedex, France 7Convenio YPFB-Orstom (UR lH), Santa Cruz de la Sierra, Bolivia, and Departement de Geologic S&Iimentaire, Universite Paris VI, Paris, France. Present address: consulting geologist, 13 rue Geolfroy I’Angevin, 75004 Paris, France ‘Chercheur Qualifie FNRS, Universite de Liege, Laboratoires Associts de Paltontologie, 7 Place du Vingt AoQt, B-4000 Liege, Belgium Abstract -

An examination

of Palaeozoic sections west of Cochabamba, and west of Lake Poopd, in western Bolivia, was

conducted during a field expedition in 1991. The Rio lglesiani valley, west of Cochabamba, surprisingly yielded a Middle Devonian age to all the visited sites, originally supposed to be Ordovician. This result is based on spores, shelly faunas (brachiopods and bivalves), and trilobites. The Copacabana de Andamarca section, west of Lake Poop& is also dated as Middle Devonian on account of its rather rich fauna (bryozoans, corals, brachiopods, conulariids, hyolithids, tentaculitids, ostracodes, trilobites, crinoids, vertebrates). Both localities correlate to the Icla and/or Huamampampa Formation of the Tarabuco area and Subandean belt, and to the Belen and/or Sica Sica Formation of the northern Altiplano. Copyright 0 1996 Elsevier Science Ltd & Earth Sciences & Resources Institute

Resumen -

En este trabajo se

presentan 10s resultados del estudio

de diversas sucesiones paleozoicas al oeste de Cochabamba

y al oeste del lago Poopb, al occidente de Bolivia, reconocidas durante 10s trabajos de campo llevados a cabo en 1991. Sorprendentemente la secci6n del valle del rfo Iglesiani, al oeste de Cochabamba. ha suministrado faunas que permiten precisar una edad Devonico

Medio,

cuando Ias localidades visitadas habfan sido originalmente consideradas coma pertenecientes al

Ordovfcico. Este resultado se ha obtenido a partir de esporas, faunas conchfferas (braquiopodos y bivalvos) y trilobites. La seccidn de Copacabana de Andamarca. al oeste del Iago Poopd, tambien se ha datado coma Devdnico Medio mediante una rica fauna de briozoos, corales, braqui6podos. conulkidos.

hiolftidos, tentaculftidos, ostracodos, trilobites, crinoideos y vertebrados.

Ambas localidades pueden correlacionarse con la Forma&k

lcla y/o Huamampampa de la region de Tarabuco y arco Subandino

y con la Formacidn Belen y/o Sica Sica del Altiplano notte.

INTRODUCTION

(AB & PYG)

regarded as the oldest American vertebrate remain, and possibly as old as Arunduspis, in Australia.

During the 1991 National Geographic Society expedition “South American Ordovician Vertebrates”, two of us (AB & PYG) went to the valley of Rio Iglesiani, WNW of Cochabamba (Fig. 1). In this valley the fossiliferous locality GEOBOL 5011 occurs “in ‘undifferentiated’ Ordovician strata currently referred to the Capinota Formation of Llanvirn age (Lower Ordovician)“, 8.5km SE of Morochata, Ayopaya Province, Cochabamba Department (Gagnier, 1991). Andinuspis suurezorum (Gagnier, 1991) was collected as a single bone fragment and was supposed to come from GEOBOL 5011. It was thus

In order to assess the age of Andinaspis and try to find additional remains of this enigmatic fossil, we prospected the Iglesiani valley, NE of the small village of Iglesiani. However none of the fossiliferous points we could find, below the Cretaceous-Paleogene cover, yielded any vertebrate remains but they have been dated Devonian on the basis of invertebrates and spores. So, if Andinaspis really comes from this valley, it is not Ordovician in age; consequently, the original geological map of the surroundings (Pacheco, 1985) has to be modified.

*Contribution to IGCP Project 328 “Palaeozoic Microvertebrates” $National Geographic Society Grant no 4394-90 IllEIS-W-B

295

A. BLIECK et al.

296

It was also during the 1991 expedition that we examined a Devonian inlier, west of Lake Poop6 (Fig. 1). The sedimentary succession which crops out west of Andamarca was correlated by geologists of YPFB and Orstom with the Lower to Middle Devonian age Icla and Huamampampa formations of the Tarabuco area and Subandean belt (e.g., Suarez Soruco, 1989; Racheboeuf, 1992; Racheboeuf et al., 1993). We measured a section SW of the small village of Copacabana and found a few vertebrate remains among a rich invertebrate assemblage. All these new data are presented herein.

GEOLOGICAL SETTING (TS) Stratigraphy The stratigraphic units considered in this paper, namely the Icla and Huamampampa formations, belong Famento the N 85 Ma-long, late Ordovician-middle nian Chuquisaca supersequence of the Bolivian Phanerozoic stratigraphy (Sempere, 1990, in press). The Chuquisaca supersequence is mostly of marine origin rocks (shales, siltand mostly consists of siliciclastic and minor conglomerates). The stones, sandstones,

PACIFIC OCEAN

‘i,_ PA R A G U A Y ‘.,\__,

'.

Fig. 1. Location of the prospected sites in the structural framework of Bolivia. Study area and Bolivia-Peru basin shown in insert. Dot lines = drainage divides; finely-dashed lines = national boundaries. Hatched: “western Andes” (Sempere et al., 1990). Randomly dashed segments: Khenayani-Turuchipa paleostructural corridor (CPKT) in the northwest, and northeastern boundary of Chaco Boreal high in the southeast. Abbreviations for structural elements and domains (most are Spanish): CALP = Main Altiplanic thrust, CANP = Main Andean thrust, CFP = Main frontal thrust, FA = Apurimac fault, FLIA = Intra-Andean Boundary fault (conjectural), SFK = Khenayani fault system; CB = Chapare buttress, Cl = Cuzco indenter, CK = Calama knot, MI = Mizque indenter, SB = Susques buttress, VH = Vilcamba hinge; FPCH = Huarina fold-thrust belt, SAB = Subandean belt, SBS = Santa Bgrbara system, 7TB = Tarija-Teoponte belt, UCU = Ulloma-Coipasa-Uyuni domain. Abbreviations for cities and fossil localities: An = Antofagasta, Ar = Arequipa, As = Asuncibn, Be = BelCn, Cb = Cochabamba (Iglesiani, west of), Ch = Charagua, Co = Copacabana de Andamarca, Cr = CorumbB, P = Potosi, S = Salta, SC = Santa Cruz, T = Tarija, Ta = Tarabuco.

New Devonian fossil localities in Bolivia shale units or members frequently show a high content of organic carbon. The Icla and Huamampampa formations belong to a late Llandovery-middle Famennian stratigraphic set, which includes many units found under different names in the literature of the Bolivian Andes, Subandean belt and Chaco-Beni plains (see Oiler, 1991). Although there still are discrepancies about the precise age of the Devonian units, the chronostratigraphic data of Racheboeuf et al. (1993) are adopted here (Fig. 2).

297

In 1987, during a first field trip in Bolivia of one of us (PRR), an unfortunate mistake led to a confusion of the Cuarcita Cruz Loma with the Cuarcita Condoriquifia in the BelCn section of the Altiplano. This error was not revealed until the publication of the stratigraphical synthesis by Racheboeuf et al. (1993). In this paper, as well as in others, chronostratigraphical data are still correct but lithostratigraphical correlations between the Altiplano and the Subandean Zone are partly wrong. The homalonotid trilobite Dipleura dekayi characterizes the lower Sica Sica

lquiri Fm -375 Ma

Los Monos Fm

Huamampampa

Ida Fm

.4QQ Ma

Tarabuco Fm Kirusillas Fm

Fig. 2. Generalized

stratigraphic

section of the Upper Silurian-Devonian

succession

of the Central Subandean Zone.

A. BLIECK et al.

298

Formation; hence the Cuarcita Condoriquiiia and the Upper Belen Formation have to be replaced by the Cuarcita Cruz Loma and the Sica Sica Formation respectively. Thus the base of the Cuarcita Cruz Loma of the Altiplano correlates with the base of the Huamampampa Formation of the Subandean Zone (Fig. 7).

for the late Llandovery-Lochkovian, Pragian-early Givetian and late Givetian-middle Famennian intervals (Sempere, in press). Thickness variations are slight in the late Llandovery-middle Famennian sedimentary pile, and the main units can be easily traced throughout the basin. This explains why petroleum geologists of the YPFB state oil company recognized in the Altiplano units they used to map in the Subandean belt and Tarabuco area. Their

Three overall thickeningand shallowing-upward megasequences respectively span the late LlandoveryLochkovian, Pragian-early Givetian, and late Givetianmiddle Famennian intervals. The first megasequence can often be divided into two lower-order sequences, respectively of late Llandovery-Pridoli and Lochkovian ages. These sequences are generally thick, begin with thick dark shales and end with sandstone-dominated units. Paleoenvironments include relatively shallow-marine, distal to proximal shelf, deltaic, littoral and locally even fluvial (as in the Lochkovian Santa Rosa Formation) deposits.

unpublished correlation sented below.

is confirmed

by the data pre-

The Icla Formation consists of dark shales, which are generally fossiliferous, especially in their upper member (transition to the Huamampampa Formation). Its lower contact with the Santa Rosa Formation may be sharp or rapidly transitional. The lower Icla has yielded early Pragian palynomorphs (Racheboeuf et al., 1993). The Icla Formation corresponds to a rapidly transgressive system tract (early Pragian) and a subsequent incipient highstand system tract (late Emsian-Eifelian), and thus include a maximum flooding episode, which is marked in the basin by an apparent condensation or hiatus of the latest Pragian-early Emsian.

A major transgression started in the early Pragian (uppermost Santa Rosa and Icla formations). Two minor transgresions are marked by the Sica Sica Formation in the northern Altiplano, and by the Los Monos Formation in the Subandean belt. The age of the latter is a matter of controversy, and the related transgression might have started in the earliest Eifelian (Lobo Boneta, 1975; McGregor, 1984; Perez Leyton, 1990, 1991; and YPFB, unpublished), late Givetian (Sempere, 1990) or early Frasnian (Racheboeuf et al., 1993). The age of the Sica Sica Formation is now admitted to be Givetian (Racheboeuf et al., 1993). However, sequence and basin analysis suggest that the Sica Sica and Los Monos transgressions are coeval (Sempere, 1990, in press), and thus that their age is approximately middle Givetian (Fig. 7). The transgressions were followed by progradation of shallower facies. Invasion of prograding sands in latest Eifelian-early Givetian time (Huamampampa Formation) indicates rapid shallowing of the basin in relation with a sea-level fall.

The Icla Formation grades vertically into the Huamampampa Formation, which mainly consists of greenish-grey, immature, locally rippled and more rarely cross-bedded, tine- to medium-grained sandstones, and represents the continuation of the late Emsian-Eifelian highstand system tract initiated with the upper Icla. Its upper part is thought to have been deposited during a lowstand episode, which thus would be of Givetian age. The Huamampampa Formation is commonly fossiliferous. In the northern Altiplano, the Icla Formation equates with the Beltn Formation, whereas the Huamampampa Formation equates with the set formed by the Cuarcita Cruz Loma, and the Sica Sica Formation,

Maximum known sedimentation rates are high: they average approximately 70, 85 and 100 m/Ma respectively

B 5eoboi 5o1’ E&ncia IGLESIANI A 3857m

/ J90CIbm / l Estancia

C

\ \ \

‘%.~oPAcABAN.~‘,

I CERRO

,.

CERRO

COSA

Fig. 3. Location map of (A) the region between Cochabamba and lake Poop& (B) Estancia Iglesiani, WNW section of Cerro Alma Suchuma, SW of Copacabana de Andamarca.

of Cochabamba; (C) the

New Devonian fossil localities in Bolivia Structural setting

ably corresponds to the GEOBOL locality 5011. It is composed of centimeter-thick, grey to rust-coloured siltstones with ferruginous nodules. This locality mainly yielded badly preserved bivalves (Bivalvia indet. + Nuculites sharpei at 91-5a, Bivalvia indet. at 91-5b; det. C. Babin and A. Dalenz Farjat). Lower in the section, in darker siltstone beds, the sample 91-5~ was acid-prepared and gave a miospore assemblage

After the proto-Andean margin of Gondwana became active in middle Ordovician time, the Bolivia-Peru basin was a wide marine back-arc basin which evolved as the “foreland” of the transcurrent and/or compressional longlasting deformations that developed along the margin until Mississippian time (Sempere, in press). Within this basin, the Khenayani-Turuchipa paleostructural corridor (CPKT, Fig. 1) perennially influenced Phanerozoic paleogeography and deformation.

(Acinosporites lindlarensis, Diatomozonotriletes franklinii, Emphunisporites rotatus, Grandispora riegelii, Samarisporites eximius, S. cf. praetervisus, Verruciretusisporu dubia) of middle Eifelian to lower-

Andean thrust deformation propagated into Bolivia in the late Cenozoic by taking advantage of several dtcollement levels located in Paleozoic shales of the BoliviaPeru basin (Sempere et al., 1990). Present-day geometries of Phanerozoic paleogeographies suggest that Andean shortening was considerable in the Bolivian orocline (Sempere, in press).

-

For this reason, the Bolivian Andes are divided into a number of tectonostratigraphic domains which have been displaced and/or shortened during the Andean orogeny. It must be stressed that these domains reflect portions of the original basin, and that they do not coincide with the present-day morphologic provinces. Thus, stratigraphic and paleogeographic characteristics should not be referred to the late Cenozoic provinces such as the Altiplano or Subandean belt, but have to be related to their original location in the now deformed basin.

-

For instance, the new locality of Copacabana de Andamarca (central Altiplano) and the classic localities of the Belen-Sica Sica area (northern Altiplano) do not belong to the same tectonostratigraphic domain. Because of the pronounced Andean shortening, their original distance in the Devonian basin was much greater than today. Their stratigraphic characteristics cannot be directly compared because the Ahiplano is a late Cenozoic feature which had neither existence nor incidence in the Devonian. In the restored Devonian basin, the Andamarca locality appears to lie in the influence area of the CPKT, as does the Tarabuco area and the southern Subandean belt, whereas the northem Altiplano lies farther to the north (Sempere, in press). The use of the simpler stratigraphic nomenclature defined in the Subandean belt and Tarabuco area, namely the Icla and Huamampampa formations, was preferred by field geologists in the Andamarca area, and is consistent with the data presented in this paper.

THE IGLESIANI LOCALITIES Lithology (AB & PYG)

Several fossiliferous sites have been collected along the track NE of the village of Iglesiani (Fig. 3-4): -

Site 91-5 is located about 2.5km from the village, just at the foot of Cerro Khari Huakhachi (4384m) where Cretaceous-Paleogene red sandstones crop out (Fig. 4A), in a turn of the track from Estancia Iglesiani, and just below a trench dug above the track. It most prob-

299

-

most Givetian age. Some undetermined plant fragments were also recovered from these points. Site 91-6 is about 0.5km NE of 91-5, in altered finegrained sandstones with small yellowish nodules. These nodules yielded trilobites (Metucryphueus sp.) and brachiopods (Metaplasia pseudoumbonata, Longispina sp. C, Pleurochonetes? condori and Aseptonetes boucoti). The trilobite is a long-ranging (Emsian?-Frasnian) genus, although the brachiopods are lower Givetian and suggestive of the Huamampampa Formation. Site 91-7 is located SW of 91-5, at about lkm from the entrance of the village, in a dark grey siltstone layer with bivalves (Phestiu sp.1, Palaeoneilo? sp.; det. C. Babin and A. Dalenz Farjat). Site 91-8 is also located along the track, NE of 91-6, two turns from the periclinal closure of the Cretaceous-Paleogene syncline. It is composed of a dark grey siltstone, among a local sequence with yellowish limonitic nodules, very similar to 91-6. It also gave bivalves (Nuculites oblongatus?, Palaeoneilo sp. aff. k? constrictu; ibid.).

Spores (SL & PS) The palynological data result from the analysis of a single sample 91-5~. Miospores are abundant but of low diversity. They are orange-coloured and most of them are corroded and even partly destroyed. Identified taxa include (Pl. I): Acinosporites lindlurensis Riegel 1968, Diatomozonotriletes franklinii McGregor and Camfield 1982, Emphanisporites rotatus McGregor 196 1, Grandispora riegelii Loboziak and Streel 1989, Samarisporites eximius (Allen) Loboziak and Streel 1989, Samarisporites cf. pruetervisus (Naumova) Allen 1965 and Verruciretusisporu dubia (Eisenack) Richardson and Rasul 1978. With the exception of G. riegelii, all these taxa are well known in all the Euramerican and Gondwanian regions. Most of them are even considered, in these regions, as zonal type species within the most commonly used Devonian reference biozonations (Fig. 5). The first occurrence of V dubia in the type marine Devonian of the ArdenneRhine regions (Streel et al., 1987, Fig. 5-6) marks the base of Oppel zone FD (Emphanisporites foveolatus Verruciretusispora dubia). The first occurrence of S. praetervisus marks the base of interval zone Pra (Sunmrisporites praetervisus) within zone FD. This FD Oppel

A. BLIECK et al.

Plate 1. Spores from locality 91-5~. Iglesiani valley, unnamed Devonian sequence (ex “Capinota Formation”). All specimens from slide no22976 are located on England Finder graticule coordinates. Magnifications: x500 (*) or xl000 (**). l-3- Grundispora riegelii Loboziak and Streel 1989: I- J39/1, 2- detail of 1, 3- L43/4. 4- Samarisporites eximius (Allen) Loboziak and Streel 1989, U3.5. 5-6Samarisporires cf. pruetervisus (Naumova) Allen 1965: 5- L43/4, 6- detail of 5. 7-8- Verruciretusispora dubiu (Eisenack) Richardson and Rasul 1978: 7- L35/4, 8- detail of 7. 9- Diarornozonorriletesfrankfinii McGregor and Camfield 1982, D43/3. 10-I I- Acinosporites lindlarcnsis Riegel 1968: IO- N44/3, I I- detail of 10.

New Devonian fossil localities in Bolivia

1988) and Bolivia (PCrez Leytbn, 1991). These recent palynological studies also demonstrated that the stratigraphical distribution of the Emsian to Frasnian miospores in these regions is similar to that of the Ardenne-Rhine areas and that a comparative biozonation is possible. Accurate dates have been proposed and the occurrences of the species restricted to Gondwana have been calibrated with respect to the range of taxa which characterize the West European zonation (Loboziak and Streel, in press b).

91-5 a

ab I-_-IO

-

B

/,

1Om

,

-e

A_

Pkm

--

- -

- -

-

301

il

1

-\

Estanc

Fig. 4. Location of the fossiliferous sites NE of Iglesiani. Ageological sketch map after Pacheco (1985, modified): 1- dips, 2- synclines, 3- thrusts, 4- faults, S- Palaeozoic with Devonian localities 91-5 to 91-8, 6- Cretaceous, Torotoro Formation, 7Cretaceous-Paleocene, El Molino Formation, 8- Paleocene, Santa Lucia Formation, 9- “Tertiary”, Suticollo Formation, IOQuatemary. B- detail of section 91-5 (ex-“Capinota Formation”): a- dark grey siltstones, b- grey to rust-coloured siltstones.

zone is dated Emsian by comparison with the conodont zonation of the Eifel region (Weddige, 1977). In the miospore biozonation of the Old Red Sandstone Continent and adjacent regions (Richardson and McGregor, 1986, Fig. 3), the first occurrence of S. eximius is noted at the base of the Grandispora douglastownense Ancyrospora eurypterota assemblage zone. According to Streel et al. (1987, Fig. 13), this last level is correlated to the base of Oppel zone AP (Acinosporites apiculatus Grandispora protea) located within the conodont serotinus or costatus patulus zones, just below the Emsian/ Eifelian boundary in the Eifel region (Streel and Loboziak, in press). Until now, G. riegelii was reported only in various western Gondwanian regions: North Africa (Loboziak and Streel, 1989; Loboziak et al., 1992), Saudi Arabia (Loboziak and Streel, in press a), Brazil (Loboziak et al.,

Among these Gondwanian species, G. riegelii first occurs very close to the limit between Oppel zone AP (Acinosporites apiculatus - Grandispora protea) and Oppel zone AD (Acinosporites acanthomammillatus Densosporites devonicus). This limit is located within the conodont costatus costatus zone of Eifelian age (&eel and Loboziak, in press). G. riegelii may be very abundant, mainly within the uppermost interval zone of AD [= interval zone Lem (Geminospora lemurata)] and the overlying Oppel zone TA (Samarisporites triangulatus Ancyrospora ancyrea) of Givetian age. The abundance criteria have not been observed in the investigated sample. Furthermore, because of the absence of Geminospora lemurata Balme emend. Playford 1983 [the first occurrence of which defines the base of interval zone Lem located in the type region of the Eifelian (Loboziak et al., 1991) a little above the first conodont Polygnathus hemiansatus which is now the best candidate for a characterization of a new Eifelian/Givetian boundary], one can assume that the sample 91-5c has to be assigned to the lower part of Oppel zone AD, in interval zone “pre Lem”. This consideration implies that this sample is most likely dated middle-upper Eifelian or possibly lowermost Givetian. Shelly Famas

(PRR)

The four sampled fossiliferous points along the track NE of the village yielded a benthic macrofauna. Identified taxa are as follows: Brachiopods

Longispina sp. C Pleurochonetes? condori

Racheboeuf, 1992

samples 91-6 91-6

Aseptonetes boucoti Isaacson,

1977

91-6

Metaplasia pseudoumbonata

(Kozlowski, 1923) Bivalves

Nuculites sharpei Reed, 1908 Phestia sp. 1 Palaeoneilo? sp. Nuculites

1841

oblongatus?

91-6 91-5a 91-7 91-7

Conrad, 91-8

Palaeoneilo sp. aff. l? constricta (Conrad, 184 1) 91-8 Bivalvia indet. 9 I-5a-b

The bivalve representatives (det. A. Dalenz Farjat) are of little stratigraphic value since most of them have a

A. BLIECK et al.

302

* TA

lemurata -magnqicus

I2.m

fevonic;

Ref

AD

MIIC

? velatus-langii

Vd AP

pro

douglastowncnse

-ewypterota

Cor Mill FD

m

annulatus -sextantii

FOV

AB

B. Biastntigraphyxcordmg ta Sireelet d. (1987. theii Fig. 13) l opp?laudImwalZoowaccordingtoSueelctal.(1987) *+ Assanblage Zmea accord& to Ricbardsoo and McGregor (1986) rE3RopoaaIage

Fig. 5. Stratigraphical

range of the spore species investigated

at locality 91-k.

wide vertical range. Palaeoneilo constricta is known from the Lochkovian up to the Upper Devonian in the United States; in Bolivia it appears in the Upper Devonian Los Monos Formation. However, Nuculites sharpei, which is restricted to the Malvinokaffric Realm, occurs in Bolivia in the BelCn Formation of the northern Altiplano and in the upper Icla, Huamampampa and Los Monos Formations of the Subandean belt, that is mainly in the Middle Devonian. Nuculites oblongatus? is a common species of the North American Middle Devonian; it also occurs in the Middle Devonian of the Parana basin. In Bolivia, this species is actually known from the Beltn and Sica Sica Formations of the northern Altiplano, and from the Los Monos Formation of the Subandean belt. Among the brachiopods, Longispina sp. C and Pieurocondori are restricted to the upper beds of the Cuarcita Cruz Loma and to the lower part of the Sica Sica Formation of the northern Altiplano (Racheboeuf, 1992; Racheboeuf and Isaacson, 1993). In the northern Altipiano, Aseptonetes boucoti occurs about 50m above the Cuarcita Cruz Loma (ibid.), while Metaplasia pseudournbonatu occurs throughout the Icla Formation and the lower Huamampampa in the Tarabuco area and throughout the BeMn and the Sica Sica Formations in the northern Altiplano (Isaacson, 1977b). chonetes?

Accordingly only locality 91-6 c;in be tentatively dated by the chonetoidean brachiopods which suggest a level equivalent to the upper part of the Cuarcita Cruz Loma and/or to the lower part of the Sica Sica Formation of the northern Altiplano, i.e., a probable lower Givetian age (Racheboeuf et al., 1993).

Trilobites (GDE)

The calmoniid trilobite represented at locality 91-6 is assigned to the long-ranging genus Metacryphaeus. In the northern Altiplano, Metacryphaeus ranges from the lower member of the BelCn Formation (above the Scuphiocoelia zone) into the Sica Sica Formation (total range Emsian?-Givetian). In the Tarabuco area, it is known from the upper member of the Icla Formation, first appearing in the concretion-bearing shales at the base of the upper member. Metucryphaeus is geographically widespread, also occurring in the Voorstehoek Formation in South Africa (Cooper, 1982), the Fox Bay Formation, Falkland Islands (Edgecombe, 1994), Ponta Grossa Formation, Parana and Chapada Group, Mato Grosso, Brazil (Carvalho and Edgecombe, 1991), and the lower Pimenteira Formation and Passagem member of the Cabeqas Formation, Piaui, Brazil (Castro, 1968; Caldas et al., 1987). These units range from late Emsian to Givetian. THE COPACABANA SECTION, ANDAMARCA Lithology

WEST OF

(AB & PYG)

This locality lies in a small creek SW of the village of Copacabana (Fig. 3C), where a good section of the Huamampampa Formation was measured. The mean dip is to the NE and the Devonian crops out below the Cretaceous red sandstones and conglomerates which top the surrounding hills. The section is composed of line-grained brown sandstones with small fossiliferous concretions and was assigned to the lower Huamampampa Formation,

New Devonian fossil localities in Bolivia

303

Aseptonetes boucoti

Isaacson, 1977

91-19-2

Antelocoelia johnsoni

Isaacson, 1977

91-19-6

Australocoelia palmata 91-19-I

(Morris & Sharpe, 1846) 91-19-10

91-q9-2

Metaplasia pseudoumbonata

91-I 9-3

(Kozlowski, 1923)

91-19-5

.... a

Australospirifer hawkinsi

2Om

91-19-4

10

(Morris & Sharpe, 1846) 91-9-8 Conulariids

91-19-6 t

91-19-7

0

Tentaculitids Ostracodes Trilobites

91-l 9-9

\

,*,;-;a

g13g_10

000

91-19-11

0

. . . . . . . . . . . . . . .*.... . .

.

.

.

. . . . . .

.

I.*Fj_%

2

0 El . . .

lb

. . . III. . . lo

Fig. 6. Schematic log of the section in the Huamampampa Formation, Copacabana de Andamarca (locality 91-19). I- Middle Devonian, Huamampampa Formation, with a- sandstones, bbrownish siltstones and shales with nodular beds; 2- Cretaceous,

Torotoro Formation, red conglomerates and sandstones.

Sensu Chamot (1965), by YPFB geologists (Fig. 6). The layer 91-19-11 is the richest one with brachiopods, conuiariids, crinoids, corals, bryozoans, trilobites and vertebrates. The detail of the fauna is given here below. The fauna1 assemblage is typical of the upper Icla and Huamampampa Formations, and is thus Eifelian-Givetian in age (Racheboeuf, 1992; Racheboeuf et al., 1993).

Fauna (PRR) The eleven levels, numbered from top to bottom, sampled in the section of the Cerro Alma Suchuma, 2km SW of Estancia Copacabana and 5km W of Andamarca, Departamento de Oruro, yielded typical Devonian decalcified fauna1 elements. Identified taxa are as follows: samples Bryozoans

Cyclorrypu sp. (encrusting Paraconularia africana)

Fenestellid Corals

Parastriatopora gigantea

Brachiopods

“Pleurodictyum” sp, Orbiculoidea sp. Salopina walmsleyi

(Knod, 1908)

Isaacson, 1977

9 l-l 9-7 91-19-11

91-19-l 1 91-19-1 91-19-2 91-19-I,3

Paraconularia africana (Sharpe, 1856) 91-19-7, Paraconularia ulrichana

(Clarke, 1913) Hyolithids

91-19-g

91-19-11

Crinoids Vertebrates

9, 11

91-19-I 1

Bolitheca steinmunni

(Knod, 1908) undetermined undetermined

91-19-9 91-19-1 91-19-4

Vogesina lacunafera

Wolfart, 1968 91-19-11 undetermined columnals 91-19-1, 9 Chondrichthyes gen. et sp. 91-19-11 indet.

According to Isaacson (1977a, b), Salopina walmsleyi is restricted to the Huamampampa Formation. Aseptonetes boucoti is known from beds possibly equivalent to the Gamoneda Formation, E of Tarija, Bolivia, and possibly from the Sica Sica Formation in the Lake Titicaca area (Isaacson, 1977a); the species is also known from the Sica Sica Formation, about 50m above the Cuarcita Cruz Loma in the northern Altiplano (Racheboeuf, 1992). In the Tarabuco area, Antelocoelia johnsoni and Australocoelia pulmata occur in the uppermost Icla Formation and in the Huamampampa Formation; in the northern Altiplano, both species have been found in the lower and upper BelCn members (Isaacson, 1977b). Austrulospirifer hawkinsi is a common species from the Icla and Huamampampa in the Tarabuco area, and from the Belen Formation in the northern Altiplano (Isaacson, 1977b). Metaplasia pseudoumbonata occurs throughout the Icla Formation and the lower Huamampampa Formation in the Tarabuco area, throughout the BelCn and the Sica Sica Formations in the northern Altiplano (Isaacson, 1977b). The vertical range of the brachiopods is shown in Fig. 7. The hyolithid Bolitheca sfeinmanni is common in the upper Icla beds of the Tarabuco area at Icla and Presto (Marek and Isaacson, 1992). Although undetermined, the same tentaculitid taxon occurs also in these localities as well as in the Cerro Alma Suchuma section. Paraconularia africana and I? ulrichana occur in the upper Icla beds of the Tarabuco area (Branisa, 1965; Babcock et al., 1987). Specimens similar to “Pleurodict)‘unP sp. have been found in the Sica Sica Formation of the northern Altiplano (Racheboeuf, unpubl.). Although undetermined, the crinoid columnals of sample 91-19-I are identical to those collected by the author in the lower part of the Huamampampa Formation in the Presto section, Tarabuco area. According to

A. BLIECK et ul.

304

/

&ES

CilLLPAClJCHO

Fig. 7. Stratigraphical northern

Altiplano

CENTML SJBANDEAN iONE

iORDlLLEKA ANDALTIPLANO

Fm

range of the species collected

and the Tarabuco

at locality

91-19,

with

correlation

area (after Isaacson, 1977a, b; Racheboeuf,

to the

Middle Devonian sequences et al., 1993).

the

of

1992; Racheboeuf

their respective vertical ranges (Fig. 7), the fauna1 components collected in the Andamarca section, and listed above, are indicative of a time interval corresponding to the upper part of the BelCn Formation-lower Sica Sica Formation of the northern Altiplano, and to the upper Icla Formation-Huamampampa Formation of the Tarabuco area. Hence the age of samples 9 l-19-1 I to 7 would probably be upper Eifelian or close to the Eifelian/Givetian boundary, while samples 91-19-6 to 1 would be Givetian (Racheboeuf, 1992; Racheboeuf et al., 1993). The occurrence of two kinds of bryozoans in the Andamarca section (samples 91-19-7 and 11) is worth noticing since Devonian Bolivian bryozoans are always very rare and they were previously unrecorded from the Middle Devonian (Bigey, 1985; but we must note that the Middle Devonian was previously practically unknown in these regions). Only two species were known: Sterlopora steinmanni Ulrich, 1893 and Monotrypa raritabulata Knod, 1908, both representatives of the Trepostomata. The two specimens from Andamarca are different: the first one (Fig. 8: I) undoubtedly belongs to the family Fenestellidae (Fenestrata) but its preservation precludes

, Fig.

8. Bryozoans

Andamarca, zoarium

from

Huamampampa

of a Fenestellidae

ple 91-19-l

locality

1 91-19,

Formation.

Copacabana I-

latex

Cystoporata),

africana,

encrusting

de

cast of

gen. et sp. indet. (Fenestrata),

I, F 28717; 2- latex cast of a zoarium of

sp. (Fistuliporidae, Paruconuluria

lcm

Qclotrypa

the conulariid

sample 9 l-1 9-7, F 287%

a

sam-

New Devonian fossil localities in Bolivia any further taxonomic assignment. The second one, which encrusts the conulariid Paraconularia africana (Fig. 8: 2) may be assigned to Cyclotrypa sp., a genus of the family Fistuliporidae (Cystoporata) (see FPB below). The specimens of Parastriatopora gigantea (sample 91-19-11; det. Y. Plusquellec) are similar to those of the locality Pisakaviha (northern Altiplano, E of Calamarca, about 200km N of Andamarca) where they have not been correctly dated. The presence of Parastriatopora at Andamarca, in a section dated with a fairly good precision, gives an indirect age to the “reef’ level of Pisakavifia which would be upper Eifelian in age; that means that the level of Pisakaviha would laterally take place in the upper part of the Beltn Formation, below the Cuarcita Cruz Loma.

305

SYSTEMATIC PALAEONTOLOGY Phylum Bryozoa (FPB) Description and comments. In his monograph devoted to the Devonian fauna from Bolivia, Kozlowski (1923) already mentioned the scarcity of some groups such as bryozoans when compared with trilobites or brachiopods. The colonies considered here come from locality 91-19 west of Lake Poop& in the Huamampampa Formation. They consist only in two decalcified colonies from which casts were prepared. Notwithstanding destruction of the original skeletal structures, an approximative determination is proposed.

The first specimen (Fig. 8: 1) is a fenestrate zoarial fragment where dissepiment sites are infrequently

Fig. 9. Trilobites: l-7- Metucryphaeus sp. from locality 91-6, Iglesiani valley, unnamed Devonian sequence (ex “Capinota Formation”). l-2- dorsal and lateral views of outstretched exoskeleton, latex cast from external mould, x3; 3-4- dorsal and oblique anterolateral views of cephalon, internal mould, x2.5; 5- dorsal view of pygidium, latex cast from external mould, x4; 6-7- posterior and dorsal views of pygidium, latex cast from external mould, x4. 8-9- Vcgesincrlacunaferu (Wolfart, 1968) from locality 91-19, Copacabana de Andamarca, Huamampampa Formation, sample 91-I 9-l 1; dorsal and lateral views of cephalon, internal mould, x2.

A. BLIECK et al.

306

preserved. Therefore, no assignment to any of the genera defined by Morozova (1974) for the genus Fenestella seems justified. Meanwhile this specimen belongs to the family Fenestellidae (Fenestrata). The second specimen (Fig. 8: 2) appears as a rather large zoarial fragment encrusting a conulariid. Low montitles are visible on the surface of the colony. Circular outline of autozooecial apertures, isolated by vesicular tissue (cystopores) and lacking in lunaria, suggests an assignment to the genus Cyclarrypa from the criteria given by Utgaard (1983). Cyclotrypa sp. belongs to the family Fistuliporidae (Cystoporata). These two representatives of the families Fenestellidae and Fistuliporidae are new for Bolivia. The two species previously described from the “Conularienschichten” auct., viz., Stenoporu steinmanni Ulrich, 1893 (Chahuarani and Tarabuco) and Monotrypu raritabulata Knod, 1908 (Icla) are assigned to Trepostomata. Fenestellid and fistuliporid bryozoans have been studied from the Devonian of Columbia (“Floresta Series”), but the poor preservation of the Bolivian material prevents from valuabIe comparison. Remark. When listing the Devonian fauna of Bolivia, Kozlowski (1923) added Lyoporu gigantea Knod, 1908. A confusion of generic names probably occurred between on the one hand Lyoporu Nicholson and Etheridge, 1878, a tabulate coral (Hill, 1981) as shown in the figure from Knod (1908), and on the other hand Liopora Girty, I9 15, a bryozoan synonym of Lioporidra Bassler, 1952. Phylum ARTHROPODA (GDE) Class TRILOBITA Walch, 177 I Suborder PHACOPINA Salter, 1864 Family CALMONIIDAE Delo, 1935 Genus Metacryphaeus Reed, I907 Metacryphaeus sp. (Fig. 9: l-7)

more material is required for it to be formalized. It is most readily distinguished from similar species by the following criteria: from M. tuberculatus (Kozlowski, 1923) by its longer (exsag.) eye and lack of tuberculate sculpture; from M. austrulis (Clarke, 1913) by its longer eye, wider (tr.) S2, and more rounded pygidial lappets; and from Eldredgeia venustus (Wolfart, 1968) by its lower visual surface, steep palpebral lobe, and lack of coarse granulation. Genus Vogesina Wolfart, 1968 Vogesina lacunuferu Wolfart, 1968 (Fig. 9: 8-9) Remarks. A single cephalon from layer 91-19-I I is assigned to Vogesina lacunafera, a species known from the lower member of the Belen Formation in the northern Altiplano. Phylum VERTEBRATA (PJ) Class CHONDRICHTHYES Huxley 1880 Chondrichthyes gen. et sp. indet. (Fig. 10) The only vertebrate remain is a portion of an endoskeleta1 element preserved as a natural cast. Its rugose surface is similar to that of the numerous other chondrichthyan endoskeletal elements from the Devonian of the Sica Sica and Beltn Formations of the La Paz area (Janvier and Suarez Riglos, 1986), and is due to the impression of the layer of prismatic calcified cartilage. The specimen (Fig. IO) is an incomplete element, with a slightly curved natural margin, and may be a fragment of a jaw element (palatoquadrate?) or gill arch. It is impossible to tell whether it belongs to an elasmobranch or a holocephalan.

Description. Only character states of potential diagnostic significance are described. Cephalic axial furrow narrow, moderately divergent forwards; frontal glabellar lobe gently inflated above plane of L I -L3; S I gently crescentic; LO raised (sag.) slightly above posterior edge of Ll; SO short (sag., exsag.), moderately deep medially; anterior edge of eye immediately adjacent to axial furrow; Large Eye Index 0.40-0.46; palpebral lobe steeply inclined, raised well above interocular fixigena; visual surface with 24-25 dorsoventral lens files, with maximum of 7-8 lenses per file; genal spine short, relatively strongly directed backwards; exoskeleton with sculpture of fine, dense granules, lacking coarse granulation or tuberculation. Pygidial lappets terminate as rounded or bluntly pointed lobes; posteromedian process short, blunt; anterior axial rings with gentle to moderate anterior curvature. Discussion. All calmoniid specimens from locality 91-6 are referred to a single species of Metacryphaeus. A precise correlation is impeded by ihe fact that the Rio Iglesiani taxon appears to be a new species, although

Fig. 10. Chondrichthyes Copacabana 91-19-I

gen. et sp. indet. from locality

de Andamarca,

Huamampampa

1: internal cast of an undetermined

in external

(A) and lateral

Yl-19.

Formation,

sample

endoskeletal

remain

(B) views. Scale bar: IOmm.

New Devonian fossil localities in Bolivia

307

nov. gen. et sp. In: Fosiles y Fucies de Bolivia W. I: (edited by R. Sutiez Soruco), Revistu Tbcnicu de

CONCLUSIONS The Devonian outcrops and sections of Bolivia presented herein have yielded important new data. The outcrops in the Rio Iglesiani valley, ?VNW of Cochabamba, were originally thought to be Ordovician but are Devonian. The section west of Lake Poop& near Copacabana de Andamarca, yielded a few vertebrate remains and a rather rich invertebrate assemblage, which allows a relatively precise dating of the section, viz., EifelianGivetian. Both localities are Middle Devonian in age and correlate to the Icla and/or Huamampampa Formation of the Tarabuco area and Subandean belt, and to the Beltn and/or Sica Sica Formation of the northern Altiplano. - We are greatly indebted to C. Babin and J. Vannier (Lyon, France). Y. Piusquellec (Brest, France) and A. Dalenz Farjat (Santa Cruz de la Sierra) for their help in taxonomic determinations. M. Truyols (Oviedo, Spain) made the Spanish translation of the abstract. M. Caridroit (Villeneuve d’Ascq, France) tried to find radiolarians in some concretions from the Copacabana de Andamarca section. The 1991 expedition would not have been possible without the help of the Centro de Tecnologia Petrolera de Yacimientos Petroliferos Fiscales Bolivianos, Santa Cruz de la Sierra, and of its director R. Stulrez Soruco. It also benefited of the help in the field of J. Pacheco (Geological Survey of Bolivia, La Paz).

Acknowledgments

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