Bulletin of the Geological Society of America Vol. 71

BULLETIN OF THE GEOLOGICAL SOCIETY OF AMERICA VOL. 71. PP. 1279-1294. 2 FIGS. SEPTEMBER 1960

VERTEBRATE-BEARING CONTINENTAL TRIASSIC STRATA IN MENDOZA REGION, ARGENTINA

BY ALFRED SHERWOOD ROMER

ABSTRACT Rusconi and others have described numerous fishes and amphibians from continental Triassic sediments in the Mendoza region of Argentina, but their stratigraphic position has been poorly understood because of conflicting stratigraphic terminology and incomplete published data on the region. All vertebrate remains appear to be derived from a sedimentary cycle termed the Cacheuta series by a majority of workers. The age appears to be Middle Triassic.

CONTENTS TEXT Page Las Higueras 1290 Page Age 1291 Introduction and acknowledgments 1279 References cited 1292 Topography 1280 Stratigraphy 1281 Continental sedimentary cycles 1281 ILLUSTRATIONS Estratos de las Cabras 1283 Estratos de Potrerillos 1284 Figure Page Estratos de Cacheuta 1284 1. Topographic sketch map of the precordil- Estratos de Rio Blanco 1285 lera in the Mendoza region, to show posi- Areal geology 1285 tion of localities mentioned in text 1282 Areas considered 1285 2. Sedimentary Triassic exposures in the area Challao region 1286 shown in Figure 1 1283 Mina Atala-Papagallos region 1286 Cerro Bayo-San Isidro 1287 Cerro Cacheuta 1288 TABLE Potrerillos 1289 Paramillos de Uspallata 1289 Table Page Salagasta 1290 1. Stratigraphic equivalencies. . 1284

INTRODUCTION AND ACKNOWLEDGMENTS published since 1946. These finds are of great interest to vertebrate paleontologists generally For nearly a century continental sediments of and have potential value for intercontinental Triassic age have been recognized in the precor- stratigraphic correlation. But because of un- dilleran region of Mendoza in the western Argen- familiarity with the complex topographic situa- tine, but, except for a few fish scales described tion of the exposures and the considerable by Geinitz in 1876, vertebrate fossils were long variation in the stratigraphic terminology unknown. In recent years, however, a large employed, foreign workers have found it dif- number of fishes, amphibians, and (to a minor ficult to gain a clear picture of the geologic extent) reptiles have been found in the Triassic position of the faunas concerned. of the area. Cabrera (1944a; 1944b) has de- During 1958, as a member of a collecting scribed a fish and an amphibian, Bordas (1944) expedition sponsored jointly by the Museum a fish, and Minoprio (1954) a therapsid. A of Comparative Zoology1 and the Museo large number of forms, collected with the Argentine de Ciencias Naturales of Buenos co-operation of Prof. Manuel Tellechea, has Aires, I spent 6 weeks studying the Triassic been described by the energetic director of the 1 The expedition was supported in part by grants Mendoza Natural History Museum, Prof. from Life magazine and the National Science Foun- Carlos Rusconi, in a long series of papers dation. 1279

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deposits of the area. As well as taking part in Cordillera irrigate the potentially fertile soil, the the collection of new materials, I visited, under western portion of this plain is an arid desert, the guidance of Doctors Tellechea and Mino- unsettled except for goatherders in scattered prio, most of the localities from which the "puestos" at infrequent springs. The plain is earlier collections had been made. Some account in great measure covered by alluvial deposits; of certain of the vertebrate localities has been older sediments underlie them but are exposed given by Professor Rusconi and other authors east of the precordilleran region only around in papers noted later. Doctor Minoprio has a few outlying hill and mountain areas (Fig. 1). most recently (1958) discussed the strati- About 25 km west of Mendoza lies an ex- graphic position of the brachyopid amphibians tended precordilleran development with eleva- of the region and has supplied valuable geologic tions reaching more than 3000 m. (Cf. Stappen- data. The present paper supplements and beck 1910, p. 3-14; 1911, p. 276-284.) This summarizes, for those unfamiliar with the begins in the Cacheuta region, about 35 km area, the geological data given by earlier workers southwest of Mendoza, and extends northward, and by Doctor Minoprio. beyond the area of present concern, into San In listing the vertebrates found at the Juan and La Rioja provinces. The southern various localities I have in no case suggested terminus is Cerro Cacheuta, separated from any taxonomic revision of the fauna and have the main mass of the precordillera by a gorge used the nomenclature under which the various through which run the Rio Mendoza, the forms were originally described. transandean railway, and a highway from I wish to express the gratitude which I, and Lujan to Potrerillos. The main transandean the other members of our party, feel for the highway, however, ascends to the summit of aid extended to us by so many inhabitants of the precordillera west of Villavicencio, about the charming and friendly city of Mendoza 50 km north of Mendoza, returns to the valley during our work in this area. Prof. Carlos of the Rio Mendoza near Uspallata, and thence Rusconi, in cordial fashion, made freely avail- begins the ascent of the cordillera proper. able for study the many valuable fossils in Various names are applied to portions of the his museum's collections. Prof. Manuel Tel- precordillera. The major summit ridge in lechea, who is most familiar with the sediments Mendoza province is frequently termed the of the area, accompanied us on various occasions Sierra de Uspallata; to the north, in San Juan and, with characteristic enthusiasm, guided province, the principal continuation of the us to areas of Triassic exposures and collection precordillera is the Sierra de Tontal. Near localities. Geologists of the Comision de Energia Mendoza a spur of the precordillera extends Atomica and the Yacimientos Petroliferos eastward from a point north of Estancia San Fiscales, notably Dr. Hector Martinez Cal for Isidro to terminate north of Challao, a short the Mendoza region, were most helpful in distance northwest of Mendoza. From a supplying geological data. Dr. H. J. Harring- point much farther north, another spur, the ton, who has worked extensively in the Men- Sierra de Las Penas and its prolongment, the doza region, furnished helpful criticism while Cerro de las Higueras, extends southeastward this paper was in preparation. We are especially (broken by a canyon for the Rio de Las Penas) grateful to Dr. Jose Luis Minoprio for his to subside into the plain in the region of constant support and aid in our work and to Salagasta, about 35 km north of Mendoza. him and Seiiora Minoprio for the cordial West of Mendoza an alluvial fan about 15 hospitality extended to all the members of the km broad slants upward about 700 m to the party. more precipitous slopes of the mountains. This fan conceals most of the much faulted TOPOGRAPHY Tertiary and older deposits present here. To the south, adjancent to the Rio Mendoza, Mendoza and the adjacent municipalities the precordillera is broken by numerous arroyos of Las Heras and Godoy Cruz lie at the western draining into that river. On its western slope, margin of the vast plain which extends west, in the region adjacent to the transandean gradually rising, about 600 miles from the highway—the bleak upland Paramillos de pampas of the La Plata River region to the Uspallata—the contours are more gentle. foothills of the Andes. Mendoza is about The main ridge of the cordillera (here 700m above sea level. Except where (as in the including Aconcagua, highest mountain of the Mendoza region) rivers descending from the Western Hemisphere) runs roughly parallel

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to the prccordillera. Toward the south the whole is excellently summarized by Groeber two are not clearly separated, although the and Stipanicic (1952). In some areas the gorge of the Rio Mendoza between Uspallata "Rhaetic" cycle is clearly separable from the and Potrerillos may be taken as the dividing underlying "Paganzo" series by intervening line. Farther north, however, a north-south andesites (the series Choiyoilitense of Groeber) trough, which has an elevation of 2100-2300 and is initiated by a prominent conglomerate. m, lies between the two ranges. This includes, In other localities, however, the andesites at the south, the Valle de Uspallata and the or conglomerate or both may be absent, and Pampa de Yalguaraz and, farther north in considerable confusion of the two cycles may San Juan province, the Llanos del Leoncito exist. In the Mendoza region this is particularly and the lower course of the Rio de los Patos true in the Paramillos de Uspallata. which flows north to join the Rio San Juan. In Mendoza province the Triassic series is present to a considerable extent in the uplands STRATIGRAPHY of the precordillera itself, but certain important areas lie around the eastern and southern Continental Sedimentary Cycles flanks of the precordillera, where the beds are present in a much folded and faulted fashion. Marine Paleozoic sediments, ranging from In great measure the Triassic beds are, even Cambrian to Pennsylvanian, are present in the here, covered by later deposits and are only precordilleran regions, and marine deposits are exposed in specific areas noted in subsequent also found in the Jurassic and Cretaceous sections. They are known to be present, under of the Andean region. The Permian and early Tertiary sediments, far to the south (cf. Mesozoic, however, are represented (apart Trumpy, 1943; Baldwin, 1944, Fig. 2) and from volcanic rocks) exclusively by continental presumably to the east as well. deposits. These are numerous and' widespread Many scientists have observed and described in Mendoza, San Juan, and La Rioja provinces, the Triassic beds of the Mendoza region. but their interpretation has been rendered Following early observations by Darwin (1846, difficult by their lateral variation and by the p. 196-207), who mentions particularly the complex folding and faulting which, as might fossil trees of the Paramillos region (cf. Rusconi, be expected, they have undergone in this 1938; 1941, p. 83-84), and by Burmeister pre-Andean region. Many workers—notably (1858; 1861; 1876), Stelzner in 1872 studied Bodenbender, Keidel, and Frenguelli—have the area seen on a traverse over the pre- demonstrated that they include two cycles cordillera (Stelzner, 1885). Later workers in- of deposition. The older cycle is primarily clude Zuber (1890); Ave-Lallemant (1890; Permian but probably includes both late 1891; 1892); Bodenbender (1893; 1896; 1897, Carboniferous and early Triassic elements as 2 p. 451-456, 483-486, plate); Stappenbeck (1910; well. These beds, termed the Paganzo series 1911; 1917); Windhausen (1916); Du Toit by Bodenbender (1911, p. 47), have been of (1927, p. 47-50); Trumpy and Lhez (1937); especial interest because of their general Fossa-Mancini (1937); Keidel (1939); Groeber correspondence (including the presence of (1939, p. 176-177, map); Harrington (1941); glacial tillites) to the Dwyka-Ecca-Beaufort Frenguelli (1948, p. 221-246); Garcia (1951). beds of South Africa and other continental Important unpublished works include the "Gondwana" sediments of the southern con- studies of Windhausen (1941, unpublished tinents and India. Data concerning them are thesis, Univ. Nacional La Plata) in the Para- summarized by Du Toit (1927) and Keidel millos area, and of Borrello (1944, unpublished (1938). thesis, Univ. Nacional La Plata) in the Potreril- We are here concerned with the second cycle los-Cacheuta region (neither of which I have of sedimentation. Early workers assigned some seen) and that of Chiotti (1946, unpublished elements of this cycle to the Carboniferous, thesis, Univ. Nacional Cordoba) concerning Permian, and Cretaceous, but it is now generally the area near Mendoza (which I have read agreed that they are exclusively Triassic in with interest). Rusconi included geological age: they have been rather arbitrarily termed data in his various papers (particularly 1957). "Rhaetic" by various authors. Our knowledge Groeber and Stipanicic (1952, p. 29-60) give of this Triassic cycle in the Argentine as a a summary of current knowledge. Minoprio's 2 Du Toit used the term "Paganzo" to include valuable paper (1958) gives sections of the se- both cycles; this is contrary to general usage. ries in a number of collecting areas.

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FIGURE 1.—TOPOGRAPHIC SKETCH MAP OF THE PRECORDILLERA IN THE MENDOZA REGION, TO SHOW THE POSITION or LOCALITIES MENTIONED IN THE TEXT Mountains named indicated by triangles. A, Agua; C, Cerro; EA, Estancia; Q, Quebrada; R, Rio Insert: Sketch map of west-central Argentina and central Chile, lat. 30°-34° S., long. 63°-73°W., to show area described

A stratigraphic terminology based on that named a number of formations and horizons of Trumpy and Lhez (1937), Trumpy (1943), (summarized in Rusconi, 1955a, p. 67, 75-76; and Borrello (1944, Unpublished thesis, Univ. 1957, p. 53-55). Since the Borrello-Frenguelli Nacional La Plata) was accepted, with some nomenclature has priority, I have here used it modification, by Frenguelli (1948, p. 237-241). as a basis for treatment—without prejudice This terminology was followed by Groeber and Stipanicic (1952, p. 31) and has been used to the merits of Rusconi's terminology, which in general by the majority of geologists, such I have attempted to equate with it in Table 1. as those of the Yacimientos Petroliferos As summarized by Groeber and Stipanicic, Fiscales, working in this region. Rusconi later the beds concerned are grouped as the Cacheuta

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LAS Ep? LJHERAS EA.-SAN-ISID" ,M[NA ATALA MENDOZA

FIGURE 2.—SEDIMENTARY TRIASSIC EXPOSURES IN THE AREA SHOWN IN FIGURE 1 Stippled portions, Las Cabras formation; ruled lines, combined Potrerillos, Cacheuta, and Rio Blanco formations

series, subdivided as follows, in descending very rapid, probably taking place over a order: relatively small portion of Triassic time. 4. Estratos de Rio Blanco 3. Estratos de Cacheuta Estratos de las Cabras 2. Estratos de Potrerillos 1. Estratos de las Cabras. The sedimentary cycle, where completely In most of the areas studied, the four forma- shown, begins with a thick red conglomerate— tions can be clearly distinguished by the nature the "fanglomerado" of Frenguelli. Above this of the sediments. Unconformity or interruption basal conglomerate lies a series of beds which of deposition is not indicated at any point in may reach 600 m in thickness, in which con- the cycle, and despite the considerable thickness glomerates decrease in importance and the of the series, its deposition may have been major components are shales and sandstones,

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red in many places. These beds, which may be Mendoza west of the Cacheuta region. Over- considered as a unit, have sometimes been lying the las Cabras beds without notable regarded as part of the "Paganzo" series or break, they reach a thickness of 700 m in have been termed Estratos de Carrizal. The some places but are incompletely represented in the Mina Atala and Cerro Cacheuta ex- TABLE 1.—STRATIGRAPHIC EQUIVALENCIES posures and are thin to absent in well sections farther south (Baldwin, 1944). Those I have Trtimpy- seen consist in the main of hard shales and Borrello- fine-grained sandstones, generally light in color. Frenguelli Rusconi terminology terminology Conglomerates and bentonites are present to a minor extent. Considerable areas of exposures of these beds are present southwest of Potrerillos, Rio Blanco on the south slopes of Cerro Cacheuta, on the margins of the precordillera due west of Cacheuta Horizonte Bayensc of Formation Mendoza, in the Challao region, on the uplands Bayoana (part) of the Paramillos de Uspallata, and near Horizonte limense of Formation Salagasta. Plant remains are numerous. Fish Challeana are abundant in certain levels in the Challao ?Horizonte Zorrense of Formation region, and some of the fish remains described Challeana from the Paramillos de Uspallata may be from these beds. (See below.) Potrerillos Horizonte Leonense (Pumense) of Rusconi includes the Potrerillos beds of the Formation Challeana Challao region in Horizontes Leonense (later Horizonte Bodeguense of Forma- Pumense) and Bodeguense of his Formacion tion Challeana Challeana; he regards the former zone as Middle Triassic, the latter as Upper Triassic. Las Cabras PHorizontc Bayense of Formation Bayoana (part) Estratos de Cacheuta The most distinctive development of the term here used (Borrello, 1944, unpublished Estratos de Cacheuta formation occurs in an thesis, Univ. Nacional La Plata; 1954; Frcn- area a few kilometers west of Mendoza, ex- guelli, 1944) derives from the Cerro de las tending from Mina Atala south toward Estancia Cabras, southwest of Potrerillos, where these Papagallos. Here the Cacheuta, conformable beds are well exposed. Extensive areas of las with both the underlying Potrerillos beds Cabras beds lie within the bounds of the pre- and the overlying Rio Blanco, is only 40 m cordillera, as well as around its margins. To thick. The lower half—the "black Cacheuta"— the south, they are absent in the Cerro de consists of dark bituminous shales; in the Cacheuta; the Potrerillos formation rests shales of the upper half, dark components are directly on the porphyrites. rarer, and the color is toward a red—the "red The situation in the Paramillos uplands is Cacheuta" (Minoprio, 1958, p. 303-304). Ex- still confused. Some of the conglomerates posures farther west, between Cerro Bayo and and shale beds of this type may pertain either San Isidro, are similar. The black Cacheuta to the las Cabras or to the earlier, late Paleozoic, in these two areas contains numerous fos- cycle of sediments. siliferous concretions; the smaller ones may Plant remains are known from the las Cabras. contain coprolites, and the larger ones may Vertebrates, however, are rare. Rusconi has contain remains of amphibians and large not in general been concerned with the las fishes. In the "red" part of the formation Cabras beds. The Higueras beds are currently concretions are present, but fossils are much included by him in his Horizonte Bayense and less abundant. Formacion Bayoana, assigned to the Upper The name derives from Cerro de Cacheuta, Permian. and extensive exposures of these beds are found at the foot of the southern slopes of this Estratos de Potrerillos mountain. The exposures of the "black Ca- cheuta" here are very similar to those seen The Estratos de Potrerillos take their name near Mendoza and, like them, include fossil- from the village of Potrerillos, on the Rio bearing nodules. In the Potrerillos region, the

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Cacheuta is well exposed in a valley which the Cacheuta) may be seen in the Mina Atala runs west just south of Potrerillos village and region a few kilometers west of Mendoza; then turns southward, east of Cerro de las their thickness here reaches 250 m. Included Cabras. In this region the formation is much are a varied sequence of sandstones, shales, thicker, as much as 210 m. Its boundaries are conglomerates, and some porphyrites. The less well marked here, however, and the upper colors are predominantly bright reds and violets, part of the Potrerillos of other regions probably like the similar red beds which concluded is included here below the typical "black Triassic sedimentary cycles in such distant Cacheuta." The Cacheuta is also present in areas as the Ischigualasto basin of San Juan the Paramillos de Uspallata area, but here and La Rioja, the Cayua beds of southern it is not so characteristically developed nor so Brasil, and the Red Beds which close the clearly distinguished from the adjacent forma- Stormberg cycle of South Africa. The Rio tions as it is near Mendoza and Cacheuta. Blanco beds are seen to some degree north Limited exposures are present near Salagasta of Cerro Bayo, farther west of Mendoza. They and Challao. are well exposed in certain areas in the plain Numerous plants have been described from west and southwest of Cerro Cacheuta, pe- the Cacheuta beds. Most of the tetrapod ripheral to the areas of Cacheuta bed exposures; vertebrate materials described from the series fossil tree trunks are present locally (Rusconi, were derived from concretions of the "black" 1941, p. 90-92). The Rio Blanco beds occur Cacheuta, and most of the material collected also on the Paramillos de Uspallata over by our expedition also comes from this zone. considerable areas west of that occupied by The "black" Cacheuta is developed in exactly the Potrerillos-Cacheuta, notably around Cerro the same fashion, with characteristic dark Colorado. The name of Rio Blanco derives from bituminous shales and included nodules, from their exposure on the hills lying west of that Mina Atala and Cerro Bayo, west of Mendoza, river south of Potrerillos village. Baldwin to the south side of Cerro Cacheuta, a distance (1944) reports that to the south of the area of 40 km. The nature of its sediments and its of precordilleran exposures, the Rio Blanco is content of amphibians and fishes, with little represented by dark and gray beds rather trace of reptiles, suggests that we are dealing similar to the underlying Cacheuta. Some with a single lagoon of great extent. plant remains have been noted in the Rio The "black" Cacheuta of the Cerro Bayo Blanco, but no vertebrates. Stappenbeck (1910, and the Cacheuta of the Mina Atala, Cacheuta, p. 66-68; 1911, p. 326-327) considered the and Potrerillos areas are termed the Horizonte Rio Blanco beds to be Cretaceous, and in Limense of the Formacion Challeana by Rusconi certain areas these beds have been confused (1949b, p. 229; 1955a, p. 67, 76; 1956, p. 67; with red Tertiary sediments overlying the 1957, p. 54-55) and considered to be of Lower Cacheuta series—as for example by Zuber Triassic age; the "red" Cacheuta (as noted in (1890) for areas west of Cerro Cacheuta. the discussion of the Cerro Bayo region) is regarded by him as distinct and earlier—the Horizonte Bayense of the Formacion Bayoana, AREAL GEOLOGY Upper Permian (Rusconi 1949b, p. 228; 1955a, p. 67, 76; 1956, p. 60; 1957, p. 55). The fish- Areas Considered bearing beds of the Paramillos (whether Cacheuta or upper Potrerillos) are termed by The discussion below is essentially confined Rusconi the Horizonte Zorrense of the Forma- to exposures of the Potrerillos, Cacheuta, and cion Challeana (Rusconi 1955a, p. 67, 75; Rio Blanco beds in and about the southern 1956, p. 67-69; 1957, p. 51-52, 53), considered part of the Mendozan precordillera (Fig. 2). by him currently to be of Middle Triassic age. Knowledge of the Triassic beds found farther northward along the precordilleran region in San Juan province is well summarized by Eslratos de Rio Blanco Groeber and Stipanicic (1952, p. 60-80, 102- The Estratos de Rio Blanco are known also 110). These areas were not visited in the course of our recent work; no vertebrates are known as the "Victor" beds (Triimpy, 1943; Baldwin, 3 1944; Chiotti, 1946, unpublished thesis, Univ. from them. Further exploration for vertebrate National Cordoba; of. Frenguelli, 1948, p. 240- 31 am informed by Dr. H. J. Harrington that 241). An admirable exposure of them (as of unpublished work by Dr. D. A. Nesossi shows that

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remains of these and other precordilleran Hedionda, beyond the small Cerro de la Triassic deposits in the San Juan-La Rioja Bodeguita. Rusconi has termed the Potrerillos region might yield interesting results. beds of the Quebrada de los Leones the Hori- zon te Leonense (or Horizonte Pumense), which Challao Region he believes to be Middle Triassic in age (1950b, (Burmeister, 1861, I, p. 277-279; 1876, p. 174; 1955a, p. 67, 75-76; 1956, p. 67; 1957, p. 262; Stelzner, 1885, p. 68-69, 76-77; Ave- p. 51-54 partim); most of the beds in the Lallemant, 1892; Bodenbender, 1897, p. 451- Hedionda area, the Horizonte Bodeguense, he 456; 1902; Stappenbeck, 1910, p. 62-63; considers Upper Triassic (Rusconi, 1950b, 1911, p. 323-324; 1917; Du Toil, 1927, p. 48-49; p. 174; 1955a, p. 75; 1956, p. 67; 1957, p. 53, Fossa-Mancini, 1937; Triimpy, 1943; Fren- 55). The type of Mendocinia brevis* is from guelli, 1948, p. 237-241; Rusconi, 1946c, the Challao Potrerillos beds (Bordas, 1944; p. 1-3; 1947c; 1948d; 1950a, p. 7; 1955a, Schaeffer, 1955), as is the denticulate plate p. 75; Groeber and Stipanicic, 1952, p. 48-51) described as fTypothorax punctulatus (Rusconi Challao is a small bathing resort 6 km 1947c, p. 523, Fig. 5; 1948d, p. 182; 1949a, northwest of the city of Mendoza. Because it is p. 146-147). Small coprolites are numerous at accessible many writers have described and some levels (Rusconi, 1947c, p. 521-522, Figs. studied the strata at this locality. The Mina 1-4; 1949c, p. 241—247, Figs. 1-5; 1951b, Atala-Papagallos and Cerro Bayo-San Isidro p. 151, 152; 1956, Figs. 96, 97). One of the regions described below are not far west, and Semionotus scales described by Geinitz (1876, certain of the references listed above apply p. 3, PI. 1, fig. 9) may have come from the to them as well as to the Challao region. Agua Salada near Challao, rather than from North of the village of Challao is the eastern the Paramillos de Uspallata, and 5. men- end of a spur running out from the precordillera, dozaenis may occur here (Rusconi 1946c, here termed the Cordon de Las Lajas. Much p. 3, 15). Rusconi described many small fishes of the spur is composed of las Cabras sedi- from Challao, including Challaia slriata (1946a, mentary rocks, about 700 m thick. Its southern p. 148, Figs. 1-3; 1948d, p. 166), Analoia face, however, consists of shales of the Estratos semiovata (1946c, p. 4-7, Figs. 1, 2, 7; 1948d, de Potrerillos, about 550 m thick. Faulting p. 181), A. debilis (1946c, p. 7-8, Fig. 8; has strongly uptilted and even overturned 1948d, p. 181), Pasambaya tellecheai (1946c, these shales to about 10° beyond the vertical p. 8-9, Figs. 3, 9; 1948d, p. 180), Echenlaia (cf. Rusconi, 1948d, perfil 2; 1956, Fig. 99), so obesa (1946c, p. 11-12, Figs. 6, 11; 1948d, that the Potrerillos beds appear to lie beneath p. 181), Caminchaia draghii (1946c, p. 10-11, the las Cabras. Limited Cacheuta exposures Figs. 4, 5, 10; 1948d, p. 181), Pholidophorus occur to the south, in the bottom of a quebrada. dentatus (1946c, p. 13; 1948d, p. 178, 181, From a point about 1 km northwest of the 182,183), Semionotus unicrislatus (1946c, p. 15), village, the Quebrada de los Leones runs deeply Gyrolepidoides multistriatus (1948d, p. 166- upward into the spur of the precordillera 167, 183), and Neochallaia leonensis (1948a, (Rusconi, 1948d, Fig. 3). Numerous well- p. 242-244 as Challaia minor; 1952a, p. 159- preserved small fishes are present in several 160). The fauna has been summarized by places in the Potrerillos beds of the region, Rusconi (1948d, p. 169; 1949a, p. 148-149; mainly in the nearly vertical shale beds on 1954, p. 132-133; 1956, p. 67, 75; 1957, p. either side of the Quebrada de los Leones. 54-55). The most prolific layer can be found a short distance below a topographic survey marker Mina Alala—Papagallos Region capping the hill east of the Quebrada and, The small Mina Atala lies in a quebrada descending west, is exposed along the road about 6 km west of Mendoza, about 3 km north- in the wall of the canyon about 100 m short west of a flood-control dam built across the of the point where the Quebrada opens north- more prominent Quebrada de Papagallos. On ward into a small circular valley and the road, the slopes between the mine region and the correspondingly, turns northeastward. Other boundaries of the city, an alluvial layer covers fossil fishes have been found more directly Tertiary and Mesozoic strata. But these beds north of Challao, in the Quebrada de la are exposed for some distance west of a north- south line extending for about 5 km from fishes described by Bordas (1944) from the Quebrada de Santa Clara, San Juan, are of Permian rather 4 A Mendocinia grandis is mentioned in the litera- than Triassic age. ture but has never been described.

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Mina Atala to a point on the Quebrada de along the steep flanks of the precordillera in Papagallos downstream from the estancia of the region of the Bajada de la Obligation. that name. The exposures here were noted by The Potrerillos beds form much of Cerro Bayo Bodenbender (1897, p. 451, PI., profile 1) and and occupy a considerable area (actively described by Stappenbeck (1910, p. 63-64, quarried) along the lower slopes to the north- 66-67; 1911, p. 324-325, 327) and have been west, downhill from the las Cabras exposures. noted by Simpson and Minoprio (1949, p. 2, The southern part of the area is crossed by Fig. 1) and Rusconi (1950a, p. 5-7); Minoprio the Rio Papagallos, emerging from the pre- has most recently published a photograph and cordillera and running down the slopes toward section of them (1958, foto. 6, perfil 2, p. Mendoza. Exposures of the Estrata de Cacheuta 313). Except for the upper part of the Potreril- are present on the banks of the quebrada los strata, the lower beds of the series are absent occupied by this stream and, barring areas here, because of faulting; the higher beds— covered by talus, can be traced most of the including about 100 m of the Potrerillos, distance north to San Isidro. Rio Blanco ex- "black" Cacheuta, "red" Cacheuta, and Rio posures are mainly limited to an area north Blanco—are well exposed. They dip sharply to of the Rio Papagallos, east of the line of the the west, apparently forming the east flank Cacheuta and near the former puesto Chambon, of a syncline the north-south axis of which near a quarry now being developed by the presumably lies several kilometers to the west. Comision de Energia Atomica. Above the Rio Blanco beds is a hard, very Over most of this area few vertebrate resistant layer of red sandstone of uncertain remains have been discovered. Our party age; above this, to the west, are exposures of saw fish scales in the las Cabras. Minoprio the Divisadero Largo beds of the lower Tertiary. (1954; 1957) has described the remains of a Rusconi reports finds of fish fragments referable therapsid, Colbertosaurus (Colbertia) muralis, to Semionotus unicrislatus and Gyrolepidoides in a slab of rock quarried from the Potrerillos (1946c, p. 15; 1949a, p. 148) and to Challaia at Cuchilla de las Vacas, on the slopes of the magna (Rusconi, 1950a, p. 6). There are precordillera northwest of Cerro Bayo and abundant concretions in the Cacheuta—par- about 20 km west of Mendoza. (The slab ticularly in the lower, black, division. Some now forms part of the house wall of a Mendoza contain coprolites (Rusconi, 1951b, p. 151- citizen who obdurately refuses to allow its re- 152). Rusconi (1951b, p. 47) notes the presence moval in the interests of science!) However, of amphibian remains, and an amphibian one small area of Cacheuta exposure here has skull has been found in a large concretion from been highly productive. this layer (Minoprio, 1958, p. 294). Directly north of Cerro Bayo, a small gulley enters the Rio Papagallos from the North; Cerro Bayo—-San Isidro5 along it runs a track, the Camino Canteras, leading uphill to quarries in the Potrerillos Cerro Bayo is a prominent hill just east of beds. West of this gully, a bluff extends along the precordillera and about 15 km west of the north side of the quebrada for about 200 Mendoza. From this point northward to the m. This is the Cerro Laberintodonte, "labyrin- estancia San Isidro, about 8 km distant, ex- thodont hill," from which nearly all Rusconi's tensive exposures of the Cacheuta series— amphibian material, and some fishes as well, broader to the south, narrower to the north— have been obtained. Down stream a short can be seen along the margin of the precordillera, distance from the hill is a small abandoned despite a partial mantle of detrital material coal mine, the Carbonera Salas, somewhat (Bodenbender, 1897, p. 451-456, PL, profile 1; farther the abandoned puesto Chambon, and Rusconi 1946d, p. 47, Fig. 1; 1950b, p. 169- still farther down the quebrada of the Rio 174, Fig. 1). The beds are considerably folded Papagallos the puesto Lima. This hill has and faulted, but in general they form the west been mentioned and discussed by Rusconi limb of an anticline of which the eastern (especially 195lb, p. 35-37, 73-74, Fig. 3; limb lies in the Mina Atala-Papagallos area; 1955a, p. 76) and is described in detail in the youngest beds lie toward the east margin Minoprio's most recent paper (1958, p. 304-306, of the area of exposure. Las Cabras beds are foto. 5, perfiles 5, 6). The greater part of the present near Cerro Bayo and extend northward face of the hill consists of typical "black" 5 These common place names are also present, Cacheuta beds, identified by Rusconi with confusingly, in the Triassic area near Potrerillos. similar beds at Mina Atala, Potrerillos, and

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Cerro Cacheuta and included in his Horizonte lies the barren Cacheuta basin, covered by Limense, of Triassic age. At the top of the upper Tertiary beds. Along most of the southern hill are layers of "red" Cacheuta. Just beyond and western base of the mountain runs a the west end of the hill is a major fault, and broad sandy wash, the Arroyo de las Minas. adjacent to it the red Cacheuta beds are tilted This face of the mountain is covered by a into a nearly vertical position; conditions here sharply dipping layer of porphyrites. Over are well shown by Minoprio (1958, perfil 6). this lie Potrerillos sedimentary rocks of variable These red Cacheuta beds are Rusconi's Hori- thicknesses, and over them, covered in part by zonte Bayense, which he considers to be Upper alluvium, lie the Cacheuta and Rio Blanco Permian. The fauna has been listed by Rusconi beds near the base of the mountain. The (1950b, p. 170-171; 1951b, p. 48-49; 1954, greater part of the Potrerillos beds lies on the p. 128-130; 1956, p. 60, 67; 1957, p. 54, 55). lower slopes of the mountain; for only a short In the black Cacheuta are found Chigutisaurus distance, in the middle of their course near tunuyanensis (Rusconi, 1948b; 1949a, p. 147; Agua de las Avispas (where there is a good 1950a, Fig. Ic; 1951b, p. 47, 75-90, Figs. plant exposure) do they reach the south bank 4-8, PL VI, fig. 1; 1956, Fig. 89, PL XVI, of the Arroyo de las Minas. The Estratos de fig. 2, Pis. XVII, XVIII), a postcranial skeleton Cacheuta follow the base of the mountain. assigned to this species (Rusconi, 195 lb, p. They are well exposed in six areas: (1) north 90-120, Figs. 9-43, Pis. II-V, IX, X), Otumini- of the divide between Arroyo de las Minas saurus limensis (Rusconi, 1948c, 1949a, p. and Rio Seco de Cacheuta (which runs north 147; 1951b, p. 36, 46-47, 71-74, Fig. 2), into the Rio Mendoza), near the La Manuelita Icanosaurus rectifrons, a form also present mine; (2) near Mina Elcha, about 3 km to the in the Cerro Cacheuta regions (Rusconi, southeast; (3) about \1A km farther southeast 1949c, p. 247; 1950a, p. 4; 195lb, p. 36, 48, and about % km toward the mountain from 122-130, Figs. 47-56, PL VI, fig. 2; 1955b, the arroyo; (4) just northwest of Agua de las p. 86), fish remains and coprolites (Rusconi, Avispas, where, like the Estratos de Potrerillos, 1949c, p, 247-251, Figs. 6, 7; 1951b, p. 151- they are exposed on the south bank of the 152). In the red Cacheuta have been found arroyo; (5) about 4 km farther east, on the Chigutisaurus tenax (Rusconi, 1949d; 1951b, north side of the quebrada near a petroleum p. 35, 47, 136-150, Figs. 65-75, Pis. VII, locality of the erstwhile Cia. Mendocina de VIII; 1956, Figs. 90-93), Challaia magna Petroleo and former bathing resort, now in (Rusconi, 1949b, p. 222-230, Figs. 1-4; 1951b, ruins; (6) about 2 km east of the last near the p. 35; 1956, Fig. 88, PL XV), Neochallaia former national petroleum headquarters for minor (Rusconi, 1948a, p. 241-244, Fig. 4; the area. 1948e, p. 254; 1949a, p. 149; 1949e, p. 231- Unless certain of the fragmentary fish 234, Fig. 1; 1951b, p. 35; 1952a, p. 157-158, remains reported by Rusconi are from the Fig. 1; 1956, Figs. 85, 86), Challaia multideniata uppermost level of the Potrerillos, all ver- (1949e, p. 234), Rhadinichthys tdlecheai (1948a, tebrates known from this region are from the p. 241-242, Fig. 1; 1948e, p. 254; 1949a, Estratos de Cacheuta which Rusconi properly p. 149; 1951b, p. 35; 1956, p. 75, Fig. 84), equates with the "black" Cacheuta of the and coprolites. Cerro Bayo region, his Horizonte Limense. The black Cacheuta type region is highly Cerro Cacheuta fossiliferous in certain areas. I do not know of any materials collected or described from (Stelzner, 1885; Zuber, 1890; Stappenbeck, localities 1 and 5. Our expedition recovered 1917, p. 22, 45; Windhausen, 1916, p. 9-11; nearly a ton of concretions containing am- Du Toit, 1927, p. 50; Triimpv and Lhez, phibian and fish remains from areas 3 and 4 1937, p. 43-49, table; Trurnpy," 1943; Fren- and an amphibian skull from area 6. guelli, 1948, p. 221-237 partim, Figs. 35, 36; The Rio Blanco beds are characteristically Rusconi, 1950a, p. 3-4; 1951b, p. 130-131, developed but are in great measure covered 132-133; Minoprio, 1958, p. 294, 296, fotos. by detritus. They are, however, well exposed 1, 2, perfiles 3, 4) northeast of the wash toward the western end Cerro Cacheuta is the southern outpost of of the exposures near Mina Elcha, where they the precordillera. Its shape is crescentic; its contain tree trunks (Rusconi, 1938; 1954, p. 90- long axis runs from northwest to southeast, 92), and, to the south of the wash, near Agua and its convex outer margin faces west to de las Avispas. southwest. South and west of the mountain Rusconi has described or listed a number of

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fishes and amphibians from the Mina Elcha Figs., 1-3), consisting of fish scales recovered region. They include Gyrolepidoides cuyanus from the las Cabras beds near milepost 44 of (1948d, p. 169), G. sp. (1946c, p. 14-15; the transandean railway, a locality on the north 1950a, p. 4-5; 1951b, p. 132-135; 1954, p. bank of the Rio Mendoza a short distance 134), Challaia cacheutensis (1950a, p. 4; 1950b, below Potrerillos. p. 172, Fig. 4; 1951b, p. 130; 1954, p. 134; 1956, p. 69, 75), Amblypterus lujanensis (1949e, Paramillos de Uspallata p. 235-236, Fig., 2; 19SOa, p. 4; 195lb, p. 130, 131; 1954, 134; 1956, p. 69, 75), Semionolus (Darwin, 1846, p. 96-207; Burmeister, 1858; unicristatus (1946c, p. 15; 1948d, p. 169; 1861, v. 1, p. 243-290; 1876, p. 263-265, 315- 1949a, p. 148; 1954, p. 134), S. mendozaensis 334; Stelzner, 1885, p. 76-79; Ave-Lallemant, (1946c, p. 15; 1948d, p. 169), Icanosaurus 1890; 1891, p. 150-163, maps; 1892; Boden- rectifrons (1950a, p. 4; 1951b, p. 48, 130- bender, 1896; 1897; Stappenbeck, 1910, p. 136, Figs. 57-64; 1954, p. 134), Chigutisaurus 58-66, PI. 9, perfile 4; 1911, p. 320-323, 326- cacheutensis (1953; 1954, p. 135; 1955b, p. 327, Figs. 7, 8, PI. 3, profile X; Du Toit, 1927, 85-94, Figs. 1-3; 1956, Fig. 94), perhaps p. 47-48; Keidel, 1938, p. 241; 1939; 1946, p. Pholidophorus vallejensis (1946c, p. 15) and 137; Groeber, 1939, p. 177; Harrington, 1941; coprolites (1948d; 1949b; 1951b, p. 48, 151-152; Windhausen, 1941, unpublished thesis, Univ. 1953). A faunal list is given by Rusconi (1955b, Nacional La Plata; Rusconi, 1938; 1941; p. 86). 1948d, p. 167-169; 1955a, p. 75; 1956, p. 67-69; 1957, p. 53; Frenguelli, 1948, 242-246; Groeber Potrerillos and Stipanicic, 1952, p. 51-58) The Cacheuta series is extensive in the up- (Ave-Lallemant, 1891, p. 156-163, Pis. 1-3; lands of the precordillera, the Paramillos de Bodenbender, 1893, p. 154-156; Stappenbeck, Uspallata, along the course of the transandean 1910, p. 64-65; 1911, p. 325-326; 1917, p. highway, where its exposures, including erect 23-24; Du Toit, 1927, p. 49-50, Fig., 5; trees (cf. Rusconi, 1938; 1941), have attracted Triimpy and Lhez, 1937; Borrello, 1944, the attention of Darwin and the later geological unpublished thesis, Univ. Nacional La Plata; workers listed above. Our party spent only a Frenguelli, 1944; 1948, p. 221-232, Fig. 34; short time here and did not clarify the strati- Rusconi, 1950a, p. 5; Groeber and Stipanicic, graphic situation. Groeber and Stipanicic (1952) 1952, p. 46-48; Minoprio, 1958, perfiles 1, 7) review the conflicting interpretations. The village of Potrerillos lies on the Mendoza The situation is complicated by numerous River between the Cordillera and the southern faults and a number of intrusive Triassic end of the precordillera. West of the village basaltic flows and sills and Tertiary sills; by rises the Cerro de las Cabras, the type locality the lack of a clear division between the of the Estratos de las Cabras, here about 600 Cacheuta series and underlying Paganzo beds; m thick. The slopes of the mountain and the and by the lack of typical development of the neighboring Cerro Bayo have broad exposures Estratos de Cacheuta. In general, successively of the Potrerillos beds, to about 700 m. A higher beds are encountered in following the narrow valley at the south foot of the mountain, highway from east to west. Harrington (1941, the Quebrada de la Mina, has good exposures p. 21-22; Groeber and Stipanicic, 1952, p. of about 210 m of the Estratos de Cacheuta; 53-54) described a thick series of sandstones hills between this valley and the Rio Blanco and shales with intercalated layers of melaphyre are mainly composed of the beds taking their and a basal conglomerate, which forms the name from that stream. Limited exposures of upper slopes of the precordillera west of Termas the series are found north of the Rio Mendoza de Villavicencio; these beds probably represent in the region of Estancia San Isidro. Despite the las Cabras. Harrington reports Semionotus the wealth of exposures in the region, little scales here. Thick series of shales and some vertebrate material has been collected. Fish conglomerates farther west, beyond the divide, scales can be found in the Cacheuta beds are presumably Potrerillos equivalents. Bitumi- (Rusconi, 1950a, p. 5), but the only described nous shales are present fairly far west and high vertebrate specimens are the weathered skull up in the series. They do not form a continuous from the Cacheuta beds, which is the type of layer and are alternated with lighter shales, but Pelorocephalus mendozensis Cabrera (1944a; presumably they represent the Estratos de Rusconi, 1955b, p. 86), and the type of Gyro- Cacheuta. To the west, particularly around lepidoides cuyanus Cabrera (1944b, p. 569-573, Cerro Colorado, are red and violet shales

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which seem clearly to be equivalent to the Rio 1928; Fossa-Mancini, 1942; Rusconi, 1948e, p. Blanco formation. 254; 1950a, p. 7-8; 1951a; 1952b, p. 19-27, Fig. The highway follows the Agua de la Zorra 1) in its descent west from the summit of the The mining region of Salagasta, north of precordillera, passing the Mina de la Zorra en Mendoza, lies at the point where a long spur route. According to Stelzner's account the from the precordillera, running down from the scales of Semionotus mendozaensis described by northwest, sinks into the plain. Restricted Geinitz (1876, p. 2-3, PL 1, figs. 7, 8) were areas of exposure are referable to the Potrerillos, collected near this mine; so also were part of the Cacheuta (with a coal zone), and typical the materials more recently described by red Rio Blanco ("Cretaceous" of early writers). Rusconi (and listed below). Other materials Most of the areas of exposure lie along either described by Rusconi came from a locality flank of a narrow north-south syncline. Our about 1 km to the south and not far removed group did not visit this area. No vertebrates stratigraphically, which Professor Tellechea have as yet been reported from Salagasta except told me is now covered by a mine dump. The "ganoid" scales (Rusconi, 1948e, p. 254; mine area is characterized by bituminous shales 1952b, p. 23). comparable to those which elsewhere form the Estratos de Cacheuta; the other locality is certainly not far from the same zone. The beds Las Higueras here may pertain to the Cacheuta, or they may be uppermost Potrerillos; the stratigraphic (Stappenbeck, 1910, p. 53-54; 1911, p. 315- difference is slight and of little importance in 316; Harrington, 1941; Rusconi, 1950b, p. 169; this continuous series of sediments. Rusconi 1955a, p. 76; 1956, p. 60-61; 1957, p. 55; considers these Paramillos localities to form the Groeber and Stipanicic, 1952, p. 58-60) Horizonte Zorrense of his Formation Challeana. Northwest of Salagasta the spur of the Except for a reptilian tooth described as precordillera mentioned above—termed the Ocoyuntaia arquata (Rusconi, 1947b; 1949a, p. Cerros de Las Higueras and, farther north, the 146; 1954, p. 131; 1956, p. 69, 75) and for Sierra de la Penas—carries, along its western coprolites (Rusconi, 1951b, p. 152), all verte- slopes, a broad area of continental deposits, the brates from the Paramillos are fishes, including Estratos de Las Higueras, with a basal con- Semionotus mendozaensis (Geinitz, 1876; glomerate and thick overlying shales. Early Rusconi, 1946a, p. 151, 153, Fig. 4c; 1947a, p. writers considered that they belonged to the 21; 1954, p. 131; 1956, p. 68, 75), S. vallejensis Paganzo series, and Harrington (1941; personal (Rusconi, 1950b, p. 173-174, Fig. 5; 1954, communication) feels certain that they belong p. 131; 1956, p. 53), Ceneckoia paramillense to the earlier cycle of deposition, specifically (Rusconi 1946a, p. 151-153, Fig. 4; 1949a, p. the Santa Clara sequence (of which the type 148; 1954, p. 131; 1956, p. 75), C. sulcata locality lies to the north in San Juan province). (Rusconi, 1947a, p. 21-23, Fig. 1; 1949a, p. The Las Higueras beds are sometimes regarded 148; 1954, p. 131; 1956, p. 69, 75), Guaymayenia as Las Cabras equivalents, and they have been paramillensis (Rusconi, 1946b, p. 186-188, tentatively mapped as such in unpublished Figs. 1-2; 1949a, p. 148; 1954, p. 131; 1956, work by the Yacimientos Petroliferos Fiscales. p. 69, 75), Gyrolepidoides multistriatus (Rusconi, 1948d, p. 167, 169; 1954, p. 131; 1956, p. 68, Rusconi early considered them as Devonian 75), Eurynotus uspallatensis (Rusconi, 1946b, (1950b, p. 169) but later (1951a, p. 5; 1955a, p. 188-190, Figs. 3, 4; 1949a, p. 148; 1954, p. p. 76) termed them the Horizonte and For- 131; 1956, p. 68, 75), and Pholidophorus macion Higuerense, of Upper Permian age, and vallejensis (Rusconi, 1947a, p. 23-24, Figs. still later (1957, p. 43-45) included them in his 2, 3; 1948d, p. 169; 1949a, p. 148; 1956, p. Horizonte Bayense. Rusconi (1951a; 1954, p. 69, 75). Faunal lists are given by Rusconi 129; 1956, p. 60-61, 75, PL XIX) has described (1948d, p. 169; 1954, p. 131). Rusconi (1947a) as Chirotherium higuerensis footprints found on also mentions Platysomus from here but gives fallen blocks derived from these beds northeast no description. of Puesto Las Higueras near the point where the Rio de las Penas breaks through the hills. Salagasta Peabody (1955) notes that these footprints are (Bodenbender, 1902; Huergo, 1906; Stappen- of a type expected in the "uppermost Lower or beck, 1910, p. 62; 1911, p. 323; Wichmann, lowest Middle Triassic."

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AGE level n (P.F.6) is clearly Liassic. Restudy of these Chilean faunas seems advisable, but the Estimates of the age of the various members evidence seems to favor assignment of the of the Cacheuta series have ranged from Cacheuta series to the Middle Triassic. Permian (or even Devonian) to Cretaceous. In The vertebrate evidence is not decisive but general, however, writers have considered most, suggests that most if not all of the Cacheuta if not all, members of the series to be of Triassic series is pre-Keuper and hence pre-Carnian. age. Closer determination has presented—and The most abundant fishes are perleidids, sub- still presents—difficulties. The series is thick, holosteans which are present elsewhere pre- but deposition appears to have been uninter- dominantly in early Triassic sediments; the rupted, and the time concerned need not have youngest known form (from Perledo, Italy) is been more than a third or half of the Triassic. from about the Ladinian-Carnian boundary In the older literature part or all of these beds (Schaeffer, 1955, p. 3). This suggests a pre- were frequently assigned—for no strong Carnian age for the Portrerillos. Reptilian reason—to the Rhaetic. Recent writers have evidence is, so far, negligible. The amphibians tended toward the belief that at least part of are exclusively Brachyopidae and suggest early the series was pre-Rhaetic in age, and Groeber Triassic times (Romer, 1947, p. 234-238). and Stipanicic (1952, table 1) suggest that Close relatives are found in South Africa in the while the nonfossiliferous red Rio Blanco beds pre-Molteno Cynognathus beds and in Indian may be Rhaetic, the older part of the series and Australian deposits also indicative of early may be slightly earlier, Noric in age. Triassic age (Mangali and Hawkesbury beds, Correlation of continental beds such as these respectively). In North America a brachyopid with the standard marine series in Europe is has been described by Welles (1947) from the extremely difficult. The most abundant fossils Moenkopi. All these zones appear to be equiva- are plants, which can be readily compared with lent to the "Eo-Triassic" Scythian stage or, at Gondwanaland floras of other southern conti- the latest, to an early phase of the Middle nental areas, but there are few northern floras Triassic. In the European upper Muschelkalk of a type with which they can be compared, and Keuper—equivalent to the Ladinian, and little interdigitation of Gondwanaland Carnian, and Norian—the brachyopids are plant-bearing beds with marine strata in any replaced by the plagiosaurs, shortheaded but area. far more specialized in nature. This suggests Currently, the only attempt at correlation is that the Estratos de Cacheuta, at least, were a very indirect one (Groeber and Stipanicic, early Triassic in age. An archaic group of 1952, p. 19-28, 46-48). The Cacheuta series is continental vertebrates may continue to underlain in some places by the Choiyoilitensian flourish in one area long after its extinction in porphyrites. In Chile, to the west, are Triassic others as is true today of Australia. But the keratophyres which may be of the same age. vertebrate evidence certainly fits better with an Below the Chilean keratophyres, in the Los assignment of the Cacheuta series to the Lower Vilos region, are marine beds with invertebrates or Middle rather than the Upper Triassic. thought to be of Carnian age (cf. Kummel and A second line of attack by means of Fuchs, 1953), and above them other beds with vertebrate evidence is less direct. Frenguelli plants comparable to those of the Cacheuta (1948) and Groeber and Stipanicic assume series and possible Noric invertebrates. Hence that the Cacheuta series is comparable to that it has been argued that the Cacheuta series seen to the northeast in the Ischigualasto must be of post-Carnian age, Norian—Upper region, and that the Estratos de Cacheuta are Keuper—at the earliest, and thus of quite late synchronous with the Ischigualasto beds proper Triassic date. However, there is no evidence (Groeber and Stipanicic, 1952, cuadro I). that the porphyrites concerned are of the same These beds appear to be definitely pre-Norian age, and closer consideration of the invertebrate and probably pre-Carnian, for dinosaurs are faunas renders these correlations doubtful. The absent, and the flourishing reptile groups are faunas below the keratophyres (horizons ft and cynodonts and rhynchosaurs—groups that 7) appear to be typically Middle Triassic in flourished in the Middle Triassic and are almost composition, except that Halobia is listed. Even entirely unknown in beds in the northern above the plant beds, zone c (P.F.2) contains continents equated with the Carnian or later Nevadites, a characteristic Middle Triassic Triassic stages. The equation of members of form. Higher, however, zone j% (P.F.4) has a this Ischigualasto-Ischichuca series with those typical Upper Triassic fauna, and, still higher, of the Cacheuta series is far from certain, but

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