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'o 10 FIELDIANA: GEOLOGY Rovereto (1914, p. 1) also regarded the Araucano faunas of Catamarca as a single unit and the fossil beds in the Valle de Santa Maria with "Corbicula" stelzneri as representing the "araucano tipico." However, the rocks and faunas so called in the Valle de Santa Maria are later in age than those encompassed by Doering's original "Araucano" (Simpson, 1974, p. 4). The Araucanian faunas from the Valle de Santa Maria on which the basic studies of C. Ameghino, F. Ameghino, Rovereto, L. Kraglievich, and others were based are all without precise stratigraphic data and have no reliable data as to levels of collection of the vertebrate fossils. They possibly represent a mixture from all the stratigraphic units recognized by Riggs & Patterson (1939), but primarily from their Araucanense (see below). A lower member, containing a guide horizon with Neocorbicula stelzneri and included by Doering (1882) in his Araucano, was distinguished by Bodenbender (1924) who called it lower Calchaqui, a name based on a stratigraphic sequence of continental red beds in the vicinity of Famatina in the province of La Rioja. Frenguelli (1937) later restricted the name Calchaqui to this unit in the Valle de Santa Maria, and this usage was followed by Riggs & Patterson (1939). Frenguelli (1930a, p. 115) divided the Tertiary strata in the Valle de Santa Maria into two lithologic units supposedly separated by a major unconformity (fig. 5). The thicker lower unit he named Santa Maria and divided into two horizons: the lowermost being the lower and upper Famatina of Bodenbender, and the uppermost, containing "Corbicula" stelzneri, he called Calchaqui. Frenguelli named the upper unit Araucaniano, which corresponded to the Araucanense of the Ameghinos and Rovereto minus Calchaqui. Frenguelli further divided his Araucaniano into three horizons: inferior, medio, and superior (fig. 5). Riggs & Patterson (1939) reproduced two stratigraphic sections made by Rudolf Stahlecker (Appendix II), who accompanied Riggs on his expedition to Cata- marca in 1926-1927 (fig. 6). One 1,525 m section was made in the vicinity of Chiquimil from the pueblo of San Jose to the pueblo of Chiquimil, Department of Santa Maria (fig. 6), and another 1,913 m section was made near Puerta de Corral Quemado, Department of Belen (fig. 4). On the basis of lithology, Stahl- ecker divided his stratigraphic sections into three major units of which the middle was divisible into three, making five units in all (figs. 5, 6). Upon study of the fauna, it became evident that the units distinguished by Stahlecker could, in part at least, be distinguished faunistically as well (Riggs & Patterson, 1939). The basal horizon recognized by Stahlecker is mainly red in color and toward the top is composed predominantly of sandstones. Below these massive red sandstones in the Chiquimil section occurs a layer of hard, brownish calcareous sandstone containing abundant shells of Neocorbicula stelzneri. Near San Jose, Stahlecker noted a fairly even transition between this basal horizon and that following, whereas near Puerta de Corral Quemado the transition was abrupt and the upper red sandstone thinner than in the section near San Jose. These facts led him to suspect that a short period of erosion had intervened before deposition of sediments of the succeeding unit (Riggs & Patterson, 1939, p. 146). Riggs & Patterson used the name Calchaqui for this basal unit with Neocorbicula, which is Doering's Araucano in this area. The only vertebrate yet found in the Calchaqui is a fragmentary glyptodont, tentatively identified by Riggs & Patterson (1939) as Parahoplophorus? sp. This Corral Quemado Didviphis inexpcctata. Thy laco- smilus atrox. Pyramiodonthcrium sp.. Pronothrotherium mirahitis. Promuhrolhcrium sp.. Orthomyc icra andina. Cardiotnys sp. nov Tetieomys sp. Cyonasu* ftrrv/ros Iris. Memihcgcthothcrium robus turn. Tremacytlus latifrons. Trcmacyllus diminutus, Xoiodon cf. X. foricunatus, Hrachythcrium more not, Brachythcrium sp. >j*%»*tm.m iWtVWt^ Tctrasxylus cf. T. diffhus /'..'.*> Tremacyllus cf. T. diminutus i^w^rvii v>---*-~--=-- g ? Parahttptophorus sp. .rjOV^Tjri" Corbicula sielmcri iiv"' .••■: aiiwtmn.- Araiuanense Chiquimil A lZ---_-_-"-_--- x\ Chiquimil B Calchaqui J V- tV-it-V"". AWJVWt Hide/phis ine\0ceimtm. t.utreolina »p . Vtiiiii^nu^ hermn>i\u>. ThxIactmlhM atro\. Thy laKOtmilmt temiis. ■Megatherium" gmmlryl. P\ ramiudantherium p . Pleurolestodon aiitus. I teulheritdai l\ lu> lu< ummnus. I'ntdolu turn* prise a. I'.-tl.-no- eavia §p.. /)olujw'.i sp . Cardiomy s ameghinorum. Cardiomys »p.. Telrastylus intermedia*. Cy nnasua sp. nov.. Memihegetoiherium ruhustum. rremae\llu< lati- fmns. Tremaey litis diminutus. Xodolon •.rislalus. Hraehy t he ri u m laternarium. Promaerauehenia antiqua. Promaerauehenia ealeha> uuiorum. Pmseelidodon cf, P. alma- groi. Cyonasua hrevirostris. Typotheriopsis internum. Xotodon cf. X. foricurvmus. mzTz "£»*£:£>«%»". Toxodontidac K«n. et. sp. indcl. .-'.-ivvsrc.Vcri -- »:->r-:-Cf •' PseudhegettMherium >p Chiquimil Area Puerta l)e Corral Quemado Area Fig. 6. Stahlecker's stratigraphic sections of Chiquimil and Puerta de Corral Quemado, as originally published by Riggs & Patterson (1939, fig. 1). 11 12 FIELDIANA: GEOLOGY determination is highly questionable. Parahoplophorus, a "Mesopotamian"4 ge- nus, is presumably (Pascual et al., 1965; Pascual & Odreman Rivas, 1973) Mon- tehermosan in age. There had been debate as to whether or not the Calchaqui sediments are separated by an unconformity from those above it. Frenguelli (1937) and Gonzalez Bonorino (1950) claimed that such an unconformity existed, although Stahlecker (as reported in Riggs & Patterson, 1939) and Peirano (1946b) were unable to detect any major break in sedimentation in the Tertiary beds in the Valle de Santa Maria. Most authors (e.g. , Frenguelli, 1937; Peirano, 1946b; Galvan & Huidobro, 1965) now agree that Calchaqui is Miocene in age, and Pascual & Odreman Rivas (1973, p. 310) have suggested that it may be of the same age as the Chasicoan. The second unit recognized by Stahlecker (fig. 6, Appendix II) is considerably thicker near Puerta de Corral Quemado than in the Valle de Santa Maria. It is composed predominantly of soft, fine-grained sandstones, although some con- cretionary layers are present at Puerta de Corral Quemado. The third unit is characterized by hard layers, sometimes conglomeratic, or gypsum-rich, yellow- ish sandstone. The names Chiquimil B and Chiquimil A were applied by Riggs & Patterson to the second and third units, respectively. Few fossils are known from the Chiquimil. One of the two specimens found in Chiquimil A, Tremacyllus cf. T. diminutus (fig. 6, Appendix IV), is a species found also in the Araucanense and Corral Quemado. The other, Tetrastylus cf. T. diffisus, compares closely with a Mesopotamian species. Neither of the fossil mammals from Chiquimil B has been found in higher levels at either locality. The undetermined hoplodontheriine toxodontid is of minimal value as an index fossil, because members of that subfamily survived into the Montehermosan. The hegetotheriid is different from the forms found in the Araucanense or Corral Quemado, but identification of it is very uncertain; the specimen is much smaller than the type of the Chasicoan Pseudohegetotherium torresi. Pascual & Odreman Rivas (1973) have tentatively assigned the Chiquimil A and B to the Chasicoan. G. Simpson (1974, pp. 4-5) justly argued that the extremely inadequate fossil evidence does not suffice to permit separation of Chiquimil A from the Arau- canense ( = Andalhuala) fauna and suggests, but is entirely inadequate to dem- onstrate, that Chiquimil B might belong to the Chasicoan. Until more fossils are found, these uncertainties will remain unresolved. The two upper units, consisting predominantly of clays, sandstones, and frequent tuff beds, yielded fossils in abundance (fig. 6, Appendix IV, V, VI). These units are separated at the Corral Quemado locality by a thick homogeneous bed of whitish sandstone containing abundant worm-shaped concretions. This marker bed5 was noted by Stahlecker in the Chiquimil area above unit XX, but was not included in his section (Riggs & Patterson, 1939, p. 146). The fourth 4When the paper by Riggs & Patterson (1939) was written, it was generally believed that the "Mesopotamiense" was earlier than the "Araucanense," whereas the reverse is now believed to be the case (Pascual & Odreman Rivas, 1973). It is even possible that the "Araucanense" and "Mesopotamiense" of earlier workers are, at least in part, time equiv- alents. 5Peirano (1956, p. 75) doubts the usefulness of this as a marker bed — ". . . es posible que se cOnvenciese luego que esa capa no era tan constante en esas mismas condiciones, experiencia que hemos tenido repedidas veces nosotros con rocas ora calcareas ora sin ese elemento." MARSHALL & PATTERSON: MAMMAL-BEARING TERTIARY, CATAMARCA 13 unit is much thicker in the Chiquimil area, whereas the fifth was studied in the Puerta de Corral Quemado region only. Riggs & Patterson (1939, p. 146) restricted the name Araucanense to the fourth unit, which is well developed in the Valle de Santa Maria. The name Corral Quemado Fm was proposed for the uppermost unit, because it is extensively exposed at that locality. This formation was also reported to occur near Chiquimil, but collections were not made from it in that area (Riggs & Patterson, 1939, p. 147n). The preliminary faunal lists presented by Riggs & Patterson (1939) were fairly extensive for the Corral Quemado and for their Araucanense. Based largely on these lists, and in accord with the conclusions of Riggs & Patterson (1939, p. 147), Pascual & Odreman Rivas (1973) assigned the mammalian fauna of the Corral Quemado an early Montehermosan age, and the fauna of the Araucanense a Huayquerian one. G. Simpson (1974, p. 5) did not feel that a significant difference in age had been demonstrated and elected to provisionally consider both faunas as Huayquerian in age. Thus, on the basis of Stahlecker's work, combined with study of the mam- malian faunas, Riggs & Patterson (1939) divided the Araucaniano of earlier au- thors (e.g., Frenguelli, 1930a, b, 1937) into three formations and one into two members. These are, from oldest to youngest, Chiquimil B (new in Riggs & Patterson), Chiquimil A (new in Riggs & Patterson), Araucanense (a restriction of the classic but invalid name), and Corral Quemado (new in Riggs & Patterson) (fig. 6). Doering's (1882) original "Araucano" is derived from the name of an Indian tribe from southern Argentina and Chile (i.e., araucanos were originally from the Arauco region of Chile) and is thus not acceptable as a time or rock unit name in modern geological nomenclature. In realization of this, G. Simpson (1940), using L. Kraglievich's (1934) term Huayqueriaense, proposed Huayque- rian as a time and time-rock (Age and Stage) designation for the Araucanense of Riggs & Patterson (1939), deriving the name from the Huayqueria Formation (a rock unit named by de Carles, 1911) from the Huayquerias region in the Department of San Carlos, province of Mendoza. That usage has since been generally adopted (e.g., Pascual et al., 1966). The rocks of Huayquerian age in the Valle de Santa Maria of Catamarca, however, are clearly distinct from the Huayqueria Formation of Mendoza (G. Simpson, 1974, p. 4). Cabrera (1944, p. 7) noted that the results of his studies did not support the opinion of Riggs & Patterson (1939) that a significant difference exists in the faunas between their Araucanense and Corral Quemado. He recorded the same species of Glyptodontidae above and below the boundary between these for- mations, although he gave no stratigraphic data to support this claim. Cabrera also noted that the Araucanense and Corral Quemado of Riggs & Patterson are more or less equivalent to the Araucaniano medio and Araucaniano superior of Frenguelli (1937). As early as 1919, Rassmus had proposed that the name Andalhuate be applied to all the so-called Araucanense of Catamarca, including rather less than Peirano's Araucanense, but distinctly more than that of Riggs & Patterson. J. L. Kraglievich (1952, plate opposite p. 30) used the name Andalhuala\ which he confined to the restricted Araucanense of Riggs & Patterson and correlated with the Huayqueria Formation of Mendoza. In a work published simultaneously in the same journal, Reig (1952, p. 123) evidently intended the same usage as J. L. Kraglievich, but specified a "Formaci6n de AndalgalaV' There is some added 14 FIELDIANA: GEOLOGY confusion because there is both an Andalgala (also sometimes spelled Andagala), Department of Belen (fig. 1), and an Andalhuala, Department of Santa Maria near Chiquimil (fig. 2), both in Catamarca. Despite Simpson's (1974, p. 4) state- ment to the contrary, Andalhuala is the more likely type locality, and that name is here retained for the formation in question. There are no Araucano beds known in the area of Andalgala (see Gonzalez Bonorino, 1950, Hoja 13d, An- dalgala). In a detailed stratigraphic study (fig. 5) of the Valle de Santa Maria, Peirano (1956) rejected the subdivisions and nomenclature of Riggs & Patterson (1939), and retrogressively called all the beds here in question Araucanense, which he believed to be a single, conformable unit in that valley. However, he did indicate an Araucanense superior, approximately the Corral Quemado of Riggs & Pat- terson, and an Araucanense inferior, approximately their Araucanense and Chi- quimil A, perhaps also including Chiquimil B (Simpson, 1974, p. 4). Peirano (1956, p. 84) noted that subdivision of the Calchaquense and Arau- canense should be based on paleontological data; however, his subdivision into levels has only lithologic value. He abstained from placing names on these lithologic levels, because to do so could, in his opinion, lead to greater nomen- clatural confusion. For this reason he applied only numbers to the distinct levels. Peirano (1956, p. 78) also proposed a tentative correlation of beds between the Valle de Santa Maria and the Quebrada de Amaicha. Galvan & Huidobro (1965) and Huidobro (1972) essentially rejected previous stratigraphic terminology altogether and proposed a number of new formational names in place of Calchaquense and Araucanense of earlier workers, which they placed in a Santa Maria Group (only in very small part equivalent to the San- tamariano of Frenguelli; see fig. 5). This included various continental formations of Late Tertiary age in the Valle de Santa Maria from Punta de Hualasto to Cerro Paranilla (fig. 2), separated by faults against the Precambrian basement of the Sierra de Aconquija and of the Cumbres Calchaquies (Galvan & Huidobro, 1965, p. 220). The total thickness of the Santa Maria Group is not possible to calculate due to these truncations, although the maximum known thickness is in excess of 3,000 meters (see below). Most of these Late Tertiary sediments are sandstones and clays, with much conglomerate above the Calchaqui and recurrent thin ash beds in the Andalhuala. Eight formations are recognized by Huidobro (1972) (from top to bottom): Fm. Zanja del Molle6 600 m Fm. Los Corrales6 120 m Fm. Yasyamayo7 80 m Fm. Andalhuala 1,200 m 6Dr. Gerardo E. Bossi (pers. comm.) regards these beds as fades of the Andalhuala Formation. 7The Yasyamayo conglomerates are roughly equivalent to the Puna Schotter of earlier authors. These beds are separated from the underlying Andalhuala by a large unconformity (G. E. Bossi, pers. comm.) and are not part of Huidobro's Santa Maria Group. Much of the area assigned by Huidobro (see fig. 2) to the Yasyamayo Fm. south of Amaicha del Valle (arroyo Las Salinas, Los Colorados, etc.) is actually San Jose Fm. with "Corbicula." This error is related to the Huidobro's mistaken claim that the Yasyamayo Fm. also has "Corbicula" (G. E. Bossi, pers. comm.). MARSHALL & PATTERSON: MAMMAL-BEARING TERTIARY, CATAMARCA 15 Fm. Loro Huasi8 650 m Fm. Las Areas8 200 m Fm. San Jose 200-230 m Fm. Saladillo 40 m Galvan & Huidobro (1965, p. 225) divided the Andalhuala Formation into two members: (1) an upper (superior) member composed of sands and clays with conglomeratic levels and tuff beds near the top; and (2) a lower (inferior) member composed of fine-grained sands and clays with abundant intercalations of gyp- sum. An attempt is made in Figure 5 to correlate Huidobro' s stratigraphic no- menclature with those employed by previous workers.9 GEOCHRONOLOGY Mineral concentrates of tuffs from two of the stratigraphic units recognized by Riggs & Patterson (1939, fig. 1) at the Puerta de Corral Quemado locality and one from the Chiquimil locality have yielded reliable radioisotope dates (fig. 7). These are — 3.54 mybp for unit 29, and 6.68 mybp for unit 8 of the Puerta de Corral Quemado section; and 6.02 mybp for unit XIX of the Chiquimil section. Magnetostratigraphic data for parts of these sections are shown in Figure 7, along with reasoned correlations with the polarity time scale. These radioisotope dates and magnetostratigraphic data support the relative ages and correlations of these beds proposed by Riggs & Patterson (1939). In addition, these data permit correlation of these Late Tertiary Land Mammal Ages with those in North America (fig. 8). A more detailed treatment of these data is presented by Marshall et al. (1979). PALEOPHYSIOGRAPHIC IMPLICATIONS The majority of known South American Early and Middle Tertiary mammal- bearing beds occur in Patagonia, southern Argentina (Simpson, 1940). During the Late Miocene (post-Friasian — ca. 12.0 mybp) — see fig. 8), the Argentine sedi- mentation center shifted from Patagonia to the Pampas10 and northwestern re- 8According to G. E. Bossi (pers. comm.), the stratigraphic relationship of these beds was reversed by Huidobro. *Dr. G. E. Bossi kindly read this paper in detail subsequent to its final completion. He feels that the exact equivalence between the named units in the Santa Maria Group and those units of Stahlecker from Chiquimil are as follows: Unit XX to XV Araucanense Fm. Andalhuala Unit XIV to XIII Chiquimil A Fm. Lorohuasi Unit XII to XI Chiquimil B Fm. Lorohuasi Unit X to VI Calchaquense Fm. Las Areas Unit V to I Calchaquense Fm. San Jose Bossi noted that Stahlecker's division of the Lorohuasi Fm. was probably influenced by the vertebrate remains. X0Pampa is a Quechua Indian name, which to some authors has been interpreted to mean plain and others to mean sea. The Pampean region, an area of extensive flat grasslands, comprises the provinces of Buenos Aires and Santa Fe, part of La Parnpa, the eastern part of Cdrdoba, the western parts of Entre Rios and Corrientes, as well as parts of Chaco and Formosa. This is the area that first received the attention of early Argentine and foreign geologists and paleontologists, particularly because of the high frequency with which fossil mammals are encountered. LITHO- VGP RADIOMETRIC MAGNETIC MAGNETIC POLARITY STRATIGRAPHY LATITUDE DATES (mybp) POLARITY ZONATION TIME SCALE (mybp) Lithologic Symbols B ^ S I tuff concretions conglomerate sond clay STRATIGRAPHIC THICKNESS is5M«i,n (in meters) 3.55 — CORRAL QUEMADO SECTION I + 90° CORRAL QUEMADO SECTION 2 6.68 — CHIQUIMIL 6.02 — -2.0 -3.0 -4.0 -5.0 5-6.0 7-7.0 -8.0 H^^ 6 - . r5.0 UJ 6 -6.0 -7.0 z UJ o o 2 ■ ' Fig. 7. Lithostratigraphy, magnetostratigraphy, and radioisotope dates. Lithostrati- graphic columns are after Riggs & Patterson (1939, fig. 1) using their numberings for lithologic units. Corral Quemado sections are continuous, but the middle portion is not illustrated. Magnetozones in polarity zonation column are labeled + for normal polarity, - for reversed polarity. Magnetic polarity time scale follows LaBrecque et al. (1977) with the addition of the short normal polarity interval (arrow) found in Iceland by Watkins & Walker (1977). Numbers to the immediate right of the polarity time scale are epoch num- bers. Geologic time scale follows Berggren & Van Couvering (1974). (After Marshall et al., 1979.) 16 Cenozoic Radio- Radio- North American South American isotope i sotope Dates on Ti me Epoch Land Mammal La nd Mammal South Scale American (mybp) Ages Ages Faunas (mybp) U "" PLEIST- OCENE RANCHOLABREAN LUJANIAN IRVINGTONIAN ENSENADAN UQUIAN ID Z CH APAD M ALALAN LU O BLANCAN — 3.55 - 0 _l MONTEHERMOSAN c Q. 0 — 6.02 HEMPHILLIAN HUAYQUERIAN — 6.68 LU 10 — z ID CHASICOAN o 0 CLARENDONIAN W//////////// — //////////////A 5 BARSTOVIAN FRIASIAN — 14.5 15 — 1 Fig. 8. Late Cenozoic radioisotope time scale and chronostratigraphy showing approx- imate correlations of North and South American Land Mammal Ages. Geologic time scale follows Berggren & Van Couvering (1974). (After Marshall et al., 1979.) 17 18 FIELDIANA: GEOLOGY gions (Pascual, 1961, p. 64; Yrigoyen, 1969, p. 319; Patterson & Pascual, 1972). The sediments changed from predominantly pyroclastic (i.e., tuffs and bentonitic clays) that characterize pre-Chasicoan units, to predominantly clastic (i.e., silts, sands, and loess) that predominate post-Friasian units of the Pampean and northwestern regions (Pascual, 1961, 1965; Pascual & Odreman Rivas, 1971). This change of sediment type coincided with a post-Friasian phase of Andean orogeny that resulted in elevation of the main Cordillera (Herrero-Ducloux, 1963; Farrar & Noble, 1976). Peirano (1956, p. 90) emphasized that during the Late Tertiary a single primary sedimentary basin existed in the Santa Maria area of northwestern Argentina. It was in this basin that the Late Tertiary sediments were deposited, and there is no clear evidence of local tectonic movements in this region during their deposition. The last major phase of Andean orogeny occurred after Montehermosan time, because all of the Late Tertiary beds in this area are now folded, faulted and, in places, removed by erosion. This orogenic phase resulted in faulting and uplift of the Sierras del Aconquija, Las Cumbres Calchaquies, and del Cajon (or Quilmes) and in formation of intermountain basins like the Valle de Santa Maria and Valle de Amaicha (Gonzalez Bonorino, 1950, p. 73). These movements were delimited by NNE-SSW oriented fracture zones, clinal structures, and block faulting, which in places brought Late Tertiary beds into thrust contact with Precambrian basement (Huidobro, 1972). The presence of this last major orogenic phase has conventionally served to mark the Plio-Pleistocene boundary in Ar- gentina (Pascual & Fidalgo, 1972). Uplift of the Andes continued and became accentuated during the Quaternary (Polanski, 1957; Peirano, 1956; Huidobro, 1965; Turner, 1970; Caminos, 1972), when they attained their present elevation. Elevation of the Andean Cordillera in the Late Tertiary acted as a barrier to moisture-laden Pacific winds (Patterson & Pascual, 1972, p. 251). The rain shadow effect of the newly elevated Andes initiated the desertization of Patagonia. The southern South American habitat changed from primarily savanna-woodland (which predominated during the Early to Middle Tertiary-Paleocene through Miocene) to drier forests and pampas, ranging from forests in northern parts of the continent to grasslands in the south (Pascual & Odreman Rivas, 1971, p. 399). Pampas habitats similar to those prevailing today probably came into prom- inence at about this time. Many subtropical savanna- woodland forms retreated northward, and new opportunities arose for those mammals able to adapt to a plains environment (Patterson & Pascual, 1972, p. 251). Gerth (1941), Just (1952), and Solbrig (1976) have shown that mesic forests that covered the southern part of the continent in the earlier Tertiary became progressively restricted as a result of these physiographic changes. Through the Miocene the fossil mammals of southern Patagonia suggest a climate sufficiently genial to permit such now mainly tropical animals as porcupines, echimyids, dasyproctids, anteaters, and primates to flourish there. The habitat suggested by these mammal faunas is a savanna-woodland that graded northward into rain forest, woodland, and savanna of the tropical zone, then no doubt more extensive than at present (Patterson & Pascual, 1972). The character of Pliocene sediments and vertebrate faunas in the province of Buenos Aires (e.g., Monte Hermoso, Chapadmalalal, and Irene Formations) indicates that this region had a warm-temperate, humid climate, contrasting to MARSHALL & PATTERSON: MAMMAL-BEARING TERTIARY, CATAMARCA 19 the cool-temperate Pampean climate of today (Pascual & Odreman Rivas, 1971, p. 407). The evidence as gleaned from the vertebrate fossils indicates that during the Pliocene the documented climatic change was gradual and was related to, and correlated with, the last major period of Andean uplift. The frequent presence of fossil trees (see Frenguelli, 1937, p. 405; O'Donnell, 1938) and anteaters (e.g. Myrmecophaga and Palaeomyrmidion, Rovereto, 1914) in the Late Tertiary sediments in the Valle de Santa Maria indicates that the climate and environment in this region was then different than it is today. It has been inferred that these western valleys, such as Santa Maria, served as corridors that permitted displacement of subtropical elements to the southwest (Pascual & Odreman Rivas, 1971). This view is supported by knowledge of the fossil ver- tebrates in these areas, and it explains the presence today of relic invertebrates of Brazilian affinity in some mountain areas of northern Patagonia (Ringuelet, 1959, 1961). The climate of northwestern Argentina during the Pliocene was presumably much like that of the present day Chaco. The region became xerophytic only after the Sierras Pampeanas, which border this area to the east, were uplifted beginning in the Pliocene (Orians & Solbrig, 1977, p. 19). During the Pliocene, the region was lower than it is today, and the Sierras Pampeanas did not then act as effective barriers to humid winds from the northeast (Solbrig, 1976, p. 23). As a consequence, the latest Pliocene provides the first unmistakable evi- dence for extensive areas of semidesert in northwestern Argentina (Simpson, 1971; van der Hammen, 1972; Orians & Solbrig, 1977, p. 63), and coincident with the rise of the Andean Cordillera we find the first indication of high moun- tain flora (Simpson, 1971; van der Hammen, 1966). In point of fact, the Pliocene uplift of the Cordillera Central of Chile and the Pleistocene uplift of the Sierras Pampeanas of Argentina produced the rain shadow effect that makes the valleys of east-central Catamarca the semideserts they are today (Solbrig, 1976, p. 24). ACKNOWLEDGMENTS Funds for field work in Argentina were provided by grant 1698 from the National Geographic Society, Washington, D.C., to L.G.M. The ^-"Ar dating was supported by NSF Grant EAR 73-00235 A01, formerly GA-40805, to G. H. Curtis, Department of Geology and Geophysics, University of California, Berke- ley, and its publication was made possible by NSF Grant 7909515 to L.G.M. Processing of the paleomagnetic samples was supported by NSF grant EAR 75- 13571 to R. F. Butler, Department of Geosciences, The University of Arizona, Tucson. Special thanks to Dr. G. E. Bossi, Facultad de Ciencias Naturales, Miguel Lillo, Tucumdn, Argentina, for helpful discussions on the geology of the Valle de Santa Maria, and to Dr. R. Pascual, Museo de La Plata, for critically reading a final draft of the manuscript. Appendices IV, V, and VI were compiled by J. G. Armstrong-Ziegler, Custodian of Fossil Vertebrates, Department of Geol- ogy, Field Museum. Field work in Catamarca during May, 1977, by L.G.M. was done in collabo- ration with R. F. Butler, R. Pascual, and G. J. Scaglia, Director, Museo Municipal de Ciencias Naturales de Mar del Plata "Lorenzo Scaglia," Mar del Plata, Ar- gentina. 20 FIELDIANA: GEOLOGY APPENDIX I The Marshall Field Paleontological Expedition to Catamarca, Argentina The Marshall Field paleontological expedition of 1926 to Catamarca Province in northwestern Argentina included Elmer S. Riggs of Field Museum as leader, Robert C. Thorne of Vernal, Utah, as collector, and Rudolf Stahlecker, a former student of F. von Huene of the University of Tubingen, as geologist (fig. 9). Riggs and Thorne sailed from New York on April 10, for Buenos Aires. While Riggs dealt with logistics problems there, Thorne proceeded to the railway ter- minus at Andalgala in the province of Catamarca (fig. 1). Riggs followed a week later. In Andalgala, Riggs met Colonel Wieser, an acquaintance he had made several years earlier, who had agreed to assist the present expedition. Two local resi- dents, Juan and Felipe Mendez, both of San Jose (fig. 9), were employed as local collectors; both were to prove useful members of the expedition. Two saddle horses and six pack mules were hired to convey the expedition's collecting and camping equipment from Andalgala over a mountain pass to the pueblo of San Jose, a distance of 120 miles, requiring some four days' travel. Thorne was sent ahead with the packtrain to establish camp. Meanwhile Riggs, employing a separate guide, made a reconnaissance trip to the valley of Ojo del Agua in the province of Tucuman, where he located bones of glyptodonts and a sloth (fig. 10). Returning hurriedly to Andalgala on the third day, Riggs met Stahlecker upon his arrival from Buenos Aires. Three Fig. 9. Expedition members in camp at Chiquimil. From left to right — Rudolph Stah- lecker, Felipe Mendez, Elmer S. Riggs, Robert C. Thorne, an unidentified boy (standing), and Juan Mendez. 21 22 FIELDIANA: GEOLOGY days later Juan Mendez returned from San Jose with the pack mules to pick up Riggs, Stahlecker, and additional provisions. The party then proceeded to join Thorne, who had since moved camp to the little Indian village of Chiquimil (fig. 11) a few miles to the southeast of San Jose (fig. 2). On May 19, the expedition was united at Chiquimil. The rainy season at Catamarca extends from December to April, and the months immediately following are most favorable for collecting. It was therefore highly desirable for the expedition to begin work there in May. The mammal-bearing beds in this area consist of a large series of massive sands and indurated clays (figs. 12-15). Remains of mammals were locally abun- dant, especially on the hill called Loma Rica. The Chiquimil area was worked from May 20 until June 25. By the end of that time the fossil beds in this area were all but exhausted, and further reconnaissance for new collecting grounds was required. In an attempt to prospect as much of the surrounding areas as possible, the party divided into two groups. One, consisting of Thorne and Stahlecker, ex- plored northward along the east side of the valley to Las Areas in the south- ernmost part of the province of Salta (fig. 3). They had little success. Riggs, with Juan and Felipe Mendez, proceeded down the valley as far as Punta Belasto, investigating localities reported to lie in that direction. Specimens were collected from Andalhuala, Ampahanco, Vallecito, and Rio de Yapis (fig. 2). After 10 days (June 29 through July 8), the two groups returned to Chiquimil and collected a few more specimens from Loma Rica before moving camp to San Jose. The expedition worked out of San Jose from July 12 to August 8 and made several short collecting trips north and south. The locality of Jujuy, about 4 km east of San Jose, was collected between July 12-14; Tio Punco (Theopunca, Teopunco, Nacimiento de Agua) was collected between July 27-29; and Am- pajango (Ampahanco) to the south was visited August 7-8. Specimens were also collected from an unspecified locality to the "East of Santa Maria" during July 21-22, and from "Peneplain Basin" on July 17. By the end of July the expedition had prospected and collected for a distance of more than 50 miles along the east side of the Valle de Santa Maria. Having found no additional promising localities in this area they decided to move camp. The collections made up to that time were packed and temporarily stored in a warehouse in San Jose. Colonel Wieser reported that he had seen bones similar to those excavated by Field Museum while excavating Indian graves near the small pueblo of Puerto de Corral Quemado some 100 miles to the southwest of San Jose. A former physician of Belen had volunteered similar information two months earlier. Fossil mammals had not previously been recorded from that area, and Riggs was eager to investigate. So, during the second week of August the pack mules were loaded, and the expedition moved to Puerta de Corral Quemado (figs. 17-22). There, residence was established in a new adobe building on the property of Sr. Don Carmen Aibar, a provincial senator and town resident (fig. 17). Considering that it was now mid-winter and that the party had just en- countered a sizable snow storm on their southward journey, the use of this new building was most appreciated. Collecting in the Corral Quemado area was carried out from mid-August through mid-November. Most collections were made from along the Rio Corral 'J 23 24 25 c o 01 I o o X K U W a, en £ 3 T3 (50 1 >< >< 3 O (X 3 i en o 0 26 u u it 27 28 FIELDIANA: GEOLOGY Fig. 16. Type specimen (FMNH P14357) of the giant predaceous ground bird Andalga- lornis ferox (left), which stood about five feet in height, collected from unit XVHIb at Chiquimil, compared with the skeleton of a golden eagle (right) (also see fig. 15). Quemado and its immediate tributaries, although prospecting was done to the west of this area and some collections were made as far away as La Conte. More specimens were obtained from Corral Quemado than from the Valle de Santa Maria. These widely exposed beds had never before been prospected by pa- leontologists, whereas those near Chiquimil had been visited frequently. Sum- mer began in November, and with it came the rains. These periodical showers interfered with collecting activities and made it necessary to discontinue work. Difficulties were encountered in finding wood to make shipping crates for the collection. Some drift logs were rescued from the Rio Corral Quemado by Don Carmen's workers, and these were placed at the expedition's disposal. A slipsaw, improvised by breaking off alternate teeth of an ordinary crosscut saw, was used 29 30 31 32 Fig. 21. Robert C. Thorne (on rope ladder) and Rudolph Stahlecker (on ledge) excavating the skeleton of a glyptodont; beds dip to WNW. 33 Wm'r A . v J ft* 1 r> im:: TVf!<' ^-- A ' 1 ) . \ ? ■ t If* • • » 23B m %k' : "WU ■PB $v; fe i1 60 c I * JI i .2 a. m BJfv W ^ XsJ 5 \ ^ S«-m ^Bi^B '**>*■ I ^"l $ o (0 B 1 ■Jft a *yam 1 o ^■#M U 01 1 0) 3 ^ J! f ' - ■ ■ 6 5 I ( > 13 V i o U BJj 1 •• • S o 1 34 MARSHALL & PATTERSON: MAMMAL-BEARING TERTIARY, CATAMARCA 35 to cut the logs into boards, which in turn were made into shipping crates. The collection was then packed and ready for transport to the railway depot at Andalgala. The smaller boxes were conveyed by pack mules (fig. 22), and a horse cart was used for the heavier ones. These were taken to the pueblo of Belen, some 40 miles south of Puerto de Corral Quemado. Striking camp at Puerto de Corral Quemado on November 19, Riggs and Stahlecker proceeded to Belen where they secured a truck and transported the collection to Andalgala. The problem then arose of claiming the collection stored at San Jose and getting it to Andalgala. The rains had caused a landslide that entirely blocked the road from San Jos£ to Tucuman, making the route impassable. Further, because of a shortage of horse feed, wagon freighters refused to make the journey from San Jos6 to Belen. With no alternatives, resort to pack mules became necessary. The collections, however, had been packed in boxes too heavy for mules. Thorne, therefore, was sent back to San Jose with the Mendez brothers and instructed to unpack the collection, cut the boxes into smaller units, and repack these for transportation by mule. By this means the collection from San Jose was conveyed by mountain and desert trails to Andalgala and from there, along with the collection from Corral Quemado, was shipped by rail to Buenos Aires. From Andalgala Riggs returned to Ojo del Agua to secure a megathere that he had located during his trip there in May. The regular members of the ex- pedition then proceeded to Buenos Aires, arriving in late December. APPENDIX II Stahlecker's Maps and Sections Rudolf Stahlecker's detailed study of the stratigraphy of the Chiquimil and Puerta de Corral Quemado areas, "To appear in Geol. Ser. Field Mus. Nat. Hist." (Riggs & Patterson, 1939, p. 162) was never published. However, Stahlecker's manuscript entitled, "Geological Observations in the Tertiary of the Province of Catamarca, Argentina," with stratigraphic sections and geological maps, was available to Riggs & Patterson during preparation of their paper. Fortunately, copies of Stahlecker's manuscript, stratigraphic sections (figs. 23, 26), and the maps upon which these sections were based (figs. 24, 25) are still available and, except for the sections and maps being redrafted and minor editorial changes to the manuscript, are here reproduced in their original form. The available text was clearly written by Stahlecker as evidenced by the awkward syntax; he was German and did not write fluent English. We have reworded some of the more cumbersome phrases, but thought it best to leave most as they were originally written. The same geologic symbols are used in the sections and maps, and Stahlecker's interpretations of the geological features are readily obvious. The fossil taxa collected by Riggs in the Valle de no Santa Maria are listed in Appendix rv and those from Puerta de Corral Quemado in Appendix V; the number of specimens and their levels of collection in each area are listed in Tables 1 and 2, on pages 40 and 42, respectively. 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