Cerro Azul Formation Research Articles

Deciduous dentition and eruption pattern in late Miocene Pachyrukhinae (Hegetotheriidae, Notoungulata) from La Pampa Province, Argentina

The study of juvenile remains of Paedotherium Burmeister from Cerro Azul Formation (La Pampa Province, Argentina; late Miocene) is presented. Upper and lower deciduous dentition (or permanent molars supposed to be associated with non-preserved deciduous teeth) are recognised. Several ontogenetic stages are distinguished among juveniles, according to the degree of wear and the replaced deciduous teeth. Besides, some morphological and metrical differences are observed along the crown height. Deciduous cheek teeth are high-crowned and placed covering the apex of the corresponding permanent tooth. The height of the crown and the degree of wear allow establishing the pattern of dental replacement of deciduous and permanent premolars in a posterior–anterior direction (DP/dp4–2 and P/p4–2), as well as the eruption of M/m3 before DP/dp4 is replaced. Some of the studied remains are recognised as young individuals of Tremacyllus Ameghino, but with complete permanent dentition, which leads to propose a different timing in the dental replacement with respect to Paedotherium; they also allow the establishment of an opposite premolar eruption pattern, from P/p2 to P/p4. This knowledge of the deciduous dentition of Paedotherium suggests the need of revising the morphological and metrical characters previously used for defining species within this taxon.

The Celliforma ichnofacies in calcareous paleosols: An example from the late Miocene Cerro Azul Formation, La Pampa, Argentina

Invertebrate trace fossils from the late Miocene Cerro Azul Formation (La Pampa, Argentina) are described and compared with known paleosol ichnofacies. The formation is a loess succession punctuated by numerous calcareous paleosols. Trace fossils were recovered from thirteen localities distributed in a wide latitudinal and longitudinal range within La Pampa Province. Paleosols from the northwestern localities display clastic dikes and pedogenic slickensides and are compared with calcic vertisols, which are typical of strongly seasonal and semiarid climate. Paleosols from the remaining localities have a Bt horizon with blocky or prismatic peds and can be compared with mollisols. The depth to the Bk horizon for all paleosols averages 0.54m, suggesting a mean annual precipitation of 450mm (±147mm), also pointing to semiarid climatic conditions during soil formation. The trace fossil assemblage from the Cerro Azul Formation is of low diversity and abundance and is typified by the presence of the insect trace fossils Celliforma, Rosellichnus, Rebuffoichnus, Fictovichnus and Teisseirei. The ichnospecies recorded are: Celliforma germanica, Celliforma cf. rosellii, Celliforma isp., Rosellichnus isp., Rebuffoichnus casamiquelai, Fictovichnus cf. sciuttoi, Fictovichnus isp., Teisseirei barattinia, Taenidium barretti, and cylindrical burrow fills. These trace fossils (along with Attaichnus kuenzelii, vertebrate burrows and medium–sized rhizoliths described in previous works) are considered comparable with the Celliforma ichnofacies. This ichnofacies is indicative of well-drained calcareous paleosols developed under low vegetation coverage. For the analyzed succession the vegetation was probably dominated by scrubs with minor participation of herbaceous plants. Coprinisphaera ispp. (including Coprinisphaera lazai, Coprinisphaera murguiai, and Coprinisphaera isp.) showing a cementation similar to associated late Miocene trace fossils were only recorded, along with Celliforma isp., in two localities. This trace fossil assemblage is comparable with the Coprinisphaera ichnofacies, suggesting dominance of herbaceous communities and wetter climate than those of the Celliforma ichnofacies. Some specimens of uncemented Coprinisphaera ispp. were produced during post-Miocene times and are not considered as a part of the trace fossil assemblage of the Cerro Azul Formation.

Leftover prey remains: a new taphonomic mode from the Late Miocene Cerro Azul Formation of Central Argentina

The Cerro Azul Formation (La Pampa Province, Argentina) comprises a rich vertebrate fauna of small mammals dominated by notoungulates and rodents. The fauna pertains to the Late Miocene specifically to the Huayquerian Stage/Age. Taphonomic analysis of micro-mammals from Estancia Re locality evidenced that the faunal assemblage was accumulated by the activity of a predator. This assemblage was compared with others from the Cerro Azul Formation in Telen and Caleufu localities (La Pampa Province), previously interpreted as products of predator activities. These microfossil accumulations differ from assemblages attributed to pellets and faeces produced by modern predators (nocturnal and diurnal bird raptors and carnivore mammals). However, due to their anatomical representation, degree of bone breakage and presence of tooth marks, they are interpreted as accumulations of uneaten prey remains discarded by the predator. The predator involved could not be determined with certainty, although the presence of tooth marks in some skeletal remains and the presence of coprolites in Telen and Caleufu suggest that it could be a carnivore mammal. Similarities in the accumulation mechanism, patterns of preservation and sedimentary contexts in the three assemblages support the recognition of a new taphonomic mode, termed ‘leftover prey remains’.

A New Species ofReigechimys(Rodentia, Echimyidae) from the Late Miocene of Central Argentina and the Evolutionary Pattern of the Lineage

The genus Reigechimys (Rodentia, Echimyidae) was originally described on the basis of two mandibular fragments recovered from Huayquerian (late Miocene) outcrops of the Cerro Azul Formation in La Pampa Province (Argentina). The included species (R. plesiodon Verzi et al. and R. octodontiformis Verzi et al.) represent a peculiar lineage characterized by its molar morphology with occlusal simplification that is extreme for the family. New materials recently found at the Cerro Azul Formation allow for a more detailed knowledge of the variation of Reigechimys and recognition of a new species, Reigechimys simplex sp. nov. characterized by the absence of mesoflexid/fossettid in the m1–2. The morphological changes of Reigechimys are described in the context of the turnover exhibited by octodontoid rodents in the Huayquerian of the Cerro Azul Formation. The polarity of changes described for Reigechimys is consistent with those of the other lineages. This evolutionary pattern enhances the biochronological interpretation of the Huayquerian in this formation.

New Records of Squamates from the Upper Miocene of South America

Abstract The Cerro Azul Formation of Argentina has yielded one of the highest diversities of squamate reptiles for the upper Miocene of South America including tupinambine teiids (Tupinambis sp.), “colubrids,” and viperids. Here, we describe new remains of Tupinambis sp. and “Colubridae” from this Formation as well as the first records of teiine teiids and boid snakes. The teiine represents the oldest record of this subfamily in South America. The squamate assemblage of the Cerro Azul Formation is consistent with the mammalian fauna in supporting the interpretation of a Chacoan-type palaeoenvironment for the upper Miocene of Central Argentina.

First record of Procariama simplex Rovereto, 1914 (Phorusrhacidae, Psilopterinae) in the Cerro Azul Formation (upper Miocene) of La Pampa Province; remarks on its anatomy, palaeogeography and chronological range

Vezzosi, R.I., June 2012. First record of Procariama simplex Rovereto, 1914 (Phorusrhacidae, Psilopterinae) in the Cerro Azul Formation (upper Miocene) of La Pampa Province; remarks on its anatomy, palaeogeography and chronological range. Alcheringa, 157–169. ISSN 0311-5518. New records of Procariama simplex in central and northwestern Argentina are reported. The fossil material includes mandibular bones, cervical vertebrae and several elements of the fore and hindlimbs. After an exhaustive comparison of anatomical characters and morphometric analysis, the fossil specimens are assigned to the psilopterine Procariama simplex. The specimen from La Pampa Province represents the first record of a psilopterine in this central region of Argentina and derives from upper Miocene sediments of the Cerro Azul Formation. Lithological features and biostratigraphical data allow the host bed to be assigned to the Huayquerian faunal stage (late Miocene). The La Pampa record broadens the geographical distribution of Procariama simplex, which was previously restricted to northwestern Argentina. Raúl Ignacio Vezzosi [vezzosiraul@gmail.com], Centro de Investigaciones Científicas y Transferencia de Tecnología a la Producción CICYTTP-CONICET, Materi y España s/n (3105), Diamante, Entre Ríos, Argentina. Received 1.4.2011, revised 28.5.2011, accepted 14.6.2011.

Late Miocene continental birds from the Cerro Azul Formation in the Pampean region (central-southern Argentina)

Cenizo, M.M., Tambussi, C.P. & Montalvo, C.I., iFirst Article. Late Miocene continental birds from the Cerro Azul Formation in the Pampean region (central-southern Argentina). Alcheringa, 1–22. ISSN 0311-5518. The oldest known birds from the Cerro Azul Formation are described, including the oldest records for the genera Eudromia and Nothura (Tinamidae), Milvago (Falconidae), Pterocnemia (Rheidae) and an undetermined Tyrannidae. The first remains of Phorusrhacidae for this formation are reported and a specimen previously referred to the giant teratorn Argentavis magnificens is reassigned to this family. We outline and update the current knowledge of the groups studied herein. The palaeornithological record from the Cerro Azul Formation is congruent with palaeoenvironmental inferences previously drawn from mammalian assemblages recovered from this unit, which point to the existence of open environments, possibly xerophyllous shrubby steppes, perhaps with some trees. These records are the first indications of a typically Pampean bird fauna at the end of the late Miocene in central-southern Argentina.

Late Miocene capybaras (Rodentia, Cavioidea, Hydrochoeridae): skull anatomy, taxonomy, evolution and biochronology

Fossil capybaras are morphologically extremely varied, but previous studies have disagreed on whether this diversity reflects intraspecific variation or the existence of multiple species. Here, we review the capybaras from the classic Argentinian Late Miocene localities of Parana River cliffs (“conglomerado osifero” of the Ituzaingo Formation, Entre Rios), and Chillhue and Guatrache shallow lakes (Cerro Azul Formation, La Pampa), and perform a morphometric analysis of their upper cheek teeth and the posterior portion of the rostrum. Our results confirm that all of the specimens from the “conglomerado osifero” belong to the single species Cardiatherium paranense. In addition, we refer a specimen from Tupungato (Rio de los Pozos Formation, Mendoza) to C. paranense, thus expanding its geographical range. The material from La Pampa represents a different taxon, and is here preliminary referred to Cardiatherium aff. orientalis. Our systematic interpretation of Late Miocene capybaras suggests that the early rad...

Dental evolution in Neophanomys (Rodentia, Octodontidae) from the late Miocene of central Argentina

The evolutionary pattern of the molar morphology of the small caviomorph (Octodontidae) Neophanomys from the late Miocene Cerro Azul Formation of central Argentina is analyzed. Two new species (chronomorphs) are recognized, which constitute an anagenetically evolving lineage with a gradual and directional pattern of increasing molar hypsodonty. Dental changes related to increasing hypsodonty are comparable to those of the octodontid lineage Chasichimys also recovered from the Cerro Azul Formation. However, Neophanomys shows comparatively less variation in gross morphology and there are no evidences that this lineage achieved euhypsodonty. In contrast, important changes in enamel microstructure (schmelzmuster) are observed among different populations of Neophanomys, supporting the hypothesis that these changes can occur at least partially independently from modifications in dental gross morphology. The patterns of dental evolution detected in the Neophanomys and Chasichimys- Xenodontomys lineages and the unequivocal polarity of the changes involved, related to increasing hypsodonty, reinforce the hypothesis that chronological differences exist among late Miocene outcroppings of Cerro Azul Formation in central Argentina.

The oldest South American Cricetidae (Rodentia) and Mustelidae (Carnivora): Late Miocene faunal turnover in central Argentina and the Great American Biotic Interchange

The discovery of a rich fauna from the late Miocene Cerro Azul Formation in Caleufú, central Argentina, is reported. This fauna includes vertebrate Holarctic immigrants, among which are the oldest South American records of mammals of the families Cricetidae (Rodentia) and Mustelidae (Carnivora). Stratigraphic, biochronological and taphonomic evidence indicates that the faunal assemblage from Caleufú is confidently synchronous and represents the late Huayquerian (Zone of Xenodontomys elongatus; late Miocene). Thus, this fauna supports hypotheses of the arrival of cricetids and mustelids prior to the Pliocene completion of the Panamanian isthmus. However, the new records do not permit inferences to be made about precise moments of entry of these groups into South America. Representation of the GABI in the fossil record is here interpreted as a major event integrated by a nested pattern of events, including geographically more restricted turnovers (implying particular taphonomic and geographic biases) and associated environmental changes. In such a hierarchical context, the record of Caleufú represents a local turnover different from those occurring with arrivals of these taxa, or their ancestors, into the continent. In accordance with biochronological data, the turnover recorded in Caleufú could be coeval with the global-scale glacial event detected for the late Miocene (ca. 5.7–5.8 Ma). In southern South America, this arid and cold pulse would have triggered the distribution drift to central Argentina of fauna previously restricted to western peri-Andean areas. Local turnovers such as the one reported here, and associated physical changes, have to be analyzed in detail as individual events in order to interpret the chronology, dynamics and paleoenvironmental context of hierarchically greater episodes such as the GABI.

Vertebrate taphonomy in loess-palaeosol deposits: A case study from the late Miocene of central Argentina

This paper deals with the taphonomic analysis of the late Miocene bone assemblage from the Cerro Azul Formation at Telén (La Pampa Province, Argentina). The faunal assemblage was assigned to the Huayquerian mammal age (late Miocene). The fossiliferous section shows a homogeneous lithology, and is interpreted as a loess deposit with two similar and slightly developed palaeosols, classified as calcic vertisols. The studied sample comprises 5598 remains anatomically and taxonomically determined. They were collected from an area of about 48,000 m 2, appearing randomly distributed through the section and with low density. Most remains are small- to very small-sized, disarticulated, and very fragmented. Different taphonomical histories are inferred for microvertebrates and macromammals. The microvertebrate assemblage is interpreted as the result of predator activities. After a brief period of pre-burial exposure, remains were dispersed from the original depositional area. On the other hand, a natural and gradual death process is envisaged for macromammals, followed by a long period of exposure to weathering and dispersal by physical agents. Remains of both groups, once buried, suffered the diagenetic processes of the host rock. Consequently, the fossil assemblage from Telén would represent a condensed assemblage corresponding to two distinct time spans, i.e., the accumulation of microvertebrates took place in a short time interval whereas that of macromammals occurred over a longer period, coincident with the development of both soils.

Snakes from the Cerro Azul Formation (Upper Miocene), Central Argentina, with a review of fossil viperids from South America

ABSTRACT South America contains a diverse Miocene snake record. Heretofore, the most significant assemblages were from the early and middle Miocene of Patagonia and Colombia. Colubroid vertebrae assignable to the ‘Colubridae’ and Viperidae are here reported from the upper Miocene Cerro Azul Formation at Caleufú, in La Pampa province, central Argentina. The viperid fossil is the oldest record of the family in South America and, together with molecular evidence, it supports the hypothesis of viperids first entering South America prior to the closure of the Isthmus of Panamá. South American viperid specimens also have been recognized from the Pliocene (aff. Bothrops) and Pleistocene of Buenos Aires province, Argentina. The presence of Bothrops during the early–middle Pleistocene near La Plata city suggests that during more humid intervals this genus had a wider distribution than at present. A previous report of a viperid from the late Pleistocene of Bolivia cannot be corroborated.

New Tupinambis Remains from the Late Miocene of Argentina and a Review of the South American Miocene Teiids

The most abundant and diverse records of teiids in the South American Miocene are from early and middle Miocene of Patagonia (Argentina) and Colombia. Only two genera of tupinambines are recognized: Paradracaena and Tupinambis. In this contribution, we describe remains assigned to Tupinambis from the late Miocene Cerro Azul Formation. The fossils were collected in exposures of this unit at several localities in the province of La Pampa, central Argentina. Evolutionary history and biogeography of South American tupinambines were affected by the environmental-climatic change subsequent to the uplift of the Andes. Among the taxa represented in the Miocene, Paradracaena became extinct, whereas Tupinambis survived restricted to environments with a more benign climate, disappearing from Patagonia but not from central Argentina.

Los Hegetotheriinae (Hegetotheriidae, Notoungulata) del Mioceno superior de la provincia de La Pampa, Argentina

Remains of Hegetotheriinae (Hegetotheriidae, Notoungulata) from several sites of La Pampa Province are studied in this paper. Specimens were collected from outcrops corresponding to the Cerro Azul Formation and the coeval levels of the Rio Negro Formation. Faunal remains from these sites reflect the presence of typical Huayquerian (late Miocene) taxa present in other areas of Argentina. The morphometrical study of these hegetotherines allows their referal to Hemihegetotherium achataleptum , a species known from the late Miocene of the provinces of Catamarca, San Juan, Mendoza, and La Pampa. Despite a slight difference in size observed between the remains of La Pampa and the known H. achataleptum specimens, a specific separation between them is not justified, especially considering the scarcity of H. achataleptum material and the absence of significant morfological differences with respect to the holotype.

Geologic Structure of a Part of the Barinas Mountain Front, Venezuelan Andes

Research Article| March 01, 1969 Geologic Structure of a Part of the Barinas Mountain Front, Venezuelan Andes CARLOS SCHUBERT CARLOS SCHUBERT Dirección de Geología, Ministerio de Minas e Hidrocarburos, Caracas, Venezuela Search for other works by this author on: GSW Google Scholar Author and Article Information CARLOS SCHUBERT Dirección de Geología, Ministerio de Minas e Hidrocarburos, Caracas, Venezuela Publisher: Geological Society of America Received: 19 Jan 1968 Revision Received: 19 Aug 1968 First Online: 02 Mar 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Copyright © 1969, The Geological Society of America, Inc. Copyright is not claimed on any material prepared by U.S. government employees within the scope of their employment. GSA Bulletin (1969) 80 (3): 443–548. https://doi.org/10.1130/0016-7606(1969)80[443:GSOAPO]2.0.CO;2 Article history Received: 19 Jan 1968 Revision Received: 19 Aug 1968 First Online: 02 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation CARLOS SCHUBERT; Geologic Structure of a Part of the Barinas Mountain Front, Venezuelan Andes. GSA Bulletin 1969;; 80 (3): 443–548. doi: https://doi.org/10.1130/0016-7606(1969)80[443:GSOAPO]2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract The following lithologic units are exposed in the Barinitas-Santo Domingo region, southeastern Venezuelan Andes: (1) the Precambrian (?) Iglesias Group, forming the metamorphosed basement; (2) the Lower Paleozoic (?) Cerro Azul Formation, a phyllite sequence; (3) the Upper Paleozoic Palmarito Formation, mostly fossiliferous limestones and shales; (4) the Triassic-Jurassic La Quinta Formation, a continental sequence of red beds; (5) the rocks of the Cretaceous transgression and regression, consisting of the Río Negro, Apón, Aguardiente, Maraca, La Luna, and Colón-Mito Juan Formations; and (6) the Upper Eocene Gobernador and Pagüey Formations, disconformably overlying the Cretaceous sequence.Three granitic intrusions crop out, two of which, the La Soledad Quartz Monzonite and the hornblende granodiorite of Cerro Azul, intrude the Cerro Azul Formation. They were dated by the potassium-argon method as Middle Pennsylvanian and Early Devonian, respectively.The principal structural units present in the map area are enormous blocks of basement rocks (Iglesias Group) which are separated by steeply northwestward-dipping, or nearly vertical reverse faults (upthrusts), along which the blocks have been uplifted or depressed. Along the east flank of the mountain range toward the Barinas Basin the sedimentary cover has been folded into a monocline which is itself broken into blocks by steep faults. In the higher parts of the region, toward the central part of the mountain range, is a zone of extension which produced grabens. horsts, and stepped faults, represented by the Boconó fault zone.The present uplift of the Venezuelan Andes took place in post-Eocene time. Upper Eocene sediments of the Pagüey Formation, poorly consolidated during the initial stages of the uplift, were deformed by slumping, into cascade folds (overturned to the southeast), and also slid down-slope as chaotically oriented blocks which cover the Upper Eocene sediments in situ. Vertical uplift, probably combined with arching or tilting of the region, produced the steep thrust faults along the margin of the range, and also the zone of extension represented by the Boconó fault zone. Strike-slip movement of great magnitude probably has not taken place along this fault. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.