Canadon Asfalto Formation Research Articles

Reconstructing the Early Evolution of the Cupressaceae: A Whole-Plant Description of a NewAustrohamiaSpecies from the Cañadón Asfalto Formation (Early Jurassic), Argentina

Premise of research. A new Early Jurassic species of Cupressaceae is reconstructed from the Canadon Asfalto Formation in Argentina, based on impressions of foliage and attached and dispersed seed a...

RelictualLepidopteris(Peltaspermales) from the Early Jurassic Cañadón Asfalto Formation, Patagonia, Argentina

Premise of research. Numerous leaf remains of pteridosperms occur at a new locality of the Early Jurassic Canadon Asfalto Formation, in Patagonia, Argentina. Fossils consist of adpressions with sup...

SPINICAUDATANS FROM THE UPPER JURASSIC OF ARGENTINA AND THEIR PALEOENVIRONMENTS

Fil: Monferran, Mateo Daniel. Universidad Nacional del Nordeste; Argentina. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Conicet - Nordeste. Centro de Ecologia Aplicada del Litoral. Universidad Nacional del Nordeste. Centro de Ecologia Aplicada del Litoral; Argentina

Environmental and climatic proxies for the Cañadón Asfalto and Neuquén basins (Patagonia, Argentina): review of Middle to Upper Jurassic continental and near coastal sequences

In this review, we include several proxies (sedimentology, palynology, invertebrates) from the Canadon Asfalto and Neuquen basins, to infer the environments and regional climatic context during the Middle to Late Jurassic of Patagonia. In central Patagonia, early in the Middle Jurassic, and associated with a magmatic arc, began the sedimentary fi lling of Jurassic continental sub-basins in the Canadon Asfalto Basin. Lacustrine and fl uvio-deltaic sediments, bearing a continental Middle Jurassic palynobiota, correspond to the Las Chacritas Member, while the sediments and palynobiota from the Late Jurassic Puesto Almada Member (both in the Canadon Asfalto Formation) indicate a palustrine wetland subenvironment immersed within an arid macroenvironment. Paleoinvertebrates (conchostracans and sponges) of this formation suggest wet-dry cycles in the water bodies they inhabited. The sedimentological information together with the continental and coastal palynomorph assemblages of the back arc Neuquen Basin, allowed distinguishing a complete regressive-transgressive sequence for the Middle Jurassic Lajas Formation. For the Upper Jurassic in this basin, the thick gypsum and anhydrite deposits of the evaporitic coastal Auquilco Formation correlate with extended deposits of eolian sandstones corresponding to the Botucatu paleodesert, and a saltmarsh environment is inferred from the palynofl ora. The palynologic associations from both basins indicate a regional warm climate with seasonal aridity. Climatic conditions would have been drier in the continental interior (Canadon Asfalto Basin), with strongly seasonally distributed temperatures, and moister in the western coast of the continent (Neuquen Basin), during the marine transgressions.

The First Record of the Family Fushunograptidae (‘Conchostraca’, Spinicaudata) from the Cañadón Asfalto Formation (Upper Jurassic), Patagonia, Argentina

Abstract. A description is provided for Wolfestheria smekali gen. and sp. nov., a new member of the family Fushunograptidae, from the “Estancia La Sin Rumbo” locality in the Puesto Almada Member of the Canadon Asfalto Formation. Assignment to the family Fushunograptidae is supported by evidence from detailed scanning electron microscope studies of this species. An assessment of the complex carapace ornamentation is also provided, as W. smekali exhibits an array of ornamentations that cover the entire carapace surface. These consist of irregular, thick radial lirae with numerous thin cross-bars on the dorsal middle-upper third of the carapace, changing to straight, thick radial lirae with fewer cross-bars restricted to the upper half of the growth band in the ventral third of the carapace, with the interspaces between the radial lirae wider than the lirae themselves, and with the radial lirae terminating in the upper part of the growth bands, where they then enlarge to form a triangular shape upon contact ...

First Record of Conifer Wood from the Cañadón Asfalto Formation (Early-Middle Jurassic), Chubut Province, Argentina

Abstract. A new fossil conifer wood —Brachyoxylon currumilii sp. nov.— is described from the Lower—Middle Jurassic of Chubut Province (Argentina). The specimens were collected at a locality where the Canadon Asfalto Formation is exposed, in the vicinity of the Cerro Condor village. The studied wood is characterized by mixed pitting in radial tracheid walls (predominantly uniseriate), araucarioid cross fields, low uniseriate rays and the absence of resin canals. The use of transmitted light and epifluorescence microscopy together with SEM imaging allowed the identification of additional characters such as the presence of pitting with torus-margo and compression wood. These characters are discussed in terms of their systematic relevance. On these grounds, the systematic affinity of the studied wood is discussed and linked to the extinct conifer family Cheirolepidiaceae, one of the dominant plant groups during the Jurassic and Cretaceous in Patagonia.

Paleontology, sedimentology and paleoenvironment of a new fossiliferous locality of the Jurassic Cañadón Asfalto Formation, Chubut Province, Argentina

Abstract A new Late Jurassic assemblage of “conchostracans”, ostracods, bivalves and caddisfly cases from the locality “Estancia La Sin Rumbo”, Chubut Province (Patagonia, Argentina) is recorded. The fossils occur in the upper part of an outcropping 45 m thick volcaniclastic lacustrine sequence of yellowish tuffs and tuffites of the Puesto Almada Member, which is the upper member of the Canadon Asfalto Formation with U/Pb age of 161 ± 3 Ma. The sequence represents one sedimentary cycle composed of a (lower) hemicycle of expansion and a (higher) hemicycle of contraction of the water body. The invertebrates lived in small freshwater bodies during the periods of expansion of the lake. The occurrence of a great number of small spinicaudatans, associated with mud-cracks, is evidence of dry climatic conditions and suggests several local mortality events. The spinicaudatan record of the fushunograptid–orthestheriid (component of the Eosestheriopsis dianzhongensis fauna) and the presence of Congestheriella rauhuti Gallego and Shen, suggest a Late Jurassic (Oxfordian to Tithonian) age. Caddisfly cases are recorded for the first time in the Canadon Asfalto Basin.

First Jurassic Triconodont from South America

A new mammal from the Middle Jurassic Canadon Asfalto Formation, Patagonia, Argentina, is reported. The specimen, an isolated lower? molariform, is erected as the type of a new genus and species of triconodont, Argentoconodon fariasorum. The molariform presents a peculiar combination of primitive and derived features that makes recognition of its affinities challenging. Argentoconodon shares similarities with poorly known triconodonts from the Jurassic of North America and Morocco and lacks the diagnostic traits of the triconodontid triconodonts. Argentoconodon resembles in general the paraphyletic ''amphilestid'' triconodonts. The specimen is too incomplete to warrant broader interpretations, but it suggests that at least this lineage of South American mammals was distinctly autapomorphic, perhaps with an origin in forms with a broader geographical distribution.

New Jurassic Mammals from Patagonia, Argentina: A Reappraisal of Australosphenidan Morphology and Interrelationships

Abstract A new mammal, Henosferus molus, n.gen. and n.sp., from the Callovian–Oxfordian (latest Middle to earliest Late Jurassic) Canadon Asfalto Formation from Chubut Province (Argentina) is described. This taxon corresponds to a new species clearly different from Asfaltomylos patagonicus from the same locality and stratigraphic level. This new species is based on three lower jaws with relatively well-preserved dentition. The lower jaw shows a primitive morphology having a Meckelian groove, a prominent medial flange associated with a lateral ridge of the dentary, and a deep dentary trough, which possibly indicates the presence, even though reduced, of postdentary bones still attached to the dentary. The lower dental formula is i4, c1, p5, m3. The premolars are simple, bearing a main cusp, while the molars appear to be tribosphenic, with an obtuse to right-angled trigonid and a basined talonid with three cusps. This association of plesiomorphic features in the jaw and derived features in the molars is doc...

Saline paleolake of the Cañadón Asfalto Formation (Middle-Upper Jurassic), Cerro Cóndor, Chubut province (Patagonia), Argentina

The carbonate-evaporitic sequence of the Canadon Asfalto Formation that crops out in Canadon Carrizal (Chubut province, Argentina) is characterized by a lacustrine facies association. This sequence includes an extensive biohermal belt, flood facies with high lake-level and low lake-level stages, and desiccation–evaporation facies. The biohermal belt shows three growth-stages of microbial communities. This belt controlled sedimentation in nearby areas, favoring the formation of the pan lake of Canadon Carrizal. High lake-level flood facies represent sedimentation during periods of great water input to the pan lake. Low lake-level flood facies are characterized by low-energy conditions and by the development of a shallow lake with marginal zones and palustrine subenvironments. Desiccation facies represent a dry mudflat that borders the saline lake. Evaporation facies are related to the shrinkage of the water body and to the migration of the shallower facies towards the center of the ephemeral lake.

Influence of a biohermal belt on the lacustrine sedimentation of the Cañadón Asfalto Formation (Upper Jurassic, Chubut province, Southern Argentina)

The Upper Jurassic Canadon Asfalto Formation (Canadon Asfalto Basin, Patagonia Argentina), consists mainly of carbonate deposits accumulated in hydrologically closed lakes, which were especially sensitive to rainfall changes. The lacustrine carbonate sedimentation also interplayed with volcanic episodes recorded by tuffs and lavas, as observed in different basin sectors. These lakes probably underwent warm, alternating humid-subarid and arid conditions that resulted in spreading and shrinkage cycles of the closed water bodies. In the Cerro Condor area, carbonates were deposited as part of a 500 m long and 39 m thick microbial biohermal body that extended over 5,5 km2, overlying a hard basalt substratum. This bioherm ridge acted as a physiographic barrier that controlled the sedimentation in the surrounding lacustrine zones, whose environments ranged from shallow and deep littoral to eulittoral (including microbial patch reefs) and palustrine. A hydrologically isolated portion of the lacustrine basin evolved into a pan lake where widespread carbonateevaporite sequences developed.

Osteology and relationships of a new theropod dinosaur from the Middle Jurassic of Patagonia

Abstract: A new taxon of theropod dinosaur is described as Condorraptor currumili gen. et sp. nov., from the Middle Jurassic (Callovian) Cañadón Asfalto Formation of Chubut Province, Argentinean Patagonia. The taxon is represented by a single fragmentary postcranial skeleton. Although incompletely known, Condorraptor is the second most complete theropod from the Middle Jurassic of Gondwana. The new taxon is characterized by the absence of a posterior incision between the fibular condyle and the medial side of the proximal articular end of the tibia, the pleurocoels in the anterior cervicals being situated posteroventral to the parapophyses, and the presence of a pronounced ‘step’ between the distal articular facet and shaft of Mt IV. Pneumatic features of the vertebral column show strong variation between the left and right side. Condorraptor gen. nov. can be referred to the Tetanurae and is a representative of a global radiation of basal tetanurans in the Early to Mid Jurassic.