Mercedes B. Prámparo

Paleoecology and paleoenvironments of Podocarp trees in the Ameghino Petrified forest (Golfo San Jorge Basin, Patagonia, Argentina): Constraints for Early Paleogene paleoclimate

During the Early Paleocene (Danian), Central Patagonia had a warm-temperate climate and was dominated by evergreen coniferous forests. Abundant permineralized conifer woods along with some dicot and palm leaf compressions were found in the Ameghino Petrified Forest, and provide evidence of this type of flora. All the permineralized wood and large trunks recovered were assigned to the species Podocarpoxylon mazzonii. An estimated tree height of 17-29m was calculated on the basis of diameter measurements. Based on 14 ring sequences, with a total of 169 rings, the mean ring width and Mean Sensitivity (MS) were 1.23 and 0.19mm respectively. The growth rings are moderately wide, extremely uniform and complacent, indicating that the environment was favourable and constant, and lacked significant stress factors limiting tree growth. Following the quantitative analysis for conifers outlined by Falcon-Lang, the growth ring anatomy of the Podocarpoxylon mazzonii suggests that these trees had an evergreen habit. The combination of the fossil flora, growth ring, and sedimentological analyses suggest that this mostly evergreen coniferous forest developed under warm-temperate conditions and without limiting factors.

Depositional environments and hydrocarbon potential of the Middle Jurassic Los Molles Formation, Neuquén Basin, Argentina: palynofacies and organic geochemical data

A multidisciplinary analysis of palynofacies in a sequence-stratigraphical framework, TOC (total organic carbon) and TAI (thermal alteration index) analyses, has been applied to outcrop samples of the uppermost Los Molles Formation (Middle Jurassic), Neuquen Basin, Argentina, in order to characterise the palaeoenvironmental and palaeo-climatic conditions during the deposition of this unit. Five types of palynofacies (P-l to P-5) have been identified and are interpreted to indicate a restricted marine to inner neritic environment. In P-1 and P-4, a marine environment close to the terrestrial source area with moderate oxidizing conditions and energy, is suggested. In P-2, the assemblage of freshwater algae, acritarchs and prasinophytes suggest a marginal marine environment influenced by fluvial discharge. In P-3, the marine microplankton content reflects conditions ranging from a marginal-marine (sub-normal salinity) to an inner neritic environment. In P-5, a dysoxic marine environment (probably marginal) is suggested. Warm and relatively humid (abundance of Cheirolepidiaceae in association withAraucariaceae) and locally humid (presence of swamps or ponds, on the alluvial plains) conditions are inferred. TOC content (65% of the analyzed samples reach TOC values over 1%), TAI values (2 to 2+, transitional between an immature phase and the window of liquid petroleum generation) and kerogen type (P-1, P-2 and P-5 show transitional characteristics between kerogen type II and III, while P-3 and P-4 show characteristics of kerogen type III and occasionally type IV), suggest that, in the studied area, the Los Molles Formation has some hydrocarbon potential. However, kerogen state suggests that the anoxic-dysoxic conditions of the site of deposition were not optimum for its preservation.

Late Maastrichtian dinoflagellate cysts from the Cerro Butaló section, southern Mendoza province, Argentina

The Late Cretaceous Atlantic transgression in southern South America is recorded in western Argentina in the upper part of the Malargüe Group. The Cerro Butaló section outcrops in the south of Mendoza Province and comprises sediments attributable to the Jagüel and Roca formations. Well-preserved palynological associations were recovered from this section. Only the marine associations – dinoflagellate cysts, acritarchs and green algae – are considered in this article. A Late Maastrichtian age is suggested for the Roca and Jagüel formations based on the presence of Deflandrea galeata and Disphaerogena carposphaeropsis in the lower part of the section and Glaphyrocysta perforata in the upper part of the section and the absence of any Danian cosmopolitan markers. Variations in dinoflagellate cyst species diversity throughout the section permit recognition of two intervals that are probably related to different palaeoenvironmental conditions connected with episodes of sea-level fluctuation.

Cretaceous Cicatricose Spores from North and Central-Western Argentina: Taxonomic and Biostratigraphical Discussion

Cicatricose spores have been described from Cretaceous basins worldwide. A complete revision of previous records from Argentina and other parts of South America is presented here, as well as the results of a detailed taxonomic study of the species found in the La Yesera and Lagarcito formations (north and central-western Argentina, respectively). Four genera and 11 species are described: Cicatricosisporites cuneiformis, C. pramparoana, C. sp. 1, Fisciniasporites sp. cf. F. brevilaesuratus, F. sp., Nodosisporites sp., Ruffordiaspora australiens is, R. cardielensis, R. ludbrookiae, R. cf. R. ticoensis and R. sp. 1. The genus Fisciniasporites is recorded for the first time in Argentina (in the La Yesera Formation), and similarly Nodosisporites in the San Luis Basin. The abundance of cicatricose spores is higher in the La Yesera Formation (8–54.2% of the total assemblage) than in the Lagarcito Formation (2–16%). An acme of cicatricose spore diversity in Argentina was recognised during the Aptian—Albian interval. Taxonomic studies of these types of spores are very important as they constitute a useful example of accurate descriptions and illustrations within a morphological group that has many misidentifications, and also considering the biostratigraphical significance of some species, e.g. Cicatricosisporites cuneiformis in Australia.

Palynological evidence for Middle Miocene vegetation in the Tehuacán Formation of Puebla, Mexico

Palynological assemblages from the Tehuacán Formation (TF), geochronologically dated as Middle Miocene (15.6 ± 0.4 Ma), provide evidence of a highly diverse flora that, at the generic level, is similar to the extant flora in the Tehuacán Valley. We propose that, during Miocene times, plant communities may have been formed of similar botanical elements to those seen today in the region, with some taxa adapted to semiarid conditions. While major temperate floristic elements of Pinus, Quercus, Juniperus, cloud forest and mexical vegetation can be recognized, components of tropical deciduous forests, such as Burseraceae, Leguminosae and Cactaceae, are also present, indicating semiarid conditions. Semiarid local conditions are also inferred from the geological record, consisting of lacustrine and alluvial fan deposits, which contain abundant evaporites beds. This lithology was formed under high evaporation and moderate precipitation conditions, as usually occurs in small basins fed by a seasonal input of water in semiarid environments. Important differences in the vegetation from the TF palynoflora as compared to older associations from south-central Mexico can be inferred, such as an increase in the diversity of semiarid taxa, belonging to Leguminosae and Burseraceae, and the oldest abundant occurrence of the Cactaceae.

Sharks (Neoselachii) and palynomorphs from Mendoza (Argentina): new evidence of the Late Cretaceous Atlantic marine transgression

Prámparo, M.B., Cione, A.L. & Gonzalez Riga, B., 2013. Sharks (Neoselachii) and palynomorphs from Mendoza (Argentina): new evidence of the Late Cretaceous Atlantic marine transgression. Alcheringa 38, 000–000. ISSN 0311–5518. Neoselachian (modern shark) teeth and palynomorphs have been recovered from the Late Cretaceous Jagüel Formation in the Province of Mendoza, Argentina. The fossiliferous beds were deposited during the Atlantic transgression that covered northern Patagonia and other parts of South America from the Maastrichtian to the Danian. Teeth of several lamniform sharks are attributed to the anacoracid Squalicorax pristodontus and cf. Serratolamna serrata of indeterminate familial affinity. These taxa became extinct at the end of the Cretaceous and confirm the late Maastrichtian age previously assigned to the Jagüel Formation in this northwestern part of the Neuquén Basin. For the first time, the selachian faunas are described together with algae and dispersed organic matter assemblages (palynofacies), revealing new elements of the neritic biota leading up to the Cretaceous–Paleogene (K–Pg) mass extinction in South America. The palynoflora consists exclusively of the prasinophyte algae Tasmanites, Cymatiosphaera and Pterospermella, indicative of stratified saline waters. Dispersed organic components in the profile (mainly opaque equidimensional phytoclasts and prasinophytes) are consistent with an inner neritic environment, with evidence (a great variety of particle sizes, lath-shaped phytoclasts increasing slightly in number and decreasing number of marine components) of slightly more nearshore conditions towards the upper part of the profile. These marine biotas confirm the presence of an epeiric sea over northern Patagonia, which extended westwards to the volcanic arc on the western flank of the Andean Cordillera in Mendoza. Mercedes B. Prámparo [mprampar@mendoza-conicet.gov.ar], IANIGLA-CONICET, CCT-Mendoza. Avda. R. Leal s/n, Parque Gral. San Martín, (5500) Mendoza, Argentina; Alberto Luis Cione [acione@museo.fcnym.unlp.edu.ar], División Paleontología de Vertebrados. Museo de La Plata. 1900 La Plata, Argentina; Bernardo González Riga [bgonriga@mendoza-conicet.gov.ar] IANIGLA-CONICET, CCT, Mendoza. Avda. R. Leal s/n, Parque Gral. San Martín, (5500) and ICB, Universidad Nacional de Cuyo, Argentina. Received 28.5.2013, revised 17.9.2013, accepted 24.9.2013.

Correlation of the Late Eocene–Early Oligocene Izúcar de Matamoros Evaporites (Cuayuca Formation) in Mexico Based on Parsimony Analysis of Endemicity

Abstract Based on the lithology of the Izucar de Matamoros (IzM) sections, and the occurrence of index taxa such as Armeria, Cicatricosisporites dorogensis, Corsinipollenites, Eucommia, Momipites coryloides, Momipites tenuipolus, Mutisiapollis, and Ranuculacidites operculatus, a correlation between the IzM sections and the Cuayuca Formation stratotypes is proposed. The IzM sections are Late Eocene–Early Oligocene, and they are part of the evaporitic member (Mcy) of the Cuayuca Formation. These new data are consistent with the paleoenvironmental interpretations proposed for the formation. It was probably deposited under local xeric conditions in a semiarid climate that allowed the development of grassland (Gramineae with Amaranthaceae–Chenopodiaceae and Ephedra) and a thorn shrub community with Acacia, other Leguminosae, Linum, and Plumbaginaceae. The neighboring communities were probably tropical deciduous forests, low tropical deciduous forest, thorn forest, and chaparral. There were also regional temperate vegetations such as a Picea–Pinus forest, and a cloud forest community. Using parsimony analysis of endemicity, a biogeographic method, a palynofloristic relationship between the Cuayuca Formation and the Pie de Vaca Formation (Late Eocene–Early Oligocene) is proposed. Both formations are within the Balsas Group, and are correlated with San Gregorio Formation (Oligocene) of southern Baja California.

Fossil record of Ephedra in the Lower Cretaceous (Aptian), Argentina

Fossil plants from the Lower Cretaceous (upper Aptian) of the La Cantera Formation, Argentina, are described. The fossils studied represent a leafy shooting system with several orders of articulated and striated axes and attached leaves with unequivocal ephedroid affinity. We also found associated remains of ovulate cones with four whorls of sterile bracts, which contain two female reproductive units (FRU). Ovulate cone characters fit well within the genus Ephedra. Special characters in the ovulate cones including an outer seed envelope with two types of trichomes, allowed us to consider our remains as a new Ephedra species. Abundant dispersed ephedroid pollen obtained from the macrofossil-bearing strata also confirms the abundance of Ephedraceae in the basin. The co-occurrence of abundant fossil of Ephedra (adapted to dry habitats) associated with thermophilic cheirolepideacean conifer pollen (Classopollis) in the unit would suggest marked seasonality at the locality during the Early Cretaceous. Furthermore, the floristic association is linked to dry sensitive rocks in the entire section. The macro- and microflora from San Luis Basin are similar in composition to several Early Cretaceous floras from the Northern Gondwana floristic province, but it may represent one of the southernmost records of an arid biome in South America.

Angiosperm association from the Río Turbio Formation (Eocene–?Oligocene) Santa Cruz, Argentina: revision of Hünicken’s (1955) fossil leaves collection

Vento, B. & Prámparo, M. B., January 2018. Angiosperm association from the Río Turbio Formation (Eocene–?Oligocene), Santa Cruz, Argentina: Revision of Hünicken’s (1955) fossil leaves collection, Alcheringa 42, 125–153. ISSN 0311-5518. The Río Turbio Formation (Eocene–?Oligocene) is of particular paleobotanical interest owing to its combination of high fossil plant diversity associated with the coexistence of warm-temperate and cool-temperate components. As the first suite of fossils related to a documented stratigraphic section, Hünicken’s fossil plant collection is one of the most important from the Paleogene of South America. A total of 34 angiosperm species from the collection were reviewed and taxonomically updated, with Nothofagus as the dominant genus. The taxa identified indicate a warm and humid climate with the development of some elements of a cool-temperate climate marked by a transitional climate change to cooler conditions. The comparison of angiosperms from different paleofloras from the southernmost of South America confirms that the assemblage of Río Turbio Formation was similar to that of the Río Pichileufú area, both from Patagonia, Argentina. Bárbara Vento [bvento@mendoza-conicet.gov.ar] Mercedes B. Prámparo [mprampar@mendoza-conicet.gov.ar] Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales (IANIGLA) CCT-CONICET, Mendoza, Adrián Ruiz Leal s/n, Casilla Correo 131, C5500, Mendoza, Argentina.

Paleofloristic assemblage from the Paleogene Río Guillermo Formation, Argentina: preliminary results of phylogenetic relationships of Nothofagus in South America

Abstract Hünickens paleobotanical collection is one of the most important in South America because it was the first one to be related to a documented stratigraphic profile. This floristic assemblage (Oligocene) recovered from Río Guillermo Formation, at Estancia Tres Marías, Río Guillermo Valley, Santa Cruz, Argentina, is described by the first time in this paper. Five species of genus Nothofagus (N. subferruginea, N. serrulata, N. crenulata, N. elongata and N. variabilis) together with Myrcia bagualense are components of the assemblage. The presence of Acaena brandmayri is confirmed for the first time for the area. Paleoenviromental and paleoclimate implications are also discussed. Characteristic species from a temperate-cold climate such as the genus Nothofagus are present in the material studied. A phylogenetic study of the fossil species herein described and the extant South American species of Nothofagus is presented. The preliminary results support the hypothesis that fossil species of Nothogafus are closely related to the modern species.