Daniela E. Olivera

The Palynology of the Cañadón Asfalto Formation (Jurassic), Cerro Cóndor Depocentre, Cañadón Asfalto Basin, Patagonia, Argentina: Palaeoecology and Palaeoclimate Based on Ecogroup Analysis

The Cañadón Asfalto Formation, Cañadón Asfalto Basin, Patagonia, Argentina, is interpreted as fluvial-lacustrine deposits. A palynological study of the lower and middle parts of the unit, at the Cañadón Lahuincó and Cañadón Caracoles sections, Cerro Cóndor Depocentre Chubut province, northwestern Patagonia, Argentina is presented. The quantitative composition of the palynofloras is characterised by the dominance of pollen produced by the conifer families Cheirolepidiaceae (Classopollis) and Araucariaceae (mainly Araucariacites and Callialasporites), suggesting that warm-temperate and relatively humid conditions under highly seasonal climate prevailed during the depositional times of the unit. The abundance of Botryococcus supports the presence of a shallow lake with probably saline conditions. Five palynomorph ecogroups (PEGs) were recognised: upland, lowland, riverside, coastal lake and aquatic. The ecological requirements of the different plant families forming the PEGs enable the inference of a sub-tropical palaeoclimate for the Cañadón Asfalto region during late Early Jurassic to mid Middle Jurassic, which is consistent with the ‘seasonally dry (winterwet)‘ biome.

The Fungal Spore Annella capitata Srivastava from the Jurassic (Late Toarcian—Late Bajocian) Cañadón Asfalto Formation of Patagonia, Argentina

The fungal spore Annella capitata Srivastava is recorded for the first time in Argentina, within the continental Jurassic strata of the Cañadón Asfalto Formation, Cañadón Asfalto Basin, Patagonia. It is identified on pollen grains belonging to the Cheirolepideaceae, Araucariaceae and Podocarpaceae. This paper contrasts A. capitata with ubisch bodies (small sporopollenin spherules attached to the exine). A. capitata has the same characteristics in the different pollen taxa, while the ubish bodies exhibit taxon-dependent differences in ultrastructure, size and morphology. The presence of hyphae and spore germlings reinforces a fungal origin of A. capitata. The degree and type of deterioration associated with these fungal microfossils are presented. Based upon the ecological requirements of the plant families recognized in the Cañadón Asfalto palynoflora, it is inferred that A. capitata Srivastava thrived in low-energy environments under warm-temperate and humid conditions.

Palynotaphofacies analysis applied to Jurassic marine deposits, Neuquén Basin, Argentina

Taphonomic analysis was performed on palynological samples of marine successions from the Cuyo Group of the Neuquén Basin. The group comprises the Los Molles and Lajas Formations (Middle Jurassic) and represents the first major marine depositional episode after the configuration of the basin. A total of 21 outcrop samples from five sections, located in the central-western part of the basin, were analyzed. The palynological counts of each sample were carried out taking into account the preservation state of the palynomorphs, which was mainly influenced by two parameters: their intrinsic properties and the environmental depositional conditions. Four main deterioration types (corrosion, degradation, mechanical damage, and concealment by authigenic minerals) and their six combinations were identified. The growth of pyrite crystals within the palynomorphs was strongly influenced by the exine structure, being dominant in bisaccate pollen grains. Mechanical damage appears to be the most important deterioration type, reflecting the highly dynamic conditions of shelfal marine environments. The term Palynotaphofacies (Pt) was proposed to characterize a sedimentary rock yielding palynological associations with distinctive preservational features. Three palynotaphofacies have been recognized: Pt-1 (tidal-influenced environments) is characterized by the highest percentage of deteriorated forms, reflecting either intermittent exposure to weathering or intense reworking. Pt-2 shows the highest percentage of well-preserved palynomorphs associated with rapid burial due to a high sedimentation rate and it comes from the delta-front facies of fluvial-dominated deltas. Finally, Pt-3 was identified in samples of prodelta hyperpycnites with a wide predominance of terrigenous components and it is characterized by the coexistence of well-preserved and deteriorated palynomorphs.

PALINOLOGÍA DEL MESO-CENOZOICO EN ARGENTINA. VOLUMEN EN HOMENAJE A MIRTA ELENA QUATTROCCHIO

Resumen . Este volumen esta dedicado a la Dra. Mirta Elena Quattrocchio, una de las investigadoras mas destacadas en el campo de la Palinologia a nivel nacional e internacional. Consta de ocho contribuciones, cuyas autorias corresponden a algunos de los investigadores que fueron orientados por la Dra. Mirta Quattrocchio, durante distintas etapas de su carrera. En la primera parte se incluyen tres articulos en depositos mesozoicos, uno en la provincia de Chubut y dos en la Cuenca Neuquina. En la segunda parte se incluyen cuatro trabajos realizados en depositos del Cenozoico, dos en la provincia de Buenos Aires y dos en Tierra del Fuego. La contribucion invitada sintetiza y actualiza la biocronoestratigrafia de la provincia de Buenos Aires a partir del registro de vertebrados. Abstract . This volume is dedicated to Dr. Mirta Elena Quattrocchio, one of the leading researchers in the field of Palynology. It includes eight contributions, whose authorship corresponds to some of the researchers who were oriented by Dr. Mirta Quattrocchio, during her career. The first section includes three articles from Mesozoic deposits, one in Chubut Province and two in the Neuquen Basin. The second part includes four articles associated with Cenozoic deposits, two in Buenos Aires Province and two Tierra del Fuego. The guest contribution summarizes and updates the biochronoestratigraphy of the Buenos Aires Province based on vertebrates record.