Silicified termite coprolites in mesquite-like wood from the Miocene of La Rioja, Argentina

Coprolite-filled borings in fragments of non-decayed wood showing affinity with the mesquite-like morphogenus Prosopisinoxylon Martinez are described from Miocene strata from La Rioja, northwestern Argentina. Borings are excavated in the secondary xylem and contain numerous cylindrical coprolites with a characteristic hexagonal shape in cross section. Coprolites are rather inconspicuous and only visible through the exposed ends of the borings. The concealed occurrence of the coprolites inside the borings, the non-decayed state of the mesquite-like wood and the overall morphology of the fossils suggest dry-wood members of the termite family (Kalotermitidae), as a probable producer. This is the first fossil record of termites from northwestern Argentina and is among the few known from South America, thereby expanding their paleobiogeographic range. The presence of dry-wood termites in the studied deposits is consistent with a forested environment set in an arid tropical to subtropical climate. In this setting termites probably had a significant role in the recycling of organic matter. Their association with mesquite-like wood suggests that the current relationship between termites and members of this genus in modern ecosystems dates back to at least the Late Miocene.Fil: García Massini, Juan Leandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Regional de Investigaciones Cientificas y Transferencia Tecnológica de Anillaco; ArgentinaFil: Pujana, Roberto Roman. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales; Argentin

Tafonomía de plantas y paleoambiente del complejo Bahía Laura, jurásico‒medio-superior, en la localidad laguna Flecha Negra (provincia de Santa Cruz, Argentina)

Los estudios tafonómicos se realizaron en la localidad Laguna Flecha Negra (Complejo Bahía Laura, Jurásico Medio-Tardío), Provincia de Santa Cruz, Argentina. Se definieron facies sedimentarias y estilos de conservación para reconocer tafofacies de plantas en la secuencia estudiada. Se identificaron once tafofacies y se proponen fuentes vegetales dentro de un sistema volcánico y geotérmico. Los restos vegetales son de origen autóctono a para-autóctono y la mejor conservación se encontró en facies distales de sistemas silíceos de aguas termales (sinter). Se encontraron diferencias tafonómicas laterales y verticales en la secuencia estudiada. Estos se deben a cambios en la entrada sedimentaria y la distancia a los fluidos geotérmicos. Los resultados permiten reconstruir la historia deposicional de esta región de la provincia geológica del Macizo del Deseado. Inferimos la formación de un sistema de aguas termales (sinterizado) que posteriormente fue destruido por un proceso de erupción freática en el margen de una cúpula efusiva andesítica en subfacies piroclásticas de otoño parcialmente reelaboradas. Después de la destrucción del sistema geotérmico, se desarrolló una subfacies epiclástica fluvial y lacustre preservando una comunidad vegetal típica del Jurásico Medio-Tardío de Gondwana. Posteriormente, la actividad volcánica produjo subfacies piroclásticas, con espesos depósitos de ceniza y flujo de diferentes fuentes y separados por un intervalo de tiempo que promovió la fosilización de un bosque in situ. Los estudios tafonómicos de estas comunidades vegetales permitieron reconstruir una cadena de eventos geológicos y cómo estos procesos han influido en la preservación de una flora jurásica de la Patagonia, contribuyendo así al conocimiento de la paleoecología de la provincia geológica del Macizo del Deseado.Taphonomic studies were carried out at Laguna Flecha Negra locality (Bahía Laura Complex, Middle–Late Jurassic), Santa Cruz Province, Argentina. Sedimentary facies and preservational styles were defined to recognize plant taphofacies in the studied sequence. Eleven taphofacies were identified and plant sources within a volcanic and geothermal system are proposed. Plant remains are of autochthonous to para-autochthonous origin and best preservation was found in distal facies of siliceous hot spring (sinter) systems. Lateral and vertical taphonomic differences were found in the studied sequence. These are due to changes in the sedimentary input and distance to the geothermal fluids. Results enable the reconstruction of the depositional history of this region of the Deseado Massif geological Province. We infer formation of a hot-spring (sinter) system that was subsequently destroyed by a phreatic eruption process at the margin of an andesitic effusive dome in partially reworked fall pyroclastic subfacies. After the destruction of the geothermal system, a fluvial and lacustrine epiclastic subfacies developed preserving a plant community typical of the Middle-Late Jurassic of Gondwana. Later, volcanic activity produced pyroclastic subfacies, with thick ash-fall and flow deposits from different sources and separated by a time gap that promoted fossilization of an in situ forest. Taphonomic studies of these plant communities allowed reconstruction of a chain of geological events and how these processes have influenced the preservation of a Jurassic flora from Patagonia, thus contributing to an understanding of the paleoecology of the Deseado Massif geological province.Fil: Sagasti, Ana Julia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Instituto de Recursos Minerales. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Instituto de Recursos Minerales; ArgentinaFil: Guido, Diego Martin. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Instituto de Recursos Minerales. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Instituto de Recursos Minerales; ArgentinaFil: García Massini, Juan Leandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Regional de Investigaciones Científicas y Transferencia Tecnológica de La Rioja. - Universidad Nacional de La Rioja. Centro Regional de Investigaciones Científicas y Transferencia Tecnológica de La Rioja. - Universidad Nacional de Catamarca. Centro Regional de Investigaciones Científicas y Transferencia Tecnológica de La Rioja. - Secretaría de Industria y Minería. Servicio Geológico Minero Argentino. Centro Regional de Investigaciones Científicas y Transferencia Tecnológica de La Rioja. - Provincia de La Rioja. Centro Regional de Investigaciones Científicas y Transferencia Tecnológica de La Rioja; ArgentinaFil: Campbell, Kathleen. University of Auckland; Nueva Zeland

Preuves d’une activité fongique dans des bois gymnospermiens de l’Éocène de la Patagonie méridionale (Argentine)

Evidence of fungal activity expressed as typical decay patterns is described from silicified podocarpaceous wood from the Eocene of Patagonia, Argentina. Decay features consist of tracheids of the secondary xylem that are degraded, resulting in thin-celled, lignin-free, translucent, circular to elliptical areas, some of which have cells devoid of all cell wall components including lignin, hemicellulose, and cellulose, and other areas that show only partial simultaneous decay of all cell wall layers. These patterns conform to the white rot and its variant white pocket rot decay patterns produced by basidiomycetes and ascomycetes in gymnosperm and angiosperm wood in modern terrestrial ecosystems. Coagulated opaque bodies in the lumen of some cells and enlarged secondary walls may represent host reactions to infection or remains of metabolic products of fungal enzymatic activity. Similar decay patterns and reaction features have been described from fossil woods ranging in age from the Devonian to the present. This record expands the fossil record of wood rot fungi and underscores their importance as drivers of biological cycles in ancient terrestrial ecosystems.Fil: Pujana, Roberto Roman. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; ArgentinaFil: García Massini, Juan Leandro. Southern Methodist University; Estados Unidos. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Rodríguez Brizuela, Rafael. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; ArgentinaFil: Burrieza, Hernán Pablo. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Biodiversidad y Biología Experimental; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Conifer root nodules colonized by arbuscular mycorrhizal fungi in Jurassic geothermal settings from Patagonia, Argentina

Premise of research. Despite the ecological significance of arbuscular mycorrhizae in modern terrestrial ecosystems, knowledge about their evolution based on the fossil record is still scarce, especially concerning the case of root nodules harboring arbuscular mycorrhizal fungi, as in some extant gymnosperms and angiosperms. Exceptionally preserved conifer nodular roots were found in the Jurassic fossil-bearing chert deposits of the Deseado Massif (Santa Cruz, Argentina), raising the possibility of studying them in association with arbuscular mycorrhizal fungi. The aim of this study is to describe the plant organs and their fungal partners and to discuss the ecological significance of the interactions observed, particularly with respect to their occurrence in the hot spring settings. Methodology. Thin sections of chert samples from the Cañadón Nahuel locality of the La Matilde Formation, Deseado Massif (Santa Cruz, Argentina) were observed using light microscopy. Pivotal results. The cortex of the nodules is occupied by several glomeromycotan fungal structures. The structures occur in a specific zone of the cortex—toward its center—and include intracellular hyphal coils and arbuscules. Glomoid spores and coenocytic hyphae possibly penetrating the epidermal cells are also described and analyzed. Conclusions. The root nodules have affinities with the Araucariales, representing the oldest record of such structures for this conifer clade. This is also the first record of nodules harboring arbuscular mycorrhizal fungi for the Jurassic; it extends our knowledge of the fossil record for this particular type of fungal association.Fil: Nunes, Cristina Isabel. Museo Paleontológico Egidio Feruglio; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: García Massini, Juan Leandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Regional de Investigaciones Científicas y Transferencia Tecnológica de La Rioja. - Universidad Nacional de La Rioja. Centro Regional de Investigaciones Científicas y Transferencia Tecnológica de La Rioja. - Universidad Nacional de Catamarca. Centro Regional de Investigaciones Científicas y Transferencia Tecnológica de La Rioja. - Secretaría de Industria y Minería. Servicio Geológico Minero Argentino. Centro Regional de Investigaciones Científicas y Transferencia Tecnológica de La Rioja. - Provincia de La Rioja. Centro Regional de Investigaciones Científicas y Transferencia Tecnológica de La Rioja; ArgentinaFil: Escapa, Ignacio Hernán. Museo Paleontológico Egidio Feruglio; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Guido, Diego Martin. Instituto de Recursos Minerales; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Instituto de Recursos Minerales. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Instituto de Recursos Minerales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Campbell, Kathleen. University of Auckland; Nueva Zeland

Restos fúngicos del primer depósito de chert de origen hidrotermal del Mesozoico, Jurásico del Macizo del Deseado, Patagonia, Argentina

Se describe e ilustra una variedad de restos permineralizados de hifas, esporas y otros propágulos fúngicos asociados a plantas vasculares en diversos estados de preservación del primer yacimiento de chert de origen hidrotermal del Mesozoico, Jurásico del Macizo del Deseado, Patagonia, Argentina. Entre los propágulos identificados hay estructuras de fructificación tipo picnidios que son en la actualidad comúnmente producidas por ascomicetes y estructuras vesiculares que recuerdan a esporangios de chitridiomycetes. Estos propágulos se han encontrado asociados a restos vegetales en diferentes grados de descomposición y a tejidos con células esclerificadas e hipertrofiadas. Aún es prematuro hablar del tipo de interacción o asociación hongo-planta que los fósiles encontrados representarían; sin embargo, en función de la asociación de varios de estos hongos con restos vegetales en estado de descomposición es probable que hubieran actuado como saprótrofos. La asociación de probables esporangios de chitridiomycetes con células esclerificadas e hipertrofiadas sugiere una interacción directa entre los hongos y los vegetales, donde los hongos habrían provocado como respuesta modificaciones a nivel celular en las plantas hospedantes. Esto brinda los primeros datos sobre hongos en depósitos de chert de origen hidrotermal del Mesozoico, en particular del Jurásico, ampliando su registro fósil, especialmente para Argentina, una región escasamente conocida paleomicológicamente. La biota descripta para los depósitos de origen hidrotermal jurásicos de Patagonia sumada al reciente hallazgo de hongos permineralizados permite realizar diferentes analogías con el ecosistema preservado en los cherts de Rhynie (Escocia). De esta manera, el análisis de los hongos fósiles de estos depósitos, provee una oportunidad única de incrementar nuestro conocimiento sobre los ecosistemas terrestres pasados, en particular aquellos de origen hidrotermal, así como sobre las características biológicas y ecológicas de las comunidades fúngicas adaptadas a las condiciones fisicoquímicas de este tipo de ambiente.Sesiones libresFacultad de Ciencias Naturales y Muse

Geyserite in Hot-Spring Siliceous Sinter: Window on Earth’s Hottest Terrestrial (Paleo)environment and its Extreme Life

International audienceSiliceous hot-spring deposits, or sinters, typically form in active, terrestrial (on land), volcanic terrains where magmatically heated waters circulating through the shallow crust emerge at the Earth's surface as silica-charged geothermal fluids. Geyserites are sinters affiliated with the highest temperature (~ 75–100 °C), natural geothermal fluid emissions, comprising localized, lithologically distinctive, hydrothermal silica precipitates that develop around geysers, spouters and spring-vents. They demarcate the position of hot-fluid upflow zones useful for geothermal energy and epithermal mineral prospecting. Near-vent areas also are “extreme environment” settings for the growth of microbial biofilms at near-boiling temperatures. Microbial biosignatures (e.g., characteristic silicified microbial textures, carbon isotopes, genetic material, lipid biomarkers) may be extracted from modern geyserite. However, because of strong taphonomic filtering and subsequent diagenesis, fossils in geyserite are very rare in the pre-Quaternary sinter record which, in and of itself, is patchy in time and space back to about 400 Ma. Only a few old examples are known, such as geyserite reported from the Devonian Drummond Basin (Australia), Devonian Rhynie cherts (Scotland), and a new example described herein from the spectacularly well-preserved, Late Jurassic (150 Ma), Yellowstone-style geothermal landscapes of Patagonia, Argentina. There, geyserite is associated with fossil vent-mounds and silicified hydrothermal breccias of the Claudia sinter, which is geologically related to the world-class Cerro Vanguardia gold/silver deposit of the Deseado Massif, a part of the Chon Aike siliceous large igneous province. Tubular, filament-like micro-inclusions from Claudia were studied using integrated petrographic and laser micro-Raman analysis, the results of which suggest a biological origin. The putative fossils are enclosed within nodular geyserite, a texture typical of subaerial near-vent conditions. Overall, this worldwide review of geyserite confirms its significance as a mineralizing geological archive reflecting the nature of Earth's highest temperature, habitable terrestrial sedimentary environment. Hot-spring depositional settings also may serve as analogs for early Earth paleoenvironments because of their elevated temperature of formation, rapid mineralization by silica, and morphologically comparable carbonaceous material sourced from prokaryotes adapted to life at high temperatures

The effects of volcanism on Oligocene-age plant communities from the Ethiopian Plateau, and implications for vegetational resilience in a heterogeneous landscape

Substantial volcanism and associated volcaniclastic sedimentation took place in association with East African Rift formation, and in some cases this would have had substantial ecological impacts. Ethiopian Late Oligocene (27.36 ± 0.11. Ma) fossiliferous volcanogenic strata provide opportunities to evaluate the magnitude of disruptive impact of volcanism on forest communities (before development of the Main Ethiopian Rift), and to assess their resilience. Fine-scale sampling and palynological analyses from the Magargaria River region of the northwestern Ethiopian Plateau tests the hypothesis that volcanism had a regional and significant disrupting effect on forest vegetation. These studies are compared with macrofossil and sedimentological data representing more local conditions previously reported from the same sediments. Results indicate that while some forests gave way to open environments dominated by herbaceous taxa, other communities remained or recovered quickly. Volcanic influences on sedimentary processes altered an existing forest ecosystem by creating a spatially heterogeneous landscape that also varied through time. This study supports the inherent significance of palynological data as indicators of ecological change at a regional scale relative to the more local view that macrofossils can provide, and underscores the importance of both kinds of fossils whenever possible for the study of the ecological dynamics of plant communities. The presence of forest taxa after repeated ashfalls indicates a degree of forest community resilience consistent with relatively limited burial by ash during the studied volcanic episodes. This study also suggests that taphonomic and diagenetic processes strongly affected the composition of palynomorph assemblages, skewing them towards thick-walled individuals, especially fungi.Fil: García Massini, Juan Leandro. Southern Methodist University; Estados Unidos. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Regional de Investigaciones Científicas y Transferencia Tecnológica de La Rioja. - Universidad Nacional de La Rioja. Centro Regional de Investigaciones Científicas y Transferencia Tecnológica de La Rioja. - Universidad Nacional de Catamarca. Centro Regional de Investigaciones Científicas y Transferencia Tecnológica de La Rioja. - Secretaría de Industria y Minería. Servicio Geológico Minero Argentino. Centro Regional de Investigaciones Científicas y Transferencia Tecnológica de La Rioja. - Provincia de La Rioja. Centro Regional de Investigaciones Científicas y Transferencia Tecnológica de La Rioja; ArgentinaFil: Jacobs, B. F.. Southern Methodist University; Estados Unido