Alluvial to lacustrine sedimentation in an endorheic basin during the Mio-Pliocene: The Toro Negro Formation, Central Andes of Argentina

A 2400 m-thick sedimentary column belonging to the Toro Negro Formation was recorded along the Quebrada del Yeso, Sierra de Los Colorados (Vinchina Basin), La Rioja province, NW Argentina. The Vinchina basin is a good example of a closed basin surrounded by the Precordillera fold and thrust belt to the west and basement-cored blocks to the north, south (Western Sierras Pampeanas) and east (Sierra de Famatina). Seven facies associations (FA) are described and interpreted to represent fluvial, lacustrine and alluvial environments developed in the southern part of the Vinchina basin from the Late Miocene until the earliest Pleistocene. The depositional evolution of the formation was divided in four phases. Phase I (∼7–6.6 Ma) represents sedimentation in medial (FA I) to distal (FA II) parts of a southward directed distributive fluvial system with a retrogradational pattern. During phase II (6.6–6.1Ma), the distributive fluvial system was replaced by a mixed clastic-evaporitic shallow lake (FA III) in a high aggradational basin. In phase III (∼6.1–5 Ma) the eastward progradation of a fluvial system (FA IV) was recorded as a distal clastic wedge. Finally, phase IV (∼5-2.4Ma) records two depositional cycles of proximal clastic wedge progradation of fluvial-dominated piedmonts (FAV, FAVII) from the southwest (Sierra de Umango) and/or the west (Precordillera) with an intervening playa lake (FA VI). Two new U-Pb ages obtained from zircons in volcanic ash layers confirm the Late Miocene age of the lower member of the Toro Negro Formation and permit a tight correlation with the central part of the basin (Quebrada de La Troya section). The sedimentation rate calculated for the dated lacustrine-fluvial interval is higher than the corresponding one in La Troya area suggesting a higher subsidence in the southern part of the basin. During the Late Miocene (∼7-6.6Ma) the ephemeral drainage was controlled by an arid to semiarid climate and initially dissipated mostly internally as terminal fan/distributive fluvial systems descending from the north. A thick lacustrine interval developed in the southern part of the basin between ∼6.6 and 6.1 Ma during a period of high subsidence and closed drainage. Besides, this interval coincides with increased aridity recorded in other basins in the Northwest of Argentina. By ∼6.1 Ma the area started to receive the first coarse-grained sediments heralding the progradation of a clastic wedge from the southwest-west (Sierra de Umango and Precordillera) which fully developed during the rest of the Pliocene to the earliest Pleistocene (∼5–2.4 Ma). The 6.1–2.4 Ma interval records ameliorating climate conditions.Fil: Ciccioli, Patricia Lucia. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Geociencias Básicas, Aplicadas y Ambientales de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Geociencias Básicas, Aplicadas y Ambientales de Buenos Aires; ArgentinaFil: Marenssi, Sergio Alfredo. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Geociencias Básicas, Aplicadas y Ambientales de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Geociencias Básicas, Aplicadas y Ambientales de Buenos Aires; ArgentinaFil: Amidon, William H.. Middlebury College; Estados UnidosFil: Limarino, Carlos Oscar. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Geociencias Básicas, Aplicadas y Ambientales de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Geociencias Básicas, Aplicadas y Ambientales de Buenos Aires; ArgentinaFil: Kylander Clark, Andrew. University of California; Estados Unido

Inland dunes on the abandoned bed of Glacial Lake Chicago indicate eolian activity during the Pleistocene-Holocene transition, southwestern Michigan, USA

Inland dune fields have recently emerged as a source of data for reconstructing paleoenvironments and climate in the western Great Lakes region of North America during the Pleistocene-Holocene transition. We employ optically stimulated luminescence (OSL) methods, radiocarbon ages, soils, and landform relationships to determine the age of inland dunes in Ottawa County, Michigan. These dunes rest on the abandoned bed of Glacial Lake Chicago, which is thought to have been exposed after ~13.6 ka. OSL analyses from two inland dunes yield ages ranging from 13.3±1.1 to 11.6±0.9 ka (uncertainty = 2 σ). Fine sand in the parabolic dunes suggests deflation of exposed glaciolacustrine nearshore sand by northwesterly and westerly winds. These new data add to a growing number of studies that demonstrate widespread eolian activity in the western Great Lakes region during the Pleistocene-Holocene transition. OSL ages from dune fields in the western Great Lakes indicate peak eolian activity and dune stabilization occurred during or following the Younger Dryas and Preboreal events. Northwesterly and westerly winds suggest the limited effect of hypothesized easterly anticyclonic winds during the Pleistocene-Holocene transition. Rapidly changing climate and newly deglaciated surfaces provided an ideal environment for dune formation

Depositional constraints from detrital zircon geochronology of strata from multiple lithotectonic belts in south-central Maine, USA

The bedrock geology of south-central Maine is characterized by a series of fault-bounded lithotectonic terranes that were accreted onto the Laurentian margin during Silurian-Devonian orogenesis.  The multiple phases of deformation and metamorphism associated with this tectonism obscured most primary features in the protolith rocks, leading to uncertainties in their pre-accretionary history. Here we present the results of detrital zircon geochronology from five of these terranes and make interpretations on their depositional ages, sediment provenance, and tectonic setting of deposition.Detrital zircon from Silurian rocks of the Vassalboro Group in the eastern-most portion of the Central Maine basin indicate sediment input in an extensional setting from both Laurentian and Ordovician sources.  Results from Ordovician rocks of the Casco Bay Group of the Liberty-Orrington belt support earlier findings that these rocks have strong peri-Gondwanan affinities.  Detrital zircon from the Appleton Ridge Formation and Ghent phyllite of the Fredericton trough are consistent with a peri-Gondwanan sediment source with no evidence of Laurentian sediment input.  These findings are consistent with that of Dokken et al. (2018) for older Fredericton trough strata (i.e., Digdeguash Formation) east of the Fredericton fault in southern New Brunswick.  Two samples from the Jam Brook complex reveal extreme differences in depositional age (Ordovician vs. Mesoproterozoic) and tectonic affinity and support the hypothesis that this narrow belt represents a fault complex containing a wide variety of stratigraphic units.  Detrital zircon from Ordovician rocks of the Benner Hill Sequence indicate a peri-Gondwanan sediment source with no Laurentian input.Collectively, the pre-Silurian rocks of the Liberty-Orrington belt, Jam Brook complex, Benner Hill Sequence, and Late Ordovician-Early Silurian strata from the Appleton Ridge and Ghent phyllite in the Fredericton trough show peri-Gondwanan affinities with no evidence of Laurentian sediment input.  This suggests a barrier exisited between the Laurentian margin and these peri-Gondwanan terranes prior to about 435 Ma.  In contrast, Silurian strata from the eastern portion of the Central Maine basin do show evidence of a Laurentian sediment source, along with deposition in an extensional setting (lacking in all other samples), thus signaling a fundamental change in tectonic regime

Stratigraphy of the Neogene succession in Bolson de Fiambalá, Famatina System, Catamarca, Argentina

La sucesión neógena del Bolsón de Fiambalá, que aflora en el centro-oeste de la provincia de Catamarca, comprende a las Formaciones Tambería, Guanchín y Rodados de la Puna. Sus respectivas edades depositacionales fueron planteadas a partir de dataciones U/Pb, trazas de fisión y magnetoestratigrafía, aunque la poca precisión estratigráfica y geográfica de estos datos, sumado a las complejidades estructurales del área, y los 6.4 km de espesor que alcanza la sucesión, tornan necesario esclarecer el ordenamiento estratigráfico de la región, a fines de poder establecer con mayor precisión la evolución de la cuenca. El análisis de las edades disponibles y las de máxima depositación presentadas en este trabajo, arrojan que la Formación Tambería comenzó a depositarse luego de los ~23 Ma. Esta formación puede separarse en un miembro inferior dominado por areniscas con intercalaciones de conglomerados y pelitas, depositadas en sistemas fluviales multicanalizados de clima semiárido, que gradan a ortoconglomerados polimícticos del miembro medio, acumulados en sistemas fluviales entrelazados. Culmina con un miembro superior constituido por depósitos areno-conglomerádicos y pelíticos, acumulados en sistemas fluviales multicanalizados con planicies areno-pelíticas. La suprayacente Formación Guanchín comenzó a depositarse a los ~6 Ma, y puede separarse en dos miembros: uno inferior compuesto de areniscas con frecuentes intercalaciones de tobas, que se acumularon en diversos sistemas fluviales arenosos; y otro superior areno-conglomerádico resultado de sistemas fluviales entrelazados. Finalmente, en discordancia erosiva se encuentran los depósitos conglomerádicos de abanicos aluviales dominados por flujos mantiformes de la Formación Rodados de la Puna, depositados durante el Pleistoceno (~1.8 Ma).Bolson de Fiambala Neogene succession crops out in the center-west of Catamarca province. It includes Tambería, Guanchin and Rodados de la Puna formations. Their respective depositional ages were raised from U/Pb dating, fission tracks and magnetostratigraphy. However, the poor stratigraphic and geographic precision of these data, added to the area´s structural complexities, and the 6.4 km thick of the succession, makes it necessary to clarify the region´s stratigraphic ordering to define with more precision the basin evolution. The analysis of available and maximum depositional ages presented in this work, show that Tambería Formation deposition began after ~23 Ma. It can be separated into a lower member, dominated by sandstones with intercalations of conglomerates and shales, deposited in semi-arid multi-channelized fluvial systems. Over these deposits are polymictic conglomerates of the middle member, accumulated in perennial braided fluvial systems. The Tambería Formation culminates with an upper member made up of sandy-conglomerates and shales that were accumulated in mutli-channelized fluvial systems with sandy to muddy floodplains. The overlying Guanchín Formation began to be deposited around ~6 Ma and can be separated into two members: a lower one composed of sandstones with frequent tuff intercalations, which were accumulated in sandy river systems; and an upper member made up of sandstones and conglomerates deposited by a braided fluvial system. Finally, older units are covered by means of an erosive unconformity by sheetflood-dominated alluvial fans conglomerates of the Pliocene Rodados de la Puna Formation.Fil: Deri, Maximiliano. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Geociencias Básicas, Aplicadas y Ambientales de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Geociencias Básicas, Aplicadas y Ambientales de Buenos Aires; ArgentinaFil: Ciccioli, Patricia Lucia. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Geociencias Básicas, Aplicadas y Ambientales de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Geociencias Básicas, Aplicadas y Ambientales de Buenos Aires; ArgentinaFil: Marenssi, Sergio Alfredo. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Geociencias Básicas, Aplicadas y Ambientales de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Geociencias Básicas, Aplicadas y Ambientales de Buenos Aires; ArgentinaFil: Amidon, William. Middlebury College; Estados Unido

A model for fire‐induced sediment yield by dry ravel in steep landscapes

Sediment flux from hillslopes to channels commonly increases following wildfires, with implications for the carbon cycle, river habitats, and debris-flow hazards. Although much of this material is transported via dry ravel, existing ravel models are not applicable to hillslopes with gradients greater than the angle of repose, which can constitute the majority of mountainous terrain. To fill this knowledge gap, we develop a continuity model for sediment storage by vegetation dams on steep hillslopes to predict sediment yields following wildfire. The maximum volume of sediment stored prior to wildfire is set to be a function of vegetation density, the capacity of plants to impound sediment, and the contributing hillslope area. Time is required after fire to establish vegetation and replenish hillslope sediment storage, which introduces vegetation regrowth rate, soil production rate, and fire recurrence interval as important variables that affect ravel yield. Model results for the San Gabriel Mountains, California, predict that sediment yield can increase by several orders of magnitude following fire. These results are consistent with field data of ravel yield (~30 mm per contributing area of hillslope in 5 months) we collected following the 2009 Station Fire, as well as postfire sediment flux recorded by 93 debris basins. In contrast to previous work, our model shows that heightened postfire sediment yields can be explained by a change in hillslope sediment storage independent of major changes in the soil production rate and landscape form over geomorphic timescales

Depositional chronology of the lower member of the Toro Negro Formation (Mio-Pliocene), Andean Foreland, La Rioja

Se presenta un análisis integrado de la magnetoestratigrafía reinterpretada, a partir de los datos de Ré (2008), en función de nuevas edades U-Pb obtenidas por Amidon et al. (2016), con modelos de estratigrafía secuencial de los sistemas fluviales del miembro inferior de la Formación Toro Negro, quebrada de La Troya, Cuenca de Vinchina, La Rioja. Este estudio permite obtener patrones de tasas de sedimentación que ayudan a mejorar considerablemente los modelos tectosedimentarios de la cuenca. Las tasas de sedimentación obtenidas para la AF1 (0,45 mm/a en el modelo 1 y 0,3 mm/a a 0,52 mm/a en el modelo 2), reflejan las condiciones de confinamiento con bajo espacio de acomodación que caracterizaron al relleno inicial del paleovalle, formado como consecuencia del ascenso de la sierra de Famatina. El pasaje a valores más altos (1,75 mm/a en el modelo 1 y 0,85 mm/a en el modelo 2), señala, de manera clara, un aumento muy probablemente vinculado al ascenso del perfil de equilibrio de los sistemas fluviales que permitió acomodar una mayor cantidad de sedimento dentro del paleovalle (alto espacio de acomodación confinado). La disminución en la tasa de sedimentación al perderse por completo el confinamiento en la SDII (0,5 mm/a), indica la transición a una etapa de mayor espacio de acomodación lateral. La nueva información magnetoestratigráfica sugiere que el paleovalle se formó entre los ~9-8 Ma y el inicio de la sedimentación de la Formación Toro Negro en la quebrada de La Troya corresponde al chron C4n sin descartar que en posiciones más profundas del paleovalle sea más antigua. Finalmente, la superficie que separa los miembros inferior y superior de la Formación Toro Negro es aquí incluida en el chron C3n.An integrated analysis of the reinterpreted magnetostratigraphy from Re (2008), based on new U-Pb ages from Amidon et al. (2016), with models of sequence stratigraphy of fluvial systems of the lower member of the Toro Negro Formation, quebrada de la Troya, Vinchina Basin, La Rioja is here presented. This study allows obtaining patterns of sedimentation rates that help to considerably improve the tectosedimentary models for the basin. The sedimentation rates obtained for FA1 (0.45 mm/y in model 1 and 0.3 mm/y to 0.52 mm/y in model 2), reflect conditions of confinement with low accommodation space that characterized the initial filling of the paleovalley, formed as a consequence of the uplift of Famatina range. The passage to higher values (1.75 mm/y in model 1 and 0.85 mm/y in model 2) is most likely linked to the rise in the equilibrium profile of the rivers that were able to accommodate a greater amount of sediment within the paleovalley (confined high-accommodation space). The decrease in the sedimentation rate, due to the complete loss of confinement in SDII (0.5 mm/y), indicates the transition to a stage of greater lateral accommodation space. The new data suggests that the paleovalley was carved between ~ 9-8 Ma and the beginning of the sedimentation of the Toro Negro Formation at this locality corresponds to the chron C4n without discarding that in deeper positions of the paleovalley it may be older. Finally, the surface that separates the lower and upper members of the Toro Negro Formation is here included within the chron C3n.Fil: Ciccioli, Patricia Lucia. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Geociencias Básicas, Aplicadas y Ambientales de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Geociencias Básicas, Aplicadas y Ambientales de Buenos Aires; ArgentinaFil: Re, Guillermo Hector. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Geociencias Básicas, Aplicadas y Ambientales de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Geociencias Básicas, Aplicadas y Ambientales de Buenos Aires; ArgentinaFil: Amidon, William H.. No especifíca;Fil: Marenssi, Sergio Alfredo. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Geociencias Básicas, Aplicadas y Ambientales de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Geociencias Básicas, Aplicadas y Ambientales de Buenos Aires; ArgentinaFil: Limarino, Carlos Oscar. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Geociencias Básicas, Aplicadas y Ambientales de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Geociencias Básicas, Aplicadas y Ambientales de Buenos Aires; Argentin

Persistent elastic behavior above a megathrust rupture patch: Nias island, West Sumatra

We quantify fore-arc deformation using fossil reefs to test the assumption commonly made in seismic cycle models that anelastic deformation of the fore arc is negligible. Elevated coral microatolls, paleoreef flats, and chenier plains show that the Sumatran outer arc island of Nias has experienced a complex pattern of relatively slow long-term uplift and subsidence during the Holocene epoch. This same island rose up to 2.9 m during the Mw 8.7 Sunda megathrust rupture in 2005. The mismatch between the 2005 and Holocene uplift patterns, along with the overall low rates of Holocene deformation, reflects the dominance of elastic strain accumulation and release along this section of the Sunda outer arc high and the relatively subordinate role of upper plate deformation in accommodating long-term plate convergence. The fraction of 2005 uplift that will be retained permanently is generally <4% for sites that experienced more than 0.25 m of coseismic uplift. Average uplift rates since the mid-Holocene range from 1.5 to −0.2 mm/a and are highest on the eastern coast of Nias, where coseismic uplift was nearly zero in 2005. The pattern of long-term uplift and subsidence is consistent with slow deformation of Nias along closely spaced folds in the north and trenchward dipping back thrusts in the southeast. Low Holocene tectonic uplift rates provide for excellent geomorphic and stratigraphic preservation of the mid-Holocene relative sea level high, which was under way by ∼7.3 ka and persisted until ∼2 ka

Formulation predictive dissolution (fPD) testing to advance oral drug product development: an introduction to the US FDA funded ‘21st Century BA/BE’ project

Over the past decade, formulation predictive dissolution (fPD) testing has gained increasing attention. Another mindset is pushed forward where scientists in our field are more confident to explore the in vivo behavior of an oral drug product by performing predictive in vitro dissolution studies. Similarly, there is an increasing interest in the application of modern computational fluid dynamics (CFD) frameworks and high-performance computing platforms to study the local processes underlying absorption within the gastrointestinal (GI) tract. In that way, CFD and computing platforms both can inform future PBPK-based in silico frameworks and determine the GI-motility-driven hydrodynamic impacts that should be incorporated into in vitro dissolution methods for in vivo relevance. Current compendial dissolution methods are not always reliable to predict the in vivo behavior, especially not for biopharmaceutics classification system (BCS) class 2/4 compounds suffering from a low aqueous solubility. Developing a predictive dissolution test will be more reliable, cost-effective and less time-consuming as long as the predictive power of the test is sufficiently strong. There is a need to develop a biorelevant, predictive dissolution method that can be applied by pharmaceutical drug companies to facilitate marketing access for generic and novel drug products. In 2014, Prof. Gordon L. Amidon and his team initiated a far-ranging research program designed to integrate (1) in vivo studies in humans in order to further improve the understanding of the intraluminal processing of oral dosage forms and dissolved drug along the gastrointestinal (GI) tract, (2) advancement of in vitro methodologies that incorporates higher levels of in vivo relevance and (3) computational experiments to study the local processes underlying dissolution, transport and absorption within the intestines performed with a new unique CFD based framework. Of particular importance is revealing the physiological variables determining the variability in in vivo dissolution and GI absorption from person to person in order to address (potential) in vivo BE failures. This paper provides an introduction to this multidisciplinary project, informs the reader about current achievements and outlines future directions