Stratigraphic and paleontologic analysis of the Upper Cretaceous in the Golfo San Jorge basin: a new lithostratigraphic unit for the Chubut Group

Las características litológicas, estratigráficas y paleontológicas del registro más moderno del Grupo Chubut en la Cuenca del Golfo San Jorge (Argentina), permiten proponer una nueva unidad litoestratigráfica dentro del grupo, la Formación Lago Colhué Huapi (nov. nom.). Esta unidad se dispone por encima de la Formación Bajo Barreal y por debajo de la Formación Laguna Palacios o de la Formación Salamanca. La base y el techo son transicionales, con excepción del contacto con la Formación Salamanca que en algunos casos es erosivo. Sus afloramientos se extienden ampliamente en el ámbito de la cuenca. Su localidad tipo se encuentra ubicada en las nacientes del río Chico y se propone un estratotipo compuesto: el holoestratotipo está constituido por el intervalo aflorante en las nacientes del río Chico (53 m de espesor), y el paraestratotipo es el intervalo aflorante en la margen sureste del Codo del río Senguerr (160 m de espesor). Los criterios para su reconocimiento consisten en la coloración rojiza de sus fangolitas y su posición estratigráfica. Se diferencia de la Formación Bajo Barreal (miembro superior) porque esta última se compone principalmente de fangolitas grises, mientras que se distingue de la Formación Laguna Palacios por la ausencia de niveles tobáceos y paleosuelos. En su localidad tipo se interpretó un paleoambiente fluvial con sistemas canalizados de alta sinuosidad con planicies de inundación bien drenadas, vinculados a un paleoclima semi-árido. El contenido paleontológico de restos de dinosaurios permitió definir una edad comprendida entre el Coniaciano-Maastrichtiano, y afinidades faunísticas con la Formación Allen de la Cuenca Neuquina.Lithologic, stratigraphic and paleontological features of the most recent record of the Chubut Group in the Golfo San Jorge Basin (Argentina), allowed us to propose the definition of a new lithostratigraphic unit in the Group: Lago Colhué Huapi Formation (nov. nom.). This unit overlies the Bajo Barreal Formation (Upper Member) and it is covered by the Laguna Palacios or Salamanca Formation. Although its base and top are transitional, this unit is sometimes limited by an erosional surface in its contact with the Salamanca Formation, and it is widely exposed in the basin. Its type locality is located in the headwaters of the Chico river and we propose a composed type-strata: the holostratotype is constituted by a stratigraphic section outcropped in the headwaters of the Chico river (53 m thick), and the parastratotype is the interval outcropped in the southeastern margin of the Senguerr river (160 m thick). Criteria for the recognition of the proposed unit are its reddish mudstones and the stratigraphic position. The Lago Colhué Huapi Fomation differs from the Bajo Barreal Formation (Upper Member) because the latter is characterized by grey mudstones. This unit also differs from Laguna Palacios Formation because of the absence of tuffaceous strata and paleosoils. In its type locality, we interpreted a fluvial paleo-environment with high-sinuosity channels and well-drained floodplains, probably developed under semiarid paleoclimatic conditions. The dinosaur record of the formation allowed us to define an age ranging between Coniacian-Maastrichtian, and faunistic affinities with the Allen Fomation of the Neuquén basin.Fil: Casal, Gabriel. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de la Patagonia "San Juan Bosco". Facultad de Ciencias Naturales - Sede Comodoro. Departamento de Geología; ArgentinaFil: Allard, Jose Oscar. Universidad Nacional de la Patagonia "San Juan Bosco". Facultad de Ciencias Naturales - Sede Comodoro. Departamento de Geología; ArgentinaFil: Foix, Nicolas. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de la Patagonia "San Juan Bosco". Facultad de Ciencias Naturales - Sede Comodoro. Departamento de Geología; Argentin

First record of stromatolites from the late Maastrichtian of the Chubut Group, Golfo San Jorge Basin, central Patagonia, Argentina

En este trabajo se reporta por primera vez la presencia de estromatolitos en afloramientos cretácicos en la localidad nacientes del río Chico en la Cuenca del Golfo San Jorge. Los mismos se encuentran en la parte superior de la Formación Lago Colhué Huapi (Coniaciano-Maastrichtiano), unidad correspondiente al Grupo Chubut. La presencia de, hasta el momento, cuatro estructuras interpretadas como estromatolitos en esta localidad, no solo tiene importancia por ser el primer registro en la cuenca, sino porque contribuye al conocimiento de estas bioconstrucciones en los ambientes continentales. Se caracteriza y discute en detalle el estromatolito denominado E1, que se encuentra asociado a un abundante y diverso registro fósil, representado por palinomorfos, fragmentos de troncos silicificados, restos de dinosaurios y cáscaras de huevos de dinosaurios. El estudio, integrado fundamentalmente con el polen y las esporas registradas, es importante para las interpretaciones paleoambientales del sitio y contribuye al entendimiento paleoecológico y paleoclimático del intervalo estratigráfico más moderno del Grupo Chubut.The presence of stromatolites from Cretaceous outcrops at the headwaters of the río Chico locality in the Golfo San Jorge Basin is reported for the first time. They are present in the uppermost part of the Lago Colhué Huapi Formation (Coniacian-Maastrichtian) of the Chubut Group. The presence of, up to now, four structures interpreted as stromatolites in this locality are not only important because it is the first record in the basin, but because it contributes to the knowledge of these bioconstructions in continental environments. The stromatolite called E1, which is characterized and discussed in detail, is associated with an abundant and diverse fossil record represented by palynomorphs, fragments of silicified trunks, dinosaur remains and eggshells. The study, integrated mainly with the recorded pollen and spores, is important for paleoenvironmental interpretations of the site and contributes to the paleoecological and paleoclimatic understanding of the most modern stratigraphic interval of the Chubut Group.Fil: Casal, Gabriel Andrés. Universidad Nacional de la Patagonia "San Juan Bosco". Facultad de Ciencias Naturales - Sede Comodoro. Departamento de Geología; ArgentinaFil: Vallati, Patricia Silvina. Universidad Nacional de la Patagonia "San Juan Bosco". Facultad de Ciencias Naturales - Sede Comodoro. Departamento de Geología; ArgentinaFil: Ibiricu, Lucio Manuel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Instituto Patagónico de Geología y Paleontología; ArgentinaFil: de Sosa Tomas, Rosaura Andrea. Universidad Nacional de la Patagonia "San Juan Bosco". Facultad de Ciencias Naturales - Sede Comodoro. Departamento de Geología; ArgentinaFil: Foix, Nicolas. Universidad Nacional de la Patagonia "San Juan Bosco". Facultad de Ciencias Naturales - Sede Comodoro. Departamento de Geología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico; ArgentinaFil: Allard, Jose Oscar. Universidad Nacional de la Patagonia "San Juan Bosco". Facultad de Ciencias Naturales - Sede Comodoro. Departamento de Geología; ArgentinaFil: Martínez, Rubén Darío. Universidad Nacional de la Patagonia "San Juan Bosco". Facultad de Ciencias Naturales - Sede Comodoro; Argentin

In Situ Reference Datasets From the TropiSAR and AfriSAR Campaigns in Support of Upcoming Spaceborne Biomass Missions

Tropical forests are a key component of the global carbon cycle. Yet, there are still high uncertainties in forest carbon stock and flux estimates, notably because of their spatial and temporal variability across the tropics. Several upcoming spaceborne missions have been designed to address this gap. High-quality ground data are essential for accurate calibration/validation so that spaceborne biomass missions can reach their full potential in reducing uncertainties regarding forest carbon stocks and fluxes. The BIOMASS mission, a P-band SAR satellite from the European Space Agency (ESA), aims at improving carbon stock mapping and reducing uncertainty in the carbon fluxes from deforestation, forest degradation, and regrowth. In situ activities in support of the BIOMASS mission were carried out in French Guiana and Gabon during the TropiSAR and AfriSAR campaigns. During these campaigns, airborne P-band SAR, forest inventory, and lidar data were collected over six study sites. This paper describes the methods used for forest inventory and lidar data collection and analysis, and presents resulting plot estimates and aboveground biomass maps. These reference datasets along with intermediate products (e.g., canopy height models) can be accessed through ESA's Forest Observation System and the Dryad data repository and will be useful for BIOMASS but also to other spaceborne biomass missions such as GEDI, NISAR, and Tandem-L for calibration/validation purposes. During data quality control and analysis, prospects for reducing uncertainties have been identified, and this paper finishes with a series of recommendations for future tropical forest field campaigns to better serve the remote sensing community.Additional co-authors: Gaelle Jaouen, David Kenfack, Lisa Korte, Simon L Lewis, Yadvinder Malhi, Herve R Memiaghe, John R Poulsen, Maxime Rejou-Mechain, Ludovic Villard, Gregoire Vincent, and Sassan Saatch

Search for the standard model Higgs boson in the H to ZZ to 2l 2nu channel in pp collisions at sqrt(s) = 7 TeV

A search for the standard model Higgs boson in the H to ZZ to 2l 2nu decay channel, where l = e or mu, in pp collisions at a center-of-mass energy of 7 TeV is presented. The data were collected at the LHC, with the CMS detector, and correspond to an integrated luminosity of 4.6 inverse femtobarns. No significant excess is observed above the background expectation, and upper limits are set on the Higgs boson production cross section. The presence of the standard model Higgs boson with a mass in the 270-440 GeV range is excluded at 95% confidence level.Comment: Submitted to JHE

Combined search for the quarks of a sequential fourth generation

Results are presented from a search for a fourth generation of quarks produced singly or in pairs in a data set corresponding to an integrated luminosity of 5 inverse femtobarns recorded by the CMS experiment at the LHC in 2011. A novel strategy has been developed for a combined search for quarks of the up and down type in decay channels with at least one isolated muon or electron. Limits on the mass of the fourth-generation quarks and the relevant Cabibbo-Kobayashi-Maskawa matrix elements are derived in the context of a simple extension of the standard model with a sequential fourth generation of fermions. The existence of mass-degenerate fourth-generation quarks with masses below 685 GeV is excluded at 95% confidence level for minimal off-diagonal mixing between the third- and the fourth-generation quarks. With a mass difference of 25 GeV between the quark masses, the obtained limit on the masses of the fourth-generation quarks shifts by about +/- 20 GeV. These results significantly reduce the allowed parameter space for a fourth generation of fermions.Comment: Replaced with published version. Added journal reference and DO

Measurement of the Z/gamma* + b-jet cross section in pp collisions at 7 TeV

The production of b jets in association with a Z/gamma* boson is studied using proton-proton collisions delivered by the LHC at a centre-of-mass energy of 7 TeV and recorded by the CMS detector. The inclusive cross section for Z/gamma* + b-jet production is measured in a sample corresponding to an integrated luminosity of 2.2 inverse femtobarns. The Z/gamma* + b-jet cross section with Z/gamma* to ll (where ll = ee or mu mu) for events with the invariant mass 60 < M(ll) < 120 GeV, at least one b jet at the hadron level with pT > 25 GeV and abs(eta) < 2.1, and a separation between the leptons and the jets of Delta R > 0.5 is found to be 5.84 +/- 0.08 (stat.) +/- 0.72 (syst.) +(0.25)/-(0.55) (theory) pb. The kinematic properties of the events are also studied and found to be in agreement with the predictions made by the MadGraph event generator with the parton shower and the hadronisation performed by PYTHIA.Comment: Submitted to the Journal of High Energy Physic

Search for a W' boson decaying to a bottom quark and a top quark in pp collisions at sqrt(s) = 7 TeV

Results are presented from a search for a W' boson using a dataset corresponding to 5.0 inverse femtobarns of integrated luminosity collected during 2011 by the CMS experiment at the LHC in pp collisions at sqrt(s)=7 TeV. The W' boson is modeled as a heavy W boson, but different scenarios for the couplings to fermions are considered, involving both left-handed and right-handed chiral projections of the fermions, as well as an arbitrary mixture of the two. The search is performed in the decay channel W' to t b, leading to a final state signature with a single lepton (e, mu), missing transverse energy, and jets, at least one of which is tagged as a b-jet. A W' boson that couples to fermions with the same coupling constant as the W, but to the right-handed rather than left-handed chiral projections, is excluded for masses below 1.85 TeV at the 95% confidence level. For the first time using LHC data, constraints on the W' gauge coupling for a set of left- and right-handed coupling combinations have been placed. These results represent a significant improvement over previously published limits.Comment: Submitted to Physics Letters B. Replaced with version publishe

Measurement of the t t-bar production cross section in the dilepton channel in pp collisions at sqrt(s) = 7 TeV

The t t-bar production cross section (sigma[t t-bar]) is measured in proton-proton collisions at sqrt(s) = 7 TeV in data collected by the CMS experiment, corresponding to an integrated luminosity of 2.3 inverse femtobarns. The measurement is performed in events with two leptons (electrons or muons) in the final state, at least two jets identified as jets originating from b quarks, and the presence of an imbalance in transverse momentum. The measured value of sigma[t t-bar] for a top-quark mass of 172.5 GeV is 161.9 +/- 2.5 (stat.) +5.1/-5.0 (syst.) +/- 3.6(lumi.) pb, consistent with the prediction of the standard model.Comment: Replaced with published version. Included journal reference and DO

Search for the standard model Higgs boson decaying into two photons in pp collisions at sqrt(s)=7 TeV

A search for a Higgs boson decaying into two photons is described. The analysis is performed using a dataset recorded by the CMS experiment at the LHC from pp collisions at a centre-of-mass energy of 7 TeV, which corresponds to an integrated luminosity of 4.8 inverse femtobarns. Limits are set on the cross section of the standard model Higgs boson decaying to two photons. The expected exclusion limit at 95% confidence level is between 1.4 and 2.4 times the standard model cross section in the mass range between 110 and 150 GeV. The analysis of the data excludes, at 95% confidence level, the standard model Higgs boson decaying into two photons in the mass range 128 to 132 GeV. The largest excess of events above the expected standard model background is observed for a Higgs boson mass hypothesis of 124 GeV with a local significance of 3.1 sigma. The global significance of observing an excess with a local significance greater than 3.1 sigma anywhere in the search range 110-150 GeV is estimated to be 1.8 sigma. More data are required to ascertain the origin of this excess.Comment: Submitted to Physics Letters