Sedimentology of a distributive fluvial system: The Serra da Galga Formation, a new lithostratigraphic unit (Upper Cretaceous, Bauru Basin, Brazil)

The Bauru Basin of SE Brazil is a large (ca. 370,000 km2) Upper Cretaceous intracratonic feature, important for its fossil remains and of particular value as a source of regional palaeoclimatic information. Historically, lithostratigraphic reconstructions have been performed mainly for successions of the central and southern parts of the basin, resulting in a lithostratigraphic scheme that is not applicable to the northernmost regions. In particular, the northeastern deposits of the Marília Formation (Serra da Galga and Ponte Alta members) reveal lithological, stratigraphic, and palaeontological differences from southeastern and northwestern counterparts (Echaporã Member). Nevertheless, these deposits are considered as a single lithostratigraphic formation in the literature. To address this problem, this study demonstrates how the northeastern deposits of the Marília Formation do not show affinity to the rest of the unit. A more suitable lithostratigraphic model is proposed for the northeastern succession as a distinct and independent unit. Lithofacies and palaeopedological analysis, combined with lithostratigraphic mapping of the northeastern deposits, reveal 11 distinct lithofacies and three pedotypes over an area of ~450 km2. Sedimentary facies and pedotypes were assigned to six interbedded architectural elements: (a) type 1 channel fill, (b) type 2 channel fill, (c) type 3 channel fill, (d) interchannels, (e) palaeosols, and (f) calcrete beds. The succession is interpreted as a distributive fluvial system with overall direction of flow to the NNW, and which developed under the influence of a semiarid climate regime. This contrasts with deposits of the southeastern and northwestern Marília Formation, previously suggested to be of fine-grained aeolian affinity with interbedded poorly channelised deposits assigned to an aeolian sand sheet environment. By revising the existing lithostratigraphic scheme for the northeastern deposits, and contrasting them with laterally equivalent strata, this work demonstrates how the previously named Serra da Galga and Ponte Alta members reveal a unique set of lithological, architectural, and genetic signatures that permits to separate them from the Marília Formation. Finally, a new lithostratigraphic classification for the unit is proposed: the Serra da Galga Formation, whose deposition relates to an ancient distributive fluvial system.Fil: Soares, Marcus Vinícius Theodoro. Universidade Estadual de Campinas; BrasilFil: Basilici, Giorgio. Universidade Estadual de Campinas; Brasil. 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: da Silva Marinho, Thiago. Universidade Federal do Triângulo Mineiro; BrasilFil: Martinelli, Agustín Guillermo. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; ArgentinaFil: Marconato, André. Universidade Federal de Ouro Preto; BrasilFil: Mountney, Nigel Philip. University Of Leeds.; Reino UnidoFil: Colombera, Luca. University Of Leeds.; Reino UnidoFil: Mesquita, Áquila Ferreira. Universidade Estadual de Campinas; BrasilFil: Vasques, Julia Tucker. Universidade Estadual de Campinas; BrasilFil: Junior, Francisco Romero Abrantes. Universidade Estadual de Campinas; BrasilFil: Ribeiro, Luiz Carlos Borges. Universidade Federal Do Triangulo Mineiro; Brasi

LHCb

The LHCb detector is designed to study CP violation and other rare phenomena in decays of hadrons with heavy flavours, in particular $\rm B_s$ mesons. Interest in CP violation comes not only from elementary particle physics but also from cosmology, in order to explain the dominance of matter over antimatter observed in our universe, which could be regarded as the largest CP violation effect ever seen. The LHCb experiment will improve significantly results from earlier experiments both quantitatively and qualitatively, by exploiting the large number of different kinds of b hadrons produced at LHC. This is done by constructing a detector which has \begin{enumerate} \item Good trigger efficiencies for b-hadron final states with only hadrons, as well as those containing leptons. \item Capability of identifying kaons and pions in a momentum range of $\sim 1$ to above 100 GeV/$c$. \item Excellent decay time and mass resolution. \end{enumerate} The LHCb spectrometer shown in the figure consists of the following detector components: \begin{itemize} \item Beam Pipe\\ A 1.8 m-long section of the beam pipe around the interaction point has a large diameter of approximately 120 cm. This accommodates the vertex detector system with its retraction mechanics, and has a thin forward window made of aluminium over the full detector acceptance. This part is followed by two conical sections; the first is 1.5 m long with 25 mrad opening angle, and the second is 16 m long with 10 mrad opening angle. The entire first and most of the second section are made of beryllium in order to reduce the production of the secondary particles. \item Magnet\\ A dipole magnet with the normal conductive Al coil provides a high field integral of 4 Tm. The polarity of the field can be changed to reduce systematic errors in the CP-violation measurements that could result from a left-right asymmetry of the detector. \item Vertex Locator\\ A total of 21 stations made from two layers of silicon detector are used as a vertex detector system (VELO). Additional two stations with only one Si layer are dedicated to the detecting bunch crossings with more than one pp interaction as a part of Level-0 trigger. The closest distance between the active silicon area and the beam is 8 mm. The silicon detectors are placed in Roman pots with 300 $\mu$m thick aluminium windows, which act as a shield against RF pickup from the circulating beam bunches. In order to avoid collapse of the windows, a secondary vacuum is maintained inside the Roman pots. During the injection and acceleration, the Roman pot system will be moved away from the beam to avoid interference with the machine operation and accidental irradiation of the detectors. \item Tracking\\ The LHCb tracking system consists of four stations; one upstream of the magnet (TT) and three just behind the magnet (T1 to T3). No tracking device is positioned in the magnet and most of the tracks are reconstructed by combining the VELO and tracking system. The first station is made of silicon detectors. The stations behind the magnet are split into Inner Tracker (IT) and Outer Tracker (OT) systems due to the high particle density close to the beam pipe. The IT system is made of Si, and drift chambers based on straw technology are used for the OT system. \item Ring Imaging Cherenkov Detectors\\ The RICH system of the LHCb detector consists of two detectors with three different radiators in order to cover the required momentum range, 1-100 GeV/$c$ . The first detector uses aerogel and $\rm C_4 F_ {10}$ gas as radiators. The second detector, used for high momentum particles, is placed after the magnet and has $\rm C F_4$ gas as radiator. The Cherenkov light is detected with planes of Hybrid Photon Detectors (HPD's) placed outside the spectrometer acceptance. \item Calorimeters\\ The calorimeter system consists of a preshower detector followed by electromagnetic and hadronic calorimeters. It also serves as the initial part of the muon filter system. The cells of the Preshower detector are made up from 12 mm-thick lead plates sandwiched by square scintillators, 15 mm thick. For the electromagnetic part a Shashlik calorimeter is used since only modest energy resolution is required. The hadron calorimeter is based on a scintillating tile design similar to that developed for the ATLAS experiment. \item Muon System\\ The Muon system consists of tracking stations and absorber layers. The first tracking station is in front of the calorimeter system, which acts as the first absorber. Behind the calorimeter system, there are four tracking stations with Fe absorber walls in between. An additional Fe absorber is placed after the last tracking station against the muon background from the accelerator tunnel. Multi Wire Proportional Chambers are used everywhere except in the region close to the beam pipe of the first station where Triple-GEM chambers are used. \item Trigger\\ The LHCb trigger has two decision levels. Using custom made electronics, the first decision is made based on high transverse momentum hadrons or electrons found in the calorimeter system, or muons found in the muon system, at the bunch crossing rate of 40 MHz. All data from the detector are then read out at a rate of 1 MHz and sent to a CPU farm for further event reduction. For this purpose, all the detector information is available. With a rate of 2 kHz, events which include calibration data are stored for offline analysis. \end{itemize} Due to the large production cross section for b-$\rm \overline{ b}$ pairs (500~$\rm \mu b$) and efficient trigger, the LHCb experiment requires only a much lower luminosity ($2 \times 10^{32}$~$\rm cm^{-2} s^{-1}$) than the nominal LHC luminosity ($10^{34}$~$\rm cm^{-2}s^{-1}$) for its physics programme. The experiment therefore can reach its full physics potential from the beginning of LHC operation. The luminosity at the LHCb interaction point can be locally tuned so that the experiment is able to continue its physics programme when the machine reaches the nominal operating condition. \end{document