Las observaciones geológicas de A. Z. Helms en 1789

Entre las observaciones geológicas más antiguas de la República Argentina se tienen las realizadas en 1789 por el “geominero” alemán Anton Zacharias Helms (Hamburgo, 1751-Viena, 1803). Helms formó parte de la misión del barón de Nordenflycht a Potosí contratada por el rey de España y fue el único de los 15 mineros alemanes que dejó plasmadas sus impresiones de viaje las que publicó en Dresden en 1798 (Tagebusch einer Reise durch Peru, von Buenos Ayres an dem grossen Platastuffe, über Potosi nach Lima, der Haptstadt des Ronigreiches Peru. Dresden, Waltherrischen Losbuchhandlung, 300 p.), trabajo que fue traducido al inglés en 1806 y al francés en 1812. Es importante destacar que a diferencia de otros viajeros coloniales, Helms tenía formación específica en el campo de la geología y mineralogía habiéndose desempeñado hasta entonces como director de minas de Cracovia (Polonia), con estudios en diferentes sistemas montañosos europeos. La rigidez del contrato con el rey de España, establecido a diez años, les impedía a los alemanes dar a conocer cualquier información política o económica sobre el estado de las colonias. Helms sorteó el problema escribiendo su libro como un “diario de viaje”. Gracias a ello contamos hoy con una información única sobre distintos aspectos del territorio argentino a fines del siglo XVIII por la pluma de un observador privilegiado. Entre las principales observaciones geológicas se cuentan las realizadas en las Sierras de Córdoba sobre granitos; un censo de minas metalíferas del país; la descripción de las pizarras, calizas y areniscas rojas en Tucumán y Salta; una descripción sobre el torrente de Volcán; la tectónica de láminas imbricadas en la Quebrada de Humahuaca; y las pizarras con cuarzo auríferos y los aluviones de oro que los acompañan en Jujuy. Encontramos en el trabajo de Helms rudimentos modernos en la descripción de rocas ígneas y sedimentarias, discordancias, placeres aluviales, menas minerales y cuestiones tectónicas. Las observaciones del alemán A.Z. Helms son así las primeras de un profesional de las ciencias geológicas y mineralógicas realizado en Argentina.Anton Zacharias Helms (Hamburg, 1751- Vienna, 1803) formerly Director of the mines in Poland and late Director of the Mines in Peru, was a scientific traveler that arrived to South America in 1789. He was one of the 15 members of the Nordenflycht Mission to Potosi. During his trip to Potosi, Helms crossed Argentina from Buenos Aires to Jujuy making very important observations on the geology of the country. In 1798 he publish a book in Dresden with results of the expedition entitled: “Tagebusch einer Reise durch Peru, von Buenos Ayres an dem grossen Platastuffe, über Potosi nach Lima, der Haptstadt des Ronigreiches Peru. Dresden, Waltherrischen Losbuchhandlung, 300 p”. The diary book contain a unique set of information among them the first geological observations made in northwestern Argentina and southern Bolivia known to date. He describe granite, limestone with fossil shells, and precious metal mines from the Cordoba hills; the large saline deposit of Salinas Grandes; the “primitive granite” (igneous origin) and alternate green and red granite in the Tucuman hills. At Salta, he mentioned blue shale’s (today Puncoviscana Fm.) that is covered by red beds and limestone (Pirgua and Yacoraite Fm.). He writes “Strata of limestone, and large masses of ferruginous sandstone, are in many places superincumbent on the argillaceous slate”. Also, he describes salt beds, coal (perhaps bituminous shale) and gypsum in the upper part of the mountains. During the journey from Eastern Cordillera to the Puna region he describe surprised the tectonic of the mountains, strongly folded and faulted, completely different to other mountains in Europe. He writes “In no place does a revolution of nature appear to have been so general as in South America”. In the Helms book we find primitive references to igneous and sedimentary rocks, unconformities, alluvial placers, ore minerals and tectonic ideas. Therefore, Helms observations are the first made by a professional on geology and mineralogy, almost 100 years before Alfred Stelzner, today considered the “father” of Argentinean geology, started modern earth science studies.Fil: Alonso, Ricardo Narciso. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Salta. Facultad de Cs.naturales. Carrera de Geología; ArgentinaFil: Egenhoff, Sven. Colorado State University; Estados Unido

Layer-cake, anoxia, and other myths: A new look at the Devonian-Mississippian Bakken Formation Reservoir, Williston Basin, North Dakota

The Upper Devonian-Mississippian Bakken Formation in the Williston Basin is one of the most prolific onshore petroleum systems in the continental U.S., consisting of a middle carbonate-siliciclastic member sandwiched between two organic-rich units, the Lower and Upper Bakken shales. Dr. Egenhoff discusses the formation’s surprising departures from standard stratigraphy models and depositional models which contribute to its unique characteristics

The first geological observations in Argentina and southern Bolivia: The diary of Anton Zacharias Helms (1788/1789)

In 1788/1789, a group of German miners and mining engineers under the guidance of Baron von Nordenflycht made their way from Buenos Aires through northwestern Argentina and southern Bolivia to Potosí. Anton Zacharias Helms, a mining engineer, documented the whole trip in his diary that was published in Dresden, Germany, in 1798. These notes on the trip contain a unique set of information among them the first geological observations made in northwestern Argentina and southern Bolivia known to date. Helm's diary was translated into English and French, but never into Spanish and therefore remained unknown in Argentina and Bolivia until today.Fil: Alonso, Ricardo Narciso. Universidad Nacional de Salta; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta; ArgentinaFil: Egenhoff, Sven O.. No especifíca

The Upper Tremadocian (Ordovician) Graptolite Bryograptus: taxonomy, biostratigraphy and biogeography

The taxonomy, biostratigraphical and palaeogeographical distribution of the Lower Ordovician graptolite genus Bryograptus is evaluated. Bryograptus is recognized as a distinct triradiate anisograptid with a multiramous, pendent rhabdosome. The species of the genus Bryograptus can be interpreted as shallow water faunal elements with a strongly limited biogeographical distribution to the Atlantic Faunal Realm. Bryograptus is restricted to a narrow interval in the Upper Tremadocian, the Bryograptus Biozone of Scandinavia and South America (Argentina), making it a taxon with a high potential for precise biostratigraphical correlations. The proximal end development can be used to differentiate the genus Bryograptus from other pendent multiramous graptoloid genera with a homoplastic rhabdosome development. Characteristics of the proximal end development and structure easily differentiate these genera in relief specimens, but not in flattened material.Fil: Maletz, Jörg. Saint Francis Xavier University; CanadáFil: Egenhoff, Sven. State University Of Colorado - Fort Collins; Estados UnidosFil: Alonso, Ricardo Narciso. Universidad Nacional de Salta. Facultad de Ciencias Naturales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Biostratigraphic precision of the Cruziana rugosa group: a study from the Ordovician succession of southern and central Bolivia

Cruziana ichnospecies have been repeatedly reported to have biostratigraphic significance. This study presents a re-evaluation of the arthropod ichnotaxa of the Cruziana rugosa Group from bio- and/or lithostratigraphically well-defined Lower to Upper Ordovician siliciclastic sections of southern and central Bolivia. With the exception of Cruziana rouaulti, the ichnofaunas contain all the members of the Cruziana rugosa Group throughout the Ordovician (Arenig to Caradoc) successions in Bolivia. The Bolivian material therefore indicates that these arthropod ichnofossil assemblages are suitable for recognizing Ordovician strata in Bolivia. These findings cast doubt on their use as reliable indicators for a global intra-Ordovician (Arenig to Caradoc) biozonation of Peri-Gondwanan sedimentary successions

The complexity of mudstone diagenesis–some insight from the Tøyen Shale, Lower to Middle Ordovician, southern Sweden

The Lower to Middle Ordovician Tøyen Shale in southern Sweden, a biostratigraphically well-dated siliciclastic mudstone unit, shows 18 distinct authigenic cements that include sulfides, carbonates, silicates, clays, and phosphates. Marcasite, sphalerite, galena, and six texturally distinct types of pyrite characterize the sulfides whereas only one type of dolomite and three different generations of calcite are observed in this unit. Quartz, phosphate, and organic matter occur as only one generation each. Authigenic clay minerals are represented by chlorite and kaolinite. The paragenetic sequence of cements is subdivided into the two pre-burial carbonates, succeeded by ten relatively early burial cements, and six late burial cements, the kaolinite being the latest of them all and potentially being of Cretaceous age. Based on textural relationships, the paragenetic sequence of alterations started with dolomite precipitation followed by calcite, and then five different generations of pyrite. All eleven other phases post-date these initial seven cements in the Tøyen Shale

New Insights into Fracture Porosity Estimations Using Machine Learning and Advanced Logging Tools

Fracture porosity is crucial for storage and production efficiency in fractured tight reservoirs. Geophysical image logs using resistivity measurements have traditionally been used for fracture characterization. This study aims to develop a novel, hybrid machine-learning method to predict fracture porosity using conventional well logs in the Ahnet field, Algeria. Initially, we explored an Artificial Neural Network (ANN) model for regression analysis. To overcome the limitations of ANN, we proposed a hybrid model combining Support Vector Machine (SVM) classification and ANN regression, resulting in improved fracture porosity predictions. The models were tested against logging data by combining the Machine Learning approach with advanced logging tools recorded in two wells. In this context, we used electrical image logs and the dipole acoustic tool, which allowed us to identify 404 open fractures and 231 closed fractures and, consequently, to assess the fracture porosity. The results were then fed into two machine-learning algorithms. Pure Artificial Neural Networks and hybrid models were used to obtain comprehensive results, which were subsequently tested to check the accuracy of the models. The outputs obtained from the two methods demonstrate that the hybridized model has a lower Root Mean Square Error (RMSE) than pure ANN. The results of our approach strongly suggest that incorporating hybridized machine learning algorithms into fracture porosity estimations can contribute to the development of more trustworthy static reservoir models in simulation programs. Finally, the combination of Machine Learning (ML) and well log analysis made it possible to reliably estimate fracture porosity in the Ahnet field in Algeria, where, in many places, advanced logging data are absent or expensive