989 resultados para Jurassic Period


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Agreed-upon procedures report on the City of Walcott, Iowa for the period July 1, 2014 through June 30, 2015

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Agreed-upon procedures report on the City of Pleasanton, Iowa for the period July 1, 2014 through June 30, 2015

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Report on a review of selected general and application controls over the Iowa Department of Human Services’ Iowa Collection and Reporting System (ICAR) for the period April 1, 2013 through April 24, 2013 and April 1, 2014 through April 29, 2014

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Report on a review of selected general and application controls over the Iowa Department of Human Services’ Targeted Case Management System (TCM) for the period March 31, 2014 through April 18, 2014

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Report on a review of selected general and application controls over the Iowa Department of Human Services’ Kindertrack System for the period March 30, 2015 through April 17, 2015

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Organic geochemical and stable isotope investigations were performed to provide an insight into the depositional environments, origin and maturity of the organic matter in Jurassic and Cretaceous formations of the External Dinarides. A correlation is made among various parameters acquired from Rock-Eval, gas chromatography-mass spectrometry data and isotope analysis of carbonates and kerogen. Three groups of samples were analysed. The first group includes source rocks derived from Lower Jurassic limestone and Upper Jurassic ``Leme'' beds, the second from Upper Cretaceous carbonates, while the third group comprises oil seeps genetically connected with Upper Cretaceous source rocks. The carbon and oxygen isotopic ratios of all the carbonates display marine isotopic composition. Rock-Eval data and maturity parameter values derived from biomarkers define the organic matter of the Upper Cretaceous carbonates as Type I-S and Type II-S kerogen at the low stage of maturity up to entering the oil-generating window. Lower and Upper Jurassic source rocks contain early mature Type III mixed with Type IV organic matter. All Jurassic and Cretaceous potential source rock extracts show similarity in triterpane and sterane distribution. The hopane and sterane distribution pattern of the studied oil seeps correspond to those from Cretaceous source rocks. The difference between Cretaceous oil seeps and potential source rock extracts was found in the intensity and distribution of n-alkanes, as well as in the abundance of asphaltenes which is connected to their biodegradation stage. In the Jurassic and Cretaceous potential source rock samples a mixture of aromatic hydrocarbons with their alkyl derivatives were indicated, whereas in the oil seep samples extracts only asphaltenes were observed.

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Report on a special investigation of the City of Hornick for the period July 1, 2003 through June 30, 2014

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Report on a special investigation of the City of Garwin Ambulance Service for the period July 1, 2010 through March 31, 2015

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The Jebel Ressas Pb-Zn deposits in North-Eastern Tunisia occur mainly as open-space fillings (lodes, tectonic breccia cements) in bioclastic limestones of the Upper Jurassic Ressas Formation and along the contact of this formation with Triassic rocks. The galena-sphalerite association and their alteration products (cerussite, hemimorphite, hydrozincite) are set within a calcite gangue. The Triassic rocks exhibit enrichments in trace metals, namely Pb, Co and Cd enrichment in clays and Pb, Zn, Cd, Co and Cr enrichment in carbonates, suggesting that the Triassic rocks have interacted with the ore-bearing fluids associated with the Jebel Ressas Pb-Zn deposits. The delta(18)O content of calcite associated with the Pb-Zn mineralization suggests that it is likely to have precipitated from a fluid that was in equilibrium with the Triassic dolostones. The delta(34)S values in galenas from the Pb-Zn deposits range from -1.5 to +11.4%, with an average of 5.9% and standard deviation of 3.9%. These data imply mixing of thermochemically-reduced heavy sulfur carried in geothermal- and fault-stress-driven deep-seated source fluid with bacterially-reduced light sulfur carried in topography-driven meteoric fluid. Lead isotope ratios in galenas from the Pb-Zn deposits are homogenous and indicate a single upper crustal source of base-metals for these deposits. Synthesis of the geochemical data with geological data suggests that the base-metal mineralization at Jebel Ressas was formed during the Serravallian-Tortonian (or Middle-Late Miocene) Alpine compressional tectonics.

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1908-1910 Iowa Library Commission Report made to the Governor of Iowa.

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1914-1916 Iowa Library Commission Report made to the Governor of Iowa.

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1916-1918 Iowa Library Commission Report made to the Governor of Iowa.

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1918-1920 Iowa Library Commission Report made to the Governor of Iowa.