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New brachiopod materials from the lower Cambrian (Global Stage 3 and lower Stage 4) of Esmeralda County, Nevada are described and their age distribution and diversity is discussed. The specimens originate from the Fritzaspis, “Fallotaspis”, “Nevadella” and Bonnia-Olenellus biozone which in the area correspond to the Campito Formation and the overlying Poleta Formation. As the specimens from the Gold Coin Member (Begadean Series) and the Montenegro Member (Waucoban Series) of the Campito Formation encompass the oldest samples, they were therefore prioritised as there was not enough time to describe all the specimens. The oldest known trilobites from Laurentia have previously been reported from the Gold Coin Member and it is of interest to determine if the brachiopods from the same member also are the oldest known from Laurentia.As many specimens are poorly preserved, especially the ones from coarse siliciclastic intervals, the determination of their systematic position is somewhat aggravated. Despite this, a diverse fauna including Lingulida, Obolellida, Naukatida, Kutorginida, Orthida and stem-group brachiopods have been successfully identified. A total of 16 taxa were noted for the Campito fauna, including the problematic and rare genera Swantonia and Spinulothele but unfortunately little new information could be gained regarding the characters for these rare genera. Four genera are reported for the first time from the area, not including material described under open nomenclature. / Under den geologiska tidsåldern Kambrium (542-488 miljoner år sedan) uppträder de första fossilerna av djurgruppen brachiopoder, eller armfotingar som de också kallas, tillsammans med många andra djurgrupper. Få platser i Laurentia (paleo-kontinent bestående av nutidens Nordamerika och Grönland) finns kvar som har bevarat de tidigaste förekommande brachiopod fossilerna. Esmeralda län i Nevada är en sådan plats och det här har det även spekulerats att Laurentias absolut äldsta brachiopod fossil skulle kunna hittas där. Denna avhandling fokuserar på att studera dessa brachiopod fossil från Nevada. När åldern för de äldsta studerade brachiopoderna (Begadean I ålder) i denna avhandling jämfördes med tidigare dokumenterade åldrar för äldre lägre Kambrium brachiopod fossiler stod det klart att dessa är de äldsta brachiopod fossilerna som hittats hittills.Många nya fossil prover har samlats in av J.S. Hollingsworth under en längre tid från Nevada och beskrivs häri. De nya fossilen innefattar både sällsynta släkten, så som Swantonia samt Spinulothele, och släkten som inte har hittats i Esmeralda län tidigare. Tyvärr erhölls lite ny information beträffande de sällsynta släktenas morfologiska egenskaper. Upptäkterna om de nya släkterna i området skulle kunna hjälpa oss att bättre kunna rekonstruera brachiopod faunan från Nevada samt att förstå spridningen av olika brachiopod grupper i framtiden.

Svalbard represents the uplifted and exhumed northwest corner of the Barents Sea Shelf. Pre-Carboniferous rocks of Svalbard are divided into the Eastern, Northwestern and Southwestern Terranes, were amalgamated during the Caledonian Orogen and are separated by north-south-trending strike-slip faults. Even though our knowledge of Svalbard’s pre-Carboniferous history has increased dramatically during the last two decades, a major issue remains: Where did the different tectonostratigraphic terranes of Svalbard originate? The answer to this question has profound significance for the entire eastern Laurentian margin, which spans two supercontinent cycles, from the amalgamation and breakup of Rodinia to the amalgamation of Pangea. This thesis constrains the tectonothermal evolution of Svalbard’s Northwestern Terrane (NWT) using ion microprobe and LA-ICP-MS U-Pb zircon geochronology and electron microprobe thermobarometry on metasediments, clastic rocks and granitoids. Detrital zircon age populations of metasediments from the NWT suggests that they (e.g. the Krossfjorden Group) were deposited at c. 1000 Ma in a remnant ocean basin setting outboard the Eastern Grenville Province and were subsequently deformed and intruded by Late Grenvillian granitoids during the final suturing of Rodinia. Thus, a northern branch of the Grenvillian/Sveconorwegian orogeny is not present. This older history of the NWT is extensively overprinted by Late Caledonian deformation and metamorphism, with peak metamorphic conditions of 850 °C at >6 kbars, and subsequent migmatization of the Krossfjorden Group at c. 420 Ma. Based on these data, together with the detrital zircon age population from overlying Late Silurian-Early Devonian clastic rocks, a unifying model is proposed involving fragments from the Grampian orogen and Avalonian crust originally accreted to the Laurentian margin, subsequently transported northwards along sinistral strike-slip faults during Scandian deformation. / At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 2: Submitted. Paper 4: In press.

Thesis (Ph. D.)--University of Montana, 2007. / Title from title screen. Description based on contents viewed July 19, 2007. Includes bibliographical references (p. 115-132).

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<p dir="ltr">The Intermontane terranes represent one of the largest composite accreted terranes that built the northern Cordillera. To better understand the interactions between the continental margin of Laurentia and the Intermontane terranes, this study analyzes twelve detrital zircon samples (n=3232) from a Neoproterozoic (?) to Cretaceous metasedimentary stratigraphic section exposed in central Alaska. Distinct detrital zircon populations have been identified and are interpreted to represent four stages in the geologic development of this part of western North America. Stage 1 extends from the Neoproterozoic (?) to the Early Paleozoic, and is characterized by Proterozoic and Archean detrital zircon populations that correlate with Laurentian sources of sediment. We interpret Stage 1 to represent deposition along the northwestern continental margin of Laurentia. Stage 2 extends from the Silurian (?) to the Devonian and is characterized by a dominant Devonian and Silurian detrital zircon population. We interpret Stage 2 to have been deposited in a backarc basin coeval with active volcanism as the Yukon-Tanana terrane was rifted away from the Laurentian continental margin as the Slide Mountain Ocean opened. Stage 3 extends from the Mississippian to the Jurassic and records a shift back to sediment sources with abundant Proterozoic and Archean zircon. We interpret this stage to represent deposition of Laurentian detritus along the eastern margin of the Slide Mountain Ocean basin. Stage 4 is represented by the Lower Cretaceous strata of the Manley basin that contain one major Late Triassic to Early Jurassic detrital zircon population. We interpret this population to be sourced from the syn-collisional and post-collisional Late Triassic to Early Jurassic plutons and related sedimentary basins of the Intermontane terranes that were exhumed and eroded during the closure of the Slide Mountain Ocean and the subsequent collision with the Laurentian continental margin. We interpret the Manley basin as a syn- to post-collisional extensional basin associated with regional detachment faults that formed because of crustal thickening in the collisional zone. From a regional perspective, an extensive clastic wedge prograded northward away from the zone of crustal thickening and can be identified in a series of Mesozoic sedimentary basins that are discontinuously exposed over 1500 km in southern Alaska. Results of our study better delineate the tectonic processes that set the framework for the construction of the Late Mesozoic and Cenozoic Cordilleran orogen.</p>