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The MacKenzie Basin, located in the District of MacKenzie in the southern part of the Northwest Territories, Canada, includes a thick succession of Middle Devonian strata. This basin, bordered to the east by the Canadian Shield and to the south by the Tathlina Uplift, was directly connected to the open ocean that lay to the northwest. Comprehensive facies analyses of the Chinchaga Formation, Lonely Bay Formation, Horn Plateau Formation, and Horn River Formation, which formed in this basin during the Early and Middle Devonian, shows that sedimentation was largely controlled by eustatic sea level changes. Accordingly, these strata reflect a long period of sea level rise during which shallow water evaporite deposition in the Eifelian was followed by open marine conditions that led to reef growth in the Givetian, and ultimately pelagic shale deposition in the Frasnian. The Horn Plateau Formation is comprised of numerous isolated reefs that are located along northeast-southwest direction over a distance of 350 km along the MacKenzie Basin ramp. Reefs in the southwest are dominated by stromatoporoids whereas those in the northeast are dominated by corals. Although difficult to prove, it appears that the distribution of the stromatoporoids and corals may have been controlled by nutrients coming from coastal upwelling or runoff from the exposed Canadian Shield. Effects of early diagenetic processes were evident on the MacKenzie Basin ramp in an intensely bioturbated facies in the Lonely Bay Formation. Burrows from this facies are dolomite-filled further down the ramp and calcite-filled proximal to the Canadian Shield in the east. Anoxic conditions and the presence of sulphate reducing bacteria may have promoted early dolomite formation in the burrows located in deeper water. Burrows further up the ramp were oxygenated and show evidence of input from the exposed Canadian Shield, both of which may have inhibited low-temperature dolomite formation.

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This thesis deals with the stratigraphy and brachiopod systematic palaeontology of the latest Devonian (Famennian) to Early Permian (Kungurian) sedimentary sequences of the Tarim Basin, NW China. Brachiopod faunas of latest Devonian and Carboniferous age have been published or currently in press in the course of the Ph.D candidature and are herein appendixed, while the Early Permian brachiopod faunas are systematically described in this thesis. The described Early Permian brachiopod faunas include 127 species, of which 29 are new and 12 indeterminate, and six new genera (subgenera) are proposed; Tarimella, Bmntonella, Marginifera (Arenaria), Marginifera (Nesiotia), Baliqliqia and Ustritskia. A new integrated brachiopod biostratigraphical zonation scheme is proposed, for the first time, for the latest Devonian-Early Permian sequences of the entire Tarim Basin on the basis of this study as well as previously published information (including the Candidate's own published papers). The scheme consists of twenty three brachiopod acm biozones, most of which replace previously proposed assemblage or assemblage zones. The age and distribution of these brachiopod zones within the Tarim Basin and their relationships with other important fossil groups are discussed. In terms of regional correlations and biostratigraphical affinities, the Late Devonian to Early Carboniferous brachiopod faunas of the Tarim Basin are closest to those from South China, while the Late Carboniferous faunas demonstrate strong similarities to coeval faunas from the Urals, central Asia, North China and South China. During the Asselian-Sakmarian, strong faunal links between the Tarim Basin and those of the Urals persisted, while at the same time links with central Asia, North China and South China weakened. On the other hand, during the Artinskian-Kungurian times, affinities of the Tarim faunas with the Urals/Russian Platform rapidly reduced, when those with peri-Gondwana (South Thailand, northern Tibet) and South China increased. Thirty lithofacies (or microfacies) types of four facies associations are recognised for the Late Devonian to early Permian sediments. Based on detailed lithostratigraphy, biostratigraphy and facies analysis, 23 third-order sequences belonging to four supcrsequences are identified for the Late Devonian to Early Permian successions, from which sea-level fluctuation curves are reconstructed. The sequence stratigraphical analysis reveals that four major regional regressions, each marking a distinct supersequence boundary, can be recognised; they correspond to the end-Serpukhovian, end-Moscovian, late Artinskian and end-Kungurian times, respectively. The development of these sequences is considered to have been formed and regulated by the interplay of both eustasy and tectonism. Using the system tract of a sequence as the mapping time unit, a succession of 47 palaeogeographical maps have been reconstructed through the Late Devonian to Early Permian. These maps reveal that the Tarim Basin was first immersed by southwest-directed (Recent geographical orientation) transgression in the late Famennian after the Caledonian Orogeny. Since then, the basin had maintained its geometry as a large, southwest-mouthed embayment until the late Moscovian when most areas were the uplifted above sea-level. The basin was flooded again in late Asselian-Artinskian times when a new transgression came from a large epicontinental sea lying to its northwest. Thereafter, marine deposition was restricted to local areas (southwestern and northwestern margins until the late Kungurian, while deposition of continental deposits prevailed and continued through the Middle and late Permian into the Triassic.

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Uranium-lead (U-Pb) geochronology and Hafnium (Hf) isotope geochemistry of detrital zircons of the Harmony Formation of north central Nevada provide new insights into the tectonic evolution of the Late Paleozoic western Laurentian margin. Using laser-ablation inductively coupled plasma mass spectrometry, 10 arenite samples were analyzed for U-Pb ages, and 8 of these samples were further analyzed for Hf isotope ratios. Three of the sampled units have similar U-Pb age peaks and Hf isotope ratios, including a 1.0-1.4Ga peak with epsilon Hf values of +12 to -3 and a 2.5-2.7Ga peak with epsilon Hf values of +7 to -5. The remaining seven samples differ significantly from these three, but are similar to one another; having age peaks of 1.7-1.9Ga with epsilon Hf of +10 to -20 and age peaks of 2.3-2.7Ga with epsilon Hf of +6 to -8. The data confirm the subdivision of the Harmony Formation into two petrofacies: quartzose (Harmony A) and feldspathic (Harmony B). The three samples with 1.0-1.4 and 2.5-2.7Ga peaks are the Harmony A, which originated in the central Laurentian craton. The other seven samples are the Harmony B, which originated in eastern Alberta-western Saskatchewan, north of the Harmony A source. We propose that all Harmony Formation strata were deposited near eastern Alberta and subsequently tectonically interleaved with Roberts Mountains allochthon strata. We interpret that the entire package was tectonically transported south along the western Laurentian margin and then emplaced eastward onto the craton during the Late Devonian-Early Mississippian Antler orogeny.

Drilling predation presents a rare opportunity to quantify ecological and evolutionary interactions in the fossil record. To date, most of this research has been done on Late Mesozoic and Cenozoic deposits, and large-scale studies have focused on temporal rather than spatial patterns. However, drilling predation occurs throughout the entire Phanerozoic, and patterns in spatial variability may mask secular trends. These issues are addressed in a series of projects presented here. An extensive survey of museum specimens and bulk materials indicate that drilling predation in Late Paleozoic brachiopod prey is relatively rare (<1% of fossil specimens are drilled) but widespread and continuously present. The intensity of drilling predation on Late Paleozoic bivalve mollusks (this is the first quantitative report of this kind) is much higher than that seen for contemporaneous brachiopod prey, but lower than what is common for Late Mesozoic and Cenozoic mollusks. Drilling intensity varies significantly between taxa and across localities, (e.g., a sample of the Pennsylvanian brachiopod Cardiarina cordata produced an estimate of 32.7%, which is an intensity similar to that seen in Cenozoic mollusks and the highest yet reported for any brachiopod). However, data for the brachiopod genus Composita, which appears to be a preferred brachiopod prey in many Late Paleozoic assemblages, show that although this genus is subject to drilling predation continuously throughout its geologic range, the over all intensity is very low (less than 1%) and at no time does the intensity ever exceed 10%. Spatial variation in Miocene assemblages from Europe is shown to be on the same order as temporal variation throughout the Cenozoic. Significant variation in drilling intensity is also documented for the Paleozoic. This emphasizes the point that to fully understand patterns of predation through time, both spatial and temporal distribution must be considered. / Ph. D.

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