Study of the evolution of crocodile-line archosaurs (Pseudosuchia) has intensified recently. Along with this increased attention have come dramatic changes in our understanding of the evolutionary relationships of the group. Modern crocodylians are generally similar-looking with most of their morphological disparity expressed in their skulls. However, phylogenetic studies have demonstrated that skull shape is highly convergent, with similar skull forms arising in distantly related lineages. Yet, crocodylians and their relatives (crocodyliforms) have traditionally been divided into taxonomic and ecomorphological groups based on skull morphology. Many of the crocodyliform groups with the most controversial affinities also share the same skull shape (long, slender snouts). This issue was assessed from multiple angles including geometric morphometrics, detailed assessment of anatomy, and expanded phylogenetic analyses. Previously proposed skull shape categories were based largely on assessments of snout length and width but ignored important features in the rest of the skull. I applied two-dimensional geometric morphometrics including landmarks and sliding semilandmarks to characterize the skull shape of 131 extant and extinct crocodyliforms. Newly developed shape categories based on normal mixture analysis show a weak correlation to phylogeny corroborating hypotheses of convergent evolution. Different skull shapes are not evenly distributed through time and the results presented here indicate that crocodyliform disparity peaked in the Late Cretaceous followed by a dramatic decline in the Maastrichtian (preceding the end-Cretaceous extinction). The emptied region of morphospace, exemplified by a short and narrow snout, was never explored by crown-group crocodylians. Modern crocodylian disparity is much lower than in the Cretaceous, but is similar to Jurassic levels. The recent increases in knowledge of pseudosuchian relationships have important implications for phylogenetic studies of crocodylomorphs. Previous studies of crocodylomorph and crocodyliform relationships have rooted trees on outgroups that in many cases are either quite distantly related to the group under study (e.g. Gracilisuchus stipanicicorum, a basal suchian), or could actually belong within the ingroup. Thalattosuchia, one of the earliest occurring groups of crocodyliforms (Early Jurassic, Sinemurian), has a controversial phylogenetic position relative to other crocodyliforms — they are recovered in either a basal position, nested high up in the tree, or sister to Crocodyliformes. Thalattosuchians lack several crocodyliform apomorphies, but share a longirostrine skull shape with highly derived neosuchian groups. These groups share a similar ecological habit, suggesting the derived position of thalattosuchians may be the result of convergent evolution. Several of the "shared" characters uniting these groups are due to ambiguously worded character state definitions - structures that are superficially similar (though anatomically different in detail) are scored the same. A new analysis of crocodylomorphs recovers the thalattosuchians as the sister-group to Crocodyliformes outside of the "protosuchians" and all other crocodyliforms. It is also demonstrated that the addition of the rauisuchid Postosuchus kirkpatricki to the outgroup of previously published analyses draws thalattosuchians down the tree as the sister-group of Crocodyliformes. These results demonstrate the importance of careful outgroup sampling, and highlight issues with current descriptions of morphological characters.

Carboniferous sedimentary units unconformably overlie eclogite-facies Paleoproterozoic basement gneisses in Holm Land, North-East Greenland and record change in provenance as a function of tectonic disturbances that happened during mid-Carboniferous time. The Visean Sortebakker Formation contains arkosic sandstone with abundant gneissic lithic grains and a heavy mineral suite dominated by titanite, apatite and rutile but lacking garnet. ICPMS U-Pb ages on detrital zircons define dominant age groups at 1.75 and 1.98 Ga, broad peaks at 1.1-1.5, 2.2-3.0 Ga, and a few Caledonian metamorphic ages between 350 and 400 Ma. In contrast, Moscovian arkosic sandstone of the unconformably overlying Kap Jungersen Formation contains a heavy mineral suite of titanite, apatite, rutile, garnet, and epidote and gives ICPMS U-Pb detrital zircon ages of 390 Ma, 1.75 Ga and 1.98 Ga. CL images demonstrate that low-U rims on some zircons record Caledonian metamorphism. The dominant peaks in all samples are most compatible with derivation from the underlying gneissic basement of the North-East Greenland eclogite province. The 1.75 and 1.98 Ga peak ages match the protolith age of the Paleoproterozoic calc-alkaline arc related basement. The CL-bright, low-U metamorphic rims yield ages of 335 to 410 Ma that are consistent with metamorphic ages observed in the Paleoproterozoic basement rocks. The large number of discordant grains observed in the detrital populations (23-47%) in all samples is similar to age spectra from basement samples as well. Grains that define broad peaks at 1.1-1.5, 2.2-3.0 Ga in the Sortebakker samples are interpreted to be from metasedimentary units in the structurally higher Caledonian nappes (e.g., Independence Fjord Group). These grains make up 30-35% of the population in the basal units, diminishing to 10% up section. The Caledonian metamorphic grains, appearance of garnet and lack of the 1.1-1.5 and 2.2-3.0 Ga signatures indicate that the basal Kap Jungersen Formation lacked input from sources external to the underlying basement. Reappearance of the 1.1-1.5 and 2.2-3.0 Ga signatures higher in the section probably reflects recycling from the underlying Sortebakker section. Results of this study clearly demonstrate that dating of metamorphic rims of detrital zircons greatly enhances characterization of provenance and depositional history.

Morphology of corals of the Late Ordovician through mid-Silurian Fish Haven and Laketown Formations were analyzed to document adaptations to inferred enviromental conditions, i.e., (bathymetry, illumination, sedimentation, currents, and energy), under which their enclosing sediment was deposited. Specimens and data were collected from six sites. Insoluble-residue tests were performed on the corals' matrices. Individual corallites of radial-lensoidal corals radiate in all directions. Vertical growth, however, was restricted in turbulent conditions. Umbrellic, radial-lensoidal corals feature downward facing corallites, considered to be an adaptation to a well illuminated environment. On tabular lensoidal corals, constituent corallites faces exclusively upward, an orientation needed under relatively poor illumination. Orientation of these coralla at oblique angles to bedding planes and to other coralla signify soft-sediment slumping or edge-first sinking into a semi-fluid substrate. Hemispherical coralla prevailed under moderately high energy condition and negligible sedimentation. Conic coralla, formed during prodigious sediment accumulation, are extreme modifications of hemispherical coralla. The lower the rate of sediment accumulation, the less acute the angle of the apex (budding center of the 11cone"). Circumrotary corals, or those that are distinguished by corallites radiating in virtually all directions, are considered to have dwelled in heavy surf, by analogy to certain modern corals. Composite corals, those that exhibit more than one morphotype or a repetition of the same morphotype, reflect a change in growth during the life of the colony. Internal features of individual corallites were examined and measured. Most of the corals in this study feature corallites suggestive of low-sediment rejection capability. Corallite packing arrangements, as well as indicating cleansing ability, are interpreted as adaptations to different levels of hydraulic stress. Several explanations are given to explain the lack of correlation between corallite variability and external morphology. Genetic differences may have resulted in differing variabilities of calical widths of different species under comparable environmental conditions (as indicated by intramorphotypic analyses of variance). Differences in variability of tabulae spacing between tabular and radial coralla are attributed to the preponderance of lateral budding in the former mrophotype. Frequent budding is considered to have been concurrent with slow upward growth, reflected by narrow tabulae spacings. A high energy fauna is represented by the abundance of tabulate and compound rugose, radial-lensoidal, and circumrotary coralla. These corals and their associated organisms in the conununity seemingly dwelled on a carbonate bank. A favositid-dominated community provides evidence of variable sedimentation rates by the presence of diverse morphologies. Hemispherical coralla predominate indicating generally high energy and low to negligible sedimentation rates. Two of the sites were dominated faunally by hemispherical, halysitid corals featuring cone-shaped bases. They are considered reflective of moderate energy and moderate sediment accumulation. Tabular halysitid and favositid corals whose basal dimensions are oriented obliquely to one another and/or bedding planes signify negligible sedimentation and placid, relatively deep water conditions. These corals dominated two collecting sites. Based on the patchiness of the occurrence of the coral assemblages, the Late Ordovician and Silurian sea floor is considered to have been an uneven, heterogeneous surface. Shallow water shelf conditions are inferred. Fluctuations in sea level elicited the observed variability in coral morphology.

When Lake Bonneville spilled through Red Rock Pass at the north end of Cache Valley, the major part of the lake in Salt Lake Valley had to drain from west-to-east through Cutler Dam Quadrangle. Here two major saddles connect the two valleys: 1. Bear River Narrows, at about 4380 feet; and 2. Cache Butte-Wellsville Mountain Pass 4.2 miles south, at about 4970 feet. Spillover levels at both places are cut into older rocks. The following history is inferred: 1. Rise of lake to Bonneville level (5180 feet) or slightly higher ; 2. Spillover and downcutting at Red Rock Pass to a point above 4940 feet; eastward flow through Bear River Narrows and Cache Butte-Wellsville Mountain Pass; 3. Red Rock Pass abandoned; westward flow through Bear River Narrows only as the lake level continued to fall; lowest point unknown; 4. Rise of lake above 4940 feet; spillover and renewed cutting of Red Rock Pass down to Provo level (4800 feet); eastward flow through Bear River Narrows; 5. Rapid fall of lake level.

Bear Lake Valley represents an eastward extension of Basin and Range structure into the Middle Rocky Mountain province. This study examines the surficial geology of the Bear Lake Valley, focusing on that portion which lies in Utah.

The Dry Lake section of the Brazer formation, totalling 3100 feet in thickness, is an excellent exposure containing an abundance of fossils many of which are well preserved. The fauna indicates that the formation is to be correlated with the Upper Iowan end Chester series of the type Mississippian system in the Mississippi Valley section. Substantial fossil evidence indicates the following correlation for the Brazer formation members. The C unit represents the western equivalent of the Middle Meramec group, i.e., the Salem and St. Louis limestones. The D member is decidedly Ste. Genevieve in general faunal aspects but, because of the presence of some Chester fauna, it must be considered as a transition between the Meramec and New Design groups. The F member is, in most respects, typically equivalent of the Chester series. There are also relationships to tho fauna or the Batesville and Moorefield deposits of Arkansas, to the Lower Caney shale of Oklahoma, and to the Paradise formation of Southeastern Arizona.

The purpose of this research was to continue the assessment of the low-temperature geothermal resources of Cache Valley, Utah initiated by the Utah Geological and Mineral Survey. Field work consisted of locating 90 wells and springs throughout the study area, collecting water samples for later laboratory analyses, and field measurement of pH, temperature, bicarbonate alkalinity, and electrical conductivity. Na+, K+, Ca+2 , Mg+2 , SiO2, Fe, SO4-2, Cl-, F-, and total dissolved solids were determined in the laboratory. Temperature profiles were measured in 12 additional, unused wells. Thermal gradients calculated from the profiles were approximately the same as the average for the Basin and Range province, about 35°C/km. One well produced a gradient of 297°C/k.m, most probably as a result of a near-surface occurrence of warm water. Possible warm water reservoir temperatures were calculated using both the silica and the Na-K-Ca geothermometers, with the results averaging about 50-100°C. If mixing calculations were applied, taking into account the temperatures and silica contents of both warm springs or wells and the cold groundwater, reservoir temperatures up to about 200°C were obtained. Considering measured surface water temperatures, calculated reservoir temperatures, thermal gradients, and the local geology, most of the Cache Valley, Utah area is unsuited for geothermal development. However, the areas of North Logan, Benson, and Trenton were found to have anomalously warm groundwater in comparison to the background temperature of 13.0°C for the study area. The warm water has potential for isolated energy development but is not warm enough for major commercial development.

General Statement The James Peak quadrangle is a topographic map unit of the Geological Survey of the U. S. Department of Interior (Plate 1). It covers 7 1/2 minutes of latitude and longitude at a scale of 1:24, 000 or 1 inch to 2, 000 feet. It is bounded by lat 41°22'30" N. and lat 41°30' N. and long 111°45' W. and long 111 °52 '30" W The quadrangle includes 56 square miles and has maximum relief of about 4, 300 feet. The James Peak quadrangle is located in northern Utah between the Wasatch Range on the west and the Bear River Range on the east (Figure 1). The eastern part includes the western flank of the Bear River Range. James Peak, 9, 500 feet in elevation, is in the southeastern part of the quadrangle and forms an imposing landmark as seen from Cache Valley to the north and Ogden Valley to the south. The area of the James Peak quadrangle is represented on various generalized geologic maps (Hardy and Williams, 1953; Stokes, 1963); how­ever, no concerted attempt has been made to study the Paleozoic stratigraphy of the area. Such an investigation is basic to an understanding of the geologic structure of northern central Utah and might also help resolve numerous stratigraphic problems of the region. The purpose of this investigation is to determine the lithology and thickness of the Paleozoic stratigraphic units present within the James Peak quadrangle. Previous investigations A preliminary map constructed by Ezell (1953, plate 9) includes the northwestern corner of the quadrangle but unfortunately leaves an internal area unmapped. The entire quadrangle was represented on a regional geo­logic map of northern Utah prepared by Hardy and Williams (1953). Certain aspects of the structure have been discussed briefly by Hardy (1957). None of these studies are based on an adequate analysis of the Paleozoic stratigraphy. The stratigraphy of certain surrounding areas is known in considerable detail. Williams (1948, 1958) studied the Paleozoic rocks of the Logan quad­rangle, Utah-Idaho, to the north and also mapped the quadrangle at a scale of 1:125, 000. The Paradise quadrangle, within the Logan quadrangle and just north of the James Peak quadrangle, has recently been mapped by Mullens and Izett (1964). The higher parts of the Wasatch Range to the west of the James Peak quadrangle have been described in general terms by Blackwelder (1910) and Eardley (1944). Finally, the quadrangle immediately east of the James Peak quadrangle is the subject of a thesis by Hafen (1961). Present understanding of regional Paleozoic stratigraphy is based on a great many detailed studies of more distant areas except for Blacksmith Fork Canyon which is a classic area of Cambrian stratigraphy. This locality is within the Logan quadrangle. Reference is made to many of these reports in the discussion of individual formations of the James Peak quadrangle. Geologic features Stratigraphic units of Paleozoic age are known largely from outcrops in the central and northwestern parts of the James Peak quadrangle (Plate 1). A succession, which dips generally northward, is found on both the eastern and western sides of the South Fork of Little Bear River (Table 1). It extends from Middle Mountain northward nearly to the margin of the quadrangle and from Public Grove Hollow northward to the lower part of Fourmile Canyon and to the northwestern corner of the quadrangle. A narrow area of Paleozoic rocks, in general poorly exposed and structurally complex, is present along the eastern margin of the quadrangle. James Peak and the southwestern part of the quadrangle are underlain by quartzites of presumed Precambrian age. The James Peak quadrangle is divided into three blocks by two north­south faults or fault zones: (1) western block, (2) central block, and (3) eastern block. James Peak is in the southern part of the central block; Middle Mountain is in the middle part of this same block near the western side. A fault or fault zone extends north-south along both the western side of James Peak and Middle Mountain. The eastern block forms the flank of the Bear River Range with McKenzie Mountain near the northern end. The front of the Bear River Range is distinctly limited by a fault or fault zone which extends southward between the main part of the range and James Peak to the west. Precambrian rocks, striking about east-west and dipping northward, are found in the southern part of the western block. The Prospect Mountain quartzite of Cambrian age, with essentially the same strike and dip as the Precambrian units, extends across the block from west to east; however, it is covered at the eastern side by the Salt Lake formation of Tertiary age. The Prospect Mountain is followed in normal stratigraphic succession by the Pioche(?) formation and younger Cambrian units. These are limited by an east-west fault, in Dips Hollow, which probably extends completely across the block. The Prospect Mountain is at the surface again north of this fault at the eastern side of the block. The Prospect Mountain, north of the fault, is over­lain by the Pioche(?) formation and 16 younger units of Paleozoic age, The northern part of the block, however, is largely covered by the Salt Lake formation. The southern part of the central block, James Peak, is formed of Precambrian rock but with north-south strike and east dip. A broad valley which extends across the block just north of James Peak and northward to the edge of the quadrangle is underlain by the Salt Lake formation which certainly covers various units of Paleozoic age. Middle Mountain, therefore, is isolated by a cover of the Salt Lake formation, except at its western side where it is bounded by a north-south fault separating the central and western blocks. The Prospect Mountain quartzite crops out at the southern end of Middle Mountain and is overlain in turn northward by 11 formations of Paleozoic age. The youngest unit, at the northern end, is the Laketown dolo­stone of Silurian age. The rocks of Middle Mountain strike west-northwest and dip northward. The part of the eastern block, south of Davenport Creek and east of James Peak, is not fully understood. Here unidentified Cambrian units, Laketown dolostone, and Garden City formation are separated by several more or less vertical north-south faults. North of Davenport Creek is a small syncline, with north-south axis, in the Garden City formation of Ordovician age. The Garden City is followed northward by the Swan Peak formation, Lodgepole limestone, and finally, making the higher part of McKenzie Moun­tain, the Great Blue limestone. These units, for the most part, strike north­south and dip gently westward. Field Work The major part of the field work was done in a two-month period during the summer of 1962. Additional time was spent in the field during the summer of 1963. The stratigraphic sections were measured with a 50-foot steel tape. A Brunton compass was used to determine dip, slope, and azimuth. Thick­nesses were subsequently computed. The terminology for bedding, used in this report, is that of McKee and Weir (1953, p. 381-389) as modified by Ingram (1954, p. 938). The Wentworth grade scale was used to describe elastic rocks. It was also used, as adapted by Payne (1942, p. 1, 706), for the crystalline carbonate rocks. Color was determined with reference to the Rock-Color Chart (Goddard, 1951).

Deformation mechanisms in the footwall of the Willard thrust fault, northern Wasatch Range, Utah, change from dominantly plastic to dominantly cataclastic (both microscopically and macroscopically) in the Ophir Formation and Maxfield Limestone before the thrust begins to ramp laterally upsection southward, just to the north of the North Ogden Canyon field area. This transition in compressional deformation style and mechanism is located within a lateral distance of 3.2-kilometers along the 22-kilometer long trace of the thrust fault. Between Willard Canyon and North Ogden Canyon penetrative deformation is localized within 200 meters of the thrust surface and is characterized by transposed bedding, solution cleavage parallel to bedding, a northeast- to northwest-dipping foliation, and tight isoclinal folds with axes plunging generally northward. A fracture overprint in the footwall is present throughout the study area. The transition in deformation mechanism and style suggests that footwall deformation is dependent on the sensitive response of limestone and shale to increased pressure and temperature conditions and also the presence of a lateral ramp in the footwall of the Willard thrust. Data from a hangingwall sequence diagram and a stratigraphic displacement diagram suggest the Taylor and Ogden thrusts formed prior to the Willard thrust (the roof thrust) and their sequential geometrical evolution may have been influenced by preexisting rifts in the underlying crystalline basement rock. It is proposed that early Cretaceous movement of the Willard thrust sheet over the structurally lower and older Taylor and Ogden thrust sheets resulted in the formation of a recumbent syncline overturned to the east, a southward rising lateral ramp in the footwall of the Willard thrust, a lateral change in footwall deformation, and the anomalous east-west trending canyons that cut through the Willard thrust complex.

The main objective of the present study is to provide a greater understanding of the strata referred to as the Silurian System in north-central Utah and southeastern Idaho and to serve as a basis for comparative regional studies in Silurian stratigraphy. It may be properly classified as a detailed reconnaissance of limited areal extent involving a single stratigraphic unit . It is based on field work done intermittently during the summer months of 1963-65 and laboratory and library work accomplished during the intervening winter months.