Academic literature on the topic 'Facies (Geology) Victoria'

ABSTRACT The study on a unique set of outstandingly preserved sedimentary surface textures (SSTs) found in the late Tremadocian Áspero Formation of northwestern Argentina, coupled with the sedimentological and ichnological analysis, indicate that they were formed in the intertidal to supratidal setting of a mixed-energy estuary recording storm and tide sedimentation. We recognize seven types of SSTs: probably biotic microbial mat-related SSTs (Kinneyia, elephant skin, exfoliating sandy laminae), abiotic SSTs (elliptical scours and convex parallel ridges type I “wrinkle marks” sensuAllen 1985), and problematic (convex parallel ridges type II and dot matrix texture). Elliptical scours and convex parallel ridges type I show features which indicate reworking of a cohesive sandy substrate in an intertidal or supratidal setting. Abundance of biotic SSTs with specific associated trace fossils reflect matground development and mat-grazing ichnofaunas, indicating the suppression of intense, penetrative bioturbation due to intense physicochemical stress. The “dot matrix” texture, described here for the first time, consists of a regular horizontal network of millimeter-scale pits; it appears associated with exfoliating sandy laminae, probably reflecting a mat-related origin. Three facies associations are defined through paleoenvironmental analysis. Facies association 1 is dominated by high-energy sandy and bioclastic storm deposits with tidal flat facies, and corresponds to the outer bay of a mixed-energy estuary; highly impoverished Cruziana assemblages and distal expressions of the Skolithos Ichnofacies reflect high energy and sedimentation rate. Facies association 2 shows tidal-channel and tidal-flat facies with subordinated storm deposits, representing the middle bay; impoverished Cruziana assemblages dominated by simple facies-crossing structures, with high-density monogeneric opportunistic suites, evidence physicochemical stress associated with subaerial exposure, frequent episodic deposition, high water turbidity, and/or brackish water conditions in these relatively sheltered tidal flats. Facies association 3 is formed by interdistributary-bay deposits with intercalation of channel-fill deposits in the upper part, and represents the river-dominated bay-head delta; low degrees of bioturbation in fine-grained facies indicate brackish- to fresh-water conditions. SSTs are found in tidal flat facies of facies association 2; they indicate an intertidal to supratidal environment subject to localized conditions of intense physicochemical stress. The paleoenvironmental interpretation of SSTs converges with the one performed through sedimentological and ichnological analysis, producing a robust and more detailed paleoenvironmental model for the Áspero Formation. Our study highlights the use of SSTs as a tool for supporting and refining paleoenvironmental analysis.

AbstractThe Lower Palaeozoic Bonney Pluton is a regionally extensive coarse-grained, variably megacrystic, monzodioritic to granitic body that crops out over 1000 km2 in South Victoria Land. It intruded upper amphibolite facies Koettlitz Group metasediments and interlayered orthogneisses. Magmatic fabrics are developed in the centre of the pluton by flow alignment of K-feldspars before the majority of phases had crystallized, whereas solid-state fabrics developed in the pluton margins by ductile–plastic deformation. Structures developed in the host-rocks vary around this elongate northwest–southeast-trending pluton. Upright, tight northwest–southeast-trending macroscopic folds are developed at the sides of the pluton, with axis-parallel stretching lineations and boudinage indicating strong northwest–southeast extension. Broad warps of tight macroscopic folds, and mesoscopic refolded folds, sheath folds and complicated interference patterns characterize areas at the ends of the pluton. Emplacement of the pluton involved radial expansion in a regional northeast–southwest compression, and growth predominantly in the northwest–southeast direction. Superposition of the radial expansion and regional compression resulted in an inhomogeneous strain field at a regional scale, with coaxial strain at the sides of the pluton and non-coaxial strain at the ends. Upright folds developed at the pluton's sides, and became tighter with continued coaxial deformation. Non-coaxial structures developed at the ends of the pluton and were pushed aside by the growing pluton into areas of coaxial deformation, resulting in complex folding, re-folding and sheath folds. Metamorphism of the host-rocks and migmatite development was more intense at the sides of the pluton than near the ends, possibly due to different P-T-t paths of host-rocks around syntectonic plutons.

The poly-deformed Priestley schist (Wilson Terrane) of north Victoria Land, Antarctica ranges in metamorphic grade from lower greenschist facies to upper amphibolite facies. All grades of schist have been affected by structurally controlled retrogressive H2O-CO2 fluids with 45–70 mole % CO2. The fluids have deposited quartz-carbonate veins with pyrite and chlorite or biotite in late stage structures. Veins typically constitute < 1% of the rock mass, but in one greenschist facies area > 10% of the rock is vein. Veins in higher grade schists have been boudinaged after formation, and many have been annealed. Primary fluid inclusions are preserved in veins in biotite zone schists in two localities. At one locality, entrapment of immiscible fluids (water with c. 8 and 45 mole % CO2) occurred during vein formation, at about 280–300°C and 700 ± 200 bars fluid pressure. The aqueous fluid is slightly saline (4 wt % NaCl equivalent). At the other primary fluid inclusion locality, veins were formed from a single phase fluid (c. 70 mole % CO2) at 200–350°C and 1600 ± 500 bars fluid pressure. Both these vein systems are inferred to have formed between 2 and 8 km depth, near the brittle-ductile transition. Retrogressive fluid mobility and vein formation occurred throughout schist in the Priestly metamorphic complex during uplift in the latter part of the Ross Orogeny (c. 490 Ma), following near-isobaric cooling at metamorphic depths.

AbstractPrecambrian continental extension is described in detail for the first time in the Victoria Land segment of the Transantarctic Mountains and is comparable with plume related intercontinental rifting of the Afar area, Africa. The Baronick Formation comprises igneous-derived conglomerate, marble and volcanic to sub-volcanic igneous layers. Volcanic and carbonate horizons were eroded in a fluvial or marine environment and provided debris for mass flow and slump deposits which formed in a marginal marine basin in the Precambrian. Clasts in these deposits include basalt, trachyte and comendite, and along with the interbedded volcanic layers of basalt, trachyte and quartz syenite, indicate proximity and contemporaneity of volcanic activity. Igneous layers and source rocks for clasts of the Baronick Formation have an enriched MORB chemistry and underwent albitization of calcic feldspar before erosion and conglomerate deposition. The Highway Suite forms a kilometre-scale body of gabbro and dolerite plugs and is interpreted as a slice of transitional continental oceanic crust. The chemistry of all igneous rocks suggests a continental rift environment and the associated sediments are consistent with such a setting. The Baronick Formation was locally intruded by sills of the Highway Suite; however, the main body of the Highway Suite was juxtaposed against the Baronick Formation during greenschist facies shearing before c. 551 Ma.

Well-preserved eclogites were found for the first time in Antarctica, at the Lanterman Range, northern Victoria Land. They are part of a mafic–ultramafic belt that lies between the Wilson Terrane, representing part of the palaeo-Pacific margin of Gondwana, and the Bowers Terrane, a Cambro-Ordovician volcanic are and related sediments, accreted to the margin during the Ross Orogeny. The eclogites formed at temperatures in the range 750–850°C and pressures above 15 kbar and subsequently experienced a decompressional path to low pressure amphibolite facies conditions. The formation and exhumation of eclogites and the attainment of the metamorphic peak in adjacent rock units is consistent with a plate convergent setting model at the palaeo-Pacific margin of Gondwana.

Highly deformed metaconglomerates, mafic to felsic in composition, characterize the eastern Lanterman Range (northern Victoria Land, Antarctica). In the literature the mafic and felsic metaconglomerates are known as Husky Conglomerate and Lanterman Conglomerate respectively. They occur in a 25 km long strip along the Lanterman Fault, which is a major tectonic boundary between the Wilson and the Bowers terranes. New field observations show that there is a gradual transition from mafic to felsic metaconglomerates: this supports a stratigraphical continuum from Husky to Lanterman Conglomerate, and indicates that they belong to the same sedimentary succession. Structural analysis indicates that Husky and Lanterman conglomerates suffered the same structural evolution. From all these evidences, there is no reason to distinguish two types of metaconglomerates, apart from the diversity in the lithological features. However the two terms “Husky Conglomerate” and “Lanterman Conglomerate” can be still used to refer to the mafic and felsic facies of the same sedimentary succession. On the basis of their lithology the Husky Conglomerate can be derived from the Glasgow volcanic arc, whereas the felsic clasts of the Lanterman Conglomerate may be derived from a continental basement below the Glasgow arc or from a continental block bounding the Bowers trough.

AbstractThe Lake Ambrose volcanic belt (LAVB) outcrops as a 45 km long northeast-trending belt of mafic and felsic volcanic rocks along the eastern side of the Victoria Lake Group in south-central Newfoundland. It comprises roughly equal proportions of mafic pillow basalt and high silica rhyolite, locally interbedded with epiclastic turbidites. Volcanic rocks have been metamorphosed in the greenschist facies and are extensively carbonatized.U-Pb (zircon) dates from rhyolite at two, widely separated localities give identical ages of 513 ± 2 Ma (Upper Cambrian), and this is interpreted as the eruptive age of the volcanic sequence. Primitive arc and low-K tholeiites can be recognized on the basis of major and trace element geochemistry, ranging from LREE-depleted to LREE-enriched. Geochemical variation between mafic volcanic types is interpreted predominantly to reflect contrasts in source characteristics and degree of partial melting; some variation within each geochemical type attributable to fractional crystallization can be recognized. Detailed examination of some samples indicates that the heavy REE and related elements have locally been mobile, probably as a result of carbonate complexing.The LAVB is the oldest well-dated island arc sequence in Newfoundland, and perhaps in the Appalachian–Caledonian Orogen. Its age requires modification of widely held models for the tectonic history of central Newfoundland. It is older than the oldest known ophiolite, demonstrating that arc volcanism was extant before the generation of the oldest known oceanic crust in this part of Iapetus. It further demonstrates that there was a maximum of approximately 30 Ma between the rift-drift transition which initiated Iapetus, and the initiation of subduction. This suggests that the oceanic sequences preserved in Newfoundland represent a series of arcs and back arc basins marginal to the main Iapetus Ocean, and brings into question whether the Appalachian accreted terranes contain any remnants of normal mid-ocean ridge type Iapetan crust.

Summary Permeability data from Permian dolomitized shallow-water platform carbonate outcrops in west Texas and New Mexico exhibit two to five orders of magnitude variability, most of which occurs within distances of a few feet [1 to 2 m] within single rock-fabric units. A variety of longer-range features are also observed, including vertical interbed average-permeability contrasts, 140- to 180-ft [42- to 54-m] lateral periodicities, and up to 2,700-ft [810-m] lateral trends. The short-range heterogeneities can be modeled with K-Bessel semivariograms having asymptotic power-law behavior at the origin. The periodicities can be modeled with "hole-effect" J-Bessel semivariograms. Stochastic two-dimensional areal and vertical cross-section models explore the effects of these heterogeneities. Fluid-flow simulations demonstrate that some long-range features control overall flow behavior even when short-range variability composes most of the variance. The short-range heterogeneities produce local smearing of displacement fronts. Introduction For more than 10 years the Bureau of Economic Geology (BEG), The U. of Texas, Austin (UT), has been collecting petrophysical data from carbonate outcrops in west Texas and New Mexico to advance knowledge of the geological, petrophysical, geostatistical, and fluid-flow aspects of this important class of hydrocarbon reservoir rocks.1–6 Most of this work has been conducted in Permian dolomitized shallow-water platform carbonate systems of the San Andres, Grayburg, and Victorio Peak (a Clear Fork equivalent) formations. The subsurface equivalents of these outcrop successions contain a majority of the hydrocarbon resources in the Permian Basin of west Texas and New Mexico and more than 17 billion [&gt;2.7 billion?m3] of remaining mobile oil.7 Although particularly applicable to Permian Basin reservoirs, these outcrops provide insight into reservoir architecture and heterogeneity in highly cyclic shallow-water platform carbonate successions around the world. The prolific Permian Khuff carbonate reservoirs of the Middle East, for example, are close analogs. This paper is focused on two outcrops: a San Andres outcrop at Lawyer Canyon, Algerita Escarpment, Guadalupe Mountains, New Mexico, and a Victorio Peak outcrop, Apache Canyon, Sierra Diablo Mountains, Texas (Fig. 1). Outcrops of the San Andres formation in the Guadalupe Mountains form a 17-mile [27-km] continuous exposure along the Algerita Escarpment. Approximately parallel to depositional dip, this section displays a spectrum of cyclic, middle to outer platform carbonate facies successions. Studies of this shallow-water carbonate platform succession based on the application of modern sequence stratigraphic concepts have created a basis for modeling of San Andres reservoirs.4 The Lawyer Canyon area, the locale for most of the measurements described in this article, exposes the ramp-crest segment of the lower San Andres platform. Cycles in the ramp crest comprise basal mudstones and wackestones and capping grainstones and grain-dominated packstones.4 Lawyer Canyon is perhaps the most thoroughly sampled carbonate outcrop in the world, at least in terms of petrophysical measurements relevant to fluid-flow modeling. The earliest known sampling at this location was conducted by Shell Oil Co. in 1969-1971.8 Sampling by the BEG and UT at Lawyer Canyon began in 1988.9 The BEG data set has been augmented with measurements collected by Chevron Petroleum Technology Co.10 and previously unpublished data collected by Mobil Technology Co. in 1992-1993. The combined ramp-crest data set at Lawyer Canyon (there are additional outer ramp data at Lawyer Canyon that we do not discuss here11) includes approximately 5,000 mechanical field permeameter (MFP) measurements, 1,200 plug samples, 830 natural gamma-ray measurements, and a variety of descriptive parameters. In this article we examine four horizontal transects of MFP data designed to reveal patterns of permeability heterogeneity that cannot be observed in vertical wells (Fig. 2). We also consider in less detail six vertical MFP transects. The transects sample three different grainstone units, the highest permeability rock fabric at Lawyer Canyon.4 Each transect is fully contained within a single grainstone unit. Outcrops in Apache Canyon provide a 1.5-mile [2.4-km] continuous exposure of the Victorio Peak formation along an oblique-to-dip section immediately landward of the platform margin. Ongoing studies of the Victorio Peak succession reveal thin cycles packaged into thicker cycle sets and sequences. Petrophysical data for this study were obtained from 414 1-in.-diameter [2.54-cm] plug samples collected in 1997 from a horizontal transect in a single high-frequency cycle at the base of a high-frequency sequence. The transect was designed to investigate petrophysical heterogeneity in a transition from tidal-flat facies updip to subtidal grainstones and grain-dominated packstones downdip. General Observations The MFP data from the four horizontal Lawyer Canyon transects are displayed in Fig. 3. The 414 Apache Canyon samples were each cut into as many 1-in.-long [2.54-cm] pieces as possible, producing 689 plugs. The Apache Canyon permeability transect is shown in Fig. 4. The Apache Canyon porosity transect (not shown) has similar properties. Perhaps the most striking feature of these data is the high degree of variability. The Lawyer Canyon transects have at least two orders of magnitude variation within single grainstone units. One transect, H1, exhibits more than three orders of magnitude variation. The Apache Canyon transect, which spans a transition from subtidal to tidal-flat facies, has five orders of magnitude variability. The larger variability at Apache Canyon is related to the larger range of rock fabrics sampled, but it is also due to the different permeability measurement methods. The lower limit of MFP measurements at Lawyer Canyon is about 1 md [9.87E-04 µm2]; the lower limit of plug permeability data at Apache Canyon is 0.01 md [9.87E-06 µm2]. Table 1 summarizes the permeability data from these five transects. The Apache Canyon transect stands out from the others; it has a smaller geometric average and a larger variance than any of the Lawyer Canyon transects. The smaller mean permeability at Apache Canyon is consistent with the generally muddier rocks sampled in that transect. The Lawyer Canyon averages, especially in transect H2b, might be slightly overestimated because of the inability of the MFP to measure permeabilities less than 1 md [&lt;9.87E-04 µm2].

The time revolution of 1859 changed forever the relationship between humans and time. In the space of a calendar year, and at a furious pace, the belief that all human history could be fitted into 6,000 years was shattered. The evidence for such a fundamental change was small, handheld stone tools found in the gravel quarries of the Somme among the bones of ancient animals. The task facing the antiquarian and the geologist was formidable. The tools had to be accepted as artificial and their association with extinct animals demonstrated beyond doubt. The successful proof, made on 27 April 1859, opened up ‘a vast lapse of ages’ for human history and led Charles Darwin to declare it ‘the most interesting subject which Geology has turned up for many a long year’. This book explores the time revolution through the Victorian world of two businessmen and a banker: John Evans, Joseph Prestwich, and John Lubbock. It draws in their sisters, wives and households and their scientific collaborators—Darwin, Falconer, Lyell, Huxley, and the French antiquary Boucher de Perthes. It tells the story of the time revolution through chapters devoted to the day, month, year, and decade. This chronology drives the narrative forward using the words and pictures of the principals. A direction emerges with each chronological step from discovery to presentation, reception, consolidation, and widespread acceptance of their case.