Floor Depression Research Articles

3D model of the El Hornito pluton, Sierras Pampeanas of Argentina: Evidence of hybridization in the re-used feeder channels for emplacement in the ductile-brittle level

A comprehensive structural, petrological, and geophysical study of the 385 ± 2 Ma Devonian El Hornito Pluton (EHP) in the Sierra Grande de San Luis, Argentina, is presented. We establish that the EHP results from the intrusion of three main magma batches. The three-dimensional shape of the pluton was modeled using stochastic litho-constrained gravity data inversion and was complemented with a field geology survey. Results suggest a shallow-rooted, irregularly shaped pluton with a mean depth of 1.5 km, 16 km long and 4 km deep with a volume of 217 km³. Two areas of negative residual Bouguer anomaly reveal the existence of two root zones interpreted to indicate feeder channels. One of the feeders does not have a surface expression, but the other coincides with the central part of the pluton. A hot mafic magma intruded into and rejuvenated a crystallizing granite mush and the thermal perturbations triggered local convection with the development of an ascending magma plume developing mixing/mingling structures. Pluton emplacement was controlled by a shear zone at the boundary between two major metamorphic units. Emplacement is evidenced by the location of the two root zones along the interpreted contacts of the metamorphic zones, and the shear zone along this basement anisotropy provided the space into which magma batches were emplaced. Internal and external structures indicate that space for pluton emplacement was generated by a combination of tectonism with ballooning and stoping assisted by floor depression, which were the most effective processes during the final emplacement of the magma. This was possible due to the contrasting rheological responses of the host rocks.

Numerical Analysis of the Effect of Floor Depression on the Extent of Thermal Interaction with the Ground and Energy Management Using a Vegetable Cold Store as an Example

The thermal interaction between cooling facilities and the ground is most often discussed in terms of the appropriate insulation of building partitions. Unfortunately, there is little information about the potential of using ground thermal accumulation to support the shaping of the microclimate in cooling facilities by embedding them in the ground. This problem is particularly important in the context of striving to reduce the energy demand of buildings. The article discusses a new scientific problem related to the effect of vegetable cold storage floors being recessed into the ground on the surrounding land’s impact range and on its energy management. Validation of the numerical model was performed based on actual year-round field surveys. These surveys were conducted in a free-standing vegetable cold storage facility located in southern Poland. The results of the study allowed us to determine the contribution of the land to the energy balance of the cold storage. A floor recessed into the ground doubled the ground’s contribution to the energy balance. The most important research results showed that the range of thermal impact on the surrounding ground also increased by 2.0 m more than that of a building with the floor located at ground level. An evaluation of the heat flow between the cold storage and the ground in the cases analyzed was also carried out. The analysis of the ground heat exchange balance on an annual basis showed high energy gains of 2055 kWh. The total energy demand for cooling was 1723 kWh, while it was 1204 kWh for heating. The results of the analysis of the heat exchange intensity between the indoor air and the ground showed that the ground contribution accounted for 16.6% of the total energy balance of the cold storage. The highest energy gains from the ground were found in October and amounted to 478 kWh. Due to the summer shutdown, there was an intense heat flow to the ground in July, which amounted to 588 kWh.

Effects of axial extension on pelvic floor displacement and abdominal muscle activity during a pelvic floor muscle task.

The effects of axial extension on pelvic floor displacement and abdominal muscle activity during pelvic floor muscle (PFM) exercises are not well known. To clarify the effect of sitting axial extension on pelvic floor displacement and abdominal muscle activity during a PFM task. Pelvic floor displacement, abdominal muscle activity, and subjective kinesthesia of the PFM were compared between the resting and axial-extended sitting positions during a pelvic floor task in 34 healthy young men. No significant difference in pelvic floor displacement was observed between the resting and axial extension sitting position. Subjective kinesthesia was significantly easier to perform in axial extension than in resting sitting position during pelvic floor depression. Abdominal oblique muscle activity was higher in axial extension than in resting sitting position during pelvic floor depression. The changes in axial extension were significantly greater in the internal oblique muscles during elevation and in the internal and external oblique muscles during depression than in the lower rectus abdominis muscles. Axial extension in the sitting position does not change pelvic floor displacement during the PFM task. However, axial extension may be effective in facilitating subjective kinesthesia of PFM and in increasing oblique abdominal muscle activity.

Shallow Gas Hydrate Accumulations at a Nigerian Deepwater Pockmark—Quantities and Dynamics

AbstractThe evolution of submarine pockmarks is often related to the ascent of fluid from the subsurface. For pockmarks located within the gas hydrate stability zone, methane oversaturation can result in the formation of gas hydrates in the sediment. An ~600 m‐wide sea floor depression in deep waters offshore Nigeria, Pockmark A, was investigated for distributions and quantities of shallow gas hydrates, origins of hydrocarbons, and time elapsed since the last major fluid ascent event. For the first time, pressure coring of shallow sediments and drilling of more than 50 m‐long cores with the sea floor drill rig MARUM‐MeBo70 were conducted in this pockmark. Unusually, high hydrate saturations of up to 51% of pore volume in the uppermost 2.5 m of sediment in the pockmark center substantiate that deepwater pockmarks are a relevant methane reservoir. Molecular and stable C and H isotopic compositions suggest that thermogenic hydrocarbons and secondary microbial methane resulting from petroleum biodegradation are injected into shallower sediments and mixed with primary microbial hydrocarbons. Two independent pore water chloride and sulfate modeling approaches suggest that a major methane migration event occurred during the past one to three centuries. A rough sea floor topography within the pockmark most likely results from combined sediment removal through ascending gas bubbles, hydrate clogging and deflection of migration pathways, gas pressure build‐up, and hydrate sea floor detachment. This study shows for the first time the chronological interrelationship between gas migration events, hydrate formation, and sea floor shaping in a deep sea pockmark.

Late Triassic extensional tectonics in the northern North China Craton, insights from a multidisciplinary study of the Wangtufang pluton

To better understand Late Triassic tectonic setting in the northern North China Craton (NCC), the emplacement mechanism of the Wangtufang pluton, which recorded the synmagmatic regional tectonic signature, has been investigated. Zircon U-Pb ages, and Hf isotopic data, and whole-rock geochemical analyses suggest that the Late Triassic Wangtufang pluton composed of syenogranite and diorite is derived from partial melting of lower crust with some depleted mantle components. Both the syenogranite and diorite appear isotropic. Anisotropy of magnetic susceptibility and gravity studies have been carried out to characterize internal fabrics and shape of the pluton. The diorite forms just thin remnants above the syenogranite. The syenogranite with a series of NW-SE trending dykes intruded into the diorite and its country rocks. In the syenogranite, the gently dipping magnetic foliations strike nearly parallel to the pluton border. The shallow plunging magnetic lineations mainly strike NE–SW. Combining NE-SW trending elongated subsurface shape with central root, unflat bottom, and moderate- to high- inward dipping sidewalls, the syenogranite could be considered as a lopolith-like intrusion. The syenogranite was likely emplaced by inflation of magma pulses from its central conduit and built up by floor depression. Emplacement of the syenogranite was in an extensional setting, considering: (1) the NE–SW striking magnetic lineation, (2) the NE–SW trending elongated subsurface pluton shape, and (3) the orthogonal NW–SE striking syenogranitic dykes considered as tension gashes during the NE–SW trending extension. The Wangtufang pluton provides reliable arguments to the Late Triassic intracontinental extensional setting already suggested in the northern NCC.

Silent Sinus Syndrome: An Uncommon Cause of Diplopia

Background: Silent sinus syndrome is a rare condition with multiple ophthalmic findings of significance. Chronic, subclinical maxillary sinus inflammation alters the pressure gradient, leading to eventual maxillary sinus collapse, orbital floor depression, enophthalmos, and diplopia.

Simplest radiological measurement related to clinical success in endoscopic third ventriculostomy

ObjectiveRadiologic criteria for a successful endoscopic third ventriculostomy are not clearly defined and there is an ongoing need for determining simplest and strongest radiological criteria for this purpose. This paper aims to determine the easiest radiological parameter related to surgical outcome MethodsBetween January 2012 and December 2015 all patients receiving endoscopic third ventriculostomy with various indications were reviewed and 29 patients whose preoperative and early postoperative 3D-CISS images were available were studied. There were 13 males and 16 females, and there were 11 pediatric cases (mean age: 9.90±5.2; range: 2–18). The mean age of the entire population was 26.58±18.32 (range: 2–68 years). Measurements were performed using the ruler tool of a freely distributed medical imaging software. Simple ruler measurements of ventricular floor depression, lamina terminalis bowing, anterior commissure to tuber cinereum distance, mamillary body to lamina terminalis distance, third ventricular width, frontal horn width and occipital horn width were recorded and compared between successful and failed interventions. ResultsOf the ventriculostomies, 22 (75.9%) were considered successful and 7 (24.1%) as failed at the last follow-up visit. Of the measurements performed, only those related to the third ventricle itself were significantly higher in the failed group. There were no association with lateral ventricular measurements. ConclusionSimple ruler measurements of the suggested distances significantly correlate with clinical success. After validating our results with higher number of patients, complex measurements and calculations to determine the link between clinical success and radiological success of ventriculostomy procedures may not be needed.

Formation of tabular plutons - results and implications of centrifuge modelling

Geophysical investigations reveal that many granitoid plutons possess a tabular shape: either laccolithic, lopolithic or phacolithic. In this study, the results of a centrifuge experiment are used to understand the formation mechanisms of these features. The model was build of a sequence of 14 differently coloured plasticine layers. Two buoyant layers - with a volume of c. 40 cm(3) each - were incorporated into the model stratigraphy at different depths to investigate, whether the rise and emplacement of buoyant material at different levels results in different intrusion structures. After centrifuging for 30 min at 700 G, both the buoyant layers had formed two lenticular sills (phacoliths) with aspect ratios (length/thickness) of 6 and 3.4 for the upper and lower phacoliths, respectively, directly above both pre-existing perturbations in the buoyant layers. During their movement, the buoyant phacoliths had pushed their roof plasticine upward. Simultaneously, their plasticine had subsided (bottom sinking). Subsidence of the material had choked the inflow of further buoyant material into the feeder channel of the developing sills and inhibited their further lateral growth. The observed forced downward movement of the plasticine of the forming PDMS (polydimethylsiloxane) phacoliths resembles the so-called floor of host rock material around an emplacing tabular pluton. Floor depression is supposed to be a very important vertical material transfer process, which provides space for the construction of lopo- and phacoliths. The subsidence of host material made space for the developing buoyant phacoliths, but also restricted their growth to a certain time slot before the influx of new buoyant material into the feeder dyke of the tabular intrusive body was shut off. Similarly, in nature, the growth of a tabular pluton might be limited not only by the rate of magma ascent and its physical properties, but also by the emplacement processes of the evolving pluton.

Large-scale mechanics of fracture-mediated felsic magma intrusion driven by hydraulic inflation and buoyancy pumping

Abstract A new fracture-mediated intrusion model resolves the sequence of magma and rock displacements generating a felsic magma system with a lower crustal source, central conduit and shallow sill pluton. Idealized intraplate conditions are assumed, to neglect regional tectonism and to focus on juvenile cracking by magma-intrinsic hydraulic and buoyant loads. The magma source is conductively heated and develops by endothermic fluid-absent melting in approximately 10 6 years. The idealized domical thermal anomaly and endothermic heat focusing yield a low aspect ratio source, with outer-porous and inner-permeable partial melt zones. An anatectic core region is unrealized owing to magma segregation. Thermal stresses are readily relaxed and unimportant to source loading while crustal uplift generates tensile stress and, upon relaxation, lateral space for tensile fractures. Dilative melting generates buoyancy overpressure (Δ P B ) and a hydraulic contribution (Δ P V ) to the magma pressure ( P M ). Δ P V develops by elastic wall-rock compression as the ‘excess magma volume’, EMV , arises too abruptly for full relaxation by inelastic deformation, inducing a brittle response. Tensile rupture criteria are met in an effective tensile stress field with low differential stress induced by magma pore pressure and wedging by pressurized cracks, which initiate by source inflation and uplift. Preferred vein geometry reflects the starting stress field. For symmetric doming, radial vertical cracks with a central nexus form a natural conduit. A vertically extensive crack system, however, requires special explanation because wedging by Δ P V reorients dykes to sills just above source. The solution is that volumetric crack growth accommodating non-relaxed EMV ( EMV *) causes Δ P V →0. Magma transport becomes buoyancy-driven and the Δ P V problem does not arise. The critical sill intrusion depth, I , is where Δ P B exceeds the regional vertical stress curve, where columns must intrude owing to Δ P B alone. Sill growth is mainly by floor depression, involving ductile shear of lower crust, creating sill volume, suppressing roof uplift, expelling source contents, processing protolith through the melting zone, reducing stress, σ H , and widening conduits for sustained flow. Two intrusive regimes are identified; Δ P V >0 (hydraulic inflation) and Δ P V =0 (buoyancy pumping). Partitioning between three sinks for EMV – inelastic uplift (ϕ), crack growth (η) and a non-relaxed portion ( EMV *) generating Δ P V – defines four hydraulic subregimes. Disequilibrium dilation occurs during crustal relaxation prior to rupture, when η=0 and EMV partitions between ϕ and EMV *. Uplift occurs readily owing to the crust's weakness in flexure, so ϕ abruptly increases while EMV * decreases, causing abrupt variations in source failure mode, geometry and rate that smooth initial Δ P V variations. During equilibrium dilation source swelling continues with ϕ dominant over EMV *. Dilatant loading rates mean that positive Δ P V is always maintained however, keeping the source near-isotropically inflated and prepared for rupture. Disequilibrium cracking begins when uplift-driven horizontal stretching initiates rupture and crack growth (η). Crack volume is initially small, but readily enlarges as dykes propagate by conversion of stored Δ P V . EMV is minimized better and faster by η than by ϕ, owing to crack-tip stress concentration, giving abrupt augmentation of η and decreases in ϕ and EMV * in a crack growth-surge until the uplift-modified stress field is balanced. In equilibrium cracking , once EMV * (and Δ P V ) decrease to incipient levels, each new increment of EMV * partitions directly into crack growth, while continued uplift maintains vertical rupture, generating a vertically extensive fracture system. The absolute volumetric equivalence of EMV *, at most a few tens of km 3 , will be exhausted during dyking, sill intrusion or surface eruption. The system then becomes buoyancy-driven and, if depth I is reached, must intrude a sill. Relaxation of sill underburden initiates crustal decoupling and buoyancy pumping, where the downward underburden-flux drives and is balanced by upward magma flow.

Structured Sun glitter recorded in an ASTER along‐track stereo image of Nam Co Lake (Tibet): An interpretation based on supercritical flow over a lake floor depression

Sun glitter and synthetic aperture radar (SAR) remote sensing techniques that respond to the small‐scale textural roughness of water surfaces often reveal a plethora of signatures indicative of the presence of bed formations submerged in shallow water (of depth <30 m), even though the electromagnetic signals employed in such methods are reflected at or near to the water surface. In homogeneous (nonstratified) regimes, these signatures are interpreted on the basis of a causal sequence involving an initial topography‐induced perturbation to a strong background current (of speed nominally >0.4 m s−1), the subsequent formation of surface current gradients (the “straining”) of order 10−3 s−1, and an ensuing local modulation of the centimeter‐scale surface roughness controlling the scattering of both light and radar. Here we consider how the presence of stratification might influence this generative sequence in an analysis of high‐sensitivity Sun glitter observations gathered when the background flow speed and surface current gradients are at least one order of magnitude lower. The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) acquired these observations on 22 July 2001 while imaging in along‐track stereo mode from slanted fields of view that encompassed Sun glitter reflected from the surface of Nam Co, a large Tibetan lake that is free from anthropogenic surface‐slick contamination. We interpret a structured Sun glitter feature appearing within a shallow embayment in the northwest of the lake as the surface roughness manifestation of a wake formed by supercritical stratified flow over a localized depression in the lake floor topography.

Muscle activation characteristics of tumbling take-offs

In the floor exercise, a gymnast may receive a general composition score deduction associated with a lack of diverse tumbling sequences. Diversity in tumbling is defined as the ability to tumble both forward and backward, as well as twist and flip. A coach's ability to direct technical and physical training for these skill varieties is enhanced when thorough descriptions of the skills are available. The aim of this study was to describe and compare muscle activation of the lower extremity in various tumbling sequences characterized by differing body orientations. The stretch–shortening cycle actions during the take-off portion of four different tumbling sequences were analysed and the results compared across muscles and type of take-off (forward vs. backward, twisting vs. non-twisting). Thirteen female gymnasts performed three trials each of round-off flic-flac to backward layout and to backward layout with longitudinal axis twist, and front flic-flac to forward layout and to forward layout with longitudinal axis twist. Activation onset was assessed as an increase of the EMG of 200% above noise before initial floor contact. The EMG was normalized to peak values for each muscle bilaterally during each take-off. Results showed that muscle activation characteristics in the pre-activation and impact phase (contact to maximal floor depression) differed between tumbling series. Backward take-offs were characterized by longer contact times, greater relative activity of the gastrocnemius compared with the vastus lateralis during pre-activation, and greater biceps femoris activation during impact compared with forward take-offs. Twisting backward was associated with reduced muscle activity of the twisting limb, while twisting forward was associated with increased muscle activation on the twisting limb. These differential effects related to the specific nature of the take-off indicate that training to enhance the stretch–shortening cycle action in gymnasts must be specific to the orientation requirements of each specific skill.

Silent Sinus Syndrome: Lack of Orbital Findings in Early Presentation

Silent sinus syndrome (SSS) is an uncommon disease process, classically described as unilateral maxillary sinus opacification that presents with enophthalmos and atelectasis of bony sinus walls from chronic negative pressure. Patients are largely free of characteristic rhinosinusitis symptoms. Operative reports, clinic notes, and radiological studies were reviewed for cases of SSS treated in a tertiary care institution over a 7-year period. Presenting symptoms, radiological features, and surgical findings were evaluated. Seventeen cases of SSS were identified. Presentation ranged from incidental computed tomography (CT) scan findings to unilateral enophthalmos with altered midface anatomy. Facial pain ipsilateral to the disease process occurred in 30% of cases. Vision changes were uncommon. Radiological studies universally revealed an opacified maxillary sinus on the affected side. Maxillary sinus walls were contracted and demineralized with significant orbital floor depression in 11 advanced cases. Four early cases revealed only lateralized uncinate process on CT scan without increased orbital volume, and two moderate cases showed increased orbital volumes on CT scan without clinical enophthalmos. All patients had a significantly lateralized uncinate process at surgery, often closely apposed to demineralized orbital walls. Some authors maintain that SSS presentation must include enophthalmos. However, our series shows cases of lateralized uncinate processes and increased orbital volumes on CT scan, as would be seen in classic SSS, but lacking clinical enophthalmos. Such cases should be considered as potentially representing early SSS, before the development of clinical orbital findings.

Magnetic fabrics and compositional evidence for the construction of the Caleu pluton by multiple injections, Coastal Range of central Chile

The Caleu pluton, which is located in the Coastal Range of central Chile, consists of three N–S elongated lithologic zones which define an across-pluton compositional variation characterized by a westward increase in SiO 2 content, the Gabbro-Diorite (GDZ), Tonalite (TZ) and Granodiorite (GZ) Zones. A total of 547 cores were drilled at 68 sites within the different zones to carry out magnetic fabric and paleomagnetic studies. The highest values of magnetic susceptibility and remanent magnetization are found in the GDZ (0.04–0.1 SI), whereas the lowest values are observed in the GZ (0.01–0.02 SI). This is consistent with the significant decrease in magnetite content from the GDZ to the GZ. The dips of the magnetic foliation planes are steep within GDZ and TZ, and shallower dips are observed in GZ. Magnetic foliations along some borders of the pluton are parallel to the corresponding contacts. The parallelism observed between the magnetic foliations and the contacts between zones suggests that these zones have recorded the same mechanism of emplacement at the magmatic state. The peculiar foliation pattern observed in the central parts of TZ and GZ is attributed to a lobe-like structure that was acquired during the late stages of emplacement and inflation. The distinct compositional characteristics of these three zones were not acquired in situ. Rather they were emplaced successively from mafic to felsic from a subjacent stratified sill-like magma reservoir, which was filled after tilting of the host volcanic succession. The rapid upward transport of these melts of different compositions up to a shallow depth is attested by both the equilibration pressure of late magmatic hornblende (∼200 MPa) and the pressure of early magmatic epidote crystallization (∼500–600 MPa). We conclude that space was created by lateral flow propagation, in which the intrusion of later pulses pushed earlier ones away from the feeder system, followed by roof lifting and possibly floor depression.

Growth of wedge-shaped plutons at the base of active half-grabens

ABSTRACTCombined field and geophysical data show that plutons from the Bega Batholith are elongate, meridional, wedge-shaped bodies which intruded during a period of regional east–west extension in the Palaeozoic eastern Lachlan orogen, eastern Australia. Plutons within the core of the batholith have intruded coeval, syn-rift sediments and co-magmatic volcanics. The batholith is bound by high-temperature, dip-slip faults, and contains several major NE-trending transtensional faults which were active during batholith construction. In the central part of the batholith, the Kameruka pluton is an asymmetric, eastward-thickening, wedge-shaped body with the base exposed as the western contact, which is characterised by abundant, shallow-dipping schlieren migmatites which contain recumbent folds and extensional shear bands. A shallow (<30°), east-dipping, primary magmatic layering in the Kameruka pluton steepens progressively westward, where it becomes conformable to the east-dipping basal migmatites. The systematic steepening of the layering is comparable to sedimentary units formed during floor depression in syn-rift settings. The present authors suggest that the wedge-shaped plutons of the Bega Batholith are the deeper, plutonic expression of a hot, active rift. The batholith was fed and sustained by injection of magma through sub-vertical dykes. Displacement along syn-magmatic, NE-trending faults suggests up to 25 km of arc-perpendicular extension during batholith construction. The inferred tectonic setting for batholith emplacement is a continental back-arc, where modern half-extension rates of 20–40 mm yr−1 are not unusual, and are sufficient to emplace the entire batholith in ∼1 Ma. This structural model provides a mechanism for the emplacement of some wedge-shaped plutons and is one solution to the ‘room problem’ of batholith emplace

Lymphocytic hypophysitis: a rare or underestimated disease?

Lymphocytic hypophysitis (LYH) is an uncommon autoimmune disease in which the pituitary gland is infiltrated by lymphocytes, plasma cells and macrophages and its function is usually impaired. It has to be suspected in pregnant women and in women with recent delivery presenting with hyperprolactinemia, headache, visual field alterations and changes of one or more pituitary hormone secretions with secondary impairment of related peripheral target glands, especially when associated with other autoimmune endocrine or non-endocrine disorders. It can also occur less frequently in prepubertal or post-menopausal women and in men. Headache, visual field impairment and more rarely diplopia are due to extrasellar pituitary enlargement with optic chiasma compression and/or to invasion of cavernous sinuses. Among the 'isolated' pituitary hormone deficiencies, ACTH deficit is usually the earliest and most frequent hormonal impairment and in rare cases can induce an acute secondary hyposurrenalism as the first sign of the disease, with high mortality in affected patients. Histopathological findings from pituitary biopsy show lymphoplasmacytic infiltrate with lymphoid aggregates surrounding atropic acini of pituitary cells; immunohistochemical analysis shows numerous mast cells randomly distributed and also localized in the vicinity of capillaries, suggesting a possible influence on capillary permeability and angiogenesis, thus favoring the inflammatory and immunological aggression against pituitary cells. Nuclear magnetic resonance imaging shows uniform sellar floor depression and an extrasellar symmetrical pituitary enlargement, usually displacing the optic chiasma, which shows a rapid homogeneous enhancement after gadolinium also involving the adjacent dura (dural tail). Antipituitary antibodies have been detected in several patients with LYH but their role needs to be clarified. Since a possible spontaneous remission can occur, a careful follow-up is required in subclinical patients without important hyposurrenalism or symptomatic extrasellar expansion. Medical (immunosuppressive, replacement and antiprolactinemic) and neurosurgical (decompression) treatments are needed in clinical symptomatic patients.

Internal nasal floor configuration in Homo with special reference to the evolution of Neandertal facial form.

The presence of a steeply sloping or depressed nasal floor within the nasal cavity of Neandertals is frequently mentioned as a likely specialization or autapomorphy. The depressed nasal floor has also been seen as contributing to a relatively more capacious nasal cavity in Neandertals, which is tied to cold-climate respiratory adaptation and energetics. These observations have been limited largely to a relatively few intact crania, and the character states associated with this trait have not been as precisely codified or analyzed as those published for Plio-Pleistocene hominins (McCollum et al., 1993, J. Hum. Evol. 24, 87; McCollum, 2000, Am. J. Phys. Anthrop. 112, 275). This study examines the internal nasal floor topography in complete crania and isolated maxillae in European, west Asian, and African fossil Homo (n=158) including 25 Neandertals, and a wide range of recent humans from Europe, the Near East, and Africa (n=522). The configuration of the internal nasal floor relative to the nasal cavity entrance is codified as: 1) level, forming a smooth continuous plane; 2) sloped or mildly stepped; or 3) bilevel with a pronounced vertical depression. The frequency of these nasal floor configurations, and their relationship to both nasal margin cresting patterning and a comprehensive set of nasofacial metrics is examined. Neandertals show a high frequency of the bilevel (depressed) configuration in both adults and subadults (80%), but this configuration is also present in lower frequencies in Middle Pleistocene African, Late Pleistocene non-Neandertal (Skhul, Qafzeh), and European Later Upper Paleolithic samples (15%-50%). The bilevel configuration is also present in lower frequencies (ca. 10%) in all recent human samples, but attains nearly 20% in some sub-Saharan African samples. Across extinct and extant Homo (excluding Neandertals), internal nasal floor configuration is not associated with piriform aperture nasal margin patterning, but the two are strongly linked in Neandertals. Variation in internal nasal floor configuration in recent humans is primarily associated with internal nasal fossa breadth and nasal bridge elevation, whereas in fossil hominins, it is associated primarily with variation in facial height. Cold-climate and activity-related thermal adaptation as an explanation for the high frequency of pronounced nasal floor depression in Neandertals is inconsistent with all available data. Alternatively, variation in internal nasal floor configuration is more likely related to stochastically derived populational differences in fetal nasofacial growth patterns that do not sharply differentiate genus Homo taxa (i.e., cladistically), but do phenetically differentiate groups, in particular the Neandertals, especially when considered in combination with other nasofacial features.

Shape and intrusion style of the Coastal Batholith, Peru

The Coastal Batholith of Peru extends over 1600 km parallel to the coast along the Andean trend. Gravity profiles on three traverses across the batholith indicate the geometry is essentially that of a flat slab with average thickness from 2.0–3.2 km, and a thick root 4–10 km wide to the west. Granitic material does not extend to depths greater than 3 km below sea level datum.This study supports recent gravity work which indicates plutons are commonly thin, 5 km or less in thickness. Detailed mapping in the Lima segment of the Coastal Batholith reveals thin plutons where space was made dominantly by downward displacement via floor depression. However, early roof uplift also created some space. Stoping occurs but is not a major space maker. Floor depression may be modelled by cantilever or piston mechanisms and although the strong marginal deformation with mylonites, tuffisites, microbreccia, faults and shear zones suggests the piston model best describes the mechanism of emplacement of much of the Coastal Batholith some space was probably made by a cantilever mechanism. In brief, space making processes involved early roof uplift and regional doming, then floor depression mainly by piston and probably subsidiary cantilever mechanisms and, finally, local stoping producing the cut-out rectilinear nature of the batholith.The Coastal Batholith formed on shallow partial melting of hydrous basaltic marginal basin rocks between 5 and 10 km. Floor depression occurred as the crustal column foundered into an actively deflating layer of partial melt. This is an efficient space making process and is limited here to shallow levels of the upper crust only. The melts ascended to within 2 or 3 km of the surface, up dyke-like conduits then spread horizontally to form tabular plutons.

Internal structure and emplacement of the Papoose Flat pluton: An integrated structural, petrographic, and magnetic susceptibility study

The Papoose Flat pluton of eastern California is commonly cited in the geologic literature as a classic example of a “forcibly” emplaced pluton, although the relative importance attributed to magmatic versus tectonic processes in controlling the structural evolution of the pluton has been controversial. Reexamination of this Late Cretaceous (83 Ma) pluton, using a combination of new structural, petrographic, microstructural, and anisotropy of magnetic susceptibility (AMS) data on the pluton–wall-rock system, has shown that the pluton is an inclined and internally zoned tabular structure, assembled by forcible intrusion of successive pulses of magma at a crustal depth of 12–15 km. Initial pluton formation involved magma ascent in a vertical west- northwest–striking feeder dike, which was arrested at a stratigraphically controlled mechanical discontinuity in the overlying Cambrian metasedimentary rocks, leading to formation of a southwest-dipping sill. Subsequent sill inflation, accompanied by horizontal infilling from the feeder dike at the base of the sill, resulted in deformation and vertical translation of previously emplaced magma pulses and local raising of the sill roof, facilitated by thermal weakening as the wall-rock temperatures progressively rose during emplacement of successive magma pulses. Cooling from the roof of the pluton downward resulted in cessation of vertical inflation on the west side of the pluton and promoted lateral expansion toward the northeast and floor depression below the eastern part of the pluton. We have been unable to document any regional-scale structures (e.g., of equivalence to similar-age synplutonic strike-slip shear zones in the Sierra Nevada batholith to the west) that may have controlled emplacement of the Papoose Flat pluton. However, this fact does not preclude the likelihood that the country rocks were subjected to a regional deviatoric stress field at this time; indeed, tectonic overpressuring was probably essential for producing sufficiently high magma pressures for laccolith formation at this midcrustal level. Simple thermal modeling, using microstructural and thermobarometric data, indicates that the total duration of emplacement of the pluton did not exceed 30 000 yr. This rapid emplacement rate may explain why the pluton appears to be anorogenic even though it was emplaced during a period of regional- scale deformation.

Repeated tabular injection of high-level alkaline granites in the eastern Bushveld, South Africa

Field observations, petrography and magnetic susceptibility fabrics are used to characterize the structure and evolution of the Nebo granite, forming part of the Bushveld Complex, in South Africa. The Nebo granite is the dominant component of the Lebowa granite suite, the largest known anorogenic granitoid complex. It is a composite tabular intrusion, comprising alkali feldspar granites and syenogranites. There are seven main petrographic units, defined by differences in modal content, crystallization sequence, magmatic water content, magnetic susceptibility and magnetic fabric. Each unit was emplaced independently and fed by vertical dykes. Anisotropy of magnetic susceptibility used to map magmatic fabrics within the granite shows that they are dominantly controlled by alignment of early-crystallizing magnetite and are similar in outcrop and pluton scale. Magnetic foliations and lineations are horizontal, reflecting vertical host-rock compression and horizontal magma flow during emplacement. Space was created by magma pressure which resulted in roof uplift and floor depression: displacements were accommodated by normal and reverse faulting and flexural-slip along bedding planes in host-rock metasediments.

Discussion on emplacement of rapakivi granite and syenite by floor depression and roof uplift in the Palaeoproterozoic Ketilidian orogen, South Greenland

Discussion on emplacement of rapakivi granite and syenite by floor depression and roof uplift in the Palaeoproterozoic Ketilidian orogen, South Greenland