The geography of tourism in France: definition,scope and themes

Conclusions The substantial body of literature produced in the last two decades bears witness to the marked development of the geography of tourism in France over this period. This research has been strongly influenced by traditional geographic thought and is notable for the logic which underlies it. At the same time much remains to be done, with various avenues for future research being suggested in this paper. French geographers might also look increasingly outwards and to the work of others. By considering new and different methodologies, theories and fields of interest, the conceptual base of the subject might be enlarged and a more systematic approach developed. This need is keenly felt and this opening up is starting to occur, particularly through the exchange of ideas with foreign geographers at meetings of the national or international (IGU) commissions on the geography of tourism.     

The volcanic stratigraphy and petrogenesis of the Oman ophiolite complex

The volcanic stratigraphy and trace element geochemistry of the Oman ophiolite complex indicate a multistage magmatic origin comprising: (1) magmatism due to sea-floor spreading in a marginal basin; (2) magmatism associated with discrete submarine volcanic centres or seamounts; (3) magmatism associated with crustal uplift and rifting; and (4) magmatism associated with continent-arc collision.Trace element petrogenetic modelling is used to investigate the nature of the mantle source region and the partial melting and fractional crystallization history for each magmatic event. The petrogenetic pathway for the sea-floor spreading lavas requires a high degree of melting of a mantle that was depleted in incompatible elements prior to subduction but subsequently selectively enriched in certain elements (mostly LIL elements and H₂O) from an underlying subduction zone; it also requires magma mixing in an open system magma chamber prior to eruption. The seamount lavas were probably derived by a similar degree of partial melting of a similar source, but fractional crystallization was restricted to smaller high-level magma chambers. The rifting lavas were derived from a mantle source that was more depleted than the seamount lavas prior to subduction but which was later modified by a larger subduction zone component. The syn-collision lavas were however derived from an enriched mantle source, which probably underlay the passive continental margin rather than the marginal basin complex. Results such as these may provide considerable insight into the petrogenetic changes accompanying the transitions from spreading to arc volcanism in a supra-subduction zone setting.     

Interactions of growing folds and coeval depositional systems

Responses of both modern and ancient fluvial depositional systems to growing folds can be interpreted in terms of interactions among competing controlling variables which can be incorporated into simple conceptual models. The ratio of the rate of sediment accumulation to the rate of structural uplift determines whether a fold develops a topographic expression above local base level. The balance between (a) stream power and rates of upstream deposition vs. (b) bedrock resistance and rates of crestal uplift and of fold widening determines whether an antecedent stream maintains its course or is defeated by a growing structure. Modern drainage configurations in actively folding landscapes can often be interpreted in terms of these competing variables, and through analysis of digital topography, detailed topographic characteristics of these folds can be quantified. Modern examples of growing folds display both defeated and persistent antecedent rivers, deflected drainages and laterally propagating structures. The topography associated with a defeated antecedent river at Wheeler Ridge, California, is consistent with a model in which defeat results from forced aggradation in the piggyback basin, without the need to vary discharge or uplift rate. Reconstruction of the long-term interplay between a depositional system and evolving folds requires a stratigraphic perspective, such as that provided by syntectonic strata which are directly juxtaposed with ancient folds and faults. Analysis of Palaeogene growth strata bounding the Catalan Coastal Ranges of NE Spain demonstrates the synchronous growth and the kinematic history of multiple folds and faults in the proximal foreland basin. Although dominated by transverse rivers which crossed fold crests, palaeovalleys, interfan lows, structural re-entrants and saddles, and rising anticlines diverted flow and influenced local deposition. In the ancient record, drainage-network events, such as avulsion or defeat of a transverse stream, usually cannot be unambiguously attributed to a single cause. Examination of ancient syntectonic strata from a geomorphological perspective, however, permits successive reconstructions of synorogenic topography, landscapes and depositional systems.     

Tectonic setting of basic volcanic rocks determined using trace element analyses

Analyses for Ti, Zr, Y, Nb and Sr in over 200 basaltic rocks from different tectonic settings have been used to construct diagrams in which these settings can usually be identified. Basalts erupted within plates (ocean island and continental basalts) can be identified using a Ti-Zr-Y diagram, ocean-floor basalts, and low-potassium tholeiites and calc-alkali basalts from island arcs can be identified using a Ti-Zr diagram (for altered samples) and a Ti-Zr-Sr diagram (for fresh samples). Y/Nb is suggested as a parameter for indicating whether a basalt is of tholeiitic or alkalic nature. Analyses of dykes and pillow lavas from the Troodos Massif of Cyprus are plotted on these diagrams and appear to the tholeiitic ocean-floor rocks.     

Infrared emission from interstellar grains heated by supernovae

The infrared emission from interstellar grains heated by a supernova in eruption is investigated. The dependence of the emission on various physical parameters, such as the depth of the supernova into the dust plane of the parent galaxy, the inclination of the galaxy to the line-of-sight, are investigated. The possibility of detecting this emission is discussed. The prospects are hopeful as far as cryogenically-cooled instruments in Earth orbit are concerned.     

The stellar content of a spiral arm of NGC 4321

The effects of the passage of a spiral arm through the disc of the giant Virgo Sc galaxy NGC 4321 are investigated with Hubble Space Telescope WFPC2 images in two colours. Concentrating on a portion of the southern spiral arm of NGC 4321, we have applied a new program to solve for the star formation histories in the arm and interarm regions separately. The observational uncertainties and the variable crowding across the spiral arm are taken into account using the results of artificial star tests. In the interarm regions the data are consistent with a constant star formation rate for the last 50 Myr while the stars in the arm region show a star formation rate four times larger than in the interarm regions in the last 5 Myr.     

Light curves of SN 1998A and comparison with similar unusual SNe

Following the proposal by Damineli that the central object of Eta Carinae may be an early-type binary, we perform numerical simulations of the X-ray emission from colliding stellar winds. A synthetic light curve has been generated which qualitatively agrees with the recent X-ray variability, and provides further support for the binary model. In particular, the model predicts a rise in the observed X-ray emission towards periastron, followed by a sharp drop and subsequent recovery. This is indeed what is seen in the RXTE light curve, although some problems concerning the X-ray spectrum at periastron still need to be explained. The simulations suggest that the width of the periastron dip will provide strong constraints on the binary and stellar wind properties of the components of Eta Car.