Search

Simon Lamb weaves three themes into this book. He describes a decade of field-based and analytical work in the Bolivian Andes, and uses his experiences as the springboard to explain how mountain ranges form. This is at a level pitched at non-geologists. In amongst the science are descriptions of Bolivia, especially the trials of working in harsh Andean terrain. The first two aims are certainly met successfully, and I recommend this book as an introduction to continental tectonics for non-geologists, especially those who want to get an insight into how a scientist develops ideas over …

This book arises out of the TRANSMED Project, which was a scientific consortium set up by the organising committee of the 32nd International Geological Congress and an association of 31 countries from the Mediterranean and nearby regions. Despite this parentage by committee, the book is a compact and accessible summary of Mediterranean tectonics. It lacks the padding of the worthy but very, very dull papers that sometimes weigh down regional volumes arising out of major conferences. To achieve this, the editors must have put in a huge amount of work, cajoling 63 authors into putting their work into a uniform style. The book is in two parts. There is a traditional ‘book’ which contains three regional review papers on tectonics, tomography and palaeogeographic reconstructions. The tectonics review by Cavazza et al. attempts to cover every region and the main …

China contains large-scale, active tectonic zones that make it an excellent place for the study of continental tectonics and basin evolution. Young fault zones related to the India–Asia collision and/or the subduction of oceanic crust at the east Asian margin are superimposed on a complex mosaic of older structures, which record the Phanerozoic assembly of a large part of Eurasia. This book contains 17 papers on many aspects of this evolution, sensibly grouped into four sections by time. Between them they cover much of China and a couple of adjacent areas, with concentrations on the geology of the North China Block and …

The age and mode of formation of the South Caspian Basin are disputed. An ~10-km-thick, predominantly middle Eocene clastic and volcanic succession is exposed in the Talysh mountains of Azerbaijan at its western margin. Here, high-K alkali basalts pass laterally to the east and southeast into volcanogenic sandstone-dominated turbidity current and debris-flow deposits. These southeasterly directed depositional systems accumulated in water depths generally greater than 200 m and fed directly into the western South Caspian Basin. New Ar-Ar ages cluster around 39 Ma, with an upper, 1400-m-thick volcanic interval being deposited in 2.2 ± 0.2 m.y. We interpret that this rapid deposition and magmatism records a major back-arc extensional/transtensional event in the Talysh, north of the north-dipping Neotethyan subduction zone. This event is recognized across much of southwest Asia and may indicate a period of significant basin formation within the adjacent South Caspian Basin. A transition into Upper Eocene–Lower Oligocene strata, dominated by fine-grained turbidity current and hemipelagic sediments with slope instability features, is interpreted to mark the end of rifting and volcanism in the Talysh and the start of the Arabia-Eurasia collision. Overlying Oligocene coarse clastic rocks are interpreted as the erosional products of localized topography created by the further propagation of compressional deformation into the Talysh region.

This book brings together 22 papers that collectively provide an overview of processes in shear zones. For anyone working on shear zones in the middle or lower crust or mantle this is an excellent resource, containing a wide variety of research, and demonstrating techniques on scales from microfabric studies to regional analysis using GIS technology. However, the emphasis of the papers is very much on ductile shear zones rather than brittle faults. Also, the flow referred to in most cases is of the material of the shear zone itself, rather than fluids from other sources. For these reasons the …

The sixteen papers in this volume represent a varied collection of studies on the interactions of tectonics and sedimentation in the geological record. It arises out of a session at the EUG meeting in Strasburg on this theme in 2001. Each paper on its own is an interesting case study, taking in Phanerozoic examples from as far apart as Siberia and the Andes. If there is any kind of regional focus, it is on Europe: twelve of the papers cover European basins and mountain ranges, including the Rhine Graben, Pyrenean forelands, the Alps, Apennines and Polish Carpathians. Only the introductory paper by the editors, Tom McCann and Aline Saintot, is a review of the …

Much of central and eastern Asia was assembled by a series of orogenies through the Palaeozoic and Mesozoic, before the Cenozoic India–Asia collision. This book presents 19 papers that describe individual areas or aspects of this vast collage. The papers are grouped thematically. The first seven describe Palaeozoic tectonic events, mainly in Mongolia and northwest China, beginning with a useful regional synthesis by Christoph Heubeck that covers the entire region. Other papers provide details on Tarim, the Tian Shan, much of the Beishan and Inner Mongolia regions, southern Mongolia and the Altun–Qaidam–Qilian regions. This is a good coverage, with little overlap or repetition, and a balanced mix of new …

Backstripping a representative stratigraphic column from the northwest of the South Caspian basin shows that ∼2.4 km of tectonic subsidence has occurred since ca. 5.5 Ma, at ∼1.5–10 times the rate recorded in typical foreland basins. Roughly half the basin's sedimentary thickness of ∼20 km has accumulated in this time, while the upper part of the succession has begun to deform by buckle folding. The South Caspian basement appears to be either thick oceanic crust, or thinned, high-velocity continental crust. Seismicity and gravity data indicate that the basement is in the initial stages of subduction under the middle Caspian region to the north. We propose that basement subduction began ca. 5.5 Ma to create the major Pliocene-Quaternary subsidence. Subduction may have been triggered by a regional reorganization in the Arabia-Eurasia collision at that time, possibly following the construction of the Turkish-Iranian Plateau.

The 2500 x 700 km Mongolian plateau (average elevation 2000 m) is situated between the Altai orogen and the Siberian craton and occupies much of Mongolia and Transbaikalia in Russia. The plateau is characterized by (1) basin and range topography and two major domes(Hentai, 600 x 300 km, and Hangai, 800 x 550 km), where altitudes reach 3905 m; (2) lithosphere that is thinner than adjacent areas (minimum ∼50 km); (3) elevated heat flow (up to 120 mW/m2); (4) dominantly alkaline basaltic volcanism in the form of cones, lava fields, and volcanic plateaus mostly of Miocene-Quaternary age, and (5) rifts, including Baikal (main evolution in the Pliocene-Quaternary), Tunka (Oligocene-early Miocene), and Hobsogol (Pliocene-Quaternary). Existing models explain these features in terms of diapiric upwelling of a mantle asthenolith below the main rifts and/or as a long-distance effect of the India-Asia collision. We propose that the late Cenozoic uplift of the whole Mongolian plateau and associated rifting, magmatism, high heat flow, and lithospherec thinning are not externally driven by the India-Asia collision, but are the expression of the interaction of a mantle plume with overlying lithosphere. Some rifts link and interact with major strike-slip faults, such as the Bolnai. Such faults may be the major expression of the India-Asia collision in this region.

The presence of a stratospheric haze layer may produce increases in both the actinic flux and the irradiance below this layer. Such haze layers result from the injection of aerosol-forming material into the stratosphere by volcanic eruptions. Simple heuristic arguments show that the increase in flux below the haze layer, relative to a clear sky case, is a consequence of "photon trapping." We explore the magnitude of these flux perturbations, as a function of aerosol properties and illumination conditions, with a new radiative transfer model that can accurately compute fluxes in an inhomogenous atmosphere with nonconservative scatterers having arbitrary phase function. One calculated consequence of the El Chichon volcanic eruption is an increase in the midday surface actinic flux at 20 degrees N latitude, summer, by as much as 45% at 2900 angstroms. This increase in flux in the UV-B wavelength range was caused entirely by aerosol scattering, without any reduction in the overhead ozone column.

This paper reviews the data base supplied by ground-based microwave measurements of water vapor in the mesosphere obtained in three separate experiments over an eight-year period. These measurements indicate that the seasonal variation of water vapor in the mesosphere is dominated by an annual component with low values in winter and high values in summer, suggesting that the seasonal variation of water vapor in the mesosphere (below 80 km) is controlled by advective rather than diffusive processes. Both the seasonal variation and the absolute magnitude of the water vapor mixing ratios obtained in microwave measurements were corroborated by measurements obtained in the Spacelab GRILLE and ATMOS experiments, and were found to be consistent with several recent mesospheric dynamics studies.

The Tien Shan Range in central Asia contains two late Paleozoic sutures. The older, southern suture marks the collision of a passive margin at the north of the Tarim block and an active continental margin; subduction under the latter was to the north. The younger, northern suture separates a northern Carboniferous island arc from an active continental margin developed over a south-dipping subduction zone. The subduction direction under the island arc is unknown. Mesozoic elastics were deposited over the doubly sutured orogen. Rate and energy of sedimentation waned until deposition of Oligocene conglomerates above a regional unconformity-interpreted as marking the onset of deformation induced by the India-Asia collision. Molasse deposition accelerated in Pliocene and Quaternary time, and deposition continues today as active thrusts generate relief. Paleozoic structures control the gross divergence of Cenozoic thrusts across the orogen.

An investigation is conducted in order to determine the relative importance of several modeled processes in controlling the magnitude and phase of the mesospheric ozone response. A detailed one-dimensional modeling study of the mesospheric ozone response to solar UV flux variations is conducted to remove some of the deficiencies in previous studies. This study is also used to examine specifically the importance of solar zenith angle, self-consistent calculation of water vapor abundance, and temperature feedback with a nonlocal thermodynamic equilibrium radiation model. The photochemical model is described, and the assumptions made for the purpose of comparing model results with the observed ozone response obtained from a statistical analysis of Solar Mesosphere Explorer data (Keating et al., 1987) are discussed. The numerical results for the theoretical ozone response are presented. The results of selected time-dependent calculations are considered to illustrate the degree to which a relatively simple model of the mesosphere is able to capture the major characteristics of the observed response.

Using the California Institute of Technology/Jet Propulsion Laboratory two-dimensional transport model, with transport coefficients taken from Yang and Tung (1989), we study the time evolution of excess carbon 14 in the stratosphere and the troposphere from October, 1963 to December, 1966. The model provides a satisfactory simulation of the observed data. Due to the impulsive nature of its source, initial distributions of excess carbon 14 exhibit large spatial gradients. This permits important constraints on the range of transport coefficients in the lower stratosphere to be derived. The standard model uses the circulation and eddy diffusivity of the year 1980. Large deviations (by factor of 2) from this standard transport are ruled out by our model. A self-consistently derived Kyy which is small (approximately 10(9) cm2 s-1) in tropical regions, but is larger (approximately 10(10) cm2 s-1) at higher latitudes is preferred. A Kzz as large as 1 x 10(4) cm2 s-1 would be inconsistent with the data. Excess carbon 14 is removed from the atmosphere with surface deposition velocities vS = 3 x 10(-3) cm s-1 and vN = 5 x 10(-3) cm s-1 in the southern and northern hemispheres, respectively. The last result is contrary to the current understanding that the oceans are the dominant sink for excess 14C.

An assessment is made of the ability of current theory to explain the phenomenology of upper atmospheric ozone as revealed by the sizeable body of measurements presently available. The chemistry of ozone in the mesosphere and lower thermosphere is closely coupled to the chemistries of other oxygen/hydrogen-containing species, which must be considered concurrently. To provide insight into the sensitivity of model calculations to the choice of values used for key chemical rate constants and climatological parameters, simple analytical expressions for ozone are derived for those situations when it is in photochemical steady state, the mesosphere during daylight hours and the lower thermosphere throughout the full diurnal period. The model is found to reproduce the detailed Aladdin 74 rocket measurements of ozone from 50 to 95 km, numerous other measurements of mid-latitude ozone in the lower mesosphere, the secondary maximum in the ozone vertical distribution at the mesopause, and the diurnal variability of ozone seen in the radio measurements of Wilson and Schwartz (1981) and other observations. The agreement with the Aladdin 74 data results from adjusting some key parameters within the uncertainties of laboratory measurements or known natural climatological variability. The variety of mid-latitude observations can be understood in terms of the estimated variability of environmental factors: diurnal, seasonal, and solar cycles in the solar illumination; the abundance of water vapor; and the details of the thermal profile of the atmosphere. The ozone secondary maximum results from the onset of the coupling between active-hydrogen and active-oxygen chemistry and its observed variability may be a consequence of secular changes in mesopause dynamics. Above ∼95 km, ozone observations are consistently higher than model results and cannot be accounted for by the set of reactions currently included in the model.

SummaryThe three-dimensional geometry of fluvial channel sand bodies has received considerably less attention than their internal sedimentology, despite the importance of sandstone body geometry for subsurface reservoir modelling. The aspect ratio (width/thickness, W:T) of fluvial channels is widely used to characterize their geometry. However, this does not provide a full characterization of fluvial sand body shape, since one W:T ratio can correspond to many different channel geometries. The resultant over- or underestimation of the cross-sectional area of a sand body can have significant implications for reservoir models and hydrocarbon volume predictions. There is thus a clear need for the generation of versatile, quantitative, and statistically robust models for sand body shape. The main aim of this research is to develop a new statistically-based approach that will provide quantitative data, derived from outcrop analogues, to fully constrain stochastic fluvial reservoir models. Here, we describe the construction of a new shape database and conduct a preliminary qualitative analysis in order to understand measurement and other uncertainties, and to explore the catalogue of shape configurations. A future quantitative analysis will develop a predictive model to enable forecasting of reservoir channel sand body geometries and shapes that can be built into existing reservoir models.

Ground-based microwave spectroscopy measurements of mesospheric CO and H2O vertical mixing ratio profiles are used to infer vertical mixing rates in the upper mesosphere. The CO and H2O data consistently imply vertical eddy diffusion coefficients in the 70- to 85-km region of 100,000-200,000 sq cm/s during spring through summer at midlatidues. Although chemical acceleration of vertical transport is substantial for O and O3, below the mesopause, the divergences of their associated fluxes are modest, with at most a factor of 2 effect on the concentrations of O and O3 for measured variability in gravity wave activity. Comparison of Solar Mesosphere Explorer (SME) O3 data with model results reinforces the conclusions of slow vertical mixing in the upper mesosphere as a consequence of the reduced HO(x) catalytic loss of odd oxygen. The changes in chemical rate constants recommended by Rusch and Eckman (1985), in conjunction with slow vertical mixing, yield good agreement with SME O3 data. The slow vertical mixing deduced in this study is consistent with upper limits obtained from studies of the mesospheric heat budget and could be construed as evidence for an advectively controlled mesosphere. A comparison of the vertical eddy diffusion coefficients for momentum stresses, constituent transport, and heat transport suggests that the eddy Prandtl number must be of order 10.

The simultaneous measurements of atomic O, O2, O3, and N2 between 90 and 110 km obtained by a rocket-borne mass spectrometer flown during the Aladdin 74 program provide an opportunity to test directly the simple atmosphperic chemical model first proposed more than 50 years ago by S. Chapman, which is today the core of the complex chemistry controlling stratospheric O3. The Aladdin 74 O3 results are found to be significantly in excess of model abundances computed using the most current values of the key chemical parameters. The calculations may possibly be in error due to uncertainties in these key parameters and/or in the measurement of the related species. However, the extra O3 may be a consequence of reactions between ground state O2 and electronically excited O2 resulting from the recombination of atomic O.

From December 1986 until April 1987 ground-based microwave observations of the diurnal variation of mesospheric ozone were made over Bern, Switzerland. These data were of sufficient quality to define the characteristics diurnal behavior of the ozone mixing ratio during winter and equinoctial conditions. The observed diurnal variation of ozone peaks at about 74 km, where its amplitude is about a factor of 6. At 65 km the observed diurnal variation is a factor of 3, whereas at 55 km it is only a factor of 1.4. One-dimensional model calculations accurately reproduce the relative diurnal variation of ozone at equinox, suggesting that the model value of the ozone photolysis rate coefficient is accurate to better that 10 percent. For winter conditions, however, the model underpredicts the observed relative diurnal variation by a factor of 2; a major part of this discrepancy is due to an observed postmidnight increase in ozone. Various suggested changes in model parameters to better produce the ozone abundance vertical profile result in only small differences in the relative diurnal variation, indicating that these observations do not provide a sensitive test of the mesospheric chemistry controlling the abundance of odd oxygen.