Spare Capacity (2003) and Peak Production in World Oil

Reliable estimates of minimum spare capacity for world oil production can be obtained by comparing production statistics before and following the collapse of the Iraqi oil industry in March 2003. Spare production was at least 3.2 M b/d (million barrels/day), and was concentrated in the Middle East, mostly in Saudi Arabia (1.7 M b/d), but also in Kuwait and the UAE. This indicates that, assuming Iraqi production returns to its prewar level, a peak in world oil production resulting from resource constraints alone (ignoring political factors) before 2008 can be rejected. This also implies that with an invigorated Iraqi industry, and with further increases in production in the Former Soviet Union and other non-OPEC areas, there would be significant short-term downward pressure on oil prices and strains within OPEC. These transient issues do not alter the projection for a resource-constrained peak or plateau in non-OPEC production between 2010 and 2018.     

Ice ages and orbital variations: Some simple theory and modeling

Possible physical mechanisms relating orbital-element variations (i.e., the “Milankovitch mechanism” of insolation regime changes) to Quaternary glacial/interglacial transitions are explored quantitatively. These include the seasonal cycle of albedo and the zonal distribution of thermal inertia. These mechanisms can interact with the perturbations to zonal average and seasonal average insolation caused by orbital-element variations to cause a global annual temperature residual, even though such variations can cause only a negligible change in global annual insolation.Numerical model experiments with a zonal energy balance model show that the relative interactions between insolation regime changes and seasonally and latitudinally varying albedo and latitudinally varying thermal inertia are roughly of comparable magnitude. Encouraging agreements between model experiments and data are evident, but these (and others') simulations are still a long way away from providing a satisfying explanation of the physical processes that could fully explain the apparent connections between orbital-element variations and Quaternary glaciations.It seems likely that no single physical process can be identified as predominate, and rather, the hypothesized physical connection between insolation regime changes and glacial/interglacial transitions will have to be built on the interactions of a number of processes on both short and long time scales.     

Fluorine contents in carbonate sequences and rare earths distribution in fluorites of Pb-Zn deposits in East-Alpine Mid-Triassic

To divulge plausible source for fluorine in the Upper Ladinian of the East Alpine geosyncline, two totally independent geochemical approaches have been made. They are (i) correlation study of the stratabound, stratiform, paleographic and regional fluorine anomalies observed in seven selected profiles of the carbonate sequences and (ii) comparative study of the distribution of rare earths (REE) in fluorspars from northern and southern Ladinian sequences. The fluorine anomalies in the entire East Alpine geosyncline were found to be confined only to a few horizons which could be stratigraphically correlated. The fluorspars of the Nördliche Kalkalpen showed REE distribution characteristic of a sedimentary formation while those of the Südliche Kalkalpen (Bleiberg area) apparently showed a hydrothermal type of REE distribution. These and various other considerations discussed in the present paper go to show that a relatively short-termed submarine exhalative source (volcanic) of a recurring nature in the Ladinian stage of the Mid-Triassic might have been plausibly responsible for the supply of fluorine found in the carbonate sequences of the East Alpine geosynclines. The noted stratigraphic correlation of fluorine anomalies suggested, in addition, that fluorine bearing layers could be used as temporaneous marker beds. An interesting side observation was that of the bi-to tri-modal fluorine distribution in four profiles which represented well mineralized areas in contrast to the unimodal fluorine distribution in the rest three profiles with no distinct zone of mineralization. Probably such a multimodal distribution of fluorine may be characteristic of the Pb-Zn deposits (or other ore bearing-units) in paragenesis, granted which, it may find application as proximity indicators of ore deposits.Paper presented on the 23^rd of August 1976 at the International Geological Congress, Sydney, N. S. W., Australia     

Shatter cones produced experimentally by impacts in limestone targets

Experimentally produced impact craters in limestone targets displayed millimeter-sized shatter cones within crater spallation zones. The craters have been produced by accelerating spherical metal projectiles by means of a light-gas gun. Variation of the impact velocity showed that at about 3 km/s shatter cone formation starts and is reproducible at any higher impact velocities. In most cases the cone apices were pointing in the direction of the impact center. The occurrence of shatter cones directly at the target surface (spallation zones of craters) does not support a theoretical model on shatter cone formation published by Gash (1971).