ALBERT

Description: The interaction between thrust and strike slip fault systems is well detailed in Pakistan where the Chaman transform zone connects the Makran and Himalayan convergence zones and contains an internal convergence zone in the Zhob district. The transform zone contains numerous strike slip faults of which the Chaman fault proper is the westernmost. We can demonstrate at least 200 km of left lateral displacement along the Chaman fault alone. In the Zhob belt N-S shortening by folds and a major thrust fault amounts to several dozen kilometres. The 400 km wide Makran convergence zone is now being shortened by E-W oriented folds, thrust faults, and reverse faults. As these faults in the Makran zone approach the transform zone, their traces bend to the N and motion on each of them becomes oblique, combining reverse and left lateral slip. They merge continuously with the strike slip faults of the Chaman transform zone. The Makran thrust system and the Chaman transform zone first became active in the late Oligocene or early Miocene. Later (Pliocene?), a component of left lateral shear occurred across the entire Makran Zone in association with the opening of the newly identified Haman-i-Mashkel fault trough S of the Chagai Hills and W of the Ras Koh. The total displacement and displacement rate across the Chaman transform zone varies in response to the rates of convergence in the plates E and W of the zone.

Description: The widespread occurrence of organic-carbon-rich strata (‘black shales’) in certain portions of Jurassic, Cretaceous and Cenozoic sequences has been well-documented from Deep Sea Drilling Project sites in the Atlantic and Pacific Oceans and from sequences, now exposed on land, originally deposited in the Tethyan ocean. These ancient black shales usually have been explained by analogy with examples of modern deep-sea sediments in which organic matter locally is preserved by (1) increasing the supply of organic matter, (2) increasing the rate of sedimentation, and/or (3) decreasing the oxygen content of the bottom water. However, detailed examination of many black shales reveals characteristics that cannot be explained by simple local models, including: their approximate coincidence in time globally; their occurrence in a variety of different environments, including open oxygenated oceans, restricted basins, deep and shallow water; their interbedding with organic-carbonpoor strata which often dominate a so-called black shale sequence; their deposition by pelagic, hemipelagic, turbiditic and other processes; and the variations in type and amount of organic matter that occur even within the same sequence. A more complex model for the origin of black shales therefore appears most appropriate, in which the cyclic preservation of organic matter depends on the interplay of the three main variables, namely supply of organic matter, sedimentation rate, and deep-water oxygenation, each of which varies independently to some extent. The variation and relative importance of these parameters in individual basins and widespread black shale deposition in general are linked globally and temporally by changes in global sea-level, climate and related changes in oceanic circulation. An important and often overlooked factor for the supply of organic matter to deep-basin sediments is the frequency and magnitude of redepositional processes. The interplay of these variables is discussed in relation to the middle Cretaceous and Cenozoic organic-carbon-rich strata, in particular, which show marked differences in the relative importance of the different variables.

Description: In years of high abundance, the short-finned squid (Illex illecebrosus) was a common prey of Atlantic cod (Gadus morhua) in summer and autumn in both inshore and offshore waters of eastern Newfoundland and in the eastern and northern Gulf of St. Lawrence.The frequency of occurrence of squid in cod stomachs and the number of squid per stomach increased with cod length. The intensity of predation by cod on squid was low compared with peak predation on capelin (Mallotus villosus) and sand lance (Ammodytes sp.). Nevertheless, the annual immigration of squid in years of high abundance provided an increase in total food availability, especially for large cod.

Description: A modified version of yield-per-recruit analysis wasused to estimate potential yields in the Loligo pealei fishery off the northe stern USA. The mode1 accepts monthly values of growth and fishing, spawning and natural mortality rates and assumes two cohorts per year class, as associated with pawning peaks. Two patterns of exploitation were examined by simulatting dominance of the international fishery (offshore, winter fishing coupled with the domestic inshore summer fishing) and the domestic fishery alone through varistion of the monthly pattern of fishing mortalita. Parameter estimates were derived from survey catch per tow and commercial catch data.

Description: Development stages for artificially fertilized and naturally spawned eggs of Illex illecebrosus were observed and a staging scheme proposed which relates to earlier studies on naturally spawned eggs of Illex coindetii and artificially fertilized eggs of Todarodes pacificus. Photographs and descriptions of stages provide a reference for embryonic development of small ommastrephid eggs and an aid to the identification of egg masses of the species in nature, an essential step in understanding its life cycle. Embryonic development in Illex illecebrosus fails at temperatures below 12.5°C. and the development rate at 21°C is nearly twice that at 12.5°C. This temperature requirement restricts the spatial and temporal distribution of spawning in this squid, and temperature-related development rates allow prediction of the age of egg masses found in nature in water masses of a particular temperature.