ALBERT

Description: Spirula spirula has stimulated considerable interest since it was first discovered. It is a member of one of the two genera of sepioids to frequent oceanic water (the other being Heteroteuthis); it has a unique spiral shell which acts as a buoyancy mechanism and can withstand considerable pressure (Denton, Gilpin-Brown & Howarth, 1967); and, until the capture by the Danish Oceanographical expeditions it was considered very rare, only 12 specimens having been captured. The Dana expeditions caught 193 individuals from 1909 to 1931 and these were described by Kerr (1931) and Bruun (1943,1955). Most of these were caught in the waters around the Canary Islands of the North Atlantic. Bruun (1943) arranged the specimens according to month and size and claimed that two size groups could be distinguished. The specimens were taken over a wide geographical area, in several years and during the months of February (1 specimen), March (40), April (3), May (8), June (1), August (1) and October (23). His conclusion concerning growth depends entirely upon his decision to split the March sample into two year-groups; those above 1.9 cm in ventral mantle length he put in a separate year-class to those below 1.9 cm in ventral mantle length. This division was arbitrary and, one suspects, based on a belief that a one-year life-span was likely. Clearly the growth of Spirula requires further study based on a larger collection and the present paper is an attempt to fulfil this need.

Description: This review is intended to cover the principal developments that have occurred within the last six years in the paleomagnetic study of marine sediments. Recent work utilizing the reflecting-light microscope indicates that detrital high-temperature Fe-Ti oxides are probably responsible for most of the magnetic remanence in marine sediments. These minerals possess a spectrum of coercivities that makes it necessary to use alternating-field—demagnetization techniques to isolate stable components. It is possible to use the standard magnetic stratigraphy for the last 4 m.y. of earth history derived from terrestrial lavas. Using the ages of the magnetic boundaries from this time scale it is possible by extrapolation and interpolation to better determine the ages of the major events. The ages of these events in increasing age are Jaramillo, 0.87 to 0.92 m.y.; Olduvai, 1.71 to 1.86 m.y.; Kaena, 2.82 to 2.90 m.y.; Mammoth, 3.0 to 3.085 m.y.; Cochiti, 3.72 to 3.82 m.y.; Nunivak, 3.97 to 4.14 m.y.; ‘c’ event of the Gilbert series, 4.33 to 4.65 m.y. Through the use of long cores from the central Pacific and through correlation using fossil datums, it has been possible to extend the magnetic stratigraphy back to the upper middle Miocene to magnetic epoch 5. It is concluded that very short magnetic events are probably short-term excursions of the field and not true magnetic events. It is shown that the field of the earth averages to an axial-dipole field within a period of 27,000 years and that the field over the last two million years has acted as a geocentric axial dipole. The evidence shows that when reversals of the dipole occur, the values of the reversed inclination are not significantly different from the normal values. The use of magnetic stratigraphy in marine geology has opened up a new era in study of sedimentary processes and evolution of marine organisms.

Description: The examination of forty two samples of Sediment coming from the “Golfe de Gascogne” Continental margin (from 150 to 4.200 metres) has established the proof of a fauna rieh in benthic and planktonic foraminifera. This research enables to set up the value of certain foraminiferal associations and to propose a zoned essay based on three major groups touching successively the infralittoral, epibathyal, mesobathyal and abyssal parts.

Description: Young tests studied in very thin sections with the light-microscope with a magnification x 1000 showed, that the results obtained hy Reiss, Be Hemleben and others cannot be true. A primary membrane with sieve-plates where pores are projected by the animal is the first formed membrane; then a hyaline layer is formed beneath the membrane with a general thickness of 2-5 (1 in the Globigerine species. Hie thickness of this primary lamella is also that of the lamella covering the proloculus and the first initial chambers and their septa which always have simple walls. In this primary lamella the pores are spared out and they are at first closed by the sieveplates which, however, may be dissolved soon but for a rim in the wall of the pores. Then a second layer Starts, now at the outside of the primary membrane, beginning with fine knobs between the pores but soon forming a whole layer of clear calcäreous matter. It is in this stage that also the first spines are formed, strengthened at their bases by a mount of calcareous matter; so these spines end at their bases at the primary membrane. The thickening of the outer lamella may continue; this lamella is formed soon after the building of the primary lamella, Not only by means of the study of the last formed chamber of several species of Globigerines this result was obtained, but also by means of the colouring of the layers in Globigerina rubra. It is shown, moreover, that Sphaeroidinella dehiscens cannot be an advanced stage of Globigerina triloba. In Globorotaliid species the primary lamella, as found by Reiss c.s., mostly is slightly thicker than in Globigerines. In this group young specimens were observed with last formed chambers having only the primary lamella covered by the primary membrane also, whereas specimens were found which have septa only built by this lamella. The second, outer lamella is formed soon after the primary lamella, so that many specimens occur which show two lamellae in the wall of the last formed chamber. The result is thus quite similar to that obtained in the Globigerines: the species around Globorotalia are monolamellar too.

Description: The application of plagioclase geothermometry to plagioclase-bearing volcanic ash layers and to the glassy margins of pillow basalts from the fast-spreading East Pacific rise, the moderately spreading Gorda and Juan de Fuca ridges, and the slow-spreading mid-Atlantic ridge has shown that magma temperatures, as well as average An contents of plagioclases, are negatively correlated with spreading rates. A detailed investigation of the major element chemistry of volcanic glasses from each of these areas suggests that the observed consistent element-element covariances among individual populations of samples have been caused by fractional crystallization of the magmas. The regularity of chemical variation and the similarity of magma temperatures within each population of samples suggest that magmas ascending from beneath each ridge have had similar evolutionary histories. Vector analysis of the chemical data of all samples of volcanic glasses indicate that each population of samples from each of the spreading centers is chemically distinct, even though all samples have been subjected to similar amounts of fractional crystallization. The compositional distinctiveness of each population of oceanic tholeiites probably reflects differences in the depths at which the magmas were generated. Calculated magma temperatures and geothermal gradients calculated from published heat flow measurements can be used to estimate depths of magma generation of about 16 km beneath the East Pacific rise and about 23 km beneath the mid-Atlantic ridge.

Description: The distinguishing features of the common squid of British waters, Loligo forbesi, are summarized, and contrasted with those of L. vulgaris. The life-cycle and growth of L. forbesi are described, based on samples from trawl catches off Plymouth. This species seems to be an annual - young squid first appear in the trawl in late May, when their length is about 10 or 11 cm. Subsequent growth is rapid, and the males reach 30 cm and the females 25 cm by November. Spawning takes place mainly in December-January, but may continue into the spring. Neither sex survives beyond a single spawning season. Hatching of the spawn probably takes 30–40 days, and if the young squid taken in the trawl in late May hatched in the early part of the same year, a growth rate of about 25 mm/month would be required. Known growth rates for other species of Loligo are about 20 mm/month, so that indicated for L. forbesi does not seem to be impossibly high. The life-cycle is summarized in Fig. 8. There is also a summer spawning population, which grows to a rather smaller size at maturity, and which also seems to be annual. During the summer L. forbesi ranges throughout the English Channel and southern North Sea, particularly in inshore areas. In October the squid migrate farther offshore and tend to occupy the western part of the Channel. Values for total weight of squid/2 h trawl are given, on a monthly basis, for 1966–9. The largest quantities are usually taken in October and November, the highest single figure being 30.54 kg/2 h trawl, in November 1967.

Description: Twenty-four out of 240 fishes caught by bottom lines at 366–3333 m had something in their stomachs. Stomach contents included parts of cephalopods, fish, cetaceans and bottom-living invertebrates, thin rubber sheet and terrestrial mammal bones. The material provides evidence that four species of cephalopod are at least partially demersal and suggests a means by which the tapeworm Phyllobothrium could pass from its secondary to its primary host. During the five biological cruises of R.R.S. ‘Discovery’ between 1967 and 1971 a total of 31 bottom lines with 1483 hooks were fished in depths of water between 366 and 3333 m. The stomachs of the 240 fish caught were examined and 216 (90%) proved to be empty. The high incidence of empty stomachs is thought to be due to frequent loss of food during the ascent from great depths and accounts for our poor knowledge of the feeding habits of demersal fish living at depths exceeding 400 m. The present collection of food from 25 stomachs (24 from ‘Discovery’ collections and one from a fish caught by Mr G. R. Forster from R. V. ‘Sarsia’) of fish belonging to 11 species (Table 1) probably gives little indication of the usual diet of the fish concerned, but its nature prompts some useful speculation and the rarity of such observations justifies placing them on record (Bigelow & Schroeder, 1948; Marshall, 1954). All the fish were caught on lines which lay on the bottom for several hours and it is our firm belief that they were hooked while on or very near the bottom.

Description: Bolli assumed. that at the beginning of an evolutionary trend of planktonic Foraminifera the coiling direction should be at random. Two sequences of such trends were studied, the one of the Globigerina-cretacea-gens (Praeglobotruncana infracretacea- P. gautierensis) in the Albian of Holland, the other of the Globigerina (Globoconusa)- daubjergensis-gens in the Danian of Denmark, to verify this assumption. Both sequences show that in the beginning of an evolutionary trend the percentages of right coiling are distinctly less than 50 % and that later in the evolution the random coiling direction is transgressed towards dominant right coiling. The eventual causes of sudden regressions towards left coiling are discussed.

Description: In their wall-structure specimens from the Miocene (Sphaeroidinellopis seminulina (Schwager) = S. subdehiscens Blow) do not differ from later forms of this gens. The walls consist of an inner calcareous lamella, covered by the primary pseudochitinous lamella, succeeded by a second calcareous lamella in which eventually spines can be detected, and then a third thicker calcareous lamella is added, as in Globigerina rubra (Hofker, 1971, Pl. VI). The difference with Sphaeroidinella is that dorsal secondary apertures are lacking. But young specimens of S. dehiscens from Basal Pleistocene in a JOIDES sample lack these openings also, whereas the chambers following the embryonic ones all show the third thickening lamella. In these pleistocene individuals remmants of the spines are found in the form of fine open canals which do not pierce the chitinous lamella nor the primary calcitic one. Last formed embryonic chambers may show traces of these spines at their outsides. Young specimens of the Recent form, S. excavata Blow, are built as the Miocene ancestor. This recent form shows bullae in many specimens. During this evolution from Miocene to Recent the gens gradually increases its size in the adult specimens, as is found in many other planktonic gentes. Ontogenetically as well as phylogenetically this gens shows no proof of the theory proposed by Be, Hemleben and Bandy, that Sphaeroidinella is the deep water form of Globigerina sacculifera Brady. The forming of secondary apertures in the later larger forms of this gens is also found in many other planktonic genes increasing their size during time, as is the forming of bullae. There is no reason to split off the genus Sphaeroidinellopsis from Sphaeroidinella as the young specimens of the latter genus should in that case be put in Sphaerodinellopsis. In the Recent form the hollows left by the spines are filled up with calcite when the third thickening lamella is formed.

Description: The 1964 Alaskan earthquake (Ms ≈ 8.4) involved a segment of the eastern Aleutian arc 800 gm long; the 1960 Chilean earthquake sequence (Ms ≈ 8.5) affected roughly 100 km of the southern Peru-Chile arc. These two major events are strikingly similar in that (1) seismicity was shallow (〈70 km), the earthquake focal regions and most of the associated tectonic deformation being between the oceanic trenches and volcanic chains of the two arcs; (2) regional vertical displacements were characterized by broad asymmetric downwarps elongate parallel to the arcs with flanking zones of marked uplift on the seaward sides and minor, possibly local, uplift on the landward sides; and (3) horizontal displacements, where determined by retriangulation, involved systematic shifts in a generally seaward direction and transverse tensile strains across the zones of subsidence. Surface displacements and seismicity for both events are compatible with dislocation models involving predominantly dip-slip movement of 20 meters or more on major complex thrust faults (megathrusts) inclined at average angles of about 9° beneath the eastern Aleutian arc and perhaps 20° beneath the Peru-Chile arc. The thrust-fault mechanism deduced for both the Alaskan and Chilean earthquakes is broadly consistent with the concept that the sectors of the Pacific rim in which they occurred are major zones of convergence along which the oceanic plates progressively underthrust the less mobile America plate. Directions of convergence between lithospheric plates at these arcs as deduced primarily from paleomagnetic data are in reasonably good agreement with the observed earthquake-related deformation; the deduced rates of convergence, however, appear to be too high in the eastern Aleutian arc and too low in the southern Peru-Chile arc. Despite gross similarities in tectonic setting and the present style of earthquake-related deformation, the geologies of the continental margins in the eastern Aleutian arc and southern Peru-Chile arc differ significantly. This difference suggests that Mesozoic and Cenozoic sediments and volcanic rocks conveyed into the eastern Aleutian trench have progressively accreted to the Alaskan continental margin, whereas most or all of the material carried into the southern Peru-Chile trench has disappeared beneath the Chilean continental margin.