ALBERT

Description: During the cruises 3 and 15 of R.V. "Meteor", representatives of 7 families of benthic abyssal gastropods were collected. The prevalent group was the Turridae; the Naticidae are represented by 2 species, the remaining families by a single species each. A survey of the frequency and distribution of the species within the study area is given. A systematic part deals with the individual species in detail, including notes on taxonomy, material and distribution. Concerning the composition of the abyssal gastropod fauna of the present material, Neogastropoda are 4 times as many as Archaeogastropoda and 6 times as many as Mesogastropoda and Opisthobranchia. 89 % of all specimens are Neogastropoda. Usually deep-sea organisms have a non-pelagic development, but many of the Iberian deep-sea Turrids have a planktotrophic protoconch, that means a long pelagic larval period. Among the 19 species, 2 are cosmopolitan, 9 show a transatlantic distribution and 8 are confined to East-Atlantic basins.

Description: IPOD Leg 49 recovered basalts from 9 holes at 7 sites along 3 transects across the Mid-Atlantic Ridge: 63°N (Reykjanes), 45°N and 36°N (FAMOUS area). This has provided further information on the nature of mantle heterogeneity in the North Atlantic by enabling studies to be made of the variation of basalt composition with depth and with time near critical areas (Iceland and the Azores) where deep mantle plumes are thought to exist. Over 150 samples have been analysed for up to 40 major and trace elements and the results used to place constraints on the petrogenesis of the erupted basalts and hence on the geochemical nature of their source regions. It is apparent that few of the recovered basalts have the geochemical characteristics of typical "depleted" midocean ridge basalts (MORB). An unusually wide range of basalt compositions may be erupted at a single site: the range of rare earth patterns within the short section cored at Site 413, for instance, encompasses the total variation of REE patterns previously reported from the FAMOUS area. Nevertheless it is possible to account for most of the compositional variation at a single site by partial melting processes (including dynamic melting) and fractional crystallization. Partial melting mechanisms seem to be the dominant processes relating basalt compositions, particularly at 36°N and 45°N, suggesting that long-lived sub-axial magma chambers may not be a consistent feature of the slow-spreading Mid-Atlantic Ridge. Comparisons of basalts erupted at the same ridge segment for periods of the order of 35 m.y. (now lying along the same mantle flow line) do show some significant inter-site differences in Rb/Sr, Ce/Yb, 87Sr/86Sr, etc., which cannot be accounted for by fractionation mechanisms and which must reflect heterogeneities in the mantle source. However when hygromagmatophile (HYG) trace element levels and ratios are considered, it is the constancy or consistency of these HYG ratios which is the more remarkable, implying that the mantle source feeding a particular ridge segment was uniform with respect to these elements for periods of the order of 35 m.y. and probably since the opening of the Atlantic. Yet these HYG element ratios at 63°N are very different from those at 45°N and 36°N and significantly different from the values at 22°N and in "MORB". The observed variations are difficult to reconcile with current concepts of mantle plumes and binary mixing models. The mantle is certainly heterogeneous, but there is not simply an "enriched" and a "depleted" source, but rather a range of sources heterogeneous on different scales for different elements - to an extent and volume depending on previous depletion/enrichment events. HYG element ratios offer the best method of defining compositionally different mantle segments since they are little modified by the fractionation processes associated with basalt generation.

Description: Calcareous nannoplankton biostratigraphy has been worked out in the eastern Mediterranean utilizing deep-sea sediments recovered from DSDP Leg 42A Sites 375 and 376. These two drill sites were located approximately 55 km west of Cyprus on the Florence Rise. Sediments, ranging in age from early Miocene (Helicosphaera ampliaperta Zone) through Holocene, contain sufficient age-diagnostic species to recognize essentially all of the lowlatitude nannoplankton zones described by Bukry, although regional, secondary marker species are needed to define some zonal boundaries. Reworked Cretaceous and Paleogene nannoplankton occur throughout the stratigraphic interval studied, but not in quantities large enough to mask indigenous species. Sedimentation rates at Sites 375 and 376 were highest in the late Miocene and late Pleistocene. Open-marine, warm-water species of discoasters are present in significant numbers throughout the Miocene and Pliocene. Earliest Pliocene assemblages contain numerous specimens of ceratoliths. Nannoplankton in post-Messinian sediments at the drill sites and the Zanclean stratotype at Capo Rossello, Sicily, indicate that the base of the Amaurolithus tricorniculatus Zone (base of Triquetrorhabdulus rugosus Subzone) corresponds with the Miocene-Pliocene boundary.

Description: Petrographic analysis of Quaternary terrigenous sand layers in eastern Mediterranean cores reveals distinct mineralogical differences between the Egyptian Shelf–Nile Cone region and the southern part of the Mediterranean Ridge. A compositionally and texturally immature suite in Ridge cores, mixed with a Nile-derived assemblage, identifies a fresh non-recycled mineral component derived from proximal igneous and metamorphic surface or near-surface exposures, probably in the south–central Ridge area rather than from distal African sources. The presence of such basement terrains would be consistent with a compressive thrust-belt origin for this part of the Mediterranean Ridge.

Description: The lipids and kerogens of 15 sediment samples from Site 547 (ranging from Pleistocene to Early Jurassic/Triassic) and 4 from Site 545 (Cretaceous) have been analyzed. A strong terrestrial contribution of organic matter was found, and significant autochthonous inputs were also present, especially at Site 545. Both strongly reduced and highly oxidized sediments have been found in the Cenozoic and Jurassic samples of Site 547. On the contrary, all the Cretaceous sections of Sites 547 and 545 are anoxic. Sediments from anoxic paleoenvironments are immature and have a high content of sterenes, diasterenes, steradienes, hopenes, and ßß hopanes. Samples from oxic paleoenvironments are mainly mature and their content of hopenes and steriod structures is below the detection level. Nevertheless, their hopane distributions have the immature ßß homologs as the predominant molecular markers. For Site 545 the most abundant molecular markers are ring A monoaromatic steranes, and their presence is attributed to microbial and chemical transformations during early diagenesis.

Description: Regional variations in abundance, morphology, and chemical composition of Fe-Mn nodules have a zonal character. Due to circumcontinental zonality of terrigenous sedimentation the main mass of the nodules occurs in the pelagic part of the ocean, in areas of minimal sedimentation rates. In spatial variations in morphology and chemical composition of the nodules the latitudinal zonality is very clear and associated with latitudinal changes in facial conditions of sedimentation. Elevated contents of Mn, Ni, and Cu and of Mn/Fe ratio occur in nodules from the radiolarian belt. Changes of chemical composition of the nodules with depth (vertical zonality of mineralization) are confirmed. Local variations in abundance, morphology and chemical composition of the nodules are caused by ruggedness of relief and depth variations, variations in sedimentation rate, age of ore formation, intensity of diagenetic redistribution of metals.

Description: Manganese nodules occurring within marine sediments of presumably Upper Miocene-Lower Pliocene age from cores obtained by the Argentine oceanographic vessel ARA Islas Orcadas in 1977 on the Malvinas (Falkland) Plateau and neighbouring Scotia Sea were studied with the aim of comparing them with other fossil nodules found on the mainland of Argentina that were also ascribed to the marine environment. After optical mineralogical, chemical, X-ray and trace element analysis, the studied "nodules" proved to be actually wacke clasts cemented by manganese oxides with a high Fe/Mn ratio corresponding to a continental environment. The studied "nodules" thus differ from the Argentine mainland nodules and are supposed to have been transported from continental environments and then deposited in the marine realms. The wacke clasts became then nuclei for the deposition of the marine manganese oxides of the coatings. The proportion of trace elements, which is high, suggests the growth of the nodules in the marine environment.

Description: Manganese nodules have been analysed at the Scripps Institution of Oceanography after having been ground to to a diameter less than 74 microns. Some analysises were performed on pellets by X-ray Emission Spectroscopy for 1000 Seconds. All concentrations have been corrected to 110 degrees Celsius drying conditions (see: https://doi.pangaea.de/10.1594/PANGAEA.854202).

Description: Deep sea photographs in the GH77-1 cruise were obtained by two methods, namely a one-shot 16 mm camera attached to the freefall (boomerang) type photo grab and an independent 35 mm deep sea camera.

Description: Phosphatized bioclastic limestones of Early Tertiary age have been dredged from the crest of a seamount in the equatorial Atlantic near 9°N, 21°W. The samples were recovered from water depths of 700 to 970 m but clearly were deposited in a high-energy reefal environment, thus indicating significant Tertiary subsidence. The vertical movement is beleived to reflect reactivation of an old structural line, the Guinée Fracture Zone, which may have had important effects on the transfer of bottom waters of polar origin between the Sierra Leone and Gambia basins. Examination of foraminiferal limestone coating the shallow water material suggests that deep-water conditions were established on the seamount by Middle Miocene time. All phosphatized samples are covered with a layer of ferromanganese oxides which, from textural and faunal evidence, is Palaeocene or Eocene in age and of shallow water origin. Pervasive phosphatization of the bioclastic limestones appears to have been accomplished before the end of the Eocene while the crest of the seamount was near sea level, because Upper Eocene limestone of shallow water facies is unaffected by such radical diagenesis. Phosphatization probably was associated with vigorous upwelling near the seamount and has been taken to an unusually advanced stage, resulting in a phosphoritesof high economic grade. P2O5 contents are in the range of 37 to 41%. The purity of the phosphorites may be related to the intensity of upwelling during the Early Tertiary, but other factors such as the paucity of terrigenous detritus, frequent reworking of the sedimentary capping of the seamount, and a high primary porosity of the limestones may have been important in their information. The Early Tertiary period of phosphorite deposition on the seamount and in northwest Africa ended before the close of Eocene time in both areas, while shallow water conditions prevailed. It is argued that the cessation of phosphorite formation reflects major changes in the surface circulation of the Atlantic during the Eocene.

Description: Morphological, mineralogical and chemical analysis are reported for a metalliferous encrustation from a seamount in the Gulf of Guinea, South Atlantic. The results are compared with published data on encrustation from similar environments. The morphology and mineralogy indicate a crust formed on the exposed rock surface with some agglutination of foram debris. Comparison of the abundance patterns for transition elements with that of known data suggests that some enrichment had resulted from the high primary productivity at this site.

Description: The rate of accumulation of a ferromanganese coating on a fragment of pillow basalt was estimated using a variety of techniques. Unsupported 230 Th activity decrease in the oxide layer, K/A dating of the basalt, fission tracks dating of the glassy layer around the basalt, thickness of the palagonitization rind, and integrated 230 Th activity give ages from approximately 3 x 10-6 years to 5 x 10-3 years. Data suggest that the ferromanganese material formed rapidly (33 mm/10-6 years) and by hydrothermal or volcanic processes.

Description: The volcanic deposits which surround Vulcano Island may be classified in four phases : a detritic phase, fed from the Island itself and from Sicily; a siliceous and carbonateous organic phase; a neogenesis mineral phase; a precipitation phase. The formation of clay and the mineralization of iron and manganese are the subject of particular study. A number of indications suggest the littoral neogenesis of kaolinite around hydrothermal issues, and the formation of smectite at greater depths. The distribution of iron mineralization in the Baie du Levant follows the physicochemical variations of the environment. Melnikovite, pyrite, marcassite and pyrrhotin are dispersed in aureoles around swallow emission points (fumaroles). Close to the hydrothermal spring, iron precipitates are found in the form of amorphous hydroxydes, while geothite and hematite characterize the deeper area as a whole. Manganese mineralizations are exclusively represented by hydroxides and oxides, locally (about - 250 m) organized as incrustations on. lapilli glasses (micronodules). These would appear to be related to the hydrothermal spring.

Description: The growth rate of a manganese nodule from the South Atlantic Ocean (Rio Grande Ridge) has been determined using a 10Be profile as measured with a Tandem Van de Graaff accelerator. This rate is 4.5 mm /My. A correlation may exist between the 10Be flux and the Mn flux to nodules.

Description: The suite of gabbroic rocks collected by the DSRV ALVIN in 1976 and 1977 from the walls of the Mid-Cayman Rise spreading center were studied in detail to provide the best available data on plutonic rocks sampled directly from the ocean floor. The rock types studied include variably deformed and altered gabbros, orthopyroxene gabbros, olivine gabbros and troctolites, and a few amphibolites. Mineral chemical analyses suggest that the various rock types are representative of a fractionation trend from magnesian troctolites through olivine and clinopyroxene gabbros to iron-enriched orthopyroxene gabbros. Within many individual samples, the primary mineral phases are apparently chemically homogeneous despite sometimes considerable alteration, which suggests reequilibration after original crystallization. Variation in mineral-chemistry across the suite is larger than previously reported for ocean-floor gabbros; this may be due to the larger population of this study. The primary or secondary nature of plagioclase and amphibole must be distinguished in discussions of the igneous processes involved in the genesis of these rocks. In this suite, textural evidence is often inconclusive, and although sodic chemistry is assumed to indicate a secondary origin for plagioclase, no chemical indicator was found to apply to amphiboles. Many different deformation textures are observed in the samples, indicating considerable variation in the conditions of deformation within this slowly accreting ridge environment. Ductile features range from mechanical twins and bent crystals (low strain) to complete recrystallization with a well-developed foliation (high strain). Textures suggestive of cataclasis include zones .1-10 mm wide containing very fine, irregular grains; kinked and cracked grains, usually very undulose; and crosscutting fractures. These textures may occur separately, or next to or overprinting each other. Of the variables controlling the formation of deformation features, temperature and water pressure are most easily estimated. Minimum temperature during deformation is suggested by minimum temperature of formation of mineral assemblages unaffected by this deformation. This temperature is greater than 550°C (epidote-amphibolite facies) for the majority of features observed, although sampling may have introduced a bias away from lower temperature features. Observations suggest enhanced recrystallization where the primary mineralogy has been hydrated to a greater extent. Theoretically, confining pressure for the gabbroic rocks in this suite may have varied from about .3-.9kb; fluid pressure should have been within these limits. Based on mineralogical evidence, cataclastic and ductile textures developed at both high and moderate temperatures. This suggests that strain rates and/or pressure vary considerably within regions where rocks are hot as well as where rocks are cooler, and that after high-temperature deformation some rocks cooled quickly enough to prevent significant recrystallization while others cooled more slowly. These interpretations indicate that the Cayman plutonics were raised to their present position by motions which varied from place to place and time to time, and suggests that the structural history of plutonic.rocks formed at slowly accreting plate boundaries is highly variable and complex.

Description: Mesozoic benthic foraminifers, recovered from five single-bit holes drilled in the southern Gulf of Mexico on Deep Sea Drilling Project Leg 77 are rare, poorly preserved, and scattered throughout the dominantly redeposited sediments. The Mesozoic sequence at basin Sites 535 and 540 consists largely of laminated limestone with smaller amounts of skeletal limestone and pure pelagic limestone, whereas the Mesozoic sediments at basement Sites 536, 537, and 538 (Hole 538A) consist largely of oolitic-oncolitic limestone.

Description: Ranging in height from gentle hills of less than a meter to steep-sided giants of more than 20 m, the mounds of the Galapagos Rift are spectacular hydrothermal features. Their internal temperatures have been measured at up to 13°C above the bottom water temperature, and total heat flow (conducted plus convected) can be several hundred to several thousand times the normal oceanic values. Fluids, when they discharge from the mound, do so at a very slow rate and at temperatures probably quite near the bottom water temperature. The mounds are principally composed of iron silicates intermixed and incrusted with lesser amounts of manganese oxides. They are generally found in rows, in a uniformly sedimented area above faults or fractures in the crustal rocks which permit fluids to escape from a deep hydrothermal aquifer. The sediment blanket in some way alters the chemistry of the ascending thermal fluids and leads to the development of mounds. The mounds field, covering an area of at least 200 km2 and consisting of thousands of individual mounds, is probably less than 300,000 years old; and many of the mounds may be only a few tens of thousands of years old or less.

Description: Leg 43 was planned to examine a wide variety of geological problems at numerous sites in the deep western North Atlantic basin. A variety of objectives were to be addressed on Leg 43,among these: 1) to investigate the sedimentary development of the North American basin, 2) to recover sediments containing late Mesozoic and Cenozoic fossils for biostratigraphic, paleobiogeographic, and paleoceanographic studies 3) to recover samples of basaltic basement from the smooth crest of the basement ridge associated with the northern part of the New England seamounts, 4) To examine the age and nature of volcanism on Bermuda and along the New England seamount chain, in order to test ideas on volcanic* origin such as the "hotspot" hypothesis, and to examine volcaniclastic lithofacies and assess the role of volcanic sources for certain North Atlantic sediments.

Description: This paper summarizes the petrography and major element chemistry of basalt collected by R/V Atlantis II at 23 °N, and compare these data with published data for 22 °N and with the preliminary shipboard data for DSDP Sites 395 and 396, in order to define the regional petrologic setting of the Leg 45 basalts.

Description: A combined mineralogical, petrological, and geochemical study of altered basaltic rock samples of the upper oceanic crust from Hole 396B IPOD Leg 46. The hole was drilled on the west flank of the Mid-Atlantic Ridge, in anomaly 5 at about 23°N. The site is located in a sediment pond at a water depth of 4450 meters; 205 meters of pillow lavas intercalated with indurated ooze and one exceptionally thick lava unit (sill or flow?) were drilled.

Description: Leg 45 of the Deep Sea Drilling Project was the inaugural cruise of the International Phase of Ocean Drilling. Its primary scientific objective was to develop an understanding of the composition, structure, and origin of oceanic crust by drilling as deeply into it as technology would permit. The feasibility of drilling deep into the oceanic crust was demonstrated during Leg 37 when one hole was drilled 586 meters into basaltic volcanic rocks near the crest of the Mid-Atlantic Ridge at about 37 °N. The areas of principal interest for Leg 45 were survey areas AT-5, situated near 23 °N, 46 °W and AT-6 near 23 °N, 43°W. The two survey areas are on opposite sides of the Mid-Atlantic Ridge, south of the Kane fracture zone. During Leg 45, Holes 395 and 395A were drilled in survey area AT-5 and Hole 396, was drilled in survey area AT-6.

Description: Unlike many cruises of the Deep Sea Drilling Project, Leg 48 was scientifically planned to drill a number of sites to systematically address the problems of passive margin evolution. Site 400 was drilled at the foot of the Meriadzek Escarpment of North Biscay in 4399 meters depth. The site was located in a half-graben forming part of a succession of tilted and rotated fault blocks near the continent/ocean boundary. Site 401 was situated on the planated edge of a tilted fault-block underlying the southern edge of the Meriadzek Terrace on the north Biscay margin. Site 402 was located on the upper slope of the northern continental margin of the Bay of Biscay. The main objectives were to establish the presence or absence of shallow water Upper Cretaceous beds, and to penetrate pre-Aptian synrift sediments and the upslope equivalent of the deep water Albian-Aptian carbonaceous mudstones penetrated at Hole 400A.

Description: Leg 49 of the International Phase of Ocean Drilling (IPOD) was designed with a wide spectrum of problems in mind. Topics investigated were (1) variation with time of mantle sources of spreading-center magmas, (2) aging of the volcanic layer, (3) degree of hydrothermal alteration and metamorphism of the volcanic layer, (4) lateral and vertical variation of the petrochemistry, magnetic properties, and structure of the volcanic layer, (5) north-south variability of spreading-center magmas through the North Atlantic, (6) initiation of glaciation during the late Pliocene, and (7) the influence of bottom currents originating at the Iceland-Faeroes Ridge on sediments of the ridge flank province of the western North Atlantic.

Description: 35 km either side of the Pacific-Cocos spreading axis at 846'N, on crust 0.6 x 10SUP-6 years old, a pair of small seamounts rises 1.4 km above the faulted terrain of young abyssal hills. A high-resolution traverse made with the sonars and cameras of a deeply towed vehicle shows that the seamounts are inactive volcanoes, with concave side slopes that steepen upwards to 30, and then abruptly flatten at 2-4 km wide summits. Ledges of pillow basalt outcrop on the lower slopes, and form some talus slopes, but the superficial rock of the upper slopes appear to be mainly hyaloclastite. A transponder-navigated deep-tow survey at the summit area of the eastern seamount mapped an asymmetric caldera containing 3 pit craters, which have vertical walls and flat floors. Dredging across the caldera floor recovered hyaloclastite, angular fragments of primitive tholeiite, and manganese nodules. The paired seamounts probably had a common origin at a 'hot spot' on the spreading axis; continued to grow after they were split by sea-floor spreading; and became extinct and suffered summit collapse after they spread too far from their magma source.

Description: In Costa Rica the manganese deposits are an integral part of the Nicoya ophiolite complex. They contain both primary mineralization and, due to weathering, small residual concentrations. The most common manganese minerals in surface outcrops are psilomelane and pyrolusite. Most of them exist in jasper bodies often in a form of breccia in contact with underlaying basalt. In some instances stratiform manganese-oxide crusts and nodule deposits cap jasper bodies and stratabound deposits being overlain by radiolarites.

Description: The main objective of the cruise was to study the sediments and sedimentary processes in an area known as Great Meteor East (GME) - part of a feasibility study into the ocean disposal of high-level radioactive waste commissioned by the Department of the Environment. Previous cruises (Discovery 118, 126, 134 and Farnella 3/81) had done much of the ground work, consequently the area was already well known but not necessarily well understood for the purposes of our investigation.

Description: One of the main objectives of the International Phase of Ocean Drilling (IPOD) of the Deep Sea Drilling Project was to determine the geological, geochemical, and geophysical character of ocean crust formed at mid-ocean spreading ridges. A series of drill holes along the Mid-Atlantic Ridge (MAR), from near Iceland south to approximately 22°N latitude, was planned to compare the crust being generated near an anomalous ridge (Iceland) with that originating near a normal slow-spreading ridge (22°N). At the same time, a series of holes in near zero-age crust at 22 °N was planned along a "flow line" (a transect parallel to local fracture zones) trending west into increasingly older crust, eventually extending the sampling to crust of apparent Jurassic date off the eastern United States coast. This age-transgressive transect was designed to test the evolution of crust formed at one point in the spreading ridge. The intersection of these two series of holes was designated Atlantic Site 5 and was positioned on the upper western flank of the Mid Atlantic Ridge near 22 °N latitude, as close as possible to the spreading ridge crest. The R/V Kana Keoki conducted a detailed 22-day survey of Atlantic Site 5 during Cruise 74-01-01, Leg 7 prior to the DSDP Leg45 was conducted.

Description: The drilling plan for Leg 74 of the Deep Sea Drilling Project was designed to address three main scientific topics: (1) the history of the deep-water circulation in the southeastern Atlantic, (2) the nature and geologic evolution of the Walvis Ridge, and (3) the biostratigraphy and magnetic stratigraphy of this region. In order to study these subjects, a suite of five sites was drilled on the Walvis Ridge that extended from its crest (near 1000 m water depth) down its northwest flank into the Angola Basin to a depth of 4400 m.

Description: Leg 73 was the middle of five legs on South Atlantic paleoenvironments planned by the JOIDES Ocean Paleoenvironment (OP) Panel during the years from 1975 to 1980. The idea of drilling a transect of holes across the 30°S parallel was entertained soon after the drilling on Leg 3, during the first phase of the Deep Sea Drilling Project (1968/69), when the surprising discovery was made that the middle Miocene sediments of the South Atlantic were largely marls and red clays. The deposition of the red clays was obviously related to the intense dissolution of calcite during the middle Miocene, when the calcite-compensation level was elevated. The objectives and tactical planning for a transect across the east flank of the Mid-Atlantic Ridge just north of 30°S were outlined by the OP Panel more fully to the Planning Committee in July of 1978. After a piston core containing Paleocene sediments was taken in 1979 at the site in the Cape Basin at the foot of the Walvis Ridge this area was designated for DSDP Leg 73 and 74.

Description: Site 530 is located in the southeastern corner of the Angola Basin, about 20 km north of the Walvis Escarpment, near the eastern end of the easternmost (or Frio) segment of the Walvis Ridge. It lies on the abyssal floor of the Angola Basin and exhibits a seismic stratigraphic sequence typical for the entire deep part of the basin. It was selected because it appears to have the oldest strata in the region preserved in a sediment pond between low basement rises.

Description: The drilling of Leg 77 is part of an overall program by the JOIDES Passive Margin Panel to study the evolution of the western North Atlantic passive margin. The history of the central North Atlantic is probably the best known of all ocean basins, but the origin and history of the neighboring Gulf of Mexico are very much uncertain. Some geologists consider it the oldest ocean basin still in existence (Paleozoic), but others doubt the existence of "true" oceanic crust under the central Gulf. The nature and origin of the transitional crust and the overlying Mesozoic sedimentary sequences in the southeastern Gulf, therefore, was the main objective of Leg 77.

Description: The principal goal of Site 543 was definition of an oceanic reference section. One of the specific objectives was to provide a physical-property profile through the undisturbed oceanplate section and thereby a basis for measuring the tectonic consolidation of any offscraped rocks of similar lithology in the area of the Tiburon and Barracuda rises which constitute prominent highs emerging from the Atlantic abyssal plain and presently intersecting the deformation front of the Barbados Ridge complex.

Description: In surface sediment at the three DOMES sites in the equatorial North Pacific, the percentage of reworked fauna and the thickness of the acoustically transparent uppermost layer increases from east to west (Sites C to B to A) and the percentage of volcanogenic products decreases. On the basis of lithology and acoustic signature (3.5 kHz) this sediment can be correlated with surface sediment recovered in Deep Sea Drilling Project cores from this same area. It has been assigned to the radiolarian ooze unit of the Clipperton Ocean Formation. The underlying Marquesas Oceanic Formation, well documented in DSDP cores, was not observed in DOMES cores but was identified in the acoustic records as an acoustically transparent to weakly reflective unit. In the study area, the Clipperton Formation is commonly deeply eroded and unconformable with the sea-floor surface, but the Marquesas Formation is present everywhere and has a fairly uniform thickness.

Description: Recent study of many box cores and deep sea photographs from DOMES Sites A, B, and C throws new light on the mode or occurrence of manganese nodules in the Horn Region o f the Pacific. Most bos cores from which the supernatant water has been carefully removed show nodules resting on a relatively firm mud surface, and deep imbedding is rare except for very large nodules; yet many bottom photographs from sites nearby show nodules well-imbedded in what appears to be soft muddy sediment. Observations of nodules still covered by sea water in box cores and experiments designed to preserve the natural relationships between nodules and sediment may explain this paradox. We conclude that at least the upper part of the original sediment, which we call the sediment-water interface "boundary layer", collapses when de-watered to form a wet mud only a fraction the thickness of the material on the sea bed. The relatively firm mud upon which nodules rest in many box cores is thought to underlie the boundary layer at a fairly abrupt contact, but the boundary layer proper probably grades upward, becoming progressively more water-rich, to a diffuse contact with sea water. Small nodules tend to be suspended in the boundary layer and grow largely or totally surrounded by it. As nodules grow, they may reach a size which permits anchoring in the firmer mud below by growth o f oxide dendrites downward, with the result that morphology becomes more asymmetrical as overall growth proceeds. Nodules grow by adding the crystalline manganese oxides todorokite and birnessite where they are in contact with sediment or sediment rich water and iron-rich amorphous oxides where they are in contact with the sea water above. Nodules which show alternating Mn-rich and Fe-rich internal layers may owe this pattern to long-continued sedentary growth during which periods of exposure to sea water alternated with periods during which the upper nodule surface was covered by the boundary layer. Similar nodule structures may also result from periodic overturn of nodules, and many nodules probably experience both kinds of events. The long-standing problem of concentration of manganese nodules at the present deep sea sediment-water interface may be partly explained by the unusual properties of the boundary layer. Although it appears to be both fragile and mobile, it also seems to have a cohesiveness or strength which permits it to hold nodules in suspension in spite of the relatively high density or most nodules. The presence o f organic material (mucoprotein) may contribute to the special properties of the boundary layer. There is photographic evidence that the boundary layer may hide small nodules from view in camera surveys, but the layer is so mobile that even bottom organisms can remove it. The use o f some kind of simple "cleaning" device during camera surveys may produce photographs which give a more accurate record o f nodule distribution than is presently possible.

Description: The major and minor element composition of ferromanganese nodules from DOMES Site A has been determined by X-ray fluorescence methods. Three phases appear to control the bulk compositions: Mn and Fe oxyhydroxides and aluminosilicates. Relatively wide compositional variations are evident throughout the area. Nodules with high Mn/Fe ratios, high Cu, Mg, Mo, Ni and Zn concentrations and high todorokite/-MnO2 ratios have gritty surface textures and are confined to an east-west trending depression with thin Quaternary sediment cover. Nodules with low Mn/Fe ratios, high concentrations of As, Ca, Ce, Co, La, P, Sr, Ti, V, Y and Zr and low todorokite/-MnO2 ratios have smooth surfaces and are confined to shallower areas with relatively thick Quaternary sediment to the north and south of the depression. All nodules in the area have compositions which are influenced by diagenesis, but those with the most marked diagenetic signature (high Mn/Fe and Cu/Ni ratios, low Ce/La ratios and more todorokite) are found in areas of very slow or non-existent sedimentation; many of these nodules are actually in contact with outcropping Tertiary sediment. This paradox may be resolved by postulating, by analogy with some shallow-water occurrences, that the nodules accrete from bottom waters which have enhanced particulate and dissolved metal contents derived from diagenetic reaction in areas remote from the site of nodule formation. The metals are supplied in a bottom flow (probably Antarctic Bottom Water) which also erodes, or prevents modern sedimentation in, the depression. Nodules on the flanks of the depression are not evidently affected by this flow and derive at least pan of their constituent metals from diagenetic reaction in the underlying Quaternary sediment. Apparently, abyssal diagenetic nodules can have an immediate and a remote diagenetic metal source. Metal fluxes derived from pore water dissolved metal gradients may not be relevant to particular accreting nodules if a significant fraction of their metals is derived from outside the area in which they form.

Description: Cores, submarine photography and dredges described in this report were taken during the R/V Knorr Cruise K79-05 in 1979. Cores and dredges were recovered for 43 stations.

Description: Measurements of Pb-210 activities, in conjunction with micropaleontological, geotechnical and sedimentological observations, on sediment cores have been used to characterize two distinctive bioturbation regimes on the continental slope and rise east of Newfoundland. On the rise (2600 m), excess Pb-210 is confined to the upper few centimeters of the coarser-grained sediments underlying the axis of the Western Boundary Undercurrent. The geological and geochemical evidence for a low rate of bioturbation in this high bottom current regime is consistent with a reduced population of deeper burrowing macrofauna, particularly the species Maldane sarsi. In contrast, a higher flux of organic-rich, fine-grained particulate material to the middle slope (1500 m water depth), and the comparatively stable sedimentological conditions that prevail in this low bottom current regime, have led to the active colonization of the sediment substrate by bioturbating organisms. Enhanced mixing of middle slope deposits is reflected by comparatively lower shear strengths within the upper 30 cm of the sediment column, and by the reduced variability of the sediment-depth distribution of the most abundant species of foraminifera. Excess Pb-210 has been transported downward from the sediment-water interface to depths greater than 12 cm. Some Pb-210 profiles from the middle slope can be interpreted in terms of a diffusion mixing model for which the biological mixing coefficients are of the order of 0.10-1.0 cm2/yr.Measurements of the two and three dimensional distribution of excess Pb-210 in one middle slope box core indicate that the mixing process in these sediments has a pronounced heterogeneous component on time scales of the same order as the half life of Pb-210 (22.3 yr). Spatial correlations between Pb-210 anomalies and artifacts of bioturbation observed in x-radiographs of the core suggest that Pb-210 maxima observed at depth may be the result of an inclined orientation of burrow structures which have introduced a significant lateral component to the downward transport of surficial sediments.

Description: Manganese nodules and associated sediment from the equatorial North Pacific have been examined to ascertain relations between nodule abundance, texture, and composition, and sediment composition, lithology and acoustic stratigraphy. Nodules are most abundant in areas where the uppermost acoustically transparent layer of sediment is less than approximately 15 m thick. Abundance drops off sharply in areas where this acoustic unit is thicker than 20 m. Nodules have average Zn/Mn and Co/Mn ratios which are approximately the same as these ratios for the component of sediment soluble in hydroxylamine hydrochloride-acetic acid. The relations between Cu and Mn and Ni and Mn in the sediment are also approximately the same as in nodules, but only for those nodules which have a smooth surface texture. Granular nodules have relatively more Ni and Cu. Antimony in nodules, similar to Ni, Cu, and Zn, is strongly correlated with Mn, whereas Co, Hf, Th, and U are strongly correlated with Fe. The insoluble component of sediment has a uniform composition which is similar to the composition of terrigenous shale. This similarity holds for the major oxides as well as for Co, Cr, Zn, Hf, Sb, Th, U, Sc, Cs, Rb, and Ta.

Description: Shebandowan Lakes, Ontario, are the site of at least 49 shallow (2-12 m) ferromanganese concretion deposits, widely distributed throughout the 48 km of the watercourse. X-ray diffraction and Mossbauer methods have revealed the presence of goethite in some of the concretions. Chemical analyses of the acid soluble portions of 72 samples gave an average composition of 43.1% Fe and 5.65% Mn with a low content of trace elements. The Shebandowan concretions are among the richest in iron of lake concretions reported, possibly because only the acid soluble portion was analysed. Their low content of trace elements suggests rapid growth rates and a relatively young age. A positive correlation was found between Mn and K, Ca, Mg, Cu, Ni, and Co and the relationship between the last three and Mn was deemed significant. Zn was independent of association with either Mn and Fe, probably due to the presence locally of zinc sulphide deposits. Analyses of lake bottom and influent waters suggested that frequent resampling of the sites would be required throughout the year to permit meaningful interpretation of the effect of water composition of concretions. Analyses of sediment cores from 20 concretion sites indicated an upward increase in Fe and Mn and in the Mn/Fe ratio, consistent with the model of upward migration of the elements, where Mn is more mobile than Fe. This study concludes that a considerable proportion of the elements have been supplied to the Shebandowan concretions via the diagenetic process; generally a minor fraction of the elements has been abstracted directly from the superjacent water.

Description: Information on possible resource value of sea floor manganese nodule deposits in the Pacific has been assessed by Deepsea ventures Inc, from the collection of manganese nodules and crusts obtained during past research vessels' cruise from the Scripps Institution of Oceanography.

Description: Mineralogical and chemical analysis of an Eastern Pacific core has been conducted in the context of a study of mineralisations in pelagic sediments; the data point out the relations between thin (2-100 m) manganese oxyhydroxide concretions and volcano-sedimentary environments. Between Clarion and Clipperton Islands, the polymetallic precipitates are precocious and they are due to the submarine volcanic activity of this spreading zone; in spite of their small size, all the elements are concentrated in the precipitates: Mn (9-46%), Fe (0.2-11%), Ni (0.1-3.4%), Cu (0.1-1.7%), Co (0.1-0.8%). The high internal structuration of micromineralisations, the splitting up of the elements in the laminations, the variability of contents according to the state of crystallinity can be explained by diagenetic processes at the scale of the grain. The contrast between the degree of evolution of these mineralisations and the situation of the area, that was submitted to important terrigenous and volcanic sedimentary inputs, lead to consideration of the micronodules as 'blocked structures', precursors of nodules, developed from diagenetic reactions of the micro-environment.

Description: Manganese nodules from six Pacific Ocean sites contain two chief oxide components which can be distinguished by both optical and X-ray diffraction methods. Optically coordinated electron microprobe spot analyses reveal that copper and nickel are concentrated in the manganese-rich crystalline oxides (birnessite and todorokite) while cobalt is concentrated in the iron-rich amorphous oxides. In the nodules studied the maximum nickel content in the crystalline material is 3.6%, while the maximum copper content is 2.95%. The highest cobalt content found in the amorphous material was 0.74%. Large variations in concentrations were found within individual nodule layers as well as from one layer to another. Most of the variations cannot be accounted for by admixed nodule components. The variations cannot be distinguished by any optical or X-ray diffraction criteria and are probably controlled by the availability of the elements during primary deposition. There does not appear to be any linear interelement relationship between concentrations of the major elements (Mn and Fe) and the minor elements (Ni, Cu and Co). Linear relationships that have been reported in the past must be interpreted with care, for crystalline oxides and amorphous oxides may have been mixed in varying amounts during the sampling. In view of the different element associations in the crystalline and the amorphous oxides, the main factor for controlling bulk chemical analysis of a particular nodule appears to be the ratio of crystalline to amorphous material in the nodule. NSF-IDOE support of this research is acknowledged with thanks.

Description: Relationships among Th and Ra isotopes in nodule, sediment and water phases at MANOP Site S establish the most likely source for Th in the nodules, the frequency of nodule turning, and the similarity of micro and macro nodules. Manganese nodules and bottom waters have 230Th/232Th activity ratios considerably higher than other phases at this site suggesting that sea water is the likely source of Th for the nodules. Similar 230Th/232Th activity ratios in nodule tops and bottoms and in certain cases departure from expected 226Ra/230Th activity ratios in nodule tops and bottoms indicate that the nodules rotate every one to ten thousand years. The micro nodules have diffusion coefficients of Ra similar to macro nodule bottoms. I suggest that they may act as a carrier phase for transporting metals through oxic sediments to nodules.

Description: In the GH77-1 cruise, manganese nodules were obtained from 31 stations among 37 total ones. Here are reported the preliminary results of the observation mainly done on-board. Special attention was paid to confirming the applicability of the nodule type classification tentatively established in the previous GH76-1 cruise and to delineating the pattern of the nodule distribution and clarifying its relation to the geological factors, such as topography, surface sediment types, and substrate stratigraphy. In addition, a short description of the obtained rock samples from a few stations is included in this chapter.

Description: Basalts from the base of a small seamount on ~1.5-m.y.-old crust west of the East Pacific Rise (EPR) at 9°N are intermediate in chemical and isotopic composition between light-rare-earth-element-depleted tholeiite (normal midocean ridge basalt (MORB)) and alkali basalt. Like oceanic alkali basalt, these rocks contain significantly more Ba, K, P, Sr, Ti, U, and Zr than normal MORB. Since the absolute abundances of these elements are still well below alkali basalt levels, the label transitional is adopted for these basalts. A series of fractionated MORB also occurs in this area, northwest of the Siqueiros Fracture Zone - Transform Fault. The normal tholeiites are either olivine-plagioclase or plagioclase-clinopyroxene phyric, while the transitional basalts are spinel-olivine phyric. Fractional crystallization quantitatively accounts for the chemical variability of the tholeiitic series but not for the transitional basalts. The tholeiitic series probably evolved in a crustal magma chamber ~4 km below the crest of the East Pacific Rise. 143Nd/144Nd and other chemical data suggest that the large-ion-lithophile-enriched transitional basalts may represent a hybrid of normal MORB and Siqueiros area alkali basalt. Incompatible element plots of K, P, and U indicate possible derivation of the transitional basalts by magma mixing. Magma mixing of unfractionated normal MORB and Siqueiros alkali basalt has been quantified. Derivation of the transitional basalts from a 1:1 mixture is supported by all available chemical data, including Cr, Cu, Nd, Ni, Sm, Sr, U, and V. This magma mixing apparently occurred at ?〈~30 km depth within a few tens of kilometers from the EPR axis. These Siqueiros area EPR transitional basalts are compared with Mid-Atlantic Ridge (MAR) transitional basalts from the Iceland and Azores areas. The Siqueiros area basalts reflect a profound chemical and isotopic heterogeneity in the upper mantle, similar to that found along the MAR. Unlike the MAR, the EPR shows no evidence of plumelike bulges and associated large-scale outpourings of nonnormal MORB resulting from these mantle heterogeneities. Siqueiros alkali basalt and MORB, as well as transitional basalt and MORB, were recovered from single dredge hauls. Such close spatial and temporal proximity of the inferred mantle sources places severe constraints on geometric and physicochemical upper mantle models.

Description: Manganiferous soil concretions have been located in pineapple and sugar cane plantations of the Schofield Plateau, Oahu, and black manganiferous coatings on the surface of soils have been observed on the crests of embankments next to pineapple plantations on Oahu, Molokai, and Lanai. The concretions and coatings are found inoxisols derived from volcanic parent material. The moisture regime of the soils is characterized by alternate wet and dry periods. This alternation facilitates remobilization and reprecipitation of manganese and to a much lesser extent iron and associated trace metals in the soils. Optimum conditions for manganiferous soil concretion development are encountered on the Schofield Plateau, where mean annual rainfall exceeds 1000 mm/year but where there is a net evaporation loss from the soils during the dry period (May through October). Remobilization of manganese is less pronounced in the oxisols of Molokai and Lanai, where mean annual rainfall is lower. Thin manganiferous coatings rather than concretions therefore form in these islands. The contents of Mn, Fe, Cu, and Ni of the soils on which Hawaiian concretions form are higher than those of New Zealand soils in which manganese soil concretions are found. This is reflected by the much redder color of the Hawaiian concretion-bearing soils compared with their New Zealand counterparts. Rare earths show an enrichment sequence: parent rock ---+ soil ---+ soil concretion. A small positive Ce anomaly is noted in the soil and is more marked in the concretions. This may be due to the increasing oxidation of Ce in the concretions relative to the soil, although contamination of the soil by concretionary material may also playa role. The parent rock shows no Ce anomaly. Barium and Pb are enriched in concretions relative to the surrounding soil, whereas D, Th, Hf, Nb, Zr, and As are present in similar or higher concentrations in the soil relative to the concretions. Arsenic may follow Fe in the soils. Todorokite is the predominant manganese mineral in the Hawaiian soil concretions, not pyrolusite as previously reported. Scanning electron microscope studies show the crystalline nature of the manganese oxide minerals in the concretions.

Description: This report presents the preliminary results of the study of rocks and sediments obtained by dredging during four cruises of the R/V Jean Charcot and R/V Le Suroit during a cooperative program between CNEXO and CEPM (CH 58: April 1975; SU 01: December 1975; CH 66: February 1976; and CH 67: March 1976). Several dredges on the continental slope of the Goban Spur recovered "granitic" rocks on two morphological structures, Granite Cliff and "Menez Bihan" (Pautot et al., 1976), in water depths ranging from 3200 to 4200 meters. According to the radiometric age and petrology, the granodiorite appears to have a close affinity with similar igneous facies which have been described in Iberia (Capdevilla et al., 1973) and attributed to the Variscan intrusive episode which is also found in the nearby continental area (southwest Great Britain and Brittany, France). They often are coated by a centimeter-thick layer of ferromanganiferous deposits (Shaaf et al., 1977).

Description: Ferromanganese micronodules have been found on Georges Bank, off the U.S. northeast coast, distributed throughout the surficial sediments within an area about 125 km long and at least 12 km wide. These coarse, sand-sized concretions have precipitated from metal-rich interstitial waters and contain many of the textural and structural features common to other neritic nodules. Most of the nodules have accreted around detrital grains, and X-ray powder diffraction analyses indicate the presence of geothite and vernadite ( delta -MnO sub(2)) in the ferromanganese layers. Chemical analyses of the micronodules, when compared with similar data on deep-sea manganese nodules, reveal lower Mn/Fe ratios, significantly higher concentrations of V and As, comparable values of Mo, and an order of magnitude less of Co, Ni, Ce and most other, metals.

Description: The purpose of this volume, the ninth in a series of similar publications (Goodell, 1964, 1965, 1968; Frakes 1971, 1973 ; Cassidy et al., 1977), is to continue a presentation to the research community of sediment core descriptions and attendant data of cored and otherwise obtained sediments retrieved in waters of the Southern Ocean aboard the research vessel, ARA Islas Orcadas (formerly, USNS Eltanin), as a part of the circumpolar survey begun by Eltanin in 1962 (see issue of Antarctic Journal of the United States, Vol. 8, No. 3, 1973). The data presented herein are concerned with the results of coring activities aboard cruise 1277 of Islas Orcadas, the third marine geology coring cruise of this vessel under the terms of the present United States-Argentine agreement. The core descriptions are organised as follows: 1) a brief summary of the coring objectives of the cruise, together with a discussion of core recovery; 2) a table and map of station location data for materials retrieved; 3) a table of tentative age-dates for each piston core; 4) an explanation of the laboratory procedures and descriptive criteria used in the description of the sediments, and 5) lithologic descriptions of the piston and trigger cores, and the piston and trigger core bag samples.