ALBERT

Description: The origin of the Campeche Escarpment in the Gulf of Mexico has been attributed to several causes. Some suggest that the scarp represents a fault scarp, others suggest that its origin is a function of upbuilding and outbuilding likened, in some cases, to that of delta building. Still others suggest that the scarp represents the detrital accumulation seaward of a barrier or reef complex. In order to clarify these possible interpretations, Site 86 was located on a bench at a depth of 780 fathoms in the vicinity of the Campeche Escarpment.

Description: Site 172 was continuously cored to a depth of 24 meters in a sediment pond 140 kilometers south of the Murray fracture zone. The upper 9 meters consist of a moderate brown pelagic clay which changes to a zeolite-rich brown clay, brown clay zeolitite and zeolitite in the lower 9 to 24 meters. An Early Oligocene (35 to 38 my) nannofossil horizon occurs near an extrusive basalt encountered at 24 meters. These sediments are older than the 29 my age indicated by a recent identification of magnetic anomaly 8 in the "disturbed" zone. The age discrepancy suggests that the magnetic anomalies in the "disturbed" zone are still not identified correctly.

Description: The main objectives of Leg 17 were to establish the regional pattern of oceanic crustal ages in the central Pacific, to obtain cores of the entire stratigraphic succession, especially from pre-Middle Eocene strata, To document the history of growth and subsidence of seamounts located along seamount chains, by drilling on the archipelagic apron of sediments near the foot of individual seamounts and to sample acoustic reflectors seen on seismic reflection profiles and to establish their physical properties and their ages.

Description: The sea floor of the western Pacific is covered by five stratigraphic units: (l) an eastward thinning wedge of late Tertiary silty clay, primarily of volcanic origin, (2) a Cretaceous to Tertiary zeolitic red clay, (3) a Late Cretaceous to Tertiary chalk/chert sequence, (4) a Cretaceous clay, and (5) a basal chalk/chert sequence. The basal chalk was deposited on the young crust at the crest of the mid-oceanic ridge, while the upper chalk was deposited beneath the equator, and the abyssal clays were deposited in abyssal depths in mid latitudes. A kinematic model has been constructed that outlines the deposition of these units on growing crust, which not only was displaced westward away from the accretion center of the mid-oceanic ridge, but northward under the equator. The average northward component of motion for the Pacific plate has been 2 cm per year from 0 to 30 m.y. and 4.4 cm per year from 30 to 100 m.y. The deep-sea deposits of the Pacific are basically and systematically time transgressive. Claims of general synchroneity for either lithostratigraphy or acoustostratigraphy are rejected as inconsistent with both the drilling data and the kinematic model of Pacific pelagic stratigraphy. A few more well sampled holes in the ancient Pacific plate combined with an appropriately refined kinematic model should yield a 'rather detailed history of the Pacific plate since the Jurassic.

Description: A seabed nuclear probe which was designed to measure up to 30 elements at parts per thousand to parts per hundred levels has been tested for the analysis of simulated manganese nodule fields. The probe contains a neutron source, californium-252, which activates the elements in the nodules. The resulting radioelements which emit characteristic gamma radiation are analyzed in situ during 2 to 200 second counting intervals with Ge{(Li) or NaI(Tl) detector systems. The spectra taken in situ in a marine environment show excellent resolution and indicated the feasibility of mapping the density and economic value of manganese nodules. The study demonstrated the feasibility of in situ analysis to map the Mn, Al, Co, V, and Cu concentrations in manganese nodule fields, and this information together with correlations between Ni, Co, Cu, and Mn obtained from a related study indicates that Ni concentrations can also be rather precisely estimated.

Description: Manganese nodules have been observed over wide areas of both the Pacific and Atlantic Oceans, however, deposits in the Pacific Ocean are generally much richer in elements of economic interest such as nickel, copper and cobalt. In understanding the genesis and the geochemistry involved in their formation and growth, it is important to know the total chemical composition of these nodules and how they vary within a given deposit and between deposits in the oceans of the world. The concentrations of elements: nickel, copper, cobalt, iron, manganese, silicon, and calcium, in all of the manganese nodules which have been analyzed were recently summarized by Horn et al. (1972). These observations indicate certain correlations, both positive and negative, between Mn and the associated elements within the nodules. Their data suggest similarities in chemical composition for nodules from a given area; however, the analyses of Mn nodules, like that of the ocean water, itself, has large errors associated with some of the measurements. This is understandable, since many of these measurements were intended to provide an approximate indication of elemental content. Where one is interested in carefully preparing a description of Mn nodule chemical composition which can serve as a basis for formulating theories regarding their genesis and subsequent geochemical changes in the ocean environment, then very precise and accurate analyses are essential. The purpose of this study has been to measure the concentrations of 18 elements in Mn nodules with a high degree of accuracy and determine what correlations exist between element concentrations. The scope of this study was seriously limited and therefore was confined to one area of the Pacific Ocean at approximately 22 N latitude, 114 W longitude, at an ocean depth of approximately 11,000 feet.

Description: This report studies the principal paramters governing the distribution of iron-manganese concretions on the sea floor of the Indian Ocean, as well as their petrography and mineralogy. The results are mainly based on the recoveries made during voyages 31, 33 and 35 of the "Vityaz"' (1959-1962) and partly during voyages 36 and 41 (1964-1966). During these voyages samples of Mn concretions and Mn crust were collected (by bottom grabs, cores, trawlings, and dredgings) at 39 stations. The following account is devoted to the problems concerning the geochemistry of these concretions.

Description: The gross changes in concentrations of several trace elements in seawater after contact with ferro-manganese particle suspensions has been determined. Cobalt, Fe, and Zn concentrations in the seawater were greatly increased after contact with the par¬ticles. The concentrations of Rb, U, Cs, Sb, and Ag were altered to a lesser degree by this treatment. Similar results were observed where seawater was con¬tacted with suspensions of pelagic sediments. Of the trace elements measured, cobalt and iron appear to be the best elemental indicators of the presence of manganese mining effluents in the ocean. The addi¬tions of the essential elements Co, Fe and Zn toge¬ther with nutrients from the bottom waters may pro¬duce increased biological productivity. However, the toxic trace metals, such as Hg, Cu and Cd which could enter ocean water from the nodules and sedi¬ment and which may be high in effluent-affected areas should be investigated before conclusions as to the likely impact can be reached. Trace element analysis of seawater samples collected at a Pacific Ocean manganese nodule dredging site showed high t race element concentrations, but these are believed to have resulted from contamination during sample collection or storage rather than from the dredging operations.