ALBERT

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: The object of the present study is to introduce a means of comparing the Vostok and marine chronologies. Our strategy has been to use the delta18O of atmospheric O2 (denoted delta18Oatm) from the Vostok ice core as a proxy for the delta18O of seawater (denoted delta18Osw). Our underlying premise in using delta18Oatm as a proxy for delta18Osw is that past variations in delta18Osw (an indicator of continental ice volume) have been transmitted to the atmospheric O2 reservoir by photosynthesizing organisms in the surface waters of the world's oceans. We compare our record of delta18Oatm to the delta18Osw record which has been developed from studies of the isotopic composition of biogenic calcite (delta18Oforam) in deep-sea cores. We have tied our delta18Oatm record from Vostok to the SPECMAP timescale throughout the last 135 kyr by correlating delta18Oatm with a delta18Osw record from V19-30. Results of the correlation indicate that 77% of the variance is shared between these two records. We observed differences between the delta18Oatm and the delta18Osw records during the coldest periods, which indicate that there have been subtle changes in the factors which regulate delta18Oatm other than delta18Osw. Our use of delta18Oatm as a proxy for delta18Osw must therefore be considered tentative, especially during these periods. By correlating delta18Oatm with delta18Osw, we provide a common temporal framework for comparing phase relationships between atmospheric records (from ice cores) and oceanographic records constructed from deep-sea cores. Our correlated age-depth relation for the Vostok core should not be considered an absolute Vostok timescale. We consider it to be the preferred timescale for comparing Vostok climate records with marine climate records which have been placed on the SPECMAP timescale. We have examined the fidelity of this common temporal framework by comparing sea surface temperature (SST) records from sediment cores with an Antarctic temperature record from the Vostok ice core. We have demonstrated that when the southern ocean SST and Antarctic temperature records are compared on this common temporal framework, they show a high degree of similarity. We interpret this result as supporting our use of the common temporal framework for comparing other climate records from the Vostok ice core with any climate record that has been correlated into the SPECMAP chronology.

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: 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: 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: 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: 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: 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: 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: Experimental substitutions of transition and alkaline earth cations into synthetic 10angstrom(Na-)-manganate show that cation uptake and the stability of the cation-substituted mineral increase with stability of the hydroxide of the cation. Hydrothermal treatment of synthetic 10angström-manganates with different metal contents as well as marine diagenetic and hydrothermal 10angstrom-manganates shows that the stabilities of their structures are enhanced with increasing temperature. The stabilization is due to reinforcement of the "tunnel" walls supporting the [Mn4+O62-] octaheral layers. The diagenetic 10angström-manganates have initially unstable buserite-like structures with each interlayer wall composed of two [Mn2+O3+x2-(OH-)3-x] octahedra (0 less-than-or-equal-to x less-than-or-equal-to 3) with either a [Na+O2x2-(OH-)n-2x] unit (n = 6 and/or 8) or less frequently a [Mn2+O2x2-(OH-)6-2x] octahedron in between. Some of these cations in the walls are post-depositionally substituted by highly hydrated divalent metal cations, particularly Cu2+ and Ni2+, while some of the Mn2+ ions are slowly oxidized to Mn4+. These interlayer changes result in higher crystal field stabilization energy and shifts from interlayer Van der Waal's forces and weak coordination links to strong coordination links which stabilize the mineral structures. Low-temperature hydrothermal 10angstrom-manganates have todorokite-like structures with "tunne"' walls constructed predominantly of [Mn2+O3+x2-(OH-)3-x] and [Mn2+O2x2-(OH-)6.2x] octahedra. High-temperature hydrothermal 10angstrom-manganates have stable todorokite structures with the walls constructed of [Mn4+O62-] octahedra. The positive correlation between the formation or post-depositional alteration temperatures and the mineral stability is due to the increase in oxidation rate of interlayer Mn2+ ions with increasing temperature of the hydrothermal fluids. Marine 10angstrom-manganates can be used as genetic indicators for manganese concretions and the sediments in which they occur and as a geothermometer in the search of ancient and modern hydrothermal vents, where massive sulphide deposits are often found.

Description: Although ferromanganese crusts from shallow depths in Lake Baykal have been described previously, the presence of nodules at depths of about 500 m are a new discovery made possible by exploration using manned submersibles. The nodules are comparable to oceanic nodules in composition, but have some significant differences, including a more rapid rate of growth. Sedimentary-diagenetic processes are mainly responsible for their formation, but there is reason to believe hydrothermal fluids play some role.

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: 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: We analyzed the oxygen and carbon isotopic composition of planktonic and benthic foraminifers picked from 13 late Eocene to late Oligocene samples from DSDP Site 540 (23°49.73'N, 84°22.25'W, 2926 m water depth) from the Gulf of Mexico. An enrichment occurs in 18O of about 0.5 to 0.8 per mil in both benthic foraminifers and surface-dwelling planktonic foraminifers between the latest Eocene and early Oligocene. This early Oligocene maximum is followed by lower 18O values. A 1.2 per mil d13C decrease in both benthic and planktonic foraminiferal data occurs from the late Eocene to the late Oligocene. There is a correspondence of the 13C signal to deep-sea records; however, the amplitude of this change is greater than previously seen in deep-sea cores, possibly as a result of proximity to terrestrial sources of carbon. The covarying isotopic changes in both benthic and planktonic foraminifers suggest global causes, such as ice volume increases and increased terrestrial carbon input to the ocean. However, during the latter part of the record (early-late Oligocene), the increases in the benthic 18O without accompanying increases observed with planktonic foraminifers suggest that changes in only one part of the system occurred; one potential explanation being a decrease in bottom-water temperatures without concomitant changes in the surface waters. The 18O differences between species of planktonic foraminifers and the difference between planktonic and benthic 18O data indicate that diagenesis problems are minimal. These preliminary results are encouraging given that these cores are partially lithified.

Description: Interglacial lacustrine sediments of 0.3-0.6 m thickness are found in the basin of Wurzach over a distance of about 9 km as detected by 5 borings. The interglacial bed is intercalated between lacustrine sediments of Würm (above) and glaciolacustrine sediments of the Younger Riss (below). Most of the Würmian sediments are silty-sandy, calcareous and varved deposits. They were deposited as bottom sediments of a delta, which had formed in the glacial lake filling the Wurzach basin during the Upper Würm. The terminal moraine of the Younger Riss is found in the N and S of the Reed of Wurzach. In the NE it is overlain by sediments of Würm and Holocene age. The pollen bearing part of the new profile represents the last interglacial period (except its earliest phases), the two Lower Würm interstadials, which are equivalents of the Brørup and Odderade interstadial phases, and a third interstadial, the Dürnten, known from other localities in the forelands of the Alps with a forest vegetation, which consisted mainly of spruce and larch trees, and the intercalated stadial phases. These interstadials are different from those described earlier by FILZER, which on the contrary represent cold periods with highly increased reworking of pollen. The equivalents of the Brørup, Odderade and Dürnten interstadials are the "Kiefer-Fichten-Kampfzeit" and part of the "Kiefernzeit mit Fichte" of FILZER. The characteristic series of climatic events known already from a great number of sites scattered all over Europe and again at Wurzach proves that the Riss/Würm- and the Eem interglacial periods are time-equivalents. Differing amounts of Carpinus and Abies at different places in the northern foreland of the Alps are related to the migration history of the two species during the last interglacial period and must not be used to distinguish different types of interglacials (type Zeifen, type Pfefferbichl).

Description: The cores and dredges described at this site were taken on the RIDA cruise from 1 May until 25 May 1984 by the Muséum National d'Histoire Naturelle from the R/V Marion Dufresne. A total of 45 cores and dredges were recovered along with underwater camera runs. They are available at MNHN for sampling and study.

Description: ree types of concretions were recovered during Leg 81 from Holes 552A, 553A, and 554A, located on the west margin of the Rockall Plateau. In the sedimentary section, these concretions are located at the level of major unconformities, in condensed sequences representing a period from early Eocene to Miocene. This study is a detailed mineralogical and geochemical investigation that permits comparison among the three holes and between the fossil Leg 81 concretions and recent polymetallic nodules found on the ocean floor.

Description: Ferromanganese crusts were sampled from the surface of a stone collected at a depth of 20 m in the northern part of Lake Biwa, Japan. These samples were analysed for 37 elements by neutron activation, X-ray fluorescence, and ICP-AE. The crusts were found to be enriched with Ba, P, B, As, and sometimes with Co, Ni, Cu and Sb. The elements were classified into 4 groups based on the varieties of host minerals (Fe-oxides, Mn-oxides or allochthonous materials) in which they were incorporated : elements mainly associated with 1) Mn-oxides : Ba, Ni, Cs, Sr and Co ; 2) Fe-oxides : P, B and As; 3) allochthonous materials : Na, K, Rb, Al, Ti, Sc, Hf and Th ; and 4) Mn-oxides plus allochthonous materials : rare earth elements and major heavy metals. The elemental compositions in the Lake Biwa concretions, including the crusts and Mn-deposits studied previously by these authors, were compared with those in other freshwater and oceanic concretions. As a result, the concentrations of rare earth elements and major heavy metals were found to be much lower, whereas those of B, P and As were higher in the Lake Biwa than in the oceanic concretions. These differences could be well explained in terms of the effects of sea salt, growth rates of the concretions, and pH of the formation environment.

Description: The wet bulk density is one of the most important parameters of the physical and geological properties of marine sediments. The density is connected directly with sedimentation history and a few sedirnent properties. Knowledge of the fine scale density-depth structure is the base for many model calculations, for both sedimentological and palaeoclimatic research. A density measurement system was designed and built at the Alfred Wegener Institute in Bremerhaven for measuring the wet buk density of sediment cores with high resolution in a non-destructive way. The density is deterrnined by measuring the absorption of Gamma-rays in the sediment. This principle has been used since the 50's in materials research and in the geosciences. In the present case, Cs137 is used as the radioactive source and the intensity is measured by a detector system (scintillator and photomultiplier). Density values are obtainable in both longitudinal core sections and planar cross-sections (the latter are a function of the axial rotation angle). Special studies on inhomogenity can be applied with core rotation. Detection of ice rafted debris (IRD) is made possible with this option. The processes that run the density measurement system are computer controlled. Besides the absorption measurement the core diameter at every measurement point is determined with a potentiometric system. The data values taken are stored on a personal computer. Before starting routine measurements on the sediment cores, a few experiments conceming the statistical aspects of the gamma-ray signal and its accuracy were carried out. These experiments led to such things as the optimum operational parameters. A high spatial resolution in the mm-range is possible with the 4mm-thin gamma-ray measurements. Within five seconds the wet bulk density can be deterrnined with an absolute accuracy of 1%. A comparison between data measured with the new system and conventional measurements on core samples after core splitting shows an agreement within +I- 5% for most of the values. For this thesis, density determinations were carried out on ten sediment cores. A few sediment characteristics are obtainable from using just the standard measurement results without core rotation. In addition to differentes and steps in the absolute density range, variations in the "frequency" of the density-depth structure can be detected due to the close spatial measurement interval and high resolution. Examples from measurements with small (9°) and great (90°) angle increments show that abrupt and smooth transitional changes of sedirnent layers as well as ice rafted debris of several dimensions can be detected and distiflguished clearly. After the presentation of the wet bulk density results, a comparison with data from other investigations was made. Measurements of the electrical resistivity correlated very well with the density data because both parameters are closely related to the porosity of the sedirnent. Additionally, results from measurements of the magnetic susceptibility and from ultra-sonic wave velocity investigations were considered for a integrative interpretation. The correlation of these both parameters and wet bulk density data is strongly dependent on the local (environmental) conditions. Finally, the densities were compared with recordings from sediment-echographic soundings and an X-ray computer tomography analysis. The individual results of all investigations were then finally combined into an accurate picture of the core. Problems of ambiguity, which exist when just one Parameter is determined alone, can be reduced more or less according to the number of parameters and sedimentary characteristics measured. The important role of the density data among other parameters of such an integrated interpretation is evident. Evidence of this role include the high resolution of the measurement, the excellent accuracy and the key position within methods and parameters concerning marine sediments.

Description: From 661 to 880 m beneath the seafloor at DSDP Sites 370 and 416 are Albian to Barremian claystone with some limestone, sandstone, and siltstone. Compressional-wave velocities ranged from 1.70 to 4.37 km/s, with an average in situ vertical velocity of 1.93 km/s. From 880 to 1430 m are Hauterivian to Valanginian turbidites of alternating graded calcareous and quartzose cycles from siltstone or fine sandstone to mudstone. Compressional-wave velocities range from 1.80 to 4.96 km/s with an average in situ velocity of 2.61 km/s. From 1430 to 1624 m are early Valanginian to Tithonian (Kimmeridgian?) turbidites, with alternating quartzose siltstone grading to mudstone cycles with hard micritic limestone and calcarenite (calciturbidites). Compressional-wave velocities range from 2.26 to 5.7 km/s, with an average in situ vertical velocity of 3.25 km/s. Acoustic anisotropy is 0 to 30% faster parallel to bedding in Cretaceous to Tithonian sandstone-siltstone turbidites in mudstone and minor limestone from 661 to 1624 m below the seafloor. Between 2.0(?) km/s and 4.2(?) km/s, anisotropy becomes particularly significant (below 1178 m), where the anisotropy is about + 0.4 km/s or greater. The mudstone, softer sandstone, and softer siltstone tend to have velocities around 2.0 to 2.5 km/s; the cemented sandstone and limestone cluster around 2.5 km/s to 4.2 km/s; thus the relative percentage anisotropy is greater for lower-velocity lithologies. Above 4.2(?) km/s, the well-cemented sandstone and limestone tend to have a smaller (less than + 0.4 km/s) absolute anisotropy, and many samples are nearly isotropic. These physical property data are separated into depth plots for (1) mudstone, (2) siltstone (3) sandstone, (4) marlstone, and (5) limestone. The mudstone's porosity and wet-bulk density curves versus depth are slightly higher and lower, respectively, than similar porosity and wet-bulk density curves summarized in Hamilton (1976). These differences could be some combination of (1) differences in laboratory methods; (2) age, lithologic, and cementation differences; or (3) overconsolidation created by a geological sequence which has been eroded away. If the average in situ vertical velocities calculated by Boyce (1980b) for Hole 416A are correct, then the 1.43-s (round-trip) reflector (blue) discussed by Lancelot and Winterer (1980) and Lancelot, Winterer et al. (1980b), would correlate to about 1500 m in Hole 416A, and not below 1624 m as suggested by Lancelot and Winterer. There appears to be a significant change in the acoustic character at or around that depth (1500 m) to a more lithified, calcareous, and cemented lithology. This does not prove Lancelot and Winterer (1980) and Lancelot, Winterer et al. (1980b) to be incorrect, but only suggests another possible interpretation.

Description: Copper porphyrins have been recognized as natural constituents of marine sediments only within the past 5 years (Palmer and Baker, 1978, Science201, 49–51). In that report it was suggested that these pigments may derive from and be markers for oxidized terrestrial organic matter redeposited in the marine environment. In the present study we describe the distribution of copper porphyrins in sediments from several north Pacific and Gulf of California DSDP/IPQD sites (Legs 56,63,64). These allochthonous pigments have now been found to be accompanied by identical arrays of highly dealkylated nickel etioporphyrins. Evaluation of data from this and past studies clearly reveals that there is a strong carbon-number distribution similarity betweeen coincident Cu and Ni etioporphyrins. This homology match is taken as reflecting a common source for the tetrapyrrole ligands of this population of Cu and Ni chelates. Predepositional generation of these highly dealkylated etioporphyrins is concluded from the occurrence of these pigments in sediments continuing essentially all stages of in situ chlorophyll diagenesis (cf. Baker and Louda, 1983). That is, their presence is not regulated by the in situ diagenetic continuum. Thus, the highly dealkylated Cu and Ni etioporphyrins represent an 'allochthonous' background over which 'autochthonous' (viz. marine produced) chlorophyll derivatives are deposited and are undergoing in situ diagenesis.