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At least 19 recordsLinked to original sources
USGS1993

Allostratigraphy of the U.S. middle Atlantic continental margin; characteristics, distribution, and depositional history of principal unconformity-bounded upper Cretaceous and Cenozoic sedimentary units

Publication of Volumes 93 and 95 ('The New Jersey Transect') of the Deep Sea Drilling Project's Initial Reports completed a major phase of geological and geophysical research along the middle segment of the U. S. Atlantic continental margin. Relying heavily on data from these and related published records, we have integrated outcrop, borehole, and seismic-reflection data from this large area (500,000 km^2 ) to define the regional allostratigraphic framework for Upper Cretaceous and Cenozoic sedimentary rocks. The framework consists of 12 alloformations, which record the Late Cretaceous and Cenozoic depositional history of the contiguous Baltimore Canyon trough (including its onshore margin) and Hatteras basin (northern part). We propose stratotype sections for each alloformation and present a regional allostratigraphic reference section, which crosses these basins from the inner edge of the coastal plain to the inner edge of the abyssal plain. Selected supplementary reference sections on the coastal plain allow observation of the alloformations and their bounding unconformities in outcrop. Our analyses show that sediment supply and its initial dispersal on the middle segment of the U. S. Atlantic margin have been governed, in large part, by hinterland tectonism and subsequently have been modified by paleoclimate, sea-level changes, and oceanic current systems. Notable events in the Late Cretaceous to Holocene sedimentary evolution of this margin include (1) development of continental-rise depocenters in the northern part of the Hatteras basin during the Late Cretaceous; (2) the appear ance of a dual shelf-edge system, a marked decline in siliciclastic sediment accumulation rates, and widespread acceleration of carbonate production during high sea levels of the Paleogene; (3) rapid deposition and progradation of thick terrigenous delta complexes and development of abyssal depocenters during the middle Miocene to Quaternary interval; and (4) deep incision of the shelf edge by submarine canyons, especially during the Pleistocene. Massive downslope gravity flows have dominated both the depositional and erosional history of the middle segment of the U. S. Atlantic Continental Slope and Rise during most of the last 84 million years. The importance of periodic widespread erosion is recorded by well-documented unconformities, many of which can be traced from coastal-plain outcrops to coreholes on the continental slope and lower continental rise. These unconformities form the boundaries of the 12 allostratigraphic units we formally propose herein. Seven of the unconformities correlate with supercycle boundaries (sequence boundaries) that characterize the Exxon sequence-stratigraphy model.

Professional Paper↗
USGS1972

Interstitial water studies on small core samples, leg XI

The sediments cored at Sites 98, 99 and 100 are predominantly biogenic; those cored at Sites 101 through 106 are composed mainly of terrigenous material. As reported previously, most constituents in pore waters from the biogenic oozes exhibit minor changes in chemistry relative to sea water. In the terrigenous-hemipelagic sediments interstitial solutions initially of sea water composition have undergone considerable reaction. These reactions have produced large changes in the concentrations of calcium (Ca), magnesium (Mg), sulfate (SO 4 ) and HCO 3 relative to sea water. In addition, this set of samples documents significant diagenetic alteration of sodium (Na) and chloride (Cl). Potassium exhibits little change in most samples, but in a few instances is depleted at depth. The analytical techniques employed are identical to those described in earlier volumes of the Initial Reports of the Deep Sea Drilling Project. In an effort to identify alteration of sample composition during storage, salinity determinations 2 are made on the pore solution immediately upon their recovery from the sediments. The same measurement is made in the laboratory when the sample containers are opened for analysis. Occasionally evidence of evaporation is found as in Sample 104-2-5; the shipboard salinity was 32%o, while the laboratory measurement yielded 38%o. Changes of 3 to 4 per cent were also noted in several other samples as noted in the tables. Adjustment of the analytically determined concentrations has been made and the corrected values presented in Tables 1 and 2. A large part of the work involved in the analyses of these samples has been done by Irene Uhlitzsch; we are indebted to her for the invaluable assistance she has rendered.

Initial reports of the Deep Sea Drilling Project↗
USGS1971

Interstitial water studies on small core samples, Deep Sea Drilling Project, Leg 8

Leg 8 sites are dominated by siliceous-calcareous biogenic oozes having depositional rates of 0.1 to 1.5 cm/1000 years. Conservative constituents of pore fluids showed, as have cores from other pelagic areas of the Pacific, insignificant or marginally significant changes with depth and location. However, in Sites 70 and 71, calcium, magnesium and strontium showed major shifts in concentration with depth. These changes appear to be related to recrystallization phenomena in skeletal debris of nannoplankton and to the relative accumulation rate of the sediments. The chemical anomalies increase relatively smoothly with depth, demonstrating the effectiveness of vertical diffusional communication, and apparent lack of bulk fluid movement, as noted in Leg 7 and other sites.

Initial reports of the Deep Sea Drilling Project↗
USGS1972

Interstitial Water studies on small core samples, deep sea drilling project, leg XII

With the exception of Site 114, all interstitial waters in Leg 12 showed marked increases in calcium, which can be attributed to diagenetic dissolution and recrystallization of calcium carbonate, especially coccolith and foraminiferal tests. Magnesium loss may be due to either or both replacement of iron in clays or the dolomitization of calcium carbonate. The lowest sample from Site 113, on the mid-Labrador Sea Ridge, yielded only 250 mg/kg magnesium but 2.56 g/kg calcium in interstitial water from a clayey, siliceous quartz silt. Strontium values close to and exceeding 100 mg/kg were noted, especially in sites showing extensive carbonate recrystallization. Few significant deviations in chloride concentration from sea water levels were noted.

Initial reports of the Deep Sea Drilling Project↗
USGS1970

Interstitial water studies on small core samples, Deep Sea Drilling Project, Leg 3

Eleven samples of fluids which had been squeezed on board ship, and four, packaged sediment samples were received in our laboratories. As in Leg 2, the volumes of fluid available were scanty and did not permit multiple determinations of constituents in many of the samples; in Hole 21 the fluid available sufficed only for refractometer readings (a few tenths of a milliliter). Therefore, analytical scatter is again responsible for partially obscuring variations (and constancy) in the conservative constituents such as sodium. However, on the whole the results confirm the features which appeared in Legs 1 and 2. Central oceanic sediments display a remarkable constancy in total salinity, chlorinity and sodium concentration to the greatest depths and ages yet penetrated in the project drillings. Variations attributable to postburial reactions do occur in the remaining major ions, but they usually show little systematic trend with depth--with the exception of potassium, which will be discussed later. Methods remain similar to those employed for Leg 2; the detailed techniques are now being prepared for submission, but a brief description may be obtained from the previous Leg reports (Manheim and Sayles, 1969; Chan and Manheim, 1970). Results from four unsqueezed samples are not complete and, therefore, do not appear here.

Initial reports of the Deep Sea Drilling Project↗
USGS1969

Interstitial water studies on small core samples, Deep Sea Drilling Project, Leg 1

The most dramatic variations in pore water composition occurred in Holes 2 and 3 in the Gulf of Mexico. Both holes showed a strong increase in salinity with depth, evidently owing to diffusion from underlying salt bodies. However, on Challenger Knoll (Hole 2) a sharp drop in salinity was observed in the cap rock of the salt dome in which chloride fell to only 4.8 percent. The drop is attributed to production of fresh water during the formation of native sulfur. Outside of the Gulf of Mexico, changes in total salinity with depth did not exceed a few percent, but differences in diagenetic modification of the ionic ratios of sea water were pronounced. In nondiapiric strata in the Gulf of Mexico (Hole 1) both magnesium and potassium were depleted in the pore waters, whereas in the open ocean holes (4, 5, 6, and 7), potassium appeared in excess. Water content (porosity) of the cores was irregular.

Initial reports of the Deep Sea Drilling Project↗
USGS1970

Interstitial water studies on small core samples, Deep Sea Drilling Project, Leg 5

Leg 5 samples fall into two categories with respect to interstitial water composition: 1) rapidly deposited terrigenous or appreciably terrigenous deposits, such as in Hole 35 (western Escanaba trough, off Cape Mendocino, California); and, 2) slowly deposited pelagic clays and biogenic muds and oozes. Interstitial waters in the former show modest to slight variations in chloride and sodium, but drastic changes in non-conservative ions such as magnesium and sulfate. The pelagic deposits show only relatively minor changes in both conservative and non-conservative pore fluid constituents. As was pointed out in earlier Leg Reports, it is believed that much of the variation in chloride in pore fluids within individual holes is attributable to the manipulation of samples on board ship and in the laboratory. On the other hand, the scatter in sodium is due in part to analytical error (on the order of 2 to 3 per cent, in terms of a standard deviation), and it probably accounts for most of the discrepancies in total anion and cation balance. All constituents reported here, with the exception of bulk water content, were analyzed on water samples which were sealed in plastic tubes aboard ship and were subsequently opened and divided into weighed aliquots in the laboratory. Analytical methods follow the atomic absorption, wet chemical and emission spectrochemical techniques briefly summarized in previous reports, e.g. Manheim et al., 1969, and Chan and Manheim, 1970. The authors acknowledge assistance from W. Sunda, D. Kerr, C. Lawson and H. Richards, and thank D. Spencer, P. Brewer and E. Degens for allowing the use of equipment and laboratory facilities.

Initial reports of the Deep Sea Drilling Project↗
USGS1985

Environmental trends among Neogene benthic foraminifers at Deep Sea Drilling Project Site 548, Irish continental margin

An analysis of diversity and abundance trends among all benthic foraminiferal genera and species, and particularly among species of Bolivina, was carried out for 59 samples of Neogene sediment from DSDP-IPOD Site 548, Goban Spur. By correlating these census data with lithological, geophysical, geochemical, and other faunal and floral measurements in the same stratigraphic interval, a record of irregularly fluctuating cycles was compiled. We interpret them as indicators of relative sea level. High sea levels are characterized by pelagic sedimentation and by high generic and total species diversities. During low sea level, diversity values were lower, and the accumulation of terrigenous detritus was more prevalent at the site. A sequence recording five highstands and five lowstands is interrupted by four unconformities in a scenario remarkably similar to that postulated in the work of P. R. Vail and his colleagues. Bolivina species diversity also varied cyclically. We interpret diversity of Bolivina species as a measure of relative oxygen and nutrient content at the water/sediment interface; high diversity indicates the presence of an oxygen-minimum layer, accompanied by nutrient enrichment. Our data show that this property generally varied directly with sea level, but sometimes varied independently.

Initial reports of the Deep Sea Drilling Project↗
USGS1973

Interstitial water studies on small core samples, Deep Sea Drilling Project: Leg 10

Leg 10 interstitial water analyses provide new indications of the distribution of rock salt beneath the floor of the Gulf of Mexico, both confirming areas previously indicated to be underlain by salt bodies and extending evidence of salt distribution to seismically featureless areas in the Sigsbee Knolls trend and Isthmian Embayment. The criterion for presence of salt at depth is a consistent increase in interstitial salinity and chlorinity with depth. Site 86, on the northern margin of the Yucatan Platform, provided no evidence of salt at depth. Thus, our data tend to rule out the suggestion of Antoine and Bryant (1969) that the Sigsbee Knolls salt was squeezed out from beneath the Yucatan Scarp. Cores from Sites 90 and 91, in the central Sigsbee Deep, were not obtained from a great enough depth to yield definite evidence for the presence of buried salt. Site 86, on the northern margin of the Yucatan Platform, provided no evidence of salt at depth. Thus, our data tend to rule out the suggestion of Antoine and Bryant (1969) that the Sigsbee Knolls salt was squeezed out from beneath the Yucatan Scarp. Cores from Sites 90 and 91, in the central Sigsbee Deep, were not obtained from a great enough depth to yield definite evidence for the presence of buried salt.

Initial reports of the Deep Sea Drilling Project↗
USGS1985

Biostratigraphy, paleoenvironmental, and paleomagnetic synthesis of the Goban Spur region, Deep Sea Drilling Project Leg 80

A composite stratigraphic section based on the four DSDP-IPOD Leg 80 drill sites provides a nearly complete record of syn-rift and post-rift events in the vicinity of Goban Spur. Syn-rift sediments were deposited in marginal marine to outer shelf environments. Above the "breakup" unconformity (hiatus spanning most of the Aptian), post-rift Albian sediments indicate the development of a deep-water seaway in the Goban Spur region. The latest Campanian/Maestrichtian interval records the initiation of rather uniform, widely distributed marine sedimentation throughout the region. Climatic changes, rather than changes in water depth, became conspicuous during the Tertiary. Widespread, nearly synchronous periods of nondeposition or erosion occurred in the Paleocene, middle Eocene, middle Oligocene, and late Miocene. Differences in the sediment record among sites are due to their varying positions (1) along the margin of the developing Atlantic seaway and (2) within their respective half-graben depositional basins.

Initial reports of the Deep Sea Drilling Project↗
USGS1981

Origin of organic-carbon-rich mid-Cretaceous limestones, Mid-Pacific Mountains and southern Hess Rise

Limestones of mid-Cretaceous age containing as much as 8.6 percent organic carbon were cored at one site (463) in the Mid-Pacific Mountains and at two sites (465, 466) on southern Hess Rise, central North Pacific Ocean, during Leg 62 of the Deep Sea Drilling Project. In the Mid-Pacific Mountains, three layers containing more than 2% organic carbon are associated with volcanic ash in silicified limestone of early Aptian age (—112-113 m.y. old), a time when the site was south of the equator and considerably shallower than at present (2525 m). The beds of laminated, organiccarbon-rich limestone, implying deposition in an oxygen-deficient environment, are interbedded with normal pelagic limestones. This sequence lies on interbedded pelagic limestones and clastic limestones containing locally derived shallow-water carbonate debris, and it is overlain by interbedded green, gray, and pink limestones. The organic-carbonrich strata on southern Hess Rise are dark-olive, laminated limestones with rare interbeds of altered volcanic ash of the late Aptian to early Cenomanian ( — 98 to 103 m.y. old), a time when the site was passing under the equatorial highproductivity zone and subsiding from shallow to intermediate water depths. The organic-carbon-rich limestone sequence overlies volcanic basement (trachyte) in this part of Hess Rise. The association of volcanogenic sediments with organic-carbon-rich strata on Hess Rise is not as striking as in the Mid-Pacific Mountains, but the occurrences do suggest a coincidence of mid-plate volcanic activity and accumulation of organic matter at intermediate water depths in the tropical North Pacific Ocean during the mid-Cretaceous. Pyrolysis assays indicate that most of the organic matter in the limestone on Hess Rise is composed of lipid-rich kerogen derived from marine organisms. Limestones from the Mid-Pacific Mountains contain lower concentrations of organic matter. Pyrolysis assays and extractable hydrocarbons indicate that the organic matter in samples from Hole 463 is also predominantly of marine origin, and that contributions of terrigenous organic matter were probably minor. Analyses of stable carbon isotopes indicate that the organic carbon in all analyzed samples is isotopically light (δ13C 24 to - 29‰) relative to most modern marine organic carbon (δ13C - 9 to - 30%), and that the lightest carbon (δ13C 28 to - 29‰) is also the most lipid-rich. The organic-carbon-rich mid-Cretaceous limestones on Hess Rise, the Mid-Pacific Mountains, and other elevated plateaus and seamounts in the Pacific Ocean are approximately equivalent in age (mid-Cretaceous, -85-120 m.y.) to organic-carbon-rich lithofacies elsewhere in the world ocean, particularly in the Atlantic Ocean and parts of the Indian Ocean. However, strata of equivalent age deposited in the Pacific Ocean at greater depths do not contain any carbon rich horizons. This observation, together with the evidence that the plateau sites were considerably shallower and close to the equator during the mid-Cretaceous, suggests that an expanded mid-water oxygen minimum, together with local restrictions in circulation, may have resulted in the preservation of organic matter in an oxygen-deficient environment where the oxygen minimum impinged on elevated platforms such as Hess Rise and the Mid-Pacific Mountains.

Initial reports of the Deep Sea Drilling Project↗
USGS1971

Interstitial water studies on small core samples, Deep Sea Drilling Project, Leg 6

Sediments from Leg 6 sites, west of the Hawaiian Islands, consisted primarily of various combinations of deep-sea biogenic oozes, volcanic ash, and its breakdown products. Pore fluids from most of the sites were similar in composition to present day ocean water, and in some sties almost identical. However, interstitial fluids from Site 53 (Philippine Sea) showed changes in ionic composition which were beyond those previously considered attributable to diagenetic influence. These samples show the beginnings of metamorphism by dramatic increases in calcium concentrations and corresponding decreases in alkali concentrations. Analytical methods were similar to those outlined in previous Leg Reports. However, obvious contamination of aliquots for sodium determination in the laboratory made it necessary to determine all sodium values by difference between anion and cation balances. These values are, if anything, more accurate than direct determinations which have been discussed in earlier legs. However, the authors will continue to analyze sodium directly, and in the future they may be able to improve the precision of the determinations to the point where small losses and gains of sodium in the pore fluids may be established accurately. Agreement between colorimetric and spectrometric determinations of silicon has improved, but there are still occasional marked differences for which the writers have no explanation. T. Takahashi has allowed the authors to compare total Carbon Dioxide (CO 2 ) measurements from his laboratory with their alkalinity determinations: both sets of data were obtained from fluids from the same squeezings of sediments and should give similar values at the indicated pH levels. Some disturbingly large discrepancies in the two sets of data are evident. The authors do not think that their back-titration alkalinity technique alone is responsible for the differences. However, they have not evaluated the possible influence of the heat-sealed polyethylene pipes on the alkalinity values; this should be considered a potential source of error. The pH data from water samples processed and measured on shipboard are reported here. In view of the major changes in pressure and temperature (laboratory temperatures were reported to be 26 to 28°C) and the sediments to new gaseous regimes prior to pH measurement, these values should be interpreted mainly as applying to the squeezed effluents, not to in situ values.

Initial reports of the Deep Sea Drilling Project↗
USGS1971

Interstitial water studies on small core samples, deep sea drilling Project, leg 7

The sediments cored on Leg 7 are predominantly deep sea biogenic oozes and chalks; only rarely were significant quantities of pelagic clays and volcanic detritus encountered. The biogenic sections include both siliceous and calcareous deposits. At three sites the drilling terminated in basalt, one of which (Site 62) is interpreted as being intrusive on the basis of intense alteration of the overlying sediment. With the exception of Ca++ and Sr , compositional changes in the pore waters are characteristically small relative to those reported previously for rapidly deposited, non-biogenic sediments. Ca++ and Sr + , however, exhibit concentrations of up to three times and ten times, respectively, those found in sea water. In several instances, constant concentration gradients as a function of depth have been found. The sampling, storage and analytical procedures employed have been briefly described in an earlier report (Sayles et al, 1970) and are detailed in a manuscript in preparation (Manheim and Chan). Sodium has been calculated as the difference between the summation of the anions and the summation of the major cations exclusive of sodium; to date, this method has proven more accurate than direct analytical methods. Agreement between the two types of silica determination used (emission spectrometric and colorimetric) is poor; the values obtained by emission spectrometry are characteristically higher. The colorimetric technique measures only "reactive" silica (monomeric and possibly dimeric) while the emission spectrometric technique will determine all of the silica in solution and in suspension. The silica content of most of the solutions is high (60 ppm) and polymerization is likely. We are currently investigating this discrepancy. The pH and water content data reported were obtained aboard the Glomar Challenger immediately after sampling

Initial reports of the Deep Sea Drilling Project↗
USGS1985

Geologic history of Goban Spur, Northwest Europe continental margin

Drilling on Leg 80 of the Deep Sea Drilling Project-International Phase of Ocean Drilling was conducted on a transect of four sites (548-551) across the continent-ocean boundary at Goban Spur, a prominent southwest-trending structural and topographic high on the Irish continental slope. Drilling results have been integrated with physiographic, gravimetric, paleomagnetic, and seismostratigraphic data to provide a comprehensive interpretation of the geologic history of this sediment-starved passive margin. The geologic history of Goban Spur and adjacent regions may be divided into three periods: (1) a pre-rift period, beginning at the end of the Hercynian orogeny, was marked by several phases of regional faulting. From the late Paleozoic to the Triassic, a major phase was responsible for the development of northeast-trending grabens and horsts, which were especially active areas of deposition during the early and middle Mesozoic. A second phase created northwesttrending listric, normal fault systems which delineated the pre-Atlantic rift system of the Early Cretaceous. (2) A terminal period of active rifting began approximately at the Jurassic/Cretaceous boundary (late Cimmerian phase), and was marked by a regional emergence. Syn-rift deposition is recorded at Goban Spur by accumulation of a transgressive sequence of hyposaline to pelagic sediments, chiefly Barremian. Interpretation of seismic profiles indicates that (?)Aptian sequences also were deposited in the deeper half-grabens during this phase of rifting. Volcanic rocks appear to be rare or absent in the syn-rift deposits on Goban Spur. (3) The post-rifting period began when ocean crust was accreted in a trough approximately 2000 m deep, beneath what is now the Porcupine Abyssal Plain. This period was marked by the outpouring of pillows and flows of typical oceanic tholeiites, some of which were recovered at Site 550. At the same time, the seaward edge of the continental crust appears to have been deeply intruded by oceanic tholeiites, forming an intermediate crust of transitional geophysical characteristics. Post-rift sedimentation started in the early Albian, and was accompanied by continuous regional subsidence. Before the Campanian, variable depositional environments produced quite diverse sedimentary sequences in the isolated halfgrabens. Carbonaceous shales were recovered in Cenomanian strata of the deepest site (550) and in lower Turonian beds at sites of intermediate depth (549-551). Depositional environments became more uniform across the margin after the late Campanian, and sedimentation was clearly influenced by more regional or global oceanographic events. Sea-level oscillations, climatic variations, changes in bottom circulation, and vertical fluctuations of the carbonate compensation depth (CCD) were responsible for lithologic changes and major hiatuses.

Initial reports of the Deep Sea Drilling Project↗
USGS1973

Interstitial water studies on small core samples from the Mediterranean Sea

Of ten Leg 13 sites studied by us, eight give definite evidence of the existence of halite-containing sediments beneath the seabed. This conclusion is based on the existence on continuous sodium and chloride enrichments in interstitial waters with depth. This is the only direct evidence of the existence of salt at these sites, for only evaporitic dolomite, gypsum, and/or anydrite were recovered in cores. Among other ionic relationships, influence of evaporites is seen in calcium, magnesium and sulfate concentrations. Record high barium (216 ppm) and strontium (345 ppm) concentrations were observed in sulfate depleted pore fluids of Site 128 in the Hellenic Trench.

Initial reports of the Deep Sea Drilling Project↗
USGS1972

Interstitial water studies on small core samples, leg 14

The interstitial waters from the sediments cored on Leg 14 exhibit characteristic compositional trends with three important exceptions. At most of the sites, the changes in Na and Cl are very small while enrichment of Ca and Sr and depletion of Mg and SO 4 is typical of patterns observed in similar types of sediment recovered on previous legs. At Sites 139 and 140, off the African coast, and Site 144, off the coast of South America, systematic increases in concentration with depth are found for Na and Cl. At these sites, the concentration changes, in Ca, Mg, SO 4 and Sr generally follow diagenic patterns observed previously, but there is some indication of other factors affecting Mg concentrations. All analyses reported here, with the exception of bulk water content and pH, were carried out on water samples which were squeezed from the sediments on board ship and preserved by heat-sealing in lengths of polyethylene tubing. Analytical methods were identical to those outlined in earlier volumes of this series. We wish to thank Wen Chang, James O'Neill and Irene Uhlitzsch for their assistance in conducting the laboratory determinations and data reduction

Initial reports of the Deep Sea Drilling Project↗
USGS1973

Interstitial water studies on small core samples, legs 16, 17, and 18

Legs 16, 17, and 18 encountered three groups of sediment types: rapidly deposited biogenic deposits, showing marked changes in interstitial calcium, magnesium, and strontium; slowly deposited biogenic deposits, showing little variability in pore fluids other than elevated silica concentrations; and terrigenous deposits. The latter showed the usual loss of sulfate and combination of diagenetic reactions culminating in loss of Na + , K + , Mg ++ , with variable changes in Ca ++ . Very high barium concentrations (to 59 mg/kg) occurred at Site 178 (Leg 18).

Initial reports of the Deep Sea Drilling Project↗