de.pangaea.dataset761966 und dataset PANGAEA

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https://www.pangaea.de/ information pointOfContact 2026-05-01T03:38:52Z https://doi.pangaea.de/10.1594/PANGAEA.761966 1991-01-01 publication https://doi.org/10.1594/PANGAEA.761966 Jarrard, Richard D

jarrard@mines.utah.edu

author Broglia, Christina

chris@ldeo.columbia.edu

author PANGAEA

info@pangaea.de

https://www.pangaea.de/ information publisher tableDigital Supplement to: Jarrard, Richard D; Broglia, Christina (1991): Geophysical properties of oceanic crust at Sites 768 and 770. In: Silver, EA; Rangin, C; von Breymann, MT; et al. (eds.), Proceedings of the Ocean Drilling Program, Scientific Results, College Station, TX (Ocean Drilling Program), 124, 75-90, https://doi.org/10.2973/odp.proc.sr.124.125.1991 Velocity, density, resistivity, and neutron-porosity logs were recorded in virtually the entire 222-m-thick section of basaltic back-arc crust drilled at Site 768 and through the 106-m section of MORB crust at Site 770. Our analysis of these logs and comparison with measurements on discrete cores permit determination of interlog relationships and evaluation of the reliability of each log. Crustal porosity (Phi) at the two sites is most accurately determinable from transit time (Delta t) and the inverse of velocity: Phi = 0.0054*Delta t - 0.259. Porosity is also closely related to resistivity (Ro), according to the Archie equation: Ro = (Rwas**-m where Rw is resistivity of the formation fluid, and a and m are empirically determined "constants." Both logs and cores indicate that a and m range from 2 to 6.5 and 1.2 to 1.6, respectively. Density values estimated from sonic porosity are broadly similar to, but more reliable than, density logs. Neutron-porosity logs yield values 10%-20% higher than actual porosities; this error is caused primarily by lack of proper tool eccentralization and secondarily by the presence of hydrous alteration minerals in the rocks. These in-situ geophysical properties of oceanic crust 18 Ma and 42 Ma help to bridge the in-situ measurement gap between 6 Ma and 110 Ma at other sites. Observed velocities, densities, and porosities are generally similar to predictions from crustal aging models. We infer that this correspondence is largely coincidental; observed properties here are related more to style of volcanism than to crustal aging, and crustal heterogeneity is so high that a 100-200-m-interval is not representative of larger scale geophysical properties. completed Jarrard, Richard D

jarrard@mines.utah.edu

principalInvestigator ODP Ocean Drilling Program theme 1995-01-01 creation PANGAEA

info@pangaea.de

https://www.pangaea.de/ information pointOfContact copyright copyright CC-BY-3.0: Creative Commons Attribution 3.0 Unported textTable und geoscientificInformation 121.2198 123.6684 5.1448 8.0 1988-12-01T14:30:00 1988-12-30T18:00:00 425.7 1259.16 Sediment depth is given in mbsf. In the publication depth for Hole 124-770C is given in mbsf, but shows too high values, which seems to be the water depth (4516 m) and the sediment depth. So the water depth was subtracted. Hole 124-768C is not effected by this. Event label thematicClassification Sample code/label thematicClassification DSDP/ODP/IODP sample designation DEPTH, sediment/rock physicalMeasurement m m Density, wet bulk physicalMeasurement g/cm**3 g/cm**3 Density, grain physicalMeasurement g/cm**3 g/cm**3 Porosity physicalMeasurement % vol % vol Velocity, compressional wave physicalMeasurement m/s m/s text/tab-separated-values unknown https://doi.pangaea.de/10.1594/PANGAEA.761966?format=textfile download dataset The data set was checked for completeness, correctness, and consistency of metainformation. Validity of used methods was checked and - if applicable - precision and range of data. EVENT LABEL: 124-768C * LATITUDE: 8.000000 * LONGITUDE: 121.219800 * DATE/TIME START: 1988-12-01T14:30:00 * DATE/TIME END: 1988-12-13T07:00:00 * ELEVATION: -4396.0 m * PENETRATION: 1268.5 m * RECOVERY: 525.69 m * LOCATION: Sulu Sea * CAMPAIGN: Leg124 * BASIS: Joides Resolution * METHOD/DEVICE: Drilling/drill rig 100 cores; 915 m cored; 0 m drilled; 57.5 % recovery 1988-12-01T14:30:00 EVENT LABEL: 124-770C * LATITUDE: 5.144800 * LONGITUDE: 123.668400 * DATE/TIME START: 1988-12-24T08:00:00 * DATE/TIME END: 1988-12-30T18:00:00 * ELEVATION: -4516.0 m * PENETRATION: 529.5 m * RECOVERY: 54.81 m * LOCATION: Mindanao Sea * CAMPAIGN: Leg124 * BASIS: Joides Resolution * METHOD/DEVICE: Drilling/drill rig 12 cores; 115.8 m cored; 0 m drilled; 47.3 % recovery 1988-12-24T08:00:00