C14 measurements reported here were made in this laboratory between December 1, 1961 and October 1, 1962. Sample descriptions are classified as follows:
I.Tree-ring dated samples.II.Modern shells from Santa Barbara County, California.III.Archaeologic samples.IV.Palynologic samples.V.Geologic samples.VI.C14 content of caliche.VII.Water samples.VIII.Modern organic sample.
The radiocarbon dating laboratory at the Smithsonian Institution, Division of Radiation and Organisms, was established in September 1962. After careful calibration with known samples and refinements in the methane synthesis system, routine analysis of samples was begun in the spring of 1963.
The carbon isotopic analyses reported here covers the period since the last list (Haynes et al., 1967) until summer 1969. All results relating to secular C14 fluctuations in atmospheric CO2 are now published separately (Damon et al., 1970). Sample preparation and counting procedures remain essentially unchanged since completion of our conversion to CO2 in 1960. All δC13 values are reported relative to PDB and all C14 dates, unless otherwise noted, are based on the 5568 year half-life, but are not corrected for C13 content. 0.95 NBS oxalic acid activity is our routine standard periodically monitored for isotopic fractionation.
Hydrocarbons seeping from the sea floor can reveal the location of commercially significant offshore-oil and gas deposits. Such seeps produce a localized increase in the concentration of hydrocarbons dissolved in the adjacent sea water, but these concentrations will be transported and dispersed by marine currents and mixing. Calculation of the resulting concentration patterns shows that an optimum search requires sampling very near the sea floor. Equipment to perform such searches has been constructed and tested.
A submersible, pump is attached to special faired tubing containing hose and electrical and support cables. An automated winch deploys or recovers the hose and pump at survey speeds. Sampling can extend to depths of 185 meters at speeds up to 6 knots. Sea water from the pumping system is passed through a rotating disk stripper, where over 95% of the dissolved light hydrocarbons are removed by a counter-current flow of purified air. Total hydrocarbon concentration is measured continuously. Ethane, propane, and isobutane are collected, and six-minute integrated samples are determined continually. Sensitivity is sufficient to measure natural levels in the open sea. The system contains integral "blank" and "calibrate" functions and is designed to function automatically without constant operator attention.
Seeps Point the Way
Oil and gas seeps have helped to guide oil exploration ever since Drake drilled a seep area to the first producing oil well. Link (1952) prepared an extensive review of their types and locations and emphasized that they have provided the first clues to most of the major oil producing regions of the world. He showed that such features are widespread, numerous, and almost always found when there are major deposits. The Texas-Louisiana area is considered anomalously free of large seeps yet Link was able to locate more than 85 oil and gas seeps within 100 miles of the coast in those two states alone. Gas seeps of dramatic strength are well known.
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