Shipboard data collected during PCS gas-release experiments at Sites 994, 995, 996, and 997 are presented in nine columns in Table 2, Table 3, Table 4, and Table 5. The nine columns are: Eastern Standard Time, run time, gauge pressure, corrected pressure, PCS opening number, gas release volume, gas sample number, gas split volume, and cumulative gas volume. The columns are discussed below because the meaning of the data in the columns is not immediately obvious, and because there is no precedent for PCS data documentation. Basic information concerning time, pressure, or gas volumes was not collected for Cores 164-991B-1P, 164-994C-9P, 164-994C-18P, and 164-997A-51P.
The Eastern Standard Time column lists watch time in hour, minutes, and seconds to the nearest 30-s interval. Dates can be found in "Operations" sections of site chapters in the Leg 164 Initial Reports volume (Paull, Matsumoto, Wallace, et al., 1996). The run time column lists the time in minutes since core recovery.
The gauge pressure column lists discrete measurements of pressure in psi using the pressure transducer. The corrected pressure column lists the pressures in megapascals such that a transducer reading for the PCS at atmospheric pressure is 14.7 psi (the transducer was variably set between 0 and 15 psi for atmospheric pressure). Most cores retrieved prior to Core 164-994C-70P do not have corrected pressures because pressure inside the PCS could not be reduced to atmospheric pressure. However, the pressure transducer gave values between 0 and 15 psi after opening the PCS for the cores. No pressure measurements are associated with initial time recordings (run time = 0) because it takes at least 7 min to connect the pressure transducer after core retrieval aboard the JOIDES Resolution. The thermal history of a PCS core from core recovery at depth to connection of the transducer on ship is unknown. Initial recorded pressures (Table 2, Table 3, Table 4, and Table 5) cannot be used as in situ pressures.
The PCS opening number column indicates each occurrence, in numerical order, when the valve between the PCS and manifold was opened to release an incremental volume of gas from the PCS. When the valve was opened for longer than a minute or in successive minutes, the opening number is kept the same but given a letter designation. The gas release volume column lists the amount of gas released for each valve opening.
The gas sample number column indicates samples in numerical order collected from the bubble chamber of the manifold for chemical analyses. In most cases only a fraction (5-60 mL) of total gas entering the bubbling chamber from a PCS core was sampled. Also, in many cases, multiple gas volume increments were accumulated in the bubbling chamber prior to gas sampling. The gas split volume column indicates the amount of gas in the bubble chamber when each gas sample was collected.
The cumulative gas volume column lists the sum of incremental gas volumes collected in the bubble chamber per incremental valve opening. Cumulative volumes only increase after the valve between the PCS and manifold is opened.
Not all PCS cores recovered at pressure have values in all nine columns. Moreover, not all data in the columns is of similar quality. For example, gas volumes at Site 994 only were determined for Core 164-994C-70P, and total gas volumes determined for early cores were not given sufficient time to equilibrate at ambient conditions. In general, the best overall PCS data was collected at Site 997 because this was the last site to be drilled on Leg 164 and we had gained considerable experience using the tool.