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This is a summary table of deployments and extrapolated values for Site 902.
Click a link under the "Deployment" heading to see a plot of measurements and a best-fitting model, plus the extrapolated equilibrium temperature.
|
Deployment |
Tool ID |
Depth |
TC low a |
TC mid a |
TC high a |
T equ, TC low b |
T equ, TC mid b |
T equ, TC high b |
Comments |
|---|---|---|---|---|---|---|---|---|---|
|
(mbsf) |
(W/m °C) |
(W/m °C) |
(W/m °C) |
(°C) |
(°C) |
(°C) |
|||
|
12 |
22.0±2.0 |
1.2 |
1.3 |
2.0 |
5.4 |
5.4 |
5.2 |
minor early disturbance |
|
|
12 |
24.5±1.0 |
1.1 |
1.3 |
2.0 |
5.5 |
5.5 |
5.4 |
||
|
18 |
34.0±1.0 |
1.0 |
1.1 |
1.3 |
5.8 |
5.7 |
5.4 |
||
|
12 |
43.5±1.0 |
irrelgular record, not used |
|||||||
|
18 |
45.0±1.0 |
1.1 |
1.4 |
1.8 |
6.5 |
6.1 |
5.8 |
||
|
12 |
50.0±1.0 |
1.0 |
1.4 |
1.9 |
6.6 |
6.4 |
6.2 |
||
|
18 |
60.0±4.0 |
1.0 |
1.1 |
1.4 |
6.8 |
6.8 |
6.8 |
early-time data used |
|
|
12 |
69.5±1.0 |
irrelgular record, not used |
|||||||
|
12 |
78.5±1.0 |
0.9 |
1.0 |
1.2 |
7.8 |
7.8 |
7.7 |
late-time data used |
|
|
18 |
79.0±1.0 |
0.9 |
1.0 |
1.2 |
7.9 |
7.8 |
7.6 |
||
|
12 |
88.5±1.0 |
1.0 |
1.2 |
1.5 |
8.0 |
7.8 |
7.6 |
||
|
18 |
79.0±1.0 |
1.0 |
1.2 |
1.5 |
8.7 |
8.5 |
8.1 |
minor early disturbance |
|
|
12 |
107.5±1.0 |
1.2 |
1.4 |
1.6 |
8.6 |
8.5 |
8.4 |
||
|
18 |
117.0±1.0 |
1.2 |
1.4 |
1.7 |
8.8 |
8.9 |
8.7 |
early-time data used |
|
|
12 |
126.5±1.0 |
1.2 |
1.5 |
1.8 |
9.2 |
9.0 |
8.7 |
||
|
18 |
131.0±4.0 |
1.0 |
1.3 |
1.8 |
9.9 |
9.7 |
9.5 |
||
|
12 |
135.0±4.0 |
1.0 |
1.3 |
1.8 |
10.2 |
10.0 |
9.8 |
||
|
18 |
140.0±4.0 |
1.0 |
1.3 |
1.8 |
10.5 |
10.2 |
9.8 |
a Thermal conductivity values used for estimation of equilibration temperatures determined from visual examination of available data and box-car average applied aroound measurement depth. Value labeled "mid" is intended to be most representative of surrounding thermal conductivity values, while values labeled "low" and "high" are intended to provide a reasonable range of possible in-situ values. See thermal conductivity summary below.
b Equilibrium temperature values correspond to the assumed "low," "mid," and "high" thermal conductivity values listed in the table.
Site 902 summary plot of thermal conductivity data and measurement locations (indicated by the triangles along the left margin of the plot). Data from four holes at Site 902 are combined, as indicated by the different symbols in the legend. Lithologic unit boundaries identified by the Leg 150 scientific party are also shown for reference. The thermal conductivity data were binned by eye over the indicated depth intervals. The horizontal width of each bin illustrates one standard deviation on either side of the arithmetic mean of values in the bin. These means and standard deviations were used as a guide in selecting likely "low," "mid," and "high" thermal conductivity values used to estimate equilibrium temperatures. In general, assuming a higher thermal conductivity results in calculation of a lower extrapolated in-situ temperature, as shown in the table above.
The following plots of data appear in order of increasing depth. Observational data are plotted as open circles, and the best-fitting idealized model is shown with a thick line superimposed on top of the observations. The length of this model curve indicates the number of data values used for calculating the fit. For purposes of clarity, every other observation point is plotted.
A few general comments on data quality. We were quite surprised to see how "messy" these data were, particularly in comparison to data collected in deep ocean basins. However, we've seen during subsequent ODP legs that measurements in turbidites, particularly measurements in shallow water, tend to indicate significant probe motion. This leads to multiple penetration "spikes" and irregular decay curves.
Our general approach to interpreting these data was, when possible, to select a consistent time interval of 240-300 s after the first 150 s following penetration. We usually skipped the first 150 s of data because experience has shown that there is often inconsistent behavior during this time, with one or more subtle kinks in the temperature-time record. This is perhaps related to the passage of a thermal front from one side of the coring shoe to the other or perhaps to some kind of dynamic associated with the advanced piston coring process, but it appears irregularly, is not predictable, and has never been properly explained. We prefer to use 240-300 s of undisturbed data, but tried to use smaller data intervals when tool motion did not allow for a smooth decay. The equilibrium temperature estimates based on these analyses have greater uncertainties. Some records were so noisy that we did not feel it was possible to use them to estimate of in-situ temperatures. All data records are included below for your inspection, consideration, and comment.
902A-3H. Generally a good record, particularly for a shallow measurement. Slight movement at about 150 sec.
902C-3H. Excellent measurement, smooth decay.
902A-4H. Excellent measurement, smooth decay.
902C-5H. Very irregular record following penetration indicates probe motion. Abrupt flattening of record at end indicates that these temperatures are probably an upper bound. Data not used.
902C-6H. Excellent measurement, smooth decay. Note slight kink at about 140 seconds.
902C-7H. Excellent measurement, smooth decay. Note slight kink at about 140 seconds.
902D-6H. Irregular record indicating probe motion at about 200 s, but the short data segment at 150-200 s looks usable, particularly considering consistency of estimated equilibrium temperature with shallower and deeper measurements.
902D-7H. Irregular record probably indicates upper limit to in-situ temperature, particularly since first 200 s indicate significant probe motion and frictional heating of sensor.
902C-10H. Initially smooth record, but probe moved after about 320 s, forcing use of a short data segment.
902D-8H. Excellent measurement, smooth decay.
902D-9H. Excellent measurement, smooth decay. Note slight kink at about 140 seconds.
902D-10H. Excellent measurement, smooth decay. Note slight kink at about 150 seconds.
902D-11H. Good measurement, smooth decay following slight disturbance after penetration.
902D-12H. Abrupt drop in temperature after 200 s may indicate loss of contact between tool wall and formation. Short segment of 150-200 s used.
902D-13H. Excellent measurement, smooth decay. Note slight kink at about 140 seconds.
902D-14H. Excellent measurement, smooth decay.
902D-15H. Excellent measurement, smooth decay.
902D-16H. Excellent measurement, smooth decay. Note slight kink at about 140 seconds.
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