This is a summary table of deployments and extrapolated values for Site 903.
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) |
|
|
17 |
28.5±2.0 |
1.0 |
1.2 |
1.5 |
8.1 |
8.1 |
8.1 |
double penetration, upper bound | |
|
18 |
38.0±1.0 |
1.0 |
1.2 |
1.5 |
8.6 |
8.6 |
8.7 |
| |
|
12 |
47.5±1.0 |
0.9 |
1.2 |
1.5 |
8.1 |
8.1 |
8.1 |
| |
|
17 |
57.0±1.0 |
1.0 |
1.3 |
1.5 |
8.1 |
8.1 |
8.0 |
| |
|
18 |
66.5±1.0 |
1.0 |
1.2 |
1.5 |
7.7 |
7.7 |
7.6 |
double penetration | |
|
12 |
76.0±1.0 |
1.1 |
1.3 |
1.5 |
7.3 |
7.1 |
6.9 |
double penetration | |
|
18 |
85.5±1.0 |
|
|
|
|
|
|
irrelgular record, not used | |
|
12 |
95.0±1.0 |
0.9 |
1.2 |
1.6 |
8.2 |
8.0 |
7.5 |
| |
|
18 |
104.5±1.0 |
|
|
|
|
|
|
irrelgular record, not used | |
|
12 |
114.0±1.0 |
1.0 |
1.4 |
1.8 |
8.8 |
8.7 |
8.5 |
| |
|
18 |
123.5±1.0 |
1.0 |
1.3 |
1.6 |
9.2 |
8.8 |
8.1 |
| |
|
12 |
133.0±1.0 |
1.0 |
1.3 |
1.6 |
9.3 |
9.1 |
9.0 |
| |
|
18 |
142.5±1.0 |
1.0 |
1.3 |
1.6 |
9.8 |
9.5 |
9.3 |
| |
|
12 |
149.0±2.0 |
1.0 |
1.3 |
1.7 |
10.1 |
9.9 |
9.6 |
|
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 903 summary plot of thermal conductivity data and measurement locations (indicated by the triangles along the left margin of the plot). Data from two holes at Site 903 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.
903A-3H. Double penetration at start adds extra heat, so interpreted equilibrium temperature must be considered as an upper bound. Note that decay of initial penetration spike would clearly result in a temperature well below 8.1 °C. Unfortunately, there are not enough decay data from the first penetration to estimate the in-situ temperature.
903A-4H. Irregular record indicates significant probe motion after about 250 s. Note that there is also a kink in the record at about 150 s, consistent with many otherwise excellent records.
903A-5H. Excellent measurement, smooth decay. This is the shallowest high-quality record from Site 903. Note that the in-situ temperature estimated here is about 2°C warmer than that determined at a similar depth at Site 902.
903A-6H. Another irregular record after about 240 s. Fortunately, there appear to be enough data during the period of 120-240 s to allow the in-situ temperature to be estimated.
903A-7H. Another irregular record, but it appears that the data at 120-275 s following penetration allow for estimation of in-situ temperature.
903A-8H. Double penetration, but the final decay curve looks good. The estimated equilibrium temperature is unlikely to be higher than that estimated, but it could be lower. There is little doubt that the in-situ temperature estimated at 76.0 mbsf is significantly lower than that measured at 47.5 mbsf in the same hole.
903A-9H. Highly irregular record could not be interpreted.
903A-10H. Excellent measurement, smooth decay. The estimated in-situ temperature is slightly less than that determined at 47.5 mbsf in the same hole. Both are excellent records.
903A-11H. Highly irregular record could not be interpreted.
903A-12H. Excellent measurement, smooth decay. With this record, we finally see an increase in temperature with depth.
903A-13H. Excellent measurement, smooth decay. Slightly shortened data segment selected because of change in slope of decay curve at about 400 s.
903A-14H. Excellent measurement, smooth decay.
903A-15H. Excellent measurement, smooth decay.
903A-16H. Excellent measurement, smooth decay.
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