Data

The logging data was recorded by the University of Montpellier (Geosciences Montpellier) who are part of the European Petrophysics Consortium (EPC) in .RD format (read by the log software package WellCAD). Data were processed by the European Petrophysics Consortium (EPC). VSP data was recorded and processed by the University of Alberta who were contracted by EPC.

Logging Runs

Tool string	Run/Pass	Top depth (m WSF)	Bottom depth (m WSF)	Pipe depth ( m DSF)	Notes
1. VSP	Through pipe	207.83	753.42	~755	3.05 m interval between shots
2. ASGR	Through pipe	0.01	757.31	~755
3. DIL45	Lower	482.87	723.87	~482	Merged with run 11
4. 2PSA	Lower 1	577.00	719.94	~482	Merged with run 5
5. 2PSA	Lower 2	482.45	576.94	~482	Merged with run 4
6. EM51	Lower	482.84	729.28	~482	Merged with run 13. Downlog used.
7. ABI40	Lower	483.20	656.53	~482
8. VSP	Through pipe	12.76	226.12	~482	3.05 m interval between shots
9. ASGR	Upper	322.22	348.02	~335
10. DIL45	Upper	340.07	347.47	~335
11. DIL45	Middle	403.67	488.16	~401	Merged with run 3
12. 2PSA	Middle	404.56	491.05	~401
13. EM51	Middle	403.67	528.44	~401	Merged with run 6

The depths given in the table are for the processed data. The raw data may contain extra data within the pipe: this data has been removed from the processed data files. The depths in bold refer to top and bottom depths of files before merging (i.e. the top and bottom depth of the final merged files are not in bold).

A complete list of tool and log acronyms is available at http://brg.ldeo.columbia.edu/data/iodp-eso/exp313/exp_documents/iodp-eso-313-acronyms.html.

Logging Nomenclature

The logged intervals in each borehole are described as lower, middle and upper. These do not match across boreholes either in terms of depth or sequence boundary. In any case, logging has not been carried out in more than three stages. These intervals can be seen at http://brg.ldeo.columbia.edu/data/iodp-eso/exp313/exp_documents/iodp-eso-313-ops-summary.pdf.

General Information

The suite of tools available for logging on Expedition 313 consisted of spectral gamma ray (ASGR), velocity (2PSA), conductivity (DIL45), acoustic borehole imaging (ABI40) and magnetic susceptibility (EM51) measurements. Each tool was run separately. Upon coring completion, the spectral gamma log was acquired through drill pipe. Subsequently the hole was conditioned with drill mud. The unfavorable borehole conditions required logging openhole in separate intervals. Difficulties pulling pipe and the development of bridges affected the ability to log certain sections of the boreholes (especially the upper, more unconsolidated sandy sections). The logger’s zero depth position was taken as the top of the drill pipe. Discrepancies in depths between initial zeroing and zeroing on removal of the tool were generally less than 0.5 m. The depths in the table are for the processed logs (after depth shift to the sea floor). Generally, small discrepancies exist between the sea floor depths determined from the downhole logs and those determined by the drillers from the pipe length. Typical reasons for depth discrepancies are ship heave, wireline and pipe stretch, tides, and the difficulty of getting an accurate sea floor from the 'bottom felt' depth in soft sediment. For New Jersey, logging was done from a platform and so there was no ship heave to account for.

Hole M0029A logging

Logging operations in M0029A began with the acquisition through pipe of VSP measurements from the base of the borehole to ~ 200 m WSF, at which point a lightning storm halted operations. Through-pipe spectral gamma ray measurements were also acquired over the entire borehole. Open hole logging operations took place in three stages:

Lower section (482 to 757 m WSF): in this section, borehole conditions were good and all tools except the spectral gamma were run in open hole. However, acquisition was slowed by technical difficulties. Technical problems with the winch began towards the end of the first run on the final section of the uplog. On the second run the primary winch failed completely at ~577 m WSF and the sonic tool was manually pulled back onto the deck. The winch was replaced with a backup and logging continued with the remainder of the sonic run followed by the magnetic susceptibility sonde. The acoustic log was the last data to be acquired following a break while a fault was fixed in the backup winch. VSP data was acquired through pipe in the upper 200 m of the hole before the pipe was pulled to log the next interval.

Upper section (above 401 m WSF): this section was logged after to the lower section. It suffered from the presence of several bridges, which resulted in logging only a small section with the spectral gamma and the conductivity tools (~322 to 335 in pipe and 335 to 348 m WSF in open hole).

Middle section (401 to 482 m WSF): this section was logged after to the upper section. Reaming and hole conditioning indicated that this interval might be open and stable enough to log. The conductivity, sonic and magnetic susceptibility tools were successfully run with sufficient overlap to enable a confident merge of the data between the lower and middle sections.

The rest of the upper section could not be logged due to time constraints.

The change to the backup winch in M0029A resulted in depths being recorded both manually by the winch and electronically through the logging software. This gave the opportunity to check electronic depths at roughly equally spaced intervals throughout the borehole. All downhole wireline logs from run 5 onwards use the backup winch and have slight adjustments applied to the electronic depths. The near-perfect repeatability in the overlapping interval between the middle and lower intervals allows precise merging of these datasets.

Processing

Depth shift: The original logs were first corrected for the difference in zero tool depths and the difference between logger’s and driller’s zero points (if applicable). For hole M0028A the logger’s zero point was located beneath the driller’s zero in order to make the tool entry and exit point easier to access. See

http://brg.ldeo.columbia.edu/data/iodp-eso/exp313/exp_documents/iodp-eso-313-depth-layout.pdf . Finally, logs were depth shifted to the sea floor using the driller’s depth to seafloor (-53.41 m below rig floor). The driller’s distance to seafloor was chosen as the reference depth because for each hole this fell within the range of the depth to seafloor given by the gamma ray log. The gamma ray log through pipe was taken as the reference log (continuous) and where appropriate other logs were depth-matched to it. In hole M0028A the magnetic susceptibility log required a downwards shift (0.86 m) and the sonic log required an upwards shift in both the middle (-1.11 m) and lower (-0.42 m) sections. The log depths are therefore m WMSF.

Data merges: Where there was an overlap the data was merged. Due to the usually excellent match in the overlap section, the data in the merged section was averaged. In hole M0029A the following logs were merged:

DIL45 middle section (run 11) / lower section (run 3)

EM51 middlesection (run 13 / lower section (run 6)

2PSA middle section (run 12) / lower section-pass1 (run 4) / lower section-pass 2 (run 5).

The acquisition of acoustic borehole images occurred in several files due to their size (see image notes for more details).

Environmental corrections: None.

Acoustic data: The 2PSA tool was run at a frequency of 15 kHz and resultant logs can be used to calculate compressional velocities. The data was processed in the WellCAD logging package. Waveform picking was done manually to ensure good quality data. Time picks were saved and the acoustic velocities were calculated using the receiver spacing of 1 ft. All presented acoustic data is accurate. Where no clear first arrivals in the waveform were present in two receivers, a null value was entered in the database.

Spectral gamma ray: Gamma ray logs recorded through drill pipe should be used only qualitatively due to attenuation of the incoming signal.

Quality Control

The quality of the data is assessed by checking against reasonable values for the logged lithologies, by repeatability between different passes of the same tool or down and up logged intervals, and by correspondence between logs affected by the same formation property (e.g. the resistivity log should show similar features to the acoustic log).

The quality of the ASGR Spectral Natural Gamma data is directly related to lithology in combination with logging speed. Where counts are lower the reliability of the statistical function used to separate raw counts into values of naturally occurring radioactive elements [potassium (K), uranium (U) and thorium (Th)] is degraded. Negative values are indicative of incorrect statistics; when this is the case, K, U and Th values at that depth has been replaced by a null (-999.25). Gamma ray logs recorded through drill pipe should be used only qualitatively due to attenuation of the incoming signal.

A wide and/or irregular borehole affects most recordings, particularly those that require eccentralization and a good contact with the borehole wall. Hole diameter was calculated from the acoustic imaging tool (ABI40).

Whenever possible, data was acquired downlog, uplog and through the pipe. In this case the uplog is usually the final output. The only exception si at hole M0029A, where the EM51 down log provides a better merge with the log from the middle section. The data recorded within the pipe are usually removed from the final log. This data has been retained in the original data files.

A null value of -999.25 may replace invalid log values.

Additional information about the drilling and logging operations can be found in the Operations section of the Site Chapter in IODP Proceedings of Expedition 313. For further questions about the data, please contact:

Jennifer Inwood

University of Leicester

Phone: 011-44-116-252-3327

Fax: 011-44--116-252-3918

E-mail: IODP-UK

Johanna Lofi

University of Montpellier 2

Phone: 033- 467-149- 309

Fax: 033- 467- 143- 244

E-mail: IODP-UK

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E-mail: Database Manager