ABI40 Image Data Processing

IODP-MSP drilling and logging contractor: ESO

Hole: M0027A

Expedition: 313

Location: New Jersey (NW Atlantic)

Latitude: 39° 38.0406' N

Longitude: 73° 37.3015' W

Logging date: May 19 - 21, 2009

Sea floor depth (driller's): 50.15 m DRF

Sea floor depth (logger's): 49.50 m WRF

Total penetration: 631.01 m DSF

Total core recovered:  471.59 m (86.21 % of cored section)

Oldest sediment recovered: Eocene

Lithologies: Clays to gravels

ABI40 Lower Section: 419.94 – 575.30 m WSF

ABI40 Middle Section: 194.25 – 328.15 m SWF

The acoustic images show the acoustic hardness of the lithologies within the depositional sequence.

In M0027A, acoustic images have been recorded in the lower and middle sections of the borehole. Images have not been recorded in the lowest part of the middle section (328 to 419 m WSF) due to borehole collapse and bridge formation. For each interval of M0027A the image logs were acquired as one continuous file. The ABI40 images of the borehole wall were apparently unaffected by borehole fluid quality. The occurrence of dark lines oriented at 180° indicates poor centralization of the tool, possibly related to an enlarged hole.

The ABI40 acoustic images in the lower interval were acquired with a resolution of 72 samples x 4 mm (increasing in resolution in the upper few metres of this section as a test) which results in a pixel size of less than 5 (horizontal) x 4 (vertical) mm. In the middle interval the acoustic images were acquired with a resolution of 288 samples x 4 mm. The presented values of the acoustic caliper were obtained by assuming a acoustic wave velocity of 1495 m/s through borehole fluid and taking the mean value of the measurements at every sample (4 mm vertical sampling).

The images of the borehole wall (360°), corrected for decentralization effects when possible, are displayed into a two-dimensional view as an unwrapped borehole cylinder. A dipping plane in the borehole will appear as a sinusoid on the image with the amplitude of this sinusoid proportional to the dip of the plane. The images are oriented with respect tothe magnetic north, hence the strike of dipping features can also be determined. A "static" normalization of the images has been applied to enhance structure visualization. Images are provided in PDF format at two different scales. The travel time and amplitude data for each interval logged have also been output in ASCII format.

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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