ABI40 Image Data Processing

IODP-MSP drilling and logging contractor: ESO

Hole: M0054B

Expedition: 325

Location: Great Barrier Reef (tropical SWF Pacific Ocean)

Latitude:17° 6.0425' S

Longitude: 146° 34.60458' E

Logging date: March 31, 2010

Sea floor depth (driller's): 110.33 m DSL

Sea floor depth (logger's): 126.25 m WRF on ASGR; 120 m WRF on all other tools

Total penetration: 33.2 m DSF

Total core recovered:  8.25 m 24.85 ( % of cored section)

Lithologies: carbonate sand, corals, bioclastic sediments

ABI40: 17.52 - 25.55 m WMSF

OBI40: 17.52 - 25.22 m WMSF

 

The ABI40 acquired acoustic images at millimetre scale resolution. The images show the acoustic hardness of the lithologies within the coral reef sequence with a pixel size of 1.1 mm horizontally by 4 mm vertically.

The images are displayed as an unwrapped borehole cylinder and are provided in .BMP and .PDF format. 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 to north, hence the strike of dipping features can also be determined. Additional processing on the accelerometer data of the image tools by a double integration of the acceleration allowed, whenever needed, a detailed repositioning of the recorded image data to its correct position with respect to the seafloor.  

The ABI40 images of the borehole wall were unaffected by borehole fluid quality. On the other hand, in regions where the borehole fluid was cloudy OBI40 images are of low quality with a burred appearance.

Acoustic images in borehole M0054B are of very high quality. Optical images were of low quality due to remnant drill 'mud' and the large amount of suspended sediment in the borehole. Borehole images were only acquired over a very narrow depth window, however the ABI40 sonde obtained detailed images over an important boundary in the coral sequence.

Additional information about the drilling and logging operations can be found in the Operations section of the Site Chapter in IODP Proceedings of Expedition 325.

For any question about the data or about the LogDB database, please contact LogDB support: logdb@ldeo.columbia.edu.