ABI40 Image Data Processing
IODP-MSP drilling and logging contractor: ESO
Hole: M0042A
Expedition: 325
Location: Great Barrier Reef (tropical SW Pacific)
Latitude: 19 50.63885° ' S
Longitude: 150° 26.8818' E
Logging date: March 8, 2010
Sea floor depth (driller's): 56.32 m DSL
Sea floor depth (logger's): 73.78 m WRF on ASGR; 65 m WRF on all other tools
Total penetration: 46.4 m DSFTotal core recovered: 10.94 m (23.58 % of cored section)
Lithologies: carbonate sand, corals, bioclastic sediments
ABI40: 7-43.2 m WMSF
OBI40: 8.2-39 m WMSF
The ABI40 acquired acoustic images at mm-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 optimal borehole diameter for both imaging tools is <15 cm, and therefore the images acquired in Hole M0042A, an API-sized hole were of low quality with very little detail recorded. Additionally, the hole, although flushed before logging, was very murky due to the use of 'mud' whilst drilling rather than just seawater - hence the images recorded by the optical imaging tool were negatively impacted.
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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.