ABI40/OBI40 Image Data Processing

 

IODP-MSP drilling and logging contractor: ESO

Hole: M0009D

Expedition: 310

Location: Tahiti Tiarei (central tropical S Pacific)

Latitude: 17° 29.3153' S

Longitude: 149° 24 2011' W

Logging date: October 22, 2005

Sea floor depth (driller's): 103.18 mbrf (118.25 mbsl)

Sea floor depth (logger's): 103.18 mbrf

Total penetration: 43.31 mbsf

Total core recovered:  23.62 m (54.54 % of cored section)

Oldest sediment recovered: Pleistocene sequence

Lithologies: Reef framework, algal crusts, and microbialite matrix

 

 

ABI40: 19.14 – 28.94 mbsf

OBI40 Lower/Upper Sections: 4.26 -28.54 mbsf

 

 

The OBI40 and ABI40 acquired optical and acoustic images respectively at millimetre scale resolution. The optical images provide continuous and color-calibrated images of the borehole wall with a pixel size of less than 1 mm horizontally by 2 mm vertically. The acoustic 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 are unaffected by borehole fluid quality. On the other hand, in regions where the borehole fluid was cloudy OBI40 images are of lower quality with a blurred appearance.

 

Acoustic images in borehole M0009D are of very high quality. Optical images were obtained in two sections of the borehole and are generally of high quality. In the lower interval, optical images are slightly affected by cloudy borehole fluids around cavities but overall the quality is good. The acquisition of optical images in the upper section was difficult due to hostile borehole conditions and the OBI40 became stuck frequently in this interval necessitating aiding it through the most problematic intervals by using hands on the cable. This resulted in a substantial degradation of image data quality in the lower part of this interval.

 

Additional information about the drilling and logging operations can be found in the Operations section of the Site Chapter in IODP Proceedings of Expedition 310. 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@le.ac.uk

 

For any web site-related problem please contact:

E-mail: logdb@ldeo.columbia.edu