Methods are provided for making, processing, and analyzing in situ measurements to indicate presence of thin bedding planes of weakness in a formation. Bedding planes as small as a few inches and smaller are identified using an ultrasonic borehole tool. In one embodiment, detected pseudo-Rayleigh waveforms are processed to determine whether multiple events are detected. If so, lamination and a likely bedding plane of weakness are identified. In another embodiment, a sonic borehole tool is run in conjunction with the ultrasonic borehole tool. Indications of shear and pseudo-shear wave speeds are compared, and where different, a bedding plane of weakness is identified. In another embodiment, a microresistivity imager is run with the ultrasonic borehole tool, and at locations where multiple events are not detected, the image obtained by the imager is inspected to find locations of sharp contrast with adjacent locations to thereby identify bedding planes of weakness.