ABSTRACT

Accurate and quick high-resolution measurements of stratigraphic thicknesses and geologic profiles exposed in surface outcrops are critically important for interpreting depositional environments, basin development, and tectonic evolution. Therefore, a high-precision instrument is required for high-resolution stratigraphic measurements. Herein, a new version of the Jacob's staff incorporating an Abney level or a geological compass, a laser pointer, and a handheld GPS is presented. Both the Abney level and the laser pointer are oppositely positioned side by side at the 1.5 m position on the 1.6-m-long fiberglass rod, and they can synchronously slide vertically and rotate horizontally. Because accurate sighting of bedding surfaces is facilitated with both the sighting tube of the Abney level and straight-line beam of the laser pointer, this novel design greatly improves the precision and speed of stratigraphic thickness measurements. More importantly, when the section requires a lateral shift, the straight-line beam can easily and precisely identify the new start point without rotating the rod, which greatly reduces potential changes in the angle of the rod. The GPS unit installed at the top of the rod synchronously records the track of the measured section and coordinates of each measurement, which enables acquisition of a topographic profile along the stratigraphic section. Uncertainties in stratigraphic thickness measurements are minimized when observations are made through the sight tube of the Abney level when the rod is oriented perpendicular to the bedding surface.

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