EXPERIMENTAL ERROR IN PEBBLE ROUNDNESS DETERMINATION BY THE MODIFIED WENTWORTH METHOD

TWO QUESTIONS ARE ADDRESSED, ACCURACY OF THE MODIFIED WENTWORTH METHOD IN DETERMINING PEBBLE ROUNDNESS AND THE NATURE OF ROUNDNESS FREQUENCY DISTRIBUTIONS. THIRTY OBSERVERS, RANGING FROM LIBRARIANS THROUGH SEDIMENTOLOGISTS, EMPLOYED THE MODIFIED WENTWORTH METHOD TO MEASURE THE RADIUS OF CURVATURE OF THE SHARPEST CORNER. WHILE THERE WERE SYSTEMATIC ERRORS ARISING FROM SOME OBSERVERS' TENDENCY TO MEASURE CONSISTENTLY HIGH OR LOW, MOST ERRORS AROSE FROM DEFINITION OF 'THE SHARPEST CORNER' AND FROM THE FACT THAT CORNERS MAY APPROACH SEGMENTS OF PARABOLAS OR HYPERBOLAS RATHER THAN A TRUE CIRCLE, SO THAT IT WAS DIFFICULT TO PICK A TEMPLATE CIRCLE. IN ANOTHER EXPERIMENT, DATA FOR RIVER AND BEACH PEBBLES WERE USED TO PLOT ROUNDNESS FREQUENCY DISTRIBUTIONS. THESE WERE FOUND TO BE ARITHMETIC-NORMAL, RATHER THAN LOG-NORMAL AS SUGGESTED BY OTHER AUTHORS. IN CONCLUSION, IT IS RECOMMENDED THAT WHEN TWO OR MORE PERSONS ARE CONDUCTING ROUNDNESS STUDIES, PEBBLES IN ANY ONE LOCALITY OR SIZE CLASS OR LITHOLOGY SHOULD BE MEASURED IN EQUAL AMOUNTS BY ALL OPERATORS.

  • Authors:
    • Folk, R L
  • Publication Date: 1972-12

Media Info

  • Features: References;
  • Pagination: p. 973-4
  • Serial:

Subject/Index Terms

  • TRT Terms: Stone
  • Uncontrolled Terms: Roundness
  • Old TRIS Terms: Pebbles
  • Subject Areas: Geotechnology; Highways;

Filing Info

  • Accession Number: 00230184
  • Record Type: Publication
  • Files: TRIS
  • Created Date: Apr 8 1973 12:00AM