Gravity Investigation of Wolf Creek Crater, Western Australia

Abstract

Wolf Creek Crater is an essentially uneroded, 875 m (average) diameter meteorite impact crater that has been partly buried under windblown sand. There is a local - 2 milligal gravity anomaly centered on the crater due largely to the substantial thickness of sand under the present crater floor. The gravity signature shows a small reversal over the center, which correlates with a central "claypan," and a small positive anomaly near the base of the inner rim in the north northeastern sector. The size and shape of the gravity signature and the measured density contrast between sand and quartzite country rock were used to "remove" the sand cover in and around the crater. The assumptions made in this exercise are thought to minimize the calculated depth to the original crater floor. The "exhumed" crater has an approximate (minimum) depth of 140-150 m below the rim crest and 95-110 m below the gently undulating country rock surface. Relative to the immediately adjacent, outside terrain, the rim crest stands 40-45 m above the original surface. The crater's circularity index is 0.70, its rim height/diameter ratio is 0.05 and its rim height/depth ratio is 0.3. All these parameters are within the normal range for impact craters although the first two lie near the extremes of tabulated values. Additional work is necessary to establish the cause of the interior positive anomaly.