Resurfacing history of Tempe Terra and surroundings

Abstract

The resurfacing history of the Tempe Terra region is determined using the Neukum and Hiller [1981] technique of breaking cumulative frequency curves into separate branches where the curves depart from a standard production curve. We find four surfaces recorded in the heavily cratered portions of Tempe Terra, with crater retention ages N(1) = [242,100], [95,700], [20,800], and [5500]. This is interpreted to indicate three major resurfacing events occurred in this region, ending at N(1) = [95,700], [20,800], and [5500]. The ridged plains on the Tempe Terra plateau have an oldest recorded surface age of [20,400], identical to that of the second resurfacing event recorded in the heavily cratered areas. A single resurfacing of the ridged plains (which may have been a second episode of ridged plains volcanism) occurred at N(1) = [7800]. The knobby plains to the north west and east of Tempe Terra also show a resurfacing at [20,000] and additional events at [5400] and perhaps [1600]. Mottled plains to the northeast record surfaces with crater retention age [7500], [5000], and [3900], where the first age is determined by a single surviving crater. It appears that the Lunae Planum Age (LPA) (at N(1) = [20,000]) resurfacing event seen elsewhere on Mars was widespread and effective in this region. A second widespread event appears to have ended at N(1) = [5000]. We estimate the thickness of the resurfacing materials corresponding to the LPA event to be less than 90 m in the heavily cratered areas but 300–500 m in the ridged plains themselves. Later resurfacing materials were generally thicker farther north in the mottled plains (300 m) than in the knobby plains (200 m).