Astronomy 23/223 In-Class Exercise:
|In a 1986 paper, K. L. Tanaka used cratering statistics to develop a detailed stratigraphy of Mars that now forms the basis for our geological stratigraphy of that planet. This stratigraphy is especially useful because it is constrained by crater abundances. So if you want to know how old any part of the martian surface is, you can simply count the numbers and sizes of craters within a given area, and estimate the age of that area as it relates to Tanakas time table for Mars.|
Table 1. (Tanaka, 1986)
Crater Density Boundaries for Martian Series
N = cumulative number of craters greater than or equal to each crater per one million km².
On the following pages, you will find two images. In the first
plot, you are looking at crater counts from before and after the
intrusion of a volcanic knob, and so you can use the table above
to determine the relative age of the knobs emplacement.
In the second plot, determine the relative ages of areas A, B, and C, using both N(16) and N(5) ages, and give the geologic time period in which each one formed.
Tanaka, K.L. (1986) The stratigraphy of Mars. Proceedings of the 17th Lunar and Planetary Science Conf., Part 1. Journal of Geophysical Research, 91, supplement, E139-E158.
|1.||This area of Mars has a prominent knob (probably volcanic) in its landscape. We'd like to know the relative age of the area before and after the knob was created. Use the table from Tanaka (1986) to determine the age of each, and give the name of the geologic time period in which each groups of units.|
|2.||Determine the relative ages of units A, B, and C, and identify the geologic time period in which each was formed.|
This page was created by Darby
Dyar and is maintained by Darby Dyar and Rebekah Robson-May.