| Autor: |
Annex, A. M.1,2,3 (AUTHOR) annex@seti.org, Lewis, K. W.3 (AUTHOR) |
| Předmět: |
|
| Zdroj: |
Journal of Geophysical Research. Planets. Nov2024, Vol. 129 Issue 11, p1-15. 15p. |
| Abstrakt: |
Crater counting is a widely applied methodology for dating large areas of planetary surfaces, but is difficult to apply the method to constrain the durations of stratigraphic unconformities. Unconformities with exhumed craters are thought to indicate long hiatuses that can only be indirectly dated through stratigraphic relationships with other surfaces with uniform exposure ages. On Mars, sedimentary deposits with prominent unconformities with exhumed craters are found in layered deposits in the Arabia Terra region as well as Gale crater within Mount Sharp. In this work, we present a Linear Crater Counting methodology and apply it to constrain these unconformities observed in Arabia Terra and in Mount Sharp. The method applies a linear sampling domain correction to conventional two‐dimensional crater size frequency distributions and Bayesian Poisson process statistics in order to constrain the likely durations of these unconformities. We found that unconformities in Arabia Terra were on the order of 0.1–1 Gyr in length and that the unconformity preserved at Mount Sharp is at least 0.2 Gyr in length given estimates of the ages of the host craters. Hiatuses of these lengths constrain the age of the overlying deposits to be Late Hesperian or Amazonian in age. Two utility plots are also provided, along with the derivation, for researchers to apply this method to dating arbitrary geologic contacts on Mars and to adapt it to other bodies. Plain Language Summary: The crater counting method is a widely used method to date planetary surfaces. Crater counting works by comparing the number of craters in an area to the expected number of craters that should be observed for that area using a model of how many craters form and their expected size through time. On Mars, geologic contacts of sedimentary deposits with exhumed craters are seen in Arabia Terra and in Gale crater in Mount Sharp. Craters exhumed in these geologic contacts are thought to indicate long gaps in time between the formation dates of the upper and lower rock layers. However, dating these time gaps directly is not possible with conventional crater counting. To solve this problem, we developed a new linear crater counting method which describes the likely number of craters for a given age that could be found along a line on the surface of Mars. We apply this method to the geologic contacts seen in Arabia Terra and in Gale crater, and find that the time gaps are hundreds of millions of years in length to over a billion years in length. Our results confirm predictions that these deposits are geologically younger than previously thought. Key Points: We describe a novel linear crater counting method to date stratigraphic unconformities using partially exhumed craters along unit boundariesWe found that layered deposits in Arabia Terra and the Upper mound unit in Gale crater could be Amazonian in Age from applying our methodOur methodology can be applied broadly to better understand chronostratigraphy across the solar system [ABSTRACT FROM AUTHOR] |
| Databáze: |
GreenFILE |
| Externí odkaz: |
|
Plný text