ANALOGUES OF TERRESTRIAL MICROBIALLY INDUCED SEDIMENTARY STRUCTURES IN SANDSTONES OF THE < 3.7 GA GILLESPIE LAKE MEMBER, MARS (Invited Presentation)

Sandstone beds of the < 3.7 Ga Gillespie Lake Member, Mars, record an ancient playa environment. On Earth, clastic paleoenvironments of similar ages had been sites of colonization by microbial mats that formed MISS. Two rock beds on Mars display structures of analogue morphology to such terrestrial MISS. The Martian structures resemble ‘erosional remnants and pockets’, 'polygonal dessiccation cracks', ‘roll-ups’, as well as ‘gas domes’. The structures on each of the two rock beds are not at random but arranged into associations. The same associations are known from equivalent MISS-bearing terrestrial rock beds. The conclusion of this study is the hypothesis that the sedimentary structures in the < 3.7 Ga Gillespie Lake Member on Mars are fossil MISS. The Gillespie Lake Member is suggested as candidate landing site for the sample return mission Mars Rover 2020.