RE: Microbially induced sedimentary structures

["Thomas R. Holtz, Jr." <tholtz@umd.edu>]

A lot of the desire to find evidence of life on Mars (past or present) is 
encouraging people to take non-parsimonious positions.

Among other things: what is the lithology of figure 5? Because if it is basalt 
(like most of Mars' surface), mere similarity of appearance to a microbialite 
means nothing.

Lithology matters.

Thomas R. Holtz, Jr.
Email: tholtz@umd.edu   Phone: 301-405-4084
Office: Centreville 1216                        
Senior Lecturer, Vertebrate Paleontology
Dept. of Geology, University of Maryland
http://www.geol.umd.edu/~tholtz/
Fax: 301-314-9661               

Faculty Director, Science & Global Change Program, College Park Scholars
http://www.geol.umd.edu/sgc
Fax: 301-314-9843

Mailing Address:        Thomas R. Holtz, Jr.
                        Department of Geology
                        Building 237, Room 1117
                        University of Maryland
                        College Park, MD 20742 USA

> -----Original Message-----
> From: owner-DINOSAUR@usc.edu [mailto:owner-DINOSAUR@usc.edu] On Behalf Of 
> Erik Boehm
> Sent: Monday, January 05, 2015 10:37 AM
> To: dinosaur@usc.edu
> Subject: Microbially induced sedimentary structures
> 
> So, its not dinosaurs, but it is paleontology... so I hope its fine for this 
> mailing list:
> 
> Recently I was in a forum discussion related to microbially induced 
> sedimentary structures - specifically, how easy they are to identify,
> and how common they are in pre-cambrian sedimentary rock.
> 
> I was under the impression that before motile multicellular organisms were 
> around to break up microbial matts, that they covered the
> earth pretty much anywhere it was wet, and furthermore that pre-cambrain 
> rocks often preserved this (such as the "elephant skin
> texture" often seen around the multicellular ediacaran biota).
> 
> The ultimate focus of this discussion, however, was about Gale crater and 
> Mars. There are many many many examples of layered
> sedimentary deposits visible in the photos from the Curiosity rover... none 
> of which looked to me to even suggest that there were
> ever biofilms there.
> 
> However, just now, a paper came out:
> http://online.liebertpub.com/doi/pdf/10.1089/ast.2014.1218
> Hypothesis Article
> 
> "Ancient Sedimentary Structures in the <3.7Ga Gillespie Lake Member, Mars, 
> That Resemble Macroscopic Morphology, Spatial
> Associations, and Temporal Succession in Terrestrial Microbialites"
> 
> And I must say, most of the pictures are unconvincing to me, However, their 
> figure 6 did pique my interest (
> http://www.astrobio.net/wp-content/uploads/2015/01/fig5.jpg - it says fig 5 
> on the website that hosts it, but its fig6 in the paper) but
> I'm far from educated about what to look for (perhaps something like this is 
> too optimistic:
> http://upload.wikimedia.org/wikipedia/commons/thumb/9/92/Runzelmarken.jpg/1280px-Runzelmarken.jpg
>  )
> 
> I was wondering if anyone here would be better able to evaluate the claims, 
> and perhaps answer my above questions about the
> prevalence of pre-cambrian MISS fossils.