[X] My Assistant

[Guest_AlexBlackwell_*]

The November 30, 2005, issue of the journal Earth and Planetary Science Letters, Volume 240, Issue 1, pp. 1-190, has just been published online. It is a special issue entitled "Sedimentary Geology at Meridiani Planum, Mars," edited by Steven W. Squyres and Andrew H. Knoll.

[CosmicRocker]

I've been looking over Grotzinger's October 13th lecture Power Point presentation, on and off, since it was released some weeks ago. It's a good read. I've tried to view the archived webcast of the lecture, but have not been able to get it to replay beyond the first few introductory words. If anyone else has been successful and has any suggestions, I'd appreciate hearing them.

Regarding interpretations of the depositional and post-depositional environments that created these rocks, it appears the team developed a composite stratigraphic section based on visual observations of rock texture along the Endurance ingress route, at Burns Cliff, and probably sites in between. Thanks to some concurrent spectral measurements, they were also able to create a chemostratigraphic section that was correlated to the textural one. Together, those two sections provide a really nice basis for an initial environmental interpretation.

In the limited section observed in Endurance, several transitions were observed, but I think the most notable was the unconformity observed at Burns Cliff. I didn't know it had been named, but it's called the Wellington Contact in Grotzinger's presentation. That contact suggests an environment that changed from wind-blown dunes to wet sediments deposited in shallow water. The chemostratigrapy also supports an arid environment that led to the deposition of quite a lot of evaporite salts within the sediments.

I've "borrowed" a couple of the images from Dr. Grotzinger's Power Point file, that I think are relevant to this discussion. But I would recommend that anyone seriously interested in this stuff check out his entire presentation. It's very good and contains images of earthly analogues. Ignore the second copy of the column. I don't know where it comes from, but it is a duplicate, and I can't delete it. Other important notes about the stratigraphic column were not attached to that image. See the original PPT file to view it as the author intended.

By the way, as I recall, they did a super-res set of images of the Wellington contact when they realized they weren't going to chance going all the way across Burns cliff to get to the contact. The "borrowed" image of that contact is the best one I have seen of it. Could it be the result of the super-res stack?

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