Tuesday, January 27, 2009

Groups, Formations, Beds, Horizons and Zones

A little snippet (edited) from an email to Dan:

Lucas et al 2007 (on the Timpoweap) raised the Thaynes and Moenkopi Formations to Group status. If we dont accept Lucas et al, do we extend the Sinbad Member into the Confusion Range or extend the Thaynes Formation into the Pahvant Range. To me the rocks in the Pahvant Range, a few thin limestone beds in a fairly thick shale sequence, are more like the rocks in the Confusion Range than they are to the rocks in the San Rafael Swell (type Sinbad) where you get a fairly thin set of limestone beds with very little shale. Having hiked up to the Virgin in Dog Valley with Arnaud and Dawn, we noticed alot more thin limestone beds above the anasibirites beds, I didnt notice a clear contact to separate the Sinbad from the "Middle Red Formation" unless you just use the first set of red beds, the Virgin could probably be mapped. Ideally a new name for the rocks in Dog Valley and the Confusion range would make me happy, but that is beyond the scope of our abstract. So I was thinking of just calling them both the lower part of the Thaynes Group. Arnaud put Sinbad Formation on his strat sections for Dog Valley, and Thaynes Group for the DH sections. I think he used Sinbad Formation because the geologic map of the Richfield Quad and The Geology of Millard County both call it Sinbad* (or we discussed it in the field?). I really dont think it should be called Sinbad.

A formation is a mappable unit of rocks, a group is a set of similar formations, what separates one formation from another?

Jim asked me yesterday if I had heard of the
Claraia Zone. I remembered seeing it somewhere like in Silberling & Tozer 1968, but Jim corrected me and read it as the Claraia Beds. It seems that Hintze used it in the Geologic History of Utah and/or The Geology of Millard County* (I will have to check on these). Is there a Claraia Zone? I also remember seeing Xxxxxx Horizon on a few papers. I think "Zone" is a formally defined unit, whereas Beds and Horizon are informal, can they be used interchangeably? Is an Horizon just a little thicker than a set of Beds?

*after reading the Geology of Millard County and the Richfield Map, It seems Hintze didn't refer to the Sinbad, he only calls it Moenkopi.

Friday, January 23, 2009

Inyoites from my "Meekoceras" Quarry

One of the Inyoites found near my old "Meekoceras" quarry. Some of the saddles seem to have the same ammonitic character as the ?Flemingites below. This is starting to look like an artifact of preservation more and more. It would be nice to see how high on the saddles the serrations of the lobe go up on the inner parts of the septa, I would have to break the suture back to see this. The preservation is such that there seems to be quite a bit of erosion from the actual surface of the internal mold.

Sunday, January 18, 2009

DH-4 Observations

I decided to drive out to the Disappointment Hills on Saturday morning. Very little snow on the south facing slopes in the House and Confusion Ranges, down quite low on the north slopes, the roads are in good shape and were actually dusty. No snow at the eastern outcrops except for a couple of drifts on some of the north slopes, I didnt get up to DH-1. The sun was shining and the temp. was about 45 most of the day, a great day.
Trying to see just which bed my old "Meekoceras" quarry is in. I found several Inyoites in float just below the quarry, they may be the widely umbilicate form common in bed 5 at DH-1. There is a very thin bed about 50cm below the quarry bed (maybe equiv. to bed 4). Below this bed is a gastropod shale, some fairly large, with body chamber molds of some acute ventered ammonoids though more like Inyoites than Aspenites (This is where the Aspenites figured in our recently accepted paper was found). This shale is also where the ?Meekoceras molds and large Arctocerid molds are found on the small knoll just north-west of the quarry. This would mean the thick bed at the base of that knoll is equiv. to bed 3, and the thin bed on the next knoll west would be bed 5. I need to map DH-4 with a little more detail.
If the quarry was equiv to bed 9, the small bed below may be bed 8 and the gastropod shale would be the same as between bed 8 and bed 6 (bed 7 would be a thin bed in the middle of the shale). To find Owenites in the quarry bed or the bed below would possibly solve this question. The lack of small "Xenoceltites" like those at DH-1 at this interval (like the lavender bed) also puts doubt on this theory.
The bedded bivalves found in the quarry level is not really like bed 9, so for now I am leaning toward an equivalence with bed 5

Saturday, January 10, 2009

Albuquerque Museum

After a week in Cuba, New Mexico, I stopped off at the museum in Albuquerque. These are pictures of the ammonoids Jim collected and donated. A very nice display.