Cambrian Trilobites, Montana, Trilobite Range In The Bob Marshall Wilderness Area?

[trilobiteruss]

I have heard about good middle Cambrian triloibtes in western Montana in the very remote

Bob Marshall Wilderness area,

and from what I can find the Trilobite Range with Trilobite Mt and Pentagon Mt are where you find this material in the middle Cambrian units along this range. I know it is darn remote, probably a bit beyond my hiking skills, wondered if anyone here has ever collected there and can tell about it?

Here is the section of interest from the 1 by 2 degree GQ of area:

Steamboat Limestone (Middle Cambrian)—Differs in lithology between western and eastern outcrops. In the west consists of a lower shaly mudstone interval and a much thicker upper limestone interval (Deiss, 1939). In the eastern exposures is about equal parts of alternating sequences of limestone and calcareous shale. The carbonate units in both areas consist mostly of nodular, hard, dark- yellowish-brown, thinly bedded limestone and dolomite with nodules and lentils of dark-yellowish-orange siltstone. The mudstone units are mainly grayish-green noncalcareous shale with interbeds of calcareous siltstone and claystone. Trilobites, locally abundant, and some brachiopods occur in limestone lenses in 9 the shales and locally near the top of the limestone units. Thickness from 65 m to 80 m.

Pentagon Shale (Middle Cambrian)—A clastic wedge that consists of very

fossiliferous, calcareous, gray to tan-gray, thick-bedded platy shale that contains some platy, blue-gray argillaceous limestone in the upper part (Deiss, 1939). Thickness ranges from less than 1 m to 88 m (Deiss, 1939).

Pagoda Limestone (Middle Cambrian)—Forms prominent light-gray cliffs in the Cambrian sequence. The upper part consists of yellowish-gray to light-yellowish-brown, thin- to thick-bedded dolomitic limestone and some dolomite overlying very thin-bedded limestone. The lower part consists of grayish-green, thinly laminated to nodular clay shale with some gray-brown limestone and minor sandstone. An intraformational conglomerate locally present in the middle and lower parts. Trilobites and brachiopods locally numerous in the shale (Deiss, 1939). Formation thickens to the south and west, and ranges in thickness from 28 m to about 120 m.

Dearborn Limestone (Middle Cambrian)—Composed of an upper thick limestone unit and a lower thin shale unit. The limestone unit is finely crystalline, yellowish- brown to gray, thin to thick bedded and irregularly bedded. The lower unit consists of gray to gray-green clayey shale with some sandy shale and thin interbedded limestone. Trilobites present in the lower part of the shale unit. Thickness from 67 m to 106 m.

Damnation Limestone (Middle Cambrian)—Consists of medium- to dark-gray, thin- to thick-bedded, finely crystalline dolomitic limestone and limestone with laminae of grayish-orange to yellowish-gray siltstone that thicken and thin. Locally they are oolitic and contain trilobites, brachiopods, and organic trails and burrows. Thickness from 30 m to 68 m.

Gordon Shale (Middle Cambrian)—Mainly a dark-gray to gray-brown, very thinly laminated shale with a greenish tint and locally maroonish-gray beds. Contains many thin beds of sandstone and some beds of limestone, especially in the middle and upper parts. In places the limestones contain glauconite, algal structures, limestone chips, grains of quartz, and fossil fragments. The upper part contains numerous fossils (Deiss, 1939), whereas the lower beds locally contain organic trails and burrows, some by trilobites. Thickness from 42 m to 90 m.

[glacialerratic]

Oh man, way back in the 70's I got an issue of Ranger Rick that had an article on Trilobite Mountain. I drooled over that until it was unreadable, and looked and looked, but could never find another reference.

Thanks for this info! There it is! My wife's best friend even lives fairly close by....

Super cool. TFF is the best!!!

Is there a reference for this? Is it a journal article or from a book?

[trilobiteruss]

Hi Russ,

You might want to track down this comprehensive publication:

Cambrian stratigraphy and trilobites of northwestern Montana

Geological Society of America (1939) Special Papers 18:1-135

Author: Charles Deiss

Your first clue would be to track it down in your email inbox

Thanks Scott, I just got it a few momemts ago. Ran across the reference but had no way of getting a copy, this PDF will be very, very helpful. That is a pretty remote wilderness area mostly but would love to some day plan a trip anyway but I need to be in a bit better shape for backpacking which I have not done in years! :blink: :wacko:

[trilobiteruss]

Oh man, way back in the 70's I got an issue of Ranger Rick that had an article on Trilobite Mountain. I drooled over that until it was unreadable, and looked and looked, but could never find another reference.

Thanks for this info! There it is! My wife's best friend even lives fairly close by....

Super cool. TFF is the best!!!

Is there a reference for this? Is it a journal article or from a book?

The Special paper 18 Scott mentioned covers the area. The stratigragraphy I listed came from a 1by 2 degree Geological Map I found on the Montana Bureau of Mines and Geology site. I also found a little post on one field trip a few folks tried backpacking into area.

russ

[piranha]

Thanks Scott, I just got it a few momemts ago. Ran across the reference but had no way of getting a copy, this PDF will be very, very helpful. That is a pretty remote wilderness area mostly but would love to some day plan a trip anyway but I need to be in a bit better shape for backpacking which I have not done in years! :blink: :wacko:

If you hit the jackpot of trilobites please remember who got you to the rodeo!

[trilobiteruss]

If you hit the jackpot of trilobites please remember who got you to the rodeo!

Yes but first funding, and getting alot better in shape will be necessary, I am a bit out of it, gaining back what I lost 5 years ago (brewing beer and BBQ competition with son-in-law does not help ) That is very remote, never did backpacking like that, just a week on Appalachian trail some 30 years ago when a bit younger, I have knee issues also (weight does not help) So such a trip is sorta on my list and am getting info but it is not happening soon! Thanks will certainly not forget if I find the mother-load!

[Scott S.]

Wow...If you go PLEASE report. Love hearing about those remote places. Especially if you make it in and out in a timely manner without having to eat any members of your party! Came close to that once!

[trilobiteruss]

Wow...If you go PLEASE report. Love hearing about those remote places. Especially if you make it in and out in a timely manner without having to eat any members of your party! Came close to that once!

First I will have to re-loose the 50 plus pounds I gained back, (cannot regain my youth-- darn) and get in shape if I am serious about going.. What I am saying it will not be this year or next but a couple down road to prepare if I go. I need to talk to my business and collecting partner as well and I met a friend on facebook who lives to west in Idaho so a couple years at best before --if things go well -- I even plan such a trip. It is really remote, rugged, and pretty tough going along the continental divide where this as, also prime grizzly area, all kinds of things that make this a pretty tough trip if I do go., but a guy can dream? :blink:

Edited September 7, 2012 by trilobiteruss

[AgrilusHunter]

Ahh The Bob, I spent four summers backpacking there in the early nineties. It is absolutely beautiful, but rugged, country. I had no idea you could find trilobites like this there though. I've been planning a week in the Sierras for this summer, that might become a trip up to Montana now instead. This is great stuff, thanks for posting the information!

Edited September 7, 2012 by AgrilusHunter

[billfernandez]

Hi Russ,

You might want to track down this comprehensive publication:

Cambrian stratigraphy and trilobites of northwestern Montana

Geological Society of America (1939) Special Papers 18:1-135

Author: Charles Deiss

Your first clue would be to track it down in your email inbox

Dear Scott,

Do you think you could send me a copy of that paper too.. as well as any others you have on Montana trilobites e.g.; from Deiss, Lochman, Walcott?

Appreciatively,

Bill

billfernandez@hotmail.com

[piranha]

On 4/29/2013 at 10:05 PM, billfernandez said:

Dear Scott,

Do you think you could send me a copy of that paper too.. as well as any others you have on Montana trilobites e.g.; from Deiss, Lochman, Walcott?

Appreciatively,

Bill

Hi Bill,

Please check your PM and email inbox for a few trilobite goodies.

If you hit the jackpot please remember who got you to the rodeo! 

[jpc]

Keep this in m ind, Y'all... if you do go backpacking in the Bob, it is thick with grizzlies. Be Bear Aware out there.

[omaro]

Hello Everybody,

I am actually planning a bckpacking trip to the Trilobite Range in five weeks and am planning on doing some rock hounding. Is it possible that anyone could send me a copy of that paper. If I find anything, I promise I will post some pictures.

Thanks!

[piranha]

Hello Everybody,

I am actually planning a bckpacking trip to the Trilobite Range in five weeks and am planning on doing some rock hounding. Is it possible that anyone could send me a copy of that paper. If I find anything, I promise I will post some pictures.

Thanks!

Papers sent.... good luck on the great trilo-trek!

[majorshel]

Hi all,

I stumbled across this conversation while trying to track down some information on the Trilobite Range. I work out of Augusta, Montana, and hoping to learn more about the geography and trilobites on this area.

Any chance anybody would be able to and willing to share the article with me?
Cambrian stratigraphy and trilobites of northwestern Montana Geological Society of America (1939) Special Papers 18:1-135 Author: Charles Deiss

Much appreciated!

[RJB]

Interesting post. Hey majorshel, supposed to be some ammonites somewhere near augusta. I went there once but only found coral.

RB

[kehaz]

I'm yet another who happened upon this topic and am interested in that paper. I've been expanding my search radius around Great Falls and, after finding a teeny tiny trilobite carapace in a little spot along near Yogo, am hungry to go hunting for some bigger bugs!

 

If I could get that paper from you @piranha that would be awesome!