Turtle Posted March 29, 2008 Report Share Posted March 29, 2008 My idea here is to have a place for interesting geology that does not merit its own thread or as a place to expand on interesting geology brought up in other threads that may drift off topic. :shrug: I know! :) Let's start with varves! :eek_big: BRB...collecting data.... Southtown and Michaelangelica 2 Quote Link to comment Share on other sites More sharing options...
Turtle Posted March 29, 2008 Author Report Share Posted March 29, 2008 Here's the varve start from the GW thread: :hihi: Note my current location and nomination. ;) I could spit on Amboy from my chair. :eek: Speaking of Amboy, roadcuts, Coopers, and global warming, if not shakiness of belief, there is a magnificant 40 to 60 foot high varve just East of Amboy on a roadcut. The individual layers measure no more than 2 or 3 mm if I recall. Not sure what formal analysis on it is around, but I visited it on a geology course field trip. Might hold some info on past climate in the area. I'll get back to y'all on it; maybe even do a field trip. :) :shrug: Roger that; done & done. I think the varve I visited is the boldened reference. Can we say ice age? :eek_big: :) {page 14}...the drained lakebed at Fargher Lake accumulated in a proglacial lake impounded by Amboy-age terminal moraines; the lake gradually filled with more than 11 m of organic-rich sand, mud, and peat, punctuated by tephra layers that record eruptions at Mount St. Helens (Rigg, 1958; Heusser and Heusser, 1980; Doh and Steele, 1983; Grigg and Whitlock, 2002). Lake beds are exposed in the south bank of Cedar Creek north-northeast of Bald Mountain. They consist of about 10 to 12 m of dark gray, rhythmically laminated silt and clay. The beds vary in attitude from subhorizontal to subvertical over a distance of 20 m and are unconformably overlain by limonite-cemented cobbly gravel that contains rip-up clasts of varved clay. The small lake in which the rhythmites accumulated probably formed when ice from the Lewis River glacier spilled over into and blocked Cedar Creek; this must have occurred when the glacier was at or near its maximum extent. Scattered angular blocks of andesite as large as 3 m across that now rest on nearby modern alluvium may be ice-rafted erratics. Another small area of lake deposits is inferred to exist about 3.5 km north of Fargher Lake, where a landslide apparently blocked a tributary of Cedar Creek. These deposits are not exposed. ...http://pubs.usgs.gov/sim/2004/2826/Arl_geol_text.pdf I checked my map, and the above varve referenced in the USGS report is West of Amboy & I now don't think it's the one I visited. I recall it was at least 12 to 15 miles East of the above feature, either near or within the Gifford Pinchot National Forest boundary. In any case, the varve I met showed layering of alternating lighter & darker material, which like tree rings corresponds to seasons. The varve is the sedimentary remnant of a mountain lake formed behind a glacial block, and during warm weather the lake was open water and the heavier material sinks quickly. During the cold season when the lake is frozen over, the lighter organic material has time and stillness under the ice that allows it to sink. Also found in the varve I met, ice-floated erratics; cobble size stones that found there way out onto the ice, and then fell to the bottom at the thaw. Field trip is in the planning. :camera: Post Script: Map coordinates for Bald Mountain: 45º 55' 09.71" N122º 34' 17.83" WGoogle Earth has some photgraphs from GE Community from around the area, and using the change elevation view feature puts the terrain in perspective. :camera: Quote Link to comment Share on other sites More sharing options...
Turtle Posted April 13, 2008 Author Report Share Posted April 13, 2008 ... I checked my map, and the above varve referenced in the USGS report is West of Amboy & I now don't think it's the one I visited. I recall it was at least 12 to 15 miles East of the above feature, either near or within the Gifford Pinchot National Forest boundary. In any case, the varve I met showed layering of alternating lighter & darker material, which like tree rings corresponds to seasons. The varve is the sedimentary remnant of a mountain lake formed behind a glacial block, and during warm weather the lake was open water and the heavier material sinks quickly. During the cold season when the lake is frozen over, the lighter organic material has time and stillness under the ice that allows it to sink. Also found in the varve I met, ice-floated erratics; cobble size stones that found there way out onto the ice, and then fell to the bottom at the thaw. Field trip is in the planning. :hihi: :) Yesterday I went & searched out the varve, and not only found it but several others along the road. I have a lot of photos, video, and notes to work up into a full report, but attached below is one small sample of what we found. The photo features a couple of ice-rafted erractics in the deposit. More to come. :) Quote Link to comment Share on other sites More sharing options...
freeztar Posted April 13, 2008 Report Share Posted April 13, 2008 Awesome Turtle! :) More pics! More pics! :hihi: Quote Link to comment Share on other sites More sharing options...
Turtle Posted April 14, 2008 Author Report Share Posted April 14, 2008 Awesome Turtle! :) More pics! More pics! :) Patience young Geology Knight. :hyper: The varves were just part of the trip, and all video is still in post-production. To slake your thirst a bit, here's the coordinates of 3 varve locations we visited. The first is the location for the photo above. It is not clear to me if these are all part of one lake, or separate small lakes? :hihi: A quick shout-out to Racoon & Buffalo, whose help was invaluable in the investigation of this interesting geology. You fellas rock! . 45º 56' 41" N122º 16' 28" W Elevation: 838 Feet 45º 56' 44" N122º 16' 06" WElevation: 771 45º 55' 34" N122º 13' 32" WElevation: 1122 Feet Quote Link to comment Share on other sites More sharing options...
Turtle Posted April 14, 2008 Author Report Share Posted April 14, 2008 45º 56' 41" N122º 16' 28" W Elevation: 838 Feet The varve at this location, we measured at 33 feet from crest to road level. Video to come of that process, but the still image below has some interesting aspects. Note the crouching figure near the base for scale, but more importanly the bright area higher up on the escarpment. This brighness is due to water leaking out of the formation and reflecting the sunlight and we happened to get on scene at just the right time. We also collected some samples, which I have in plastic bags, and as soon as practical I plan to make some high-res scans @1200dpi so we can better see the component particles. Quote Link to comment Share on other sites More sharing options...
Turtle Posted April 14, 2008 Author Report Share Posted April 14, 2008 45º 56' 41" N122º 16' 28" W Elevation: 838 Feet The varve at this location, we measured at 33 feet from crest to road level. Video to come of that process. Buffalo, Racoon, & Turtle measure a varve. If we estimate an average thickness of 3/8" per annual deposit, then this exposed portion represents ~1,056 years. I don't know if, or how far, the deposit continues below the road-bed level. YouTube - Measuring a Varve http://www.youtube.com/watch?v=S5O_nSfGh6M Quote Link to comment Share on other sites More sharing options...
Thunderbird Posted April 14, 2008 Report Share Posted April 14, 2008 Have there been any fossils recoverd from this deposit? Quote Link to comment Share on other sites More sharing options...
Turtle Posted April 14, 2008 Author Report Share Posted April 14, 2008 Have there been any fossils recoverd from this deposit? My thoughts exactly. I have not found a formal study of this exact deposit, nor seen mention of fossils in the reports I have read. It seemed logical to me, and we did look purposefully for fossils but found none. I have a composite video rendering for posting that is a compilation of all the clips I took at this first site. I hasten slowly.... Quote Link to comment Share on other sites More sharing options...
Turtle Posted April 14, 2008 Author Report Share Posted April 14, 2008 The round holes in the face appear to contain some kind of bees. YouTube - Extreme Varving http://www.youtube.com/watch?v=yjvSt9d-Das Quote Link to comment Share on other sites More sharing options...
Turtle Posted April 15, 2008 Author Report Share Posted April 15, 2008 45º 56' 41" N122º 16' 28" W Elevation: 838 Feet ...We also collected some samples, which I have in plastic bags, and as soon as practical I plan to make some high-res scans @1200dpi so we can better see the component particles. Well, scanning at 1200 dpi works as long as I don't expect to post it. Here's a suitably sized snippet of varve collected from about 6 feet above road level; scale divisions 1/64th inch. Quote Link to comment Share on other sites More sharing options...
Turtle Posted April 16, 2008 Author Report Share Posted April 16, 2008 I think I have the GoogleEarth marked now with the location of the varve I have been describing. Can I get some feedback on if the file below attached works to take you to the site? Takk. Mmmm...the new setup does not allow .kmz files as attachments. Here's the thread instead at GEC: >> Google Earth Community: Varves - glacial lake sediment deposits That is all. :lightning Quote Link to comment Share on other sites More sharing options...
Turtle Posted April 16, 2008 Author Report Share Posted April 16, 2008 Further up road #54, past the varves, we stopped for a scenic overlook and there I found on the roadcut a very different rock & formation. What I found was a pyroclastic eruption deposit, and I made a short video of it. Sadly, I don't seem to have made a record on the GPS. :eek: Here we go then; gettin' on with gettin' 'er done. YouTube - Pyroclastic Deposit http://www.youtube.com/watch?v=1U8SkbQRpfY Quote Link to comment Share on other sites More sharing options...
Turtle Posted April 16, 2008 Author Report Share Posted April 16, 2008 This video is taken of the varve at the 3rd location I gave, 45º 55' 34" N, 122º 13' 32" W, Elevation: 1122 Feet. It has a different character from the first, and notice a very wide band just above the midway point; I think this is a volcanic eruption deposit. Also notice, if not chuckle at, how I flinch when the gunshot up the road goes off! :doh: :hihi: Onward................................... :xparty: /forums/images/smilies/banana_sign.gif YouTube - Extreme Varving 2 http://www.youtube.com/watch?v=Bhevdu1ZsbY Quote Link to comment Share on other sites More sharing options...
Thunderbird Posted April 16, 2008 Report Share Posted April 16, 2008 Hey Turtle come out out of your shell and in front of the camera and narrate for me what im am seeing. please... Quote Link to comment Share on other sites More sharing options...
Turtle Posted April 16, 2008 Author Report Share Posted April 16, 2008 Hey Turtle come out out of your shell and in front of the camera and narrate for me what im am seeing. please... :doh: I'm in front of the camera & narrating in the varve measurement vid. :computerkick: I have to do more practice editing before I can add a narration, but the large cobble I reach for is an ice-rafted erratic that is embedded firmly in the deposit. In the earlier Extreme Varving video, I dig out 2 such erratics. (Racoon has them & is doing clean-up). Feel free to ask for any clarification, but let's not forget that a turtle out of its shell, is a dead turtle. :xparty: :hihi: Quote Link to comment Share on other sites More sharing options...
Thunderbird Posted April 16, 2008 Report Share Posted April 16, 2008 : Feel free to ask for any clarification, but let's not forget that a turtle out of its shell, is a dead turtle. ;) I wonder if one could genetically reverse engineer a turtle to be born without a shell. I would hold it, and fed it, and make it my little reptile/puppy friend. Turtle 1 Quote Link to comment Share on other sites More sharing options...
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