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gb
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gb
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PostMon Jul 20, 2015 9:31 am 
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I was looking for exposed limestone/related rocks of the High North Cascades and found this website.

http://pubs.usgs.gov/sim/2940/
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Stones
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PostMon Jul 20, 2015 10:29 am 
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You'll find some limestone exposures along the Ridley Creek Trail and another, longer way, to get to the Park Butte fire lookout.

Ridley Creek Trail - Geology Guide

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mike
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PostMon Jul 20, 2015 11:00 am 
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I think you can find occasional chunks of limestone scraped off during subduction. Not NC but we have a big chunk here inter mixed with basalt. Much of it was mined, processed and used to build west coast cities, e.g. SF after the earthquake.
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Ringangleclaw
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PostMon Jul 20, 2015 11:51 am 
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The Geologic Map of the North Cascades is a major work and a piece of art.  It was derived form a lifetime of work by many, notably Roland Tabor, Joe Vance, Peter Misch, Don Swanson, Ned Brown, Bob Miller and  Scott Babcock.  All are probably 70 plus, and Peter Misch has been deceased for almost thirty  years.

This map was derived from earlier published maps by the USGS and the Wa DNR.  All are maps are 30x60 Quadrangles and Roland Tabor is listed as the first scientist. The works concerning the North Cascades and marble are:
Sauk (2002) map I 2592
Snoqualmie Pass (2000) I 2538
Skykomish (1993) I 1963
Chelan (1987) I 1661
Mount Baker (2003) I 2660

The map units denoting marble, limestone or a marble granulite are:
TKem marble knockers in the eastern melange.  Sno, Sky, and Sauk sheets
TKwm knockers in the western melange.  Sky sheet
KJbm knockers in the Bell Pass melange of the Northwest Cascade System.  Sauk and Mount Baker sheets

Kcm marble in the Chiwaukum schist.   Sky, Sauk and Chelan sheets.

PDcl NWCS Chilliwack group marble.  Sauk and Mount Baker sheets
This is the marble comprising the outcrops at Concrete

TKcma Cascade River schist marble. Sauk sheet

TKnm Napeequa schist marble.  Sauk and Mount Baker.

TKsm  marble lensoids in the Skagit gneiss.  Mount Baker

TKsfm  Fine grained granulite marble in the Ross Lake fault zone.  Mount Baker map.

Peter Misch's 1979 Marblemount map did not show any marble.  Joe Dragovich of the Wa DNR has done a lot of mapping elsewhere in the Cascades.
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mike
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PostTue Jul 21, 2015 10:22 am 
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As a kid I remember a marble quarry somewhere between Newhalem and the Thorton Lk Rd. Left side of and very near the road heading east. Some of it ended up in a chimney my father built.
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Ringangleclaw
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PostTue Jul 21, 2015 10:33 am 
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There's rockeries made of marble all over Bellingham
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gb
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PostTue Jul 21, 2015 9:00 pm 
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By the way, thank you for this information, Ringleclaw. When I get some time I will make an effort to understand these maps sufficiently to answer my questions (which relates to the distribution of a rare plant).

Incidentally, I have a good-sized chunk of pure white Marble from the Straight Creek fault (I presume) as igneous rocks and areas of Actinolite are adjacent to the area with Marble.
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Ringangleclaw
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PostTue Jul 21, 2015 9:22 pm 
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gb wrote:
When I get some time I will make an effort to understand these maps sufficiently to answer my questions (which relates to the distribution of a rare plant)

Do you mind telling us what the question is?  But much of the marble and limestone in the Cascades is going likely be tectonized or metamorphosed to the point where most will not be able to make identifications.

gb wrote:


Incidentally, I have a good-sized chunk of pure white Marble from the Straight Creek fault (I presume) as igneous rocks and areas of Actinolite are adjacent to the area with Marble.

Do you remember where exactly?  Actinolite is common in the Easton Metamorphic Suite (Shuksan schist) and can be found in any of the three big melange complexes - the Bell Pass structural sheet structurally beneath the  Easton,  and the western and eastern melange belts which make up the western portion of the Cascades until they are interupted by the Hackstack Devils Mountain fault zone.  Limestone could also be found in all of those units.  The igneous rocks could be the Cretaceous rocks east of the Straight creek, or any number of the plutons which intruded around and thru the Straight Creek up to about 20 ma.
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Ringangleclaw
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PostWed Jul 22, 2015 10:17 pm 
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I looked on a map, the Concrete marble quarry is the Chilliwack group.  There seems to be additional  marble outcrops to the north and west, but I am having a hard time differentiating colors on the map, and they could be another structural unit
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HitTheTrail
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PostSat Jul 25, 2015 8:29 pm 
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The rocks in the big slide up around 8-mile lake look like a calcareous sandstone and weather sort of like limestone. That geologic map calls the unit "Jis" which is the Ingalls Terrane. That just lumps them into a suite of metamorphic rocks without really breaking them out. I would bet they have a limestone origin.
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Ringangleclaw
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PostSat Jul 25, 2015 9:44 pm 
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HitTheTrail wrote:
The rocks in the big slide up around 8-mile lake look like a calcareous sandstone and weather sort of like limestone. That geologic map calls the unit "Jis" which is the Ingalls Terrane. That just lumps them into a suite of metamorphic rocks without really breaking them out. I would bet they have a limestone origin.

Except for a very few supra crustal rocks, the Ingalls is a tectonically dissected ophiolite representing a section of the oceanic crust from a thin veneer of deep sea sediments to pillow basalts to sheeted dikes then intermediate magma chambers and finally the serpentinized peridotites of the upper mantle.  Unlikely that what you saw is limestone.

Many intact knockers of magic rocks can weather to a dun color with an irregular surface as you noted, and can be erosional resistant in comparison the their serpentine surroundings.
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HitTheTrail
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PostSun Jul 26, 2015 5:47 am 
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Ringangleclaw wrote:
Unlikely that what you saw is limestone.

But I have an excuse. Even though I did graduate work in geology I never worked one day as a geologist. My first job was with a seismic oil exploration crew and I spent my entire career doing geophysics. First on field crews shooting seismic surveys and later in processing centers doing velocity analysis of the weathering layer to work out a near-surface datum correction model. Somehow later I got into database administration. Then I ended my career writing PERL code on a UNIX workstation reformatting large seismic volumes so the hardcore geophysicistís could port them into different vendor products and do their inversion models. Thatís where you convert amplitude to impedance so you can work out lithology and porosity of subsurface layers. NoÖI havenít carried a hand lens to look at rocks in over 30 years!
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gb
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gb
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PostSun Jul 26, 2015 7:24 am 
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Ringangleclaw wrote:
gb wrote:
When I get some time I will make an effort to understand these maps sufficiently to answer my questions (which relates to the distribution of a rare plant)

Do you mind telling us what the question is?† But much of the marble and limestone in the Cascades is going likely be tectonized or metamorphosed to the point where most will not be able to make identifications.

gb wrote:


Incidentally, I have a good-sized chunk of pure white Marble from the Straight Creek fault (I presume) as igneous rocks and areas of Actinolite are adjacent to the area with Marble.

Do you remember where exactly?† Actinolite is common in the Easton Metamorphic Suite (Shuksan schist) and can be found in any of the three big melange complexes - the Bell Pass structural sheet structurally beneath the† Easton,† and the western and eastern melange belts which make up the western portion of the Cascades until they are interupted by the Hackstack Devils Mountain fault zone.† Limestone could also be found in all of those units.† The igneous rocks could be the Cretaceous rocks east of the Straight creek, or any number of the plutons which intruded around and thru the Straight Creek up to about 20 ma.

On your first question, I am interested in one plant I believe to be very rare, and I suspect Washington Rare Plants does not realize just how rare it is. I recently essentially surveyed one of four locations where it is known to exist and found one population of roughly 250, another of 20, and another of 10, spread over a couple of miles. It is known by the Burke and the Consortium of Herbariums to exist in about 4 locations in Washington State; I suspect I surveyed the largest population. Anyway, last weekend in the process of this survey (and scenic hike) a young man came up to me and told me he was also interested in botany and thought he had seen this same plant (I described to him) on Vancouver Island. (He had been mentored by Hans Roemer, one of the authors of the Pojar series of books he told me.) He told me on Vancouver Island the plant is very rare and only found on limestone. I again looked up where the plant had been found in Washington (in photographs and collections) and became immediately aware that the locations I've seen it and where it has been identified were all either limestone or see floor derived (not basalt but sediments). Subsequently, I looked up a couple of locations where it had been found in Alaska (much more common there) and indeed found the mention of limestone.

Before encountering this young fellow, I still thought the plant rare and was surveying visually the terrain in which it might be found (elevation limited and not cliffy, and not meadowed - in other words scarce). Now I know the search can be narrowed even further to the aforementioned terrain in the correct regions to strictly soils and scree derived from limestone and sea floor sediments and probably where not covered by ice in the Pleistocene; quite interesting.

I've seen this plant two other places, and no surprise, in one case there were perhaps 100-150 plants in a small limestone band, not cliffy, not meadowed, and in another location far removed, where I only saw four plants; though I was not looking at the time. I'll visit the first of these two locations this Wednesday and the second this fall. It won't be in bloom but the leaves are distinctive.

I'll try to locate the population of this plant which was collected in the 70's on another trip perhaps this fall. I find all of these destinations to be outstanding hikes anyway, and now I am fascinated by the limestone/sea floor sediment connection.

This means that to find the potential locations for this plant I don't have to look everywhere but only in appropriate regions, elevations, and topography with this known geologic origin. Interesting! I'm intrigued.

The Burke already has my photos and will get additional ones from last weekend and this fall I will pass on my observations to Washington Rare Plants. The plant is currently under review for status designation: Endangered, Threatened, Sensitive, or Watch List. I would expect Threatened.

On your second question I would prefer not to say, but it is in the Marblemount area.
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rbuzby
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PostThu Jul 30, 2015 7:08 pm 
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Ringangleclaw wrote:
Except for a very few supra crustal rocks, the Ingalls is a tectonically dissected ophiolite representing a section of the oceanic crust from a thin veneer of deep sea sediments to pillow basalts to sheeted dikes then intermediate magma chambers and finally the serpentinized peridotites of the upper mantle.  Unlikely that what you saw is limestone.

Pure poetry.

Hard to understand, but one take-away might be that there was a lot of chaos and upheaval on this planet in it's history.
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Forum Index > Pacific NW History > Very cool USGS website on the geology of North Cascades
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