Monday, April 16, 2007

How Life has helped create slates and limestones



Glacial National Park Elderhostel (June 27, 04)

After the disastrous forest fire of 2003, I scheduled a one week Elderhostel, arranged by the Flathead Valley Community College, in Kalispell, Montana for my wife Helen and me. There were 28 in attendance, mostly couples and single women, past the age of 70.
Arriving early, I met Mitsue Pataky- a participant- at the registration desk; she was a native of Japan, who had married a Hungarian transplanted to the USA. Both of them were American citizens, and the husband had passed away some ten years earlier, leaving her to remain in the Chicago area. She had no desire to return permanently to Japan, and had adjusted to being a city-dweller. But she had been on this particular program three times, and loved the mountains. Remembering some Nihongo, from military days, I greeted her in the language. “O-hi-yo gazai-mas” I gurgled, and she enjoyed my fractured speech. She encouraged me, and I began to regurgitate some of my phrases learned during fall 1951 with my Korean War stint in Nagoya, Japan:
She complained about her room plumbing and asked if I knew how to stop the continual flushing, after the first night.
“Moshe, moshe- Benjo no flushee
AIO, kudesai” Ι intoned, remembering what my brother had memorized from his two year tour in Honshu (AIO was the air installation office).
She giggled, but winced when I mentioned that I would lead off in my usual Elderhostel story about her encounter with me. This did not inhibit her, and she remained communicative during the entire week- I enjoyed watching her doing Yoga and other disciplines which inspired me to reorganize my own habits. She was very spry on the mountain hikes, and easily outpaced me.
Glen and Joan Wasson attended also, ensuring that there would be a continuous string of humorous stories and poems. I should have had some new material ready in response, but was inhibited because of a continual negotiation for my house sale in Arizona, which had taken up a lot of my time in the last months and had distracted me. However, I resolved to overcome this impediment and arranged the following rhyme for the occasion:

Flathead Musings

My wife thought that it would be nice
If we reflected on the ice,
Which was reputed to occur?
In the mountains of the chain
That stretched abruptly from the plain
And the wilds of the island, where we were.

However, we found to our dismay
That global warming had its’ say
And the Glaciers which had beckoned
Were long gone, so some had reckoned,
So that we were soon chagrined
That we had missed the goal, tho’ had not sinned.

Nevertheless we remained undaunted.
Since the mountains and rocks soon flaunted
Sufficient scenes and majestic colors along the way,
That we felt inspired to write
Phrase and sonnet which sound jus-trite,
And non-fiction which was most appropriate for the day.

Now in the ultimate scheme of things
We rely on Fate which shortly brings
More of Serendipity and Chance for us to ponder;
We will in future leave to ‘Hostel
Further programs- so to jostle-
And to vagaries of raw Chance, for Trips out Yonder.

Somehow I have not had the “muse” to inspire a general appraisal of this Elderhostel, but I did accomplish a bit of scientific re-appraisal (not agonizing) on the forays into the faulting and upthrown Precambrian outcrops which were scheduled for the trip..
I noticed that the Proterozoic had no shales in the beds; they did have many siltstones and fine-grained metamorphic sediments. There were some organic remains such as stromatolites, and this indicates that the algae were at work in those 0.6- 1.6 billion year age rocks. The siltstones also had much calcitic cementation, indicating that limestones were beginning to form; in this age of silicic rocks, carbonates were beginning to take their place. I noticed the following features:
1. The incidence of bedded limestones increases as organic remains- mainly algae- increase with time (observing the sediments from Precambrian to late Paleozoic); that is, life in the ancient seas incorporates CO2 from the atmosphere and incorporates it into the seafloor- the end result of which becomes limestone, CaCO3, or calcareous cement;
2. Oxygen is given off by this process, and therefore the atmosphere would increase in O2 composition with time (all the way through the Paleozoic into the Mesozoic where silicates again predominate);
3. Life would have to accommodate this process, and would adjust to increasing oxygen gradually; this would involve oxygen-using invertebrates in the Cambrian and later.
I theorize that soil is directly involved in this conversion of the atmosphere in the following way:
a. As the seafloor rises with all of its’ attendant organic deposition, it becomes mulch for life, when the seafloor is raised with subduction or other thermal expansion. This creates the first soil, as the mulch, organic remains and living creatures, oxygen, and mineralized waters create a regime in which vegetation can live, in the land elevated above the sea (distant from the salt water);
b. This soil with its organic components and gases and water, is converted to shale when it is buried throughout time. Shales are created as the carbonate cycle is replaced by the silicate cycle at the end of the Paleozoic (these are more like the obsolete marls until the occurrence of redbeds in the Permian and later Mesozoic);
c. By the time of the Carboniferous, the oxygenating influence is dominant, resulting in overkill- by Permian time, the atmospheric oxygen is toxic (the air has excessive oxygen, killing off most of the life which cannot accommodate this process). By Jurassic time, the survivors have adjusted, the atmosphere is decreasing in oxygen fraction, and the carbonates form limestones again in the Cretaceous (man may be able to restart this process, with his release of CO2 from coals and hydrocarbons). Evidently the Cretaceous has a buildup of carbonates from the increasing CO2 in the atmosphere (at least until the beginning of the Tertiary).
d. So long as life remains in terrestrial soil, shales will accompany the burial of organic sediments, and carbonates will not be the dominant deposition. The decreased formation of carbonates is an indicator of the health of the life-sustaining atmosphere and water system. Whenever CO2 builds up from combustion of carbon compounds (or from a paucity of trees), there is a decrease of the oxygen fraction. This helps dissolve the exposed carbonates with the increase of acidity in the air and moves the earth towards a new life mix (water-dwelling creatures, at the expense of land dwellers).
Another indicator that the atmosphere was changing by the late Paleozoic, is the occurrence of massive cherts (which are secondary, not depositional) in the Permian. Whenever the atmosphere was acidic, as with carbonic acid, the solubility of silica was greater in the water (some lab data dispute this, maintaining that solubility does not increase with acidity). When the atmosphere changed from acidic towards neutrality in late Carboniferous (as vegetation created increased oxygen during the massive forests of the Mississippian and Pennsylvanian), the chert would have precipitated in subterranean waters (as they became more alkaline); this is noticed Particularly in the Permian, even in the shallow waters of the Kaibab seas, but also in the dunal sandstones later.
A part of this changing atmosphere also caused increased occurrence of manganese and iron in the Permian- hence the color change from black shales in the Carboniferous to red beds in the Permian and Triassic. The change to alkaline waters must be responsible for the desert varnish seen in Permian rocks, because of the perpetuation of Mg and Fe from Mesozoic times. There is some part of this relation which increases the fraction of Mg/Fe, compared to nowadays, and this should allow a way of interpreting what was happening to the subsurface.