Ken Van Dellen

John,

You’ve posted two replies to my comments, so you’re way ahead of me. In an exchange like this, the last person to post is perceived as winning the argument, so I’ll have to get to work and keep responding. Another problem is that someone can post something that needs a response, but it would take a book, or at least a chapter, to rebut it. This happens with letters to the editor, where I’ve been unable to get an adequate response published because of space issues. Perhaps there is a bit more space here, although I’ve wasted a bunch with this paragraph, and you’ve raised several issues, when it would be better to address one at a time.

Early attempts to estimate the age of Earth (various researchers, 1800, time for deposition of “total sedimentary record” based on average present rates; Kelvin, 1897, cooling from a theoretical molten condition; Joly, 1899, increase in salinity of sea from freshwater to present salinity) did not allow for factors that we have since learned about. While such measurements cannot give us the age of Earth, similar strategies can give us information about the amount of time involved in the formation of parts of the geologic record. We can get a good estimate of how long it took for a large body of magma to crystallize in a mountain belt or for a coral reef in a limestone quarry to grow or for tectonic plates to diverge, based on measurements we take today. Unless you choose to believe that God created the world with a lot of apparent history in the rock record, of events that never happened, or that the “laws of nature” (i.e., the way God usually operates) were suspended in past times, so processes occurred much more rapidly than today, then you have to accept that Earth is very old.

You talk about what could happen and what geologists can’t do, and I prefer to talk about what does happen and what geologists can do. Perhaps we should take each of your concerns, one at time, and examine them.

Since you’ve talked mostly about sediment, let’s just take note of a few things. Sediment that is made of solid particles (clay, silt, sand, pebbles, cobbles, and boulders, in increasing size), has to have a source (region that yields particle of that composition), an agent of transportation, and a depositional environment. The rocks that form from these particles can indicate certain things about the source (such as the kind of rock), the direction the sediment was transported, the agent of transportation (stream, wind, glacier, etc.), and if it was deposited in a sand dune, lake, sea coast, etc. Sediment that is made of material deposited from solution (salt, gypsum, some limestones, etc.) might have come from the other side of the globe, so they tell us little more than the depositional environment, although studies of modern, similar environments can tell us about rates of deposition, revealing something about the time involved. For example, one researcher estimates that the Silurian salt beds in the center of the Michigan Basin are 2000 feet thick, with one single bed about 500 feet thick. It would be easy to calculate how much sea water would have to evaporate to yield that much salt (assuming present salinity), and then do calculations on how long that might take with various temperatures and with intermittent influxes of fresh water.

Perhaps I’m telling you things you already know. I looked in vain at your profile to try to get to know you better.

If you want to talk about paleosols (buried soils), etc., let’s do it one topic at a time. My tired old brain gets overwhelmed, otherwise.

Ken

1. A geologic feature called the Michigan Basin has its margins roughly up along the Niagara Escarpment along the east side of the Bruce Peninsula in Ontario, through the islands in northern Lake Huron and throught the Upper Peninsula of Michigan, down along the west side of the Door Peninsula of Wisconsin, and then around across northern Illinois, Indiana, and Ohio, where it cannot be associated with any surficial features. The topographic features mentioned are the edge of a "saucer" of rock belonging to the time period geologists call the Silurian.

2. The Silurian rocks are primarily limestone and dolomite around the margins of the Basin, where many "patch reefs" of corals and other marine (saltwater) organisms are found in the rocks in outcrops and in the subsurface. (Geologists call these "pinnacle reefs" because of the way they appear on cross-sections with vertical exaggeration.) However,  along with limestone and dolomite, major salt beds (referred to above) toward the interior of the Basin and gypsum beds in a crude ring around the salt. This salt has been extracted in mines at Detroit and Windsor, and through brine wells at other places in the Basin, while the gypsum has been mined at Grand Rapids and the Tawas City areas of Michigan. This pattern can be correlated with the solubility of these rocks, salt being most soluble, and requiring the highest salinity to precipitate it.

3. While fossil organisms are found in the Silurian strata contiguous with the strata containing salt and gypsum, they are not found in those evaporites. We would not expect to find life in such a hypersaline body, any more than in the Dead Sea (as the name suggests) or in the Gulf of Karaboghaz on the Caspian Sea, where similar conditions exist.

4. The structure of the Michigan Basin indicates it underwent much more rapid subsidence in the Silurian than in much of the rest of the Paleozoic Era. That, the rock types (evaporites), and the presence of the peripheral reefs all suggest that the model of a lagoon with restricted seawater circulation is feasible to explain what happened here.

5. When we talk about the time factor, we need to consider the time needed for the reefs to grow, the subsidence to occur, and the evaporites to precipitate from the sea water.

I hope this answers some of your questions. I don't understand the parts about the mountains moving from under the sea or the Great Lakes having a high salinity.