The Varves! The Varves! (And Skinny Dipping :) )

I love to go swimming in our local lake, shown above, especially when the weather is very hot. It is quite remote and isolated, so it's like having my own, private, maintenance free swimming pool, but one which is hundreds of yards/meters long and wide! :)

One thing, but it doesn't bother me much, is that the soil around here is very, very fine clay, so the water is always a bit cloudy, especially in summer. The soil settles very slowly down to the bottom of the lake, so I am careful to stir it up as little as possible.

In lake bed sediments, there is a cycle of the type of sedimentation that reflects changes over the year. Finer soil particles settle most when it is cold. Organic material, particularly pollen grains, are laid down in a sequence that reflects the different times in the year when each particular plant or tree species releases its pollen. These facts make it easy to identify distinct layers within a lake bed, each layer having been produced in one year. These annual layers are called "varves", from the Swedish word, "varv".

Because lake beds are relatively protected from disturbances by changes in conditions above the lakes, researchers have found them to be particularly useful in studying changes year on year. Data on weather and climate changes, and changes in the local ecology are reflected by changes in the varve record. Many lakes have had lake bed core samples taken for this purpose. The best-known source of core samples is Lake Suigetsu in Japan.

Below are some images of vertical sections of lake bed core samples.

 

So grain size and pollen sequence provide proof that varves are indeed what they are identified as - annual sediments. They can be distinguished from other laminae that can be caused by weather events that may occur multiple times in some years.

Embedded in varves, we find other organic matter besides pollen grains. Leaves and twigs and seeds, for example. Now when you have organic matter, you can measure the ratios of the different isotopes of carbon. This is the well-known 14C (carbon-14) dating technique. 

Varve-count and 14C dates from the carbon-yielding contents of the varves have been compared and used to produce a "calibration curve". This is a cross check between two completely independent dating methods to see if they agree, and to check their validity, applicability and accuracy. The prediction was that if they are both accurate, and valid, they will correspond (correlate) closely.

They do.

The important thing to note is that in dating things using different techniques, based on completely different natural processes (lake bed sedimentation, carbon isotope radioactive decay, ice layer formation, coral ring growth, tree ring formation) - if any of these things did not agree with any of the others, if they were faulty or unreliable, or based on mistaken assumptions, it would show up as a lack of correspondence, or correlation. 

It doesn't.

The latest Suigetsu varve count I could find at the time of writing is 70,000. 70,000 years. And I haven't even talked about fossilised varves that takes the record back way, way earlier. This completely blows away the chronology of the Bishop of Ussher, which he divined from poring over a bible, and upon which young earth creationist (YEC) fantasies are based. Varves were being laid down well before the supposed creation of the world some 6,000 years ago, and no varve record, anywhere, shows any sign of a Noachian Flud.

https://www.google.com/search?q=google+lake+varve+chronologies