Geological Cycles

Some geological cycles notes from the past

Sedimentary Climate Cycles

In 1996 Malcolm McClure wrote:
The Geological Sociey London, has just published Special Publication 85 on the subject of sedimentary cycles co-edited by M.R. House. and A.S. Gale It is called Orbital Forcing Timescales and Cyclostratigraphy. In his intro House lists the factors as follows:
1. Earth-Sun distance (perihelion and precession cycles: 19 & 25 ka)
2. Tilt in Earth's axis with respect to ecliptic (obliquity cycles 41 & 54 ka)
3. Changes in the geometry of earth's orbit around the sun (eccentricity cycles of 106 and 414 ka)
4. 26 Ma oscillations related to the cosmic year (260 Ma)
(Before anybody asks, House concluded that extinction events are not cyclical.)
Other shorter period cycles are
1. The Earth year (length decreased from 400 to 365.25 days in 400 Ma)
2. The Chandler Wobble (434-436 days, which nobody understands
3. The Lunar perigee (8.85 a)
3. The Solar year (11.0 a)
4 The Lunar Nodal cycle (18.6 a)
5. The Hale cycle (22.0 a of sunspot activity)
This book also corrects the magnetostrat dates during the Neogene.

Nanocycles Method

In 1997 Ray Tomes wrote:
[Note: my Russian knowledge is zero and so translation is risky]

In "Nanocycles Method" Professor S Afansiev of Moscow University describes
how he has determined accurately the variations in short term cycles laid down
in rock strata. These variations are due to the changing period of the lunar
nodal cycle which affects rainfall and hence the variations in thickness of silt
deposits in making the rocks.

As well as the nodal cycle itself it is possible to detect the interaction periods
of the cycle with the annual cycle of the seasons. Using these interaction
periods the nodal cycle period can be determined to high precision, and as
the period varies continuously due to tidal interaction with the earth, the exact
date of deposits can be determined. The book contains some 80 pages of tables
showing the nodal period and the interaction periods at 0.2 million year intervals
for the last 600 million years. A brief summary of the recent values is:

Million years ago       100     80     60     40     20      0

Nodal period (years)   3.278  3.814  4.523  5.504  6.951  9.298

In any given age, the Nodal period interacts with the seasons so as to
produce further cycles. The first of these is calculated by dividing
the nodal period by its difference from the nearest integer, so that at
present the nodal period of 9.298 years would produce an
interaction cycle of 9.298/(9.298-9) = 31.2 years. This interaction
period is very sensitive to the length of the nodal cycle, for example
varying from 46 to 31 years as the nodal cycle varies from 9.2 to 9.3
years, and so measuring it allows the very accurate measure of the
nodal cycle and therefore the age of the strata.

Using the established ages in this manner Prof Afansiev was able to
determine the periods of other geological cycles in strata to an
unprecedented high precision.

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