shows wave ripples that are remarkable
firstly by their age. From
radiometric datings we know that the particular sandstone (Chorhat
the Kheinjuan Formation in Central India)
1,6 billion years old. In other words: these ripples formed three times
ago as the Cambrian Revolution!
the ripple crests in this slab are doubled. In contrast to the
mud cracks of Namibia
(#1), this is not a result of secondary deformation, but a primary
we have seen, ripple distances have a certain -- though non-linear --
relationship to the wave regime in which they formed. Consequently,
decrease in a given place as wave energy wanes after a storm. But since
are constrained not only by the momentary regime, but also by their own
history, ripple distances adjust not gradually, but by phase doubling.
cases small secondary crests emerge in the middle of the troughs until
reach the same size as the primary ones, now with half the previous
distance. That in the present case period doubling initiated in the
have do with the slight asymmetry of these ripples. It indicates that
action was combined with a weak current from the upper left.
Of course, we did not
travel to India
just to cast ripple marks. Rather we were lured by presumed worm traces
professor Pradip Bose
from these sandstones. When he and his assistant, Dr. Subir Sarkar kindly guided us to
most of the markings turned out to be pseudofossils
("Manchuriophycus"). But others look like burrows of worm-like
undermat miners. This is impossible in view of the new radiometric
challenge now is to find another, non-biological explanation.