AN ESSEX FOSSIL ZIPHOID WHALE 349
Sub-crag bones are invariably very heavily mineralised and
stained from yellowish brown to black and when subjected to
prolonged weathering never acquire a chalk-like character, they
tend to be splintery. It may well be to record here that the
condition of fossil remains varies with the type of sand, gravel or
clay in which they were buried and if under wet or dry conditions.
The portion of whale rostrum is said to have been brought up
from below the water table by the dragline excavator but its
condition could only be produced by prolonged action of percolat-
ing rain water in otherwise dry sand, or sandy gravel. No late
marine deposits have been recorded in eastern Essex and the
complete absence of abrasions or striation on the soft bone rules
out any possibility of derivation from an older deposit. The
bones and teeth of land animals occuring in old river gravels are
the remains of beasts caught by floods in the valley bottoms, and
usually bear scars caused by stones moved by increased current
flow in times of flood.
Figure 2.—Diagrammatic section (top) of situation at the site of Ardleigh
Gravel Pit. Section through the strata at Ardleigh, not to scale. 1 and 2,
upper gravel and sand—glacial outwash. 3, disturbed zone representing
a cold period above the water table. 4, London Clay which underlies the
whole region.
To review briefly some published and unpublished geological
observations of the region the most important fact is that the
Thames formerly flowed via Ilford and Clacton and was probably
a tributary of the Rhine at one stage. A notable remnant of the
old Thames deposits exists at Clacton in the so-called "Elephant
Bed" which has yielded very primitive flint artifacts of prehistoric
men. Another deposit occurs at East Mersea where bones of