Vol. XXVII—Part VI. Oct., 1942—Mch, 1943.
THE
Essex Naturalist:
BEING THE
Journal of the Essex Field Club.
THE DRIFTS OF SOUTH-WESTERN ESSEX
By S. HAZZLEDINE WARREN, F.G.S.
(Conclusion.)
Part II.
Glacial Deposits [Whitaker 1889, Dines and Edmunds,
1925, Wooldridge, 1927, 2 ; 1938, etc.] The country from
Brentwood to Bishop's Stortford was a focus of dispersal of the
southern termination of the ice of the Glacial Period. The chain
of hills, although small, from Epping Forest, through Havering
and Brentwood to Billericay, checked the enfeebled edge of the
ice, but one big lobe pushed down the Lea Valley to Chingford
and Finchley ; another lobe passed to the Estuary of the Crouch ;
while the most southerly reached Hornchurch (q.v.). As the ice
melted it left, besides the Boulder Clay, many accumulations of
outwash gravels at various points from Epping Forest to Danbury.
The gravel in the last named locality has, in the past, given rise
to much discussion. [Turner, 1937.] Although trivial in
comparison with almost mountainous accumulations like the
Cromer Ridge, these outwashes are essentially in the nature of
terminal moraines.
The hill-tops of S. Essex were either above the ice, or only
lightly touched, but on the Epping Forest ridge Boulder Clay is
well developed on the Epping Plain at over 350 O.D. The
anti-tank ditches (see under "Epping Forest") disclosed some
festoons, particularly about 1/4 mile S.E. of the "Wake Arms,"
that are composed, not of Pebble Gravel, but of decalcified
Boulder Clay with striated erratics, and scattered evidences
extend to the highest point at 385 O.D. This proves an ice
thickness of not less than 260 feet in the Roding Valley. Glacial
outwash gravels are found at Monk Wood at 300 O.D. ; also on
Strawberry Hill, near Loughton Church, and further south to
Woodford at lower levels. At Danbury an ice thickness of
about 300 feet is indicated.