EXPOSURE OF LONDON-CLAY AT CHINGFORD ESSEX. 75
(3) Brown loam...... aft 6in. Water is thrown out at the junction
of this with :—
(4) Tenacious brown clay, to bottom of working......4 to 5 ft.
Strata I to 3 (which are not separated from each other by
any hard and fast lines) represent the Claygate Beds, or "passage
beds" between the London Clay and the Bagshot sands. Stratum
4, at the bottom of the pit, marks the highest part of the London
Clay proper.
More recently, a brickyard has been opened on the side of
Park Hill, Chingford, a few hundred yards to the south-east
of the section just described. In autumn, 1914. the section here
showed (in descending order) :—
Surface, about 230 ft. O.D.
(1) Tenacious brown clay, with fossiliferous Septaria......3 ft.
(2) Brown loamy clay, sandy in places......3 ft.
(3) Tenacious brown clay ......3 ft 6in.
(4) Brown loamy clay with streaks of sand ..... .2 ft., to bottom of
working.
The section is by no means a large one, and it is quite possible
that the sandy beds 2 and 4 are only portions of large lenticular
masses. The surface of the ground in this pit is about
15ft. below the bottom of the Pole Hill section, so it will be seen
that the fossiliferous Septaria, occurring as they do but a little
way below the base of the Claygate Beds, and just above two
distinctly sandy seams, occupy a position very near the top of
the London Clay.
Many of the Septaria have a distinct element of sand in their
composition and exhibit traces of stratification. Small crystals
of selenite are abundant in the clay, while radiating crystals
of Barytes are found in cavities on top of the fibrous calcite
which lines the cracks in the Septaria.
The Septaria in this Park Hill pit. contain numerous fossils.
These have been kindly named by Mr. E. T. Newton, F.R.S.,
F.G.S., and the following is a list of the species obtained, those
which occur plentifully being marked with an asterisk (*):—
LAMELLIBRANCHIA, Modiola simplex (Sby.)
Avicula media (Sby.) * ,, ,, elegans (Sby.)
* „ ,, papyracea „ ,, tubicola (S. Wood)
Pecten corneus *Axinea (Pectunculus) decussatus
Pinna. sp. (Sby.)