«7 



GEOLOGICAL NOTES IN THE NEIGH- 

 BOURHOOD OF ONGAR, ESSEX. 



By HORACE W. MONCKTON, F.L.S., F.G.S. 



npHE following notes were made during the years 1887-88-89-90, 

 -^ during which I had numerous opportunities of exploring the 

 country round Ongar when on visits to my kind friend, the late Mr. 

 A. H. Christie. One of the most interesting sections, and one which 

 I visited many times, is the sand pit, five furlongs south-east of 

 Chipping Ongar Castle, and three furlongs south of High Ongar Mill. 

 It was described by Mr. S. V. Wood in 1883 as a pit in Bagshot 

 Sand.^ Mr. Penning, who mapped the district, considered that the 

 sands belonged to the Glacial Gravel Series, and it is mapped 

 accordingly. 



In Whitaker's " Geology of London," vol. i. (1889), it is referred 

 to on page 276 as a sand pit at High Ongar, and on page 314 as a pit 

 nearly a mile south-east of Chipping Ongar Station. Mr. Whitaker 

 considers it to be Glacial Drift made up of Bagshot Sand. 



The section when I first saw the pit was as follows : — 



1. Dark reddish earthy clay with numerous bits of broken 



flint, small pebbles of flint and quartz, and some 

 pebbles of old rock, 2 feet to 7 feet. 



2. Yellow and white sand stratified in a very irregular 



manner and broken up by numerous small faults. 

 In one place the sand included a small patch of red 

 clay, 4 feet to 5 feet. 



The sand bed extends from about 175 to 150 feet above ordnance 

 datum level, and there are small sections in it at various levels on 

 both sides of the road from High Ongar to Hallsford Bridge. I 

 agree with Mr. Whitaker that the sand is derived from the Bagshot 

 Beds, and that it is not Bagshot Sand in situ. I am inclined to 

 think that the following is its true history. There was a time before 

 the coming of the Boulder Clay when the Bagshot Beds extended 

 over all this part of the country. Through them and the underlying 

 London Clay the River Roding cut its valley, and the sands of the 

 High Ongar sand pit are the remains of a landslip which occurred 

 in the Roding Valley before the period of the Boulder Clay. 

 Subsequently the Bagshot Beds have been worn and denuded back as 



I Trans. Essex Field Cluh, vol. iv., p. 76. 



