The Cartularium Monasterii Sancti Johannis Baptiste de Colecestria (ed. Moore 1897) has several references to a property of St John’s called Chalcra (Chaucre, Cealchre).   No county is specified (and Essex is not on chalk), and this property is not mentioned in the VCH history of the abbey (http://www.british-history.ac.uk/report.aspx?compid=39827).

The only candidate I can find is Chalk Wood near Goring, which is cealc-ōra (PN Ox 51).    But all the early forms contain the -o- [*], and moreover there is no evidence that St John’s had property as far away as Oxfordshire.   Are there any other possibilities?

Keith

*however, note that the cartulary calls Walkerne Walc(h)ra.

PS: see Ann Cole, The distribution of usage of the OE place-name Cealc JEPNS 19 (1986-7) 45-55.