Wrabness & Harwich, Essex
Essex Rock & Mineral Society Field Trip, 21 September 2002

After congregating at Wrabness Station members of our Society and the Tertiary Research Group departed on mass for Wrabness Church. Here we were given a very informative introduction to the area, its geology and history, by the field trip leaders Bill George and Graham Ward.

We were presented with an excellent handout prepared by Bill and treated to a fine display of fossils and a few artefacts that had been found by Graham & Bill from this location. On display was the half noble found thirty years earlier (by Bill) and Graham's fossil collection of mostly Pleistocene age from this location.

Bill recounted the 1701 tale of the discovery of fossil elephant bones that at the time were attributed to the Romans who may have buried an elephant they brought with them! Interestingly, in Graham's fossils on display was bone material from the same location.

Before departing to the foreshore we visited the church for a quick guided tour by Bill and a look at the stone font mentioned in the handout.

Although it has been suggested that the font was carved from septarian nodules, Graham concluded that due to the size they were not of local origin and probably originated from the Oxford Clay.

It seems like our members are more interested in finding another half noble!

As we walked along the beach, Graham pointed out the various marker horizons, especially the Harwich Stone Band which marks the base of the ash bands. We went as far as the junction with Pleistocene deposits.

The light markings in the cliff section form the remnants of the volcanic ash bands. Some 37 layers have been recorded, unfortunately due to recent erosion of the cliffs, many are now obscured. Graham said that the light bands are formed of a montmorillonite clay and that the most likely source for the original volcanic ash was probably Scotland. He also discussed the correlation of these volcanic deposits with the layer viewed at the Naze a few weeks earlier.

(I am totally ignorant on this point, and have not studied any of the papers relating to these exposures. Graham wouldn't have said Scotland without good reason. That aside, my main thought was 'How does one interpret these ash bands?'

Initially, one may concluded that they are from 37 volcanic events (pulses from one source) and that they are the settlement of airborne ash through the water at this location! However this is a marine sedimentary rock sequence. These are subject to erosion, transportation and deposition. It did make me wonder whether other interpretations would work like, one event with the ash being eroded (seasonally, rain, rivers, etc) and transported into the marine environment where it later becomes deposited here. Whatever, it is worth keeping an open mind on the subject)