FINDING THE CHALK MAKERS OF TODAY

(RECENT FORAMINIFERA)

by Brian Darnton, UK

THE DEPOSITION ZONES OF EMPTY TESTS.

The Foraminifera are valuable markers in the sea as the species vary according to the temperature, and salinity of the sea water.

Deposition in our seas is an ongoing process. These simple yet beautiful microscopic shells can be found in the tide mark in various situations around our coasts.

Bays that are larger than half a mile across are potential hunting grounds, but in tidal Northern Europe the zone of deposition is restricted to a limited area. In round terms it can be found near the headland from which the tidal flow comes. So along the South coast of England the place to look is at the most Westerly end of the bay: Weymouth, Tor Bay and Swanage are good ones to visit. Along our East coast the flow is mostly from the North and the Northern end is the one to search: Scarborough and the Wash are good sites.

Black coal and brown lignite have similar characteristics to forams and generally form an identifiable black and white banding in the tide mark with the forams. Where prevailing winds are continuous on the Atlantic seaboard, Foram Dunes can be created. The most famous of these is at Dogs bay W.Ireland and there are others on the W. coast of Scotland like Calgary Bay, Mull. and near the northern tip of Scotland.

LIVING CREATURES. To the lee of sheltered headlands growths of the Japanese Seaweed Sargassum muticum are often covered in colonies of the species Elphidium crispum. With a good X10 hand lens the minute shells wreathed in protoplasmic threads can be found seeking the protection of nodal swellings on fronds of seaweed near the surface. Elphidium enjoys an association with various commensal algae which make the living tests appear to be green in colour.

COLLECTION.

From the shorline this is best achieved with a small flat childrens spade. Only the superficial material is scraped up.

PREPARATION.

Sorting the Foram tests from the sand can be like finding a needle in haystack but the litle shells are slightly lighter than the sand . When the sample is shaken up vigrously in a bottle of water, after one second most of the sand will have settled. At that point the suspension is poured off into a filter. One can at least concentrate the sample of Forams and wash it free from salt under the tap. When dried out and placed in a dish Horizontal shaking will cause the shells to work their way to the suface where they can be picked out. The careful use of sieves can help in the sorting out of types.

MOUNTING.

Tests that are larger than 150 microns are better dry mounted as they can dry out arkwardly and slowly in resinous mountants. Forams destined for mounting in Canada Balam are better sieved so that the sample contains material that is less than 150 microns. Any strew made should contain a small amount of adhesive like Gum Tragacanth to prevent them moving before and after mounting, particularly if the slides are to be stored "on edge".

OBSERVATION.

Recent Forams are much clearer than fossil types and in mountants can be enjoyed in dark field illumination

Comments to the author Brian Darnton welcomed.

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Editor's notes

Read Brian's July 1998 Micscape article on finding older Foraminifera.

Brian prepares and sells a selected range of strewn and type microscope slides of foraminifera. Visit Brian's Home Pages for details.

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