Lecture 2

Collection, Preparation

and Examination

Collection, Preparation and Examination (Technical methods)

• Foraminifera occur on a wide variety of substrates.

• At all depths in the marine realm.

• They are also transported by currents before burial in the sediment.

• They are therefore found fossilized in most types of sedimentary rock, particularly in clays and marls.

• Foraminifera are usually scarce in coarse sands but they are often abundant in silts and fine sands, especially if glauconitic.

• Many limestones are built up of foraminifera but are often too hard, they can then only be studied in thin section.

(A)-Field (surface) Sampling

•Normally, smaller foraminifera are only rarely seen in hand specimens of rock samples.

•Larger foraminifera can be collected in the field like other macroscopic invertebrate fossils as in the case of fusulinids, alveolinids and nummulitids.

•They may also be observed in the weathered surfaces as well as on bedding and joint planes.

•Larger foraminifera may also be picked up or sieved out of sediment on talus slopes.

•Nummulites gizehensis is so- abundant in the middle Eocene of the Sahara especially from the Mokattam limestone of the Great Pyramids in Egypt.

•An investigation of the stratigraphic distribution of microfossils should commence with study of a set of samples representing the standard stratigraphic sequence of the area.

•Samples for stratigraphic purposes are taken at regular intervals, the interval depending upon the rock, the thickness and character of strata involved and the available time.

•Collecting of rock specimens should be supplemented by a special search for soft, easily washed rocks as sandy clays, marls, fine argillaceous sands and shales.

•About 250 gm weight of sample is usually considered sufficient. •A graphic lithological log should be drawn to accompany the detailed description with the position of the samples shown exactly.

•If possible Polaroid photographs should be taken of the section with sample bags in position.

(B)- Samples from borings (bore holes):

•Samples from deep wells, from cores, are the most suitable material for the stratigraphic application of micropaleontology.

•Samples representing each 10 ft (3m) interval are usually taken.

•The drilling mud is washed off and the material split into sub samples.

•Contamination with fossils and rock fragments from higher parts of the section must be anticipated in all loose material from wells.

•In such material only the first appearance of species in the course of drilling provides useful stratigraphic horizons.

Sample Preparation

The general procedure is as follows:

• Crushing and boiling.• Decanting.• Drying. • Storage.• Separation of microfossils. • Mounting of microfossils.• Identification and recording.

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Transmitted binocular microscope

Reflected binocular microscope

Diagram of scanning electron microscope

scanning electron microscope

This includes a gold coating MED

Paleontology Teaching Laboratory

Reflected light binocular microscope

Washing sieve