Collection, Preparation

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Lecture 2

• Collection, Preparation
• and Examination

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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.

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(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.

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• 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.

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(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.

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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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Diagram of scanning electron microscope
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scanning electron microscope
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Paleontology Teaching Laboratory
Reflected light binocular microscope
Washing sieve