FORAMINIFERA: PART 1 - AN INTRODUCTION

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FORAMINIFERAPART 1 - AN INTRODUCTION
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FORAMINIFERA

• Single-celled
• Amoeba- like
• Testate usually
• multichambered
• Net-like pseudopods
• Anastomosing
• Reticulating
• Dimorphic life cycles are complex
• Nearly 4 000 genera known
• 60 000 species known!

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LIVE FORAM

• Note pseudopodia capturing food particles
• Note multichambered calcareous skeleton

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MULTICHAMBERED FORAM SKELETON
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DIFFERENT SPECIES OF FORAMS
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FORAMINIFERA

• 50 to 60 species of living planktic forams
• Many thousands of living benthic species
• 1 000 genera living
• Up to 1 million individuals per square metre
  benthos
• Movement-feeding categories
• Crawling
• Mudeaters (detritus feeders)
• Micropredators
• Herbivores
• Burrowing mudeaters
• Reclining suspension feeders
• Encrusting suspension feeders

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Microscopes used in Studies

• Transmitted light whole mounts
• Transmitted light thin sections
• Reflected light
• SEM

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Sample Preparation

• Study unconsolidated sediments as the 1st choice
• Wash (heat baking soda) any fines from
  sediments
• Sieve coarse and separate sand fractions
• Juveniles tend to look alike even among
  different genera, so pick 0.125 mm fraction
  above
• Some shale can be broken down by heating in water
  soaking in organic solvents. Then, treated as
  above.
• Other rocks Simply boiling crushed samples with
  baking soda helps to release some sediment
• Thin sections may be resorted to, but usually
  thin section studies not very effective, except
  for fusulinids a few other kinds of forams.

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Generalized History Based on Wall Composition
Structure

• Note
• Early organic walled arenaceous forams in
  Cambrian
• Calcareous microgranular forams in Ordovician
• Porcelaneous in Carboniferous
• Hyaline in Permian
• Planktic in Late Jurassic
• Nummulitids Late K to Early Cenozoic

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Review Early History of Forams
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Review Later History of Forams
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CHALK FORAMS IN A "FINE-GRAINED MATRIX"
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Application of Foram Studies

• Very useful indicators for
• Biostratigraphy
• Dating
• Correlation
• Paleoenvironments
• Depths
• Climates
• Habitats
• Paloeautecology (species) paleosynecology
  (community)
• Evolution
• Gradualistic phenomena
• Punctuated equilibrium examples

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CLIMATE CHANGES INTERPRETEDFROM DEEP-SEA CORES

• Identification of planktic foraminiferal species
• Date layers in deep-sea cores.
• Plotting the abundance of cold and warm climate
  species from core samples indicates climatic
  changes through time.

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CLIMATE CHANGES INTERPRETEDFROM DEEP-SEA CORES

• O18/O16 ratios from used to determine
• Paleotemperature changes with planktic species
• Ice-volume changes with benthic species

Triserial, planktic
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