FORAMINIFERA: PART 1 - AN INTRODUCTION

1. FORAMINIFERA:PART 1 - AN INTRODUCTION

2. FORAMINIFERA • Single-celled • Amoeba- like • Testate (skeleton) & usually multichambered • Net-like, thin, pseudopods • Anastomosing & • Reticulating • Dimorphic life cycles are complex • Nearly 4 000 genera known • 60 000 species known!

3. LIVE FORAM • Note pseudopodia capturing food particles • Note multichambered calcareous skeleton • Planktic

4. MULTICHAMBERED FORAM SKELETON • SEM image of a planktic foram (note scale)

5. DIFFERENT SPECIES OF FORAMS • SEM images of planktic forams

6. 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 of benthos • Movement-feeding categories: • Crawling: • Mudeaters (detritus feeders) • Micropredators • Herbivores • Burrowing mudeaters • Reclining suspension feeders • Encrusting suspension feeders (= red Homotremarubrum)

7. Microscopes used in Studies • Transmitted light – whole mounts • Transmitted light – thin sections • Reflected light • SEM

8. 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. • If carbonate cement present, it won’t break down. • Other rocks: Simply boiling crushed samples with baking soda helps to release some sediment particles & microfossils • Thin sections may be resorted to, but usually thin section studies are not very effective, except for fusulinids & a few other kinds of forams with complex internal structures & morphology.

9. Generalized History Based on Wall Composition & Structure • Note: • Early organic walled & arenaceous forams in Cambrian • Calcareous microgranular forams appear in Ordovician • Porcelaneous walls appear in Carboniferous • Hyaline in Permian • Planktic in Late Jurassic • Nummulitids = Late K to Early Cenozoic

10. Review Early History of Forams • Early organic walled & arenaceous forams in Cambrian • Calcareous microgranular forams appear in Ordovician • Porcelaneous walls appear in Carboniferous • Hyaline in Permian

11. Review Later History of Forams • Planktic in Late Jurassic • Nummulitids = Late K to Early Cenozoic

12. Applications of Foram Studies • Very useful indicators for • Biostratigraphy • Dating (many spp. w/ short ranges) • Correlation • Paleoenvironments • Depths • Ocean water mass & current studies • Climates (Recent, Pleistocene Ice-Age studies, Cenozoic, Mesozoic, and Paleozoic, including biogeochemical studies of foram tests) • Habitats • Paloeautecology (species) & paleosynecology (community) • Evolution • Gradualistic phenomena found • Punctuated equilibrium examples are also known “Globigerina” ooze = chalk

13. CLIMATE CHANGES INTERPRETEDFROM DEEP-SEA CORES • Identification of planktic foraminiferal species • Live in near-surface waters where affected by climate above • Date layers in deep-sea cores. • Plotting the abundance of cold and warm climate species from core samples indicates climatic changes through time.

14. CLIMATE CHANGES INTERPRETEDFROM DEEP-SEA CORES • O18/O16 ratios from tests used to determine • Paleotemperature changes with planktic species & • Ice-volume changes with benthic species Triserial, planktic

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