FORAMINIFERA:

PART 1 - AN INTRODUCTION

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!

LIVE FORAM

• Note pseudopodia capturing food particles• Note multichambered calcareous skeleton• Planktic

MULTICHAMBERED FORAM SKELETON

• SEM image of a planktic foram (note scale)

DIFFERENT SPECIES OF FORAMS

• SEM images of planktic forams

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 Homotrema rubrum)

Microscopes used in Studies

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

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.

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

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

Review Later History of Forams

• Planktic in Late Jurassic

• Nummulitids = Late K to Early Cenozoic

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

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.

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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