ESC 241 Trace and Microfossils

Micropaleontology

Study of microscopic fossils

Protists

Single-celled eukaryotic organisms

Protists types

Autotrophic (plant-like) and heterotrophic (animal-like)

Acritarchs

Organic marine microfossils (<100 μm), Proterozoic–Recent

Dinoflagellates

Organic aquatic microfossils (5–150 μm), Silurian–Recent

Coccolithophores

Calcite marine microfossils (<50 μm), Triassic–Recent

Diatoms

Silica aquatic microfossils (<200 μm), Jurassic–Recent

Radiolarians

Silica marine microfossils (0.03–1.5 mm), Cambrian–Recent

Foraminifera

Organic/agglutinated/calcareous marine microfossils (0.01–100 mm), Cambrian–Recent

Ostracods

Calcareous aquatic microfossils (1–10 mm), Cambrian–Recent

Conodonts

Phosphatic marine microfossils (0.1–5 mm), Cambrian–Triassic

Spores

Organic terrestrial microfossils (5 μm–4 mm), Devonian–Recent

Pollen

Organic terrestrial microfossils (5–200 μm), Devonian–Recent

Microfossils groups

Protists, multicelled organisms, plant parts

Ostracods

Small crustaceans with two valves

Ostracod shell

Calcareous carapace

Ostracod morphology

Bean-shaped with hinged valves

Ostracod habitat

Benthic (marine and freshwater) and pelagic (marine)

Freshwater ostracods

Thin, smooth shells

Marine benthic ostracods

Thick, ornamented shells

High-energy ostracods

Thick shells with ribs/spines

Infaunal ostracods

Elongated smooth shells

Pelagic ostracods

Rounded smooth shells

Foraminifera

Single-celled protozoans with shells (tests)

Foraminifera habitat

Benthic and planktonic

Foraminifera shell

Test

Foraminifera chambers

Added in spiral arrangement

Foraminifera aperture

Last chamber opening

Foramina

Pores for pseudopodia

Foraminifera test types

Organic, agglutinated, calcareous

Porcelaneous test

Translucent

Microgranular test

Common in Paleozoic

Hyaline test

Transparent

Foraminifera growth patterns

Planispiral, trochospiral, biserial, uniserial

Planktonic forams

Globular, porous, buoyant

Benthic forams

Flattened or elongated

Epifaunal forams

Feed on diatoms

Infaunal forams

Feed on organic matter and bacteria

Foraminifera environment

Controlled by temperature and salinity

Photic zone

0–200 m (light penetration zone)

Foraminifera uses

Paleoclimate, paleoceanography, biostratigraphy

Foraminifera evolution

Cambrian agglutinated → Silurian calcareous → Devonian multi-chambered → Jurassic planktonic

Diatoms

Silica microfossils used in environmental reconstruction

Diatom skeleton

Frustule (silica)

Diatom groups

Centric and pennate

Diatom analysis steps

Core sampling, dating, extraction, counting, identification

Diatom use

Paleoclimate and paleoenvironment reconstruction

Trace fossils

Evidence of organism activity

Ichnology

Study of trace fossils

Trace fossils definition

In situ records of behavior

Trace fossil types

Tracks, burrows, borings, coprolites

Ichnotaxa

Classification based on trace, not organism

Ichnogenus

Genus of trace fossil

Ichnospecies

Species of trace fossil

Trace fossil principles

Same organism produces different traces

Trace fossil principle

Same trace produced by different organisms

Trace fossil preservation

Varies with sediment

Trace fossil modification

Affected by environment

Burrowing reasons

Protection, feeding, respiration, reproduction

Burrowing methods

Compression, excavation, displacement

Cubichnia

Resting traces

Repichnia

Locomotion traces

Fodinichnia

Feeding traces

Domichnia

Dwelling traces

Pascichnia

Grazing traces

Agrichnia

Farming traces

Fugichnia

Escape traces

Praedichnia

Predation traces

Equilibrichnia

Equilibrium adjustment traces

Environmental controls

Energy, depth, salinity, nutrients, oxygen, substrate

Facies

Rock characteristics reflecting depositional environment

Ichnofacies

Trace fossil assemblage indicating environment

Ichnofacies importance

Behavior consistent through time

Bioturbation

Sediment disturbance by organisms

Bioturbation meaning

Indicates sedimentation rate and oxygen levels

No bioturbation

Rapid sedimentation or anoxic conditions