Type s o f fo s s ilizatio n C arbo nizatio n • c he m ic al re ac tio n whe re wate r trans fo rm s the o rg anic m ate rial o f plant o r anim al to a thin film o f c arbo n. • Nitro g e n, hydro g e n, and o xyg e n are drive n o ff as g as e s , le aving an o utline o f the o rg anis m . • fis h, le ave s and the wo o dy tis s ue s o f plants . Mo lds Ho w are fo s s ils pre s e rve d?
Type s o f fo s s ilizatio n • Trac e fo s s ils • trac ks • trails • burro ws • bo ring s Ho w are fo s s ils pre s e rve d?
Appropriate characteristics of fossils used for correlation (Zone Fossils)(1) • Easily preserved – bones and shells, not jellyfish! • Easily identified – distinctive characteristics, as with ammonites, that are better than freshwater clams
Appropriate Characteristics of Zone Fossils (2) • Abundant – forams are better than dinosaurs • Geographically widespread – to enable long distance correlation • Environmentally tolerant – facies independent
Commonly used groups of fossils include: • graptolites, trilobites (Paleozoic) • corals, brachiopods (Paleozoic) • goniatites (Paleozoic) • ammonites (Mesozoic)
Commonly used groups of fossils include: • microfossils – calcareous nannofossils (Cretaceous & Cenozoic) – conodonts (Paleozoic) – forams (Cenozoic) – pollen and spores
Petroleum Micropaleontology • The petroleum industry uses microfossils (particularly forams) because they are small and abundant, so that large numbers can be recovered from well cuttings
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