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Biostratigraphy

Biostratigraphy. Amoeboceras bauhini: Amoeboceras bauhini. Staatliches Museum für Naturkunde Stuttgart. I. Intro. Aim is to establish correlations between time-equivalent strata by presence of a particular fossil species.

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Biostratigraphy

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  1. Biostratigraphy Amoeboceras bauhini: Amoeboceras bauhini Staatliches Museum für Naturkunde Stuttgart

  2. I. Intro • Aim is to establish correlations between time-equivalent strata by presence of a particular fossil species. • generally straightforward, i.e. presence of a specific fossil species in two geographic localities indicates the rocks containing the fossil specimens were deposited at about the same time • in practice biostratigraphic studies tend to be complex

  3. II. What is a Fossil? • Term fossil from Latin word for "dug up," • originally -- anything dug out of the earth. • Today, refers to remains or other evidence of ancient life forms. Generally, more than about ten thousand years old • Hussam Zaher / University of Sao Paulo via AP updated 10:08 a.m. PT,Wed., April 19, 2006 NEW YORK - A new fossil discovery has revealed the most primitive snake known, a crawling creature with two legs, and it provides new evidence that snakes evolved on land rather than in the sea.Snakes are thought to have evolved from four-legged lizards, losing their legs over time. But scientists have long debated whether those ancestral lizards were land-based or marine creatures. The new find reveals a snake that lived in the Patagonia region of Argentina some 90 million years ago, said Hussam Zaher of the University of Sao Paulo in Brazil, who describes the find in Thursday's issue of the journal Nature. Its size is unknown, but it wasn't more than 3 feet long, he said in a telephone interview.

  4. III. Index Fossils • Used to establish correlation • Critieria 1. must have a widespread distribution • Most limited to a small region or found only in particular depositional environment) 2. must show rapid evolution 3. must be present in substantial numbers 4. fossils should be robust mineralogically so that depositional and diagenetic processes do not remove the fossils from the rock record). 5.Best index fossils are planktonic or nektonic 6.benthic organisms, tend to be less widespread, fewer in numbers, and typically found in particular environments

  5. IV. Origin & Basis of Biostratigraphy • A. William “Strata” Smith (1769-1839) • 1. orderly succession in fossil • 2. correlated rks w/fossils • i. major advance • 3. major achievements followed --maps

  6. Biostrat Continued • B. Principle of Faunal Succession • 1.Non-reversible evolutionary change • 2. species had limited existence • 3. species fundamental taxon

  7. Biostrat Cont • C. Biozone • 1. rk defined by presence, absence, relative abundance of certain species or other taxa or of assemblages of species or other taxa

  8. Biostrat Cont • D. d’Orbigny used stages/zones • 1. zones subdivision of stages • 2. defined zone fossils

  9. IV Biozone Types • A. 3 major types • 1. Interval • 2. Assemblage • 3. Abundance

  10. B. Interval zone • 1. taxon range zone • i. max stratigraphic range of species, taxon

  11. 2. concurrent & partial range zone • i. interval of overlap between 1st appearance of one species & last appearance of different taxa • ii. also uses gaps--partial range zones

  12. 3. Interzones • I. barron interzones • ii. unfossiliferous zones delineated by biozones above & below

  13. 4. lineage zone • i. evolutionary connection • ii interval between last appearance of one taxa and first appearance of descendent

  14. C. Assemblage zone • 1 biozone characterized by association of 3+ taxa • i unique and distinguishable form assemblage above and below • ii biocoenosis • iii thanatocoenosis • a. problem--reworking of older strata

  15. D. Abundance zone • 1. strata containing maximum abundance in numbers of individuals of one or more species or taxa. • 2. acme zone • 3. difficult to use • 4. sparseness above and below due to sed environment, preservation, etc. • i. correlation risky

  16. V. Correlation Problems • A. Subjective taxonomic procedures • B. Missing Taxa • 1. generate gaps in range zones • 2. facies control • 3. not preserved • 4. rare (missed) • 5. misidentified • C. No agreement on zone

  17. Fossil Record Bias • FOSSILS IN STRATIGRAPHY • • Abundance and size: smaller fossils are more • abundant than larger ones, thus are more • useful in biostratigraphy • • Preservation Potential: Fossil record • represents only a minor portion of the past life • because (a) only hard parts are fossilized with • few exceptions (b) different environments have • different fossilizable potential (c) stratigraphic • record is incomplete, only few environmental • niches are preserved in sedimentary rocks • • Rate of Speciation: Differing rates of • speciation observed in fossil record

  18. A. SPECIES CONCEPT IN PALEONTOLOGYSpecies is the basic unit biological classification, i.e. organisms can be related to each other in a hierarchical manner. It is also used to classify fossils • • Kingdom • • Phylum • • Class • • Order • • Family • • Genus • • Species

  19. Stop Here

  20. Interval Zones

  21. Interval Zone

  22. Interval Zone

  23. Taxon Range Zone

  24. Concurrent Range Zone

  25. Lineage Zone

  26. Assemblage Zone

  27. Assemblage Zone

  28. Barron Zone

  29. Abundance Zone

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