112lect11 - GY 112 Lecture Notes D. Haywick (2006) 1 GY 112...

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GY 112 Lecture Notes D. Haywick (2006) 1 GY 112 Lecture Notes Significance of Fossils: Paleoenvironmental Interpretations Lecture Goals : A) The oceans today B) Estimating water depths C) Adaptations to environment Textbook reference: Levin 7 th edition (2003), Chapters, 3 & 4; Levin 8 th edition (2006), Chapter 6 (especially pages 144-149) A) The oceans today In this lecture, I will attempt to explain how fossils can be used to interpret paleo- environments of deposition . Environments of deposition (paleo or otherwise) are diverse, but if a geologist is careful (and methodical), he or she can distinguish even the most subtle varieties. Beaches and reefs are easy to distinguish, but tide-dominated deltas and macrotidal estuaries look pretty much the same (especially in the rock record). Fossils can help to refine your interpretations. Strictly speaking, fossils give information about paleoecology (this is the interaction of life with the environment) rather than paleoenvironment of deposition, but I don’t really distinguish between the two terms. You don't have to either (that is unless you really want to). In order to see how fossils can help with paleoenvironmental interpretations, it is constructive to look at the modern world. Since most useful fossils are marine, let’s stick to the ocean realm. The oceans can be divided up into a series of zones. There are three specific types of zonation schemes: 1) morphological ( nearshore , shelf, shelf break, slope, abyssal plain ), 2) hydrodynamic (i.e., water depth; supratidal, intertidal, neritic, oceanic ) and 3) trophic (several divisions in both the pelagic and benthic realms). The diagrams on the next page summarize where each zone lies. It is the trophic zonation scheme that we are most concerned with in this lecture. These are the “ecological” zones where beasties live. In the simplest manner, marine organisms can be divided into either pelagic forms (floaters and swimmers) or benthic forms (bottom dwellers and burrowers). More complex classifications (like that depicted in the cartoon) recognize that both pelagic and benthic organisms are depth controlled. For example, there are 4 pelagic and 5 benthic divisions. The pelagic divisions are: epipelagic (0 to 200 m), mesopelagic (200 to 1000 m), bathypelagic (1000 to 5000 m) and abyssopelagic (>5000 m).
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GY 112 Lecture Notes D. Haywick (2006) 2
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GY 112 Lecture Notes D. Haywick (2006) 3 And the benthic divisions are: littoral (intertidal water depths) sublittoral (0 to 200 m) bathyal (200 to 5000 m) abyssal (>5000 m) and hadal (trenches up to 11,000 m deep). All this classification stuff might seem daunting and confusing, but it really is necessary to group oceanic environments into discrete packages. It makes paleoenvironmental interpretations much easier. Here is an example of how it all works.
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This note was uploaded on 02/04/2012 for the course GLY 112 taught by Professor Haywick during the Spring '12 term at S. Alabama.

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112lect11 - GY 112 Lecture Notes D. Haywick (2006) 1 GY 112...

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