GLY-1102 Lecture 12: Geologic time Periods and stuff
17 Sep 2018
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Laurentia n america, grenland, ireland, scotland, baltic (russia) Orogenies mountain building events, indication of tectonic plate theory. Ea le(cid:448)els drop i(cid:374) glaciatio(cid:374)s, rise (cid:449)he(cid:374) glaciers (cid:373)elt, do(cid:374)"t coi(cid:374)cide e(cid:454)actly. Ssf small shelly fauna, begin at the base of the cambrian. Some of the first organisms to make shells. Cambrian explosion all sorts of invertebrate organisms come in mid to late cambrian period, sponges, mollusks, arthropods, etc. Charles walcott discovered the burgess shale, 1909 side of a mountain in british colombia. Held both hard bodied shell and sft bodied organisms. All had so(cid:373)e features that did(cid:374)"t (cid:373)atch e(cid:454)isti(cid:374)g ph(cid:455)la. Sponges appear at base of the cambrian, multicellular, but hard to classify as metazoan. Fossilizable hard part, skeletal structures out of biominerals. One of the most diverse phylums (cid:862) eg(cid:373)e(cid:374)ted parts(cid:863) Some are blind, some have simple eyes, some have hundreds of lenses made of calcium carbonate. Proto spiral cleavage in cells, gastrulation, blastopore -> mouth.
