1	Early Paleozoic: Ordovician
2	Earth in the Ordovician ~490-444 ma Summary 2^nd period of the Paleozoic Era Rapid evolution of many new animals 1^st land plants North America was tropical/subtropical Taconic Orogeny deforms North America Gondwana supercontinent drifted over the south pole, initiating a great Ice Age End of period marked by major mass extinction event
3	Early Ordovician Setting: Sauk Sea North America (Laurentia) is tropical to sub-tropical Highest sea levels of Earth up to that point Hypersaline epieric seas = low diversity of fauna Normal salinity outer banks = flourishing life Very little land is exposed Predominate deposition type is carbonate Limestones, dolomites Sauk Sea environment lasted for several million yrs
4	Mid-Ordovician: Onset of REGRESSION Land surface exposed Widespread erosion results New deposition of St. Peter Sandstone Thick deposits, widespread (IL, IN, MO, MN, NB) Transgression again Redistributes sediment Towards center of craton
5	The Taconic Orogeny Mountain Building in the Mid-Ordovician 1^st Phanerozoic Orogenic Belt in NA, 445-435 ma Modern day Appalachian region, also Novia Scotia, Newfoundland in Canada, Greenland 1st mountain-building event of the ancestral Appalachians Subduction leads to Orogeny Iapetus Ocean floor subducts eastward under with eastern Laurentia Causes collision of offshore volcanic island arcs & microcontinents Began Mid-Ordovician Ended Early Silurian
6	Cross- Sections of Eastern North America, as it may have looked
7	Position of Continents Cambrian through Early Silurian Animation shows us closing of Iapetus Sea, and approaching land masses of Baltica and Avalonia --Paleomap Project by Christopher Scotese
8	By the Late (Upper) Ordovician………… Laurentia Setting Once Again: Transgression Tippecanoe Sea Floods Laurentia; highest sea levels to this point Upper Ordovician strata of Ohio & Indiana among the most fossiliferous rocks in the world Contain well-preserved, rich & diverse fauna Final Act: Gondwana glaciation Triggers global cooling Triggers mass extinction event
9	Life of the Ordovician Flourished in the Mid to Late shallow epeiric seas Dramatically different from that of the Cambrian High diversity of life: Greater than 400 families Had calcite (sometimes massive) skeletons Development of a New complex food chain, including predators Plants- first terrestrial plants tetrahedral spores
10	Common Marine Invertebrates Filter Feeders articulate brachiopods (most common) Bryozoans (2^nd most common) Crinoids-“sea lilies” True reefs, composed of: corals rugosid & tabulate Sponges (stromatoporoids) algae (sunflower corals) Scavengers Trilobites Snails
11	More Marine Life Predators Nautaloids- top predator Sea stars “starfish” Non-restricted fossils Graptolites Vertebrates (jawless fish)
12	Mass Extinction End of Ordovician marked by first great mass extinction in the history of life. > 100 families went extinct Primarily affected tropical organisms >50% brachiopod and bryozoan species died out Reef communities & nautaloids were decimated Trilobites declined Surviving groups were adapted to either deep or colder water Suggests severe cooling event (Gondwanaland glaciation)
13	End Ordovician