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Geology 106
| Question | Answer |
|---|---|
| During what time period was the Paleozoic? | 542 MYA - 245 MYA |
| What is a craton? | relatively stable and immobile parts of a continent - foundation for Phanerozoic sediments |
| What is a shield? | exposed portion of craton. |
| What is a platform? | covered portion of craton. |
| What are epeiric seas? | continent covered by shallow waters due to high sea level (lack of glaciation/plate movement) |
| What are arches, domes, and basins? | gentle flexures. Arches and domes stood above epeiric seas |
| What are mobile belts? | elongated areas of mountain building activity along margins of continents |
| What five mobile belts were formed during the Paleozoic? | Franklin, Cordilleran, Ouachita, Appalacian, Caledonian |
| How many continents existed? | 6 major - after Rodinia breaks up / some micro continents |
| Was there glaciation? | No - only mountains above water |
| What is Iapetus? | Iapetus was an ocean between Laurentia and Baltica. It widened with the Late Cambrian - Narrowed in the Late Ordivician - and finally began to close in the Middle Silurian periods |
| What did Gondwana do? | It shifted southward to the south pole until the Late Devonian period where it began to move upward toward Laurentia |
| What major continent is forming during the Paleozoic? | Pangaea |
| What happens to Laurentia and Baltica? | They combine into Laurasia by the Late Devonian period - eliminating the Iapetus Ocean through subduction |
| What happens during the Late Ordivician (450MYA)? | sea level lowers. Iapetus begins closing. Gondwana moves south. |
| What happens during the Middle Silurian ( | no glaciation - sea level rises. Iapetus very narrow. Gondwana reaches the south pole |
| What happens during the Late Devonian? | Laurasia is formed. Gondwana is moving up towards Laurasia |
| What happens during the Early Carboniferous? | Gondwana collides with Laurasia. There's glaciation at the poles |
| During which period does Pangaea form? | Permian - 250 MYA |
| What is the climate of Pangaea? | arid and semi arid due to size of land - humidity disappears the further inland you go. Rain shadow deserts. |
| What is the effect of the climate of Pangaea? | The formation of extensive evaporates, like salt flats. These are easily chemically worn when water enters the chat. |
| What are transgressions? | when the ocean rises onto continent - passive margins. They produce a limestone, shale, sandstone pattern. |
| What are regressions? | when the ocean lowers from continent. They produce a sandstone, shale, limestone pattern |
| Who divided the US into 6 sequences? | Laurence Sloss in 1963 |
| What are the 6 sequences? | Sauk, Tippecanoe, Kaskaskia, Absaroka, Zuni, Tejas |
| What is a cratonic sequence? | a major transgressive and regressive event bounded by craton-wide unconformities |
| How can igneous rock change the sea level? | as rock cools, it contracts. The building of an ocean mountain range displaces a huge volume of water. As it cools, the water goes down to fill the space. |
| What is the first sequence on the North American craton? | The Sauk Sequence |
| When did the Sauk sequence occur? | Late Proterozoic - Early Ordivician |
| What were the conditions during the beginning of Sauk? | Beginning: craton above sea level - experiencing extensive weathering and erosion. No ice, no vegetation, low tropical latitudes. |
| What was the epeiric sea situation during the middle of Sauk? | small portion of craton and some islands above sea level. |
| What were the large islands above sea level during Sauk? | The Transcontinental Arch |
| What were in the shallow waters during Sauk? | carbonate, shells, stromalites, reefs, oolites |
| What were the conditions during the end of Sauk? | • Sauk Sea regressed from craton during Early Ordovician (505 Ma) • Exposed limestones deeply eroded in tropical environment • Large unconformity marks the boundary between Sauk and Tippecanoe |
| What was the second cratonic sequence and when did it take place? | Tippecanoe - Ordivician and Silurian |
| What is new about the Tippecanoe sequence? | New life!- Reefs, chemical precipitates, and fossil fragments. Clean, well-sorted quartz sand deposited over most of the craton. |
| What were the Tippecanoe reefs? | limestone structures constructed by living organisms – Various reef-building organisms • Archaeocyathids (Cambrian) • Stromatoporoids • Corals (today) – Warm, clear, shallow water – Constricted to 30°N and S |
| What is the Michigan Basin? | an evaporate basin (circular) surrounded by large barrier reefs. |
| During which periods was the Kaskaskian Sequence? | Middle Devonian to Middle Mississippian |
| What process is the quartz sands from Kaskaskia used for? | Glass manufacturing |
| What type of rocks predominated the Kaskaskia sequence? | Carbonate (including reefs), and other evaporates |
| What were the Kaskaskian reefs like | Widespread, petroleum reservoirs, typical of Silurian and Devonian periods - including a back reef and fore reef used now for potash |
| What orogeny were Black Shales associated with? | Acadian orogeny |
| When was the Absaroka Sequence? | Pennsylvanian - Early Jurassic |
| What are Cyclothems? | Alternating stratigraphic sequences of marine and non-marine sediments, sometimes interbedded with coal seams |
| How were the Ancestral Rockies created? | collision of Gondwana with Laurasia (craton deformation) Erosion produced red, coarse arkosic sands and conglomerates |
| What is Arkose? | Feldspar-rich sandstone - associated with the Absaroka Sequence |
| When was the Appalachian Mobile Belt? | During the Sauk sequence |
| Which orogenies took place in the Appalachian Mobile Belt? | Taconic, Caledonian, Acadian, Hercynian |
| When was the Taconic orogeny? | Appalachian: Middle Ordivician |
| Notable characteristics of the Taconic include: | Subduction of Iapetus ocean Taconic Highlands erode build up clastic wedge: Queenston Delta |
| Evidence for Taconic Orogeny | – Volcanic activity – Metamorphism and igneous intrusions • Radiometric ages: 440-480 Ma |
| What is a clastic wedge? | thick accumulation of sediments or sedimentary rocks eroded and deposited landward of a mountain chain |
| What's the Catskill Delta? | a clastic wedge formed in the Acadian orogeny in upstate NY. It was formed in a tropical climate and contains fossil roots |
| When was the Acadian orogeny? | Appalacian: Late Silurian - Devonian Collision of Baltica and Laurentia Evidence of Acadian Orogeny – Metamorphic and igneous rocks Radiometric age: 360-410 Ma – Catskill Delta clastic wedge • Weathering of Catskill Mountains |
| When was the Hercynian-Alleghenian Orogeny? | Final orogeny of the Appalachian mobile belt |
| What's important about the Hercynian-Alleghenian orogeny? | Gondwana (Africa and South America) converged with Laurasia |
| When was the Cordilleran Mobile Belt? | Devonian |
| Antler Orogeny? | Cordilleran Caused by subduction 1st orogeny in the west |
| When was the Ouachita Mobile Belt? | Mississippian - Permian |
| What are some important details about the Ouachita Mobile Belt? | 2,100 km from Mississippi to Marathon, TX Most (80%) covered under younger sediments Exposed in Ouachita Mountains of OK and AR, and Marathon Mountains of TX Part of collision of Laurasia with Gondwana |
| What is the importance of microplates and terranes? | they helped to form Pangaea and explain anomalous geologic and paleo situations |
| What types of minerals came from the Paleozoic? | Sand Rock salt Gypsum/anhydrite (sheetrock) Limestone (cement) Tin, copper, gold (depleted) Lead, zinc, iron Petroleum, natural gas Coal |
| What was the Cambrian Explosion? | 520-535 Ma: “Evolution’s big bang” All principal phyla appeared within 10 m.y. Since then, these groups were modified by evolution |
| What caused the Cambrian Explosion? | Debated- possibilities: Extinction of life during Snowball Earth followed by global warming Not enough oxygen during Proterozoic Rifting of Rodina Transgression: expansion of shallow marine life Evolution of predators |
| What type of fauna emerged from the Cambrian? | Shelled! |
| What are the benefits of having a skeleton as fauna during the Cambrian? | Protection against UV Prevents drying out Increase of possible size Protection against predators |
| What is the Burgess Shale? | best preserved soft bodied fauna and flora |
| What are the three major groups of the Cambrian Marine Community? | Trilobites Brachiopods Archaeocyathids |
| What was new in the Ordovician Marine Community following the Cambrian MC? | Addition of 250 families mass extinction at end increase in predators - Nautiloids |
| What was the Ordovician Mass Extinction? | Second most severe in Earth history More than 100 families extinct Mostly tropical groups extinct Replacements adapted to deep or cold water Major cooling event: glaciation of Gondwana |
| What was new in the Silurian Marine Community? | Rediversification after Ordovician extinction. Sea Scorpions (Eurypterids) - new top predator - common throughout Paleo- increase in Silurian - spread into brackish water, fresh water, and swamps |
| When were the times of major reef building? | Silurian and Devonian |
| What was the Devonian mass extinction? | End of Devonian Worldwide near collapse of reef communities Land unaffected |
| What was the Permian Mass Extinction? | The largest extinction event ever • Took 8 m.y. |
| Why did the Permian Mass Extinction happen? | • Regression? • Climate change? • Deep sea anoxia? • Combination of events? |
| What are the Big Five Extinctions? | 1. Ordovician-Silurian extinction 439 mya 2. Late Devonian extinction 364 mya 3. Permian-Triassic extinction 251 mya 4. End Triassic extinction 199 - 214 mya 5. Cretaceous-Tertiary extinction 65 mya |
Created by:
Illogical