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by: Nia Greenfelder


Nia Greenfelder
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This 26 page Study Guide was uploaded by Nia Greenfelder on Tuesday October 13, 2015. The Study Guide belongs to GEOL 1003 at Louisiana State University taught by Staff in Fall. Since its upload, it has received 21 views. For similar materials see /class/222787/geol-1003-louisiana-state-university in Geology at Louisiana State University.




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Date Created: 10/13/15
Geol 1003 Study Guide for Exam 2 Tuesday March 9 2010 Read chapters 610 Know all terms that are written in bold letters use the glossary at the back of the book to help you better understand the terms At the end of each chapter Chapter Summary should prove to be useful The following are key concepts you should know Understand that exam questions may include other material mentioned in the textbook but most questions will come directly from the ppt lectures Chater 6 What is a biozone Zone 7 a rock unit who s upper and lower boundaries are based on the ranges of one or more taxa usually species in the biostratigraphic record What is a good index fossil 1 It is abundant enough in the stratigraphic record to be found easily 2 It is easily distinguished from other taxa 3 It is geographically widespread and thus can be used to correlate rocks over a large area 4 It occurs in many kinds of sedimentary rocks and therefore can be found in many places 5 It has narrow stratigraphic range which allows for precise correlation if its mere presence rather than its lowermost or uppermost occurrence is to used to de ne a zone Know the principles of magnetic stratigraphy and the time rock units associated with it Magnetic Stratigraphy is the use of magnetic properties of rocks for correlation Normal Intervals are when the polarity of the poles is the same that it is today and Reverse Intervals are when the poles were of opposite polarity Each interval is designated as a chron which is a polarity time rock unit A chron is either assigned a number or formally named for a geographic locality Know the various lithostratigraphic units Lithostratigraphy Subdivision of the stratigraphic record on the basis of physical or chemical characteristics of rock Lithostratigraphic units 39239 Formation 0 Local threedimensional bodies of rock 0 v Group v Member Stratigraphic section 2 Local outcrop of a formation that displays a continuous vertical sequence Type section v Locality where the unit is well exposed that de nes the unit What is a regression In a regression what sort of facies changes would you expect in a vertical sequence Remember Walther s Law see Figure 6716 to help answer the question Regression 7 A seaward migration ofa marine shoreline and ofnearby environments Walther s Law 7 States that when depositional environments migrate laterally sediments of one environment come to lie on top of sediments of an adjacent environment The facies one would expect to see in a regression or progradation would be a lagoon then a barrier island with the stratigraphic sections at a 3545 type angle headed toward the barrier island What is a hallllil e Ifthere are 100 parent isotopes of element X how many will remain after 4 hallllives Hallllil e 7 Interval of time for half ofparent to decay 625 isotopes of element x would remain What is alpha decay What is the atomic weight of an alpha particle An alpha particle consists oftwo protons and two neutrons a helium ion Hell Loss of an alpha particle L 39 two fewer protons converts Uranium Alpha Thorium 238 particle 234 Protons 92 7 2 go Neutrons 146 7 2 144 Who were Sedgwick and Murchison Which systems did they name Adam Sedgwick and Roderick Murchison were British geologists who named the Cambrian and Silurian systems in a joint paper published in 1835 principally based off of geologic studies of the distribution of Silurian rocks in Wales What is a marker bed What are examples ofmarker beds Marker bed 7 a distinctive bed of sediment that is useful for stratigraphic correlation Same age throughout 0 Ash fall 0 Bishop Tuff 0 Top of the Cretaceous system which is a thin layer of sediment over earth What are adaptations Adaptation Specialized features of animals and plants that perform one or more useful functions that allow that organism to excel in its environment What is homology Homology Presence in two different groups of animals or plants of organs that have the same ancestral origin but serve different functions What is particulate inheritance Who came up with this idea Gregor Mendel Organisms retain identities through generations 39239 Peas No blending Colors could be masked for generations What are mutations Mutations Alteration of genes provides for variability What is speciation Speciation Origin of a new species from two or more individuals of a preexisting species What are evolutionary radiations Evolutiona radiations Pattern of expansion from some ancestral adaptive condition represented by descendant taxa What is evolutionary convergence What are some examples Evolutiona Convergence Evolution of similar forms in two or more different biological groups Marsupials and placental mammals 7 Similar form 7 Isolated adaptive convergent evolution after initial divergence What is extinction In general terms what causes it Extinction Caused by extreme impacts of limiting factors 7 Predation 7 Diseases 7 Competition Pseudoextinction 7 Species evolutionary line of descent continues but members are given a new name High rates of extinction make useful index fossil 7 Ammonoids What is Cope s rule Cope s rule 7 Body size increases during evolution of a group of animals 7 Structural limitations on size Specialized adaptations limit evolution 7 Elephants 7 Manatees What is Dollo s Law Dollo s Law Evolutionary transition from at least several genetic changes is unlikely to be reversed by subsequent evolution Know the concept of continental drift and misinterpretations ofvarious observations Continental Drift 7 The idea that continents move horizontally over earth s surface One misobservation was that continents could not move due to their large size Scientists assumed that enormous felsic corridors of rock once connected the continents as a s 011 of bridge that later rested on the sea oor They used Madagascar and the fauna of India as their evidence Similar fossil record in different places made scientists assume that land bridges were real Who was Alfred Wegener Which supercontinent did he proposed existed in the late Paleozoic Alfred Wegener was a German meteorologist who proposed that virtually all the large continental areas of the modern world were once united in the late Paleozoic He labeled the supercontinent Pangaea Know the similarities of stratigraphic in r 39 39 39 quot Which four continents are mentioned in Figure 8 7 Brazil and South Africa have nearly identical geologic sequences India and Antarctica have similar geologic sequences as well 7 Glacial sediments 7 Coal AanCtlca South Africa South America Brazil India Triassic l Iraushales x Mesummmt Carboniferous What are DuToit s evidence for the existence ofGondwanaland 7 Expanded Wegener s ideas 7 Mesosaurus fossils Found on Gondwana continents Freshwater 7 Could not swim across Atlantic 7 Glossopeleris ora in Antarctica South Africa India and South America What is apparent polar wander The orientation of glacial markings on all continents suggests they were linked The Magnetic Pole is the point where all magnetic compasses point It is a long way away from the geographic pole due to anomalies in the way the Earth39s magnetic eld is generated by the rotation of its core According to Wikipedia its last measured location was 78 18 North 104 West and it is gradually moving to the northwest 7 First studies indicated poles had moved 7 Instead plates had moved 7 North American and European paths met pp 184 185 Harry Hess s explanation of the apparent youth ofthe ocean basins 7 Geopoetry Continents didn t plow through sea oor Entire crust moved 7 Crust must be created and destroyed Sedimentary cover too thin for four billion years of accumulation 7 Driven by convective cells Know how paleomagnetism provided a de nite test of plate tectonic theory see Figure 8 17 7 Vine and Matthews 1963 7 Measured magnetization of rocks across the Indian Ocean central ridge Found normal and reversed stripes Mirror image Age minions ofyears Zone of Cooling and magnetization What are features of subduction zones pp 189 190 Subduction 7 Descending slab undergoes dehydration which causes partial melting of the overlying mantle Volcanoes and Deepfocus earthquakes that originate more than 190 miles below earth s surface 7 Molten material is less dense rises Common around Paci c 7 Ring of Fire Location of most of the world s trenches What are hot spots What is an example Hotspot Small geographic area where heating and igneous activity occur within the crust Yellowstone Hawaii 39239 Thermal plume creates volcano 39239 Plate moves away from plume 39239 Stranded volcano cools leaves a chain 39239 Chain indicates direction and rate What is a guyot m 7 Had identi ed attopped seamounts in Paci c 7 Realized they were volcanoes that had been eroded by waves at sea level 7 Postulated as crust moved away from ridge it cools and sinks Chater 9 What are triple junctions Triple junction 7 Threearmed grabens at plate boundaries 7 Associated with doming Hot spot 7 May have multiple types of plate boundaries What are active margins Passive margin 7 Tectonically inactive areas of continental crust that accumulate sediment along shallow shelves Eastern US Active margin 7 Zones of tectonic deformation and igneous activity Western US What are synclines Syncline 7 Rocks folded concave up 7 Veitices at bottom Anticline 7 Rocks folded concave down 7 Veitices at top What is orogenesis Orogenesis 7 Process of mountain building 7 Orogenies Mountain building events What are ophiolites 7 Ophiolite Remnant of sea oor pinched up along suture 7 Sutuiing Uni cation of two continents along a subduction zone What is a foreland basin Foreland basin 7 Downwarping of lithosphere beneath actively forming mountain chain beyond fold and thrust belt 7 AXis is parallel to mountain chain 7 Rapid formation 7 Deep often ooded What is a molasse A thick prismlike body of molasse is also known as a Clastic Wedge 7 Molasse Nonmarine sediments 7 Mountain evolves 7 Fold and thrust moves inland 7 Chokes basin folds ysch 7 Alluvial fans oodplains etc i M Shales turbidites 7 Floods rapidly 7 Turbidites accumulate What mountain chain formed when Iberia collided with Europe The arenees 7 Formed when Iberia collided with Eurasia 7 Cretaceous and Paleogene 7 Iberia originally part of Eurasia 7 Subduction began reattached toward north 7 Ophiolites in northern Pyrenees mark suturing 7 Foreland basin received ysch then molasse Refer to Figure 9 16 The rate of plate movement and the angle of subduction Stationary plate Magma shifting inland as subduction angle is reduced 0 Change in angle means change in plate movement What are exotic terranes Exotic Terranes 7 a black of lithosphere that has been sutured to a much larger continent EX Black Hills of South Dakota The Pyrenees Mountains Michigan Basins Chater 10 What is a greenhouse gas What is an example named in the textbook 0 Greenhouse gases 7 Atmospheric gases that trap warming solar radiation near Earth s surface 7 Climate change throughout Earth s history 7 Carbon Dioxide Know what the flux M 7 Expansion and contraction of reservoirs with changes in rates at which elements or compounds ow through them Know about decomposers pp 220 221 Decomposers 7 Break down dead organic debris not consumed by animals 7 Bacteria Fungi Use respiration to break down tissues 7 Extract 02 release C02 How does burial alter the atmosphere How does burial alter the reservoir of reduce carbon Burial of plant debris affects atmospheric chemistry 39239 Removal of plants from system 0 Reservoir of reduced Carbon 0 Erosion usually balances it Change in burial can increase atmospheric concentrations 39239 Oz increases when carbon is buried o Decomposers cannot act on reduced carbon 0 Oxygen remains in atmosphere 0 In marine systems aquatic planktonic algae ful lls roles of plants P 223 Which carbon isotope do plants preferentially use in photosynthesis Carbon isotopes can trace some aspects of atmospheric chemistry 12C used by plants in greater proportion than present in the atmosphere Rapid burial impacts atmospheric isotopic ratio 7 Remove proportionately more 12C 7 Atmosphere emiched in 13C 7 Oceans follow Know Figure 108 and text associated with it A Burial rate of carbon B Burial rate of carbon balance weathering rate mm weathering rate At times a relatively large proportion of the carbon 12 from the atmosphere becomes locked up in the reservoir of buried organic matter leaving the atmosphere with an elevated ratio of carbon 13 to carbon How does chemical weathering affect C02 concentration in the atmosphere Weathering of CaC03 releases Ca and HCO339 7 Carried to oceans 7 Precipitate limestone skeletal material 7 Carbon is stored for long time period 7 Released upon subduction Why did atmospheric C02 declined during the Devonian Paleozoic Era 7 Devonian decrease Widespread forests Increase in weathering Know the effect temperature has regarding incorporation of oxygen isotopes into their shells p 232 7 Evolution of calcareous nannoplankton and foramjnifem I Pelagic oozes I Stored COZ as CaCOs 7 160 and 180 7 Organisms incorporate oxygen into shells I Ratio depends on I Temperature I Salinity I Ratio of water 7 Precipitate skeletons in proportion to water they live in What effect does ice sheet growth has on oxygen isotopes in the ocean p 234 I Salinity and glaciers affect seawater ratios 7 Salinity increases 180 abundance 7 Glaciers increase 160 abundance in ice on land and 18O abundance in seawater a 4 lsmopiully ArrV jam Isumpically 3 V WW quot9 lt quot541 s W C w H10 1 0 sysst is in balunze drops and he Mean heroines isotopically heavy mum WWW mm WWW Geol 1003 Study Guide for Exam 3 Thursday April 1 2010 Read chapters 1113 Know all terms that are written in bold letters use the glossary at the back of the book to help you better understand the terms At the end of each chapter Chapter Summary should prove to be useful The following are key concepts you should know Understand that exam questions may include other material mentioned in the textbook The Hadean and Archean Eons combined represent 45 0o of Earth s history p 242 Why are Archean rocks rare on the Earth s surface p 242 Precambrian rocks form less than 20 of the total area of rocks exposed at earth s surface Erosion has even destroyed many post Hayden rocks and metamorphism has so altered others that they can no longer be dated and therefore cannot be recognized as Precambrian Still other Precambrian rocks lie buried beneath younger sedimentary and volcanic rocks These problems are more profound for the Achaean record than the Proterozoic In addition simple unicellular fossils of Achaean rocks are un common and dif cult to assign to species and genera so that few are recognized as index fossils There is an absence of useful biostratigraphic data but despite its de ciencies the Achaean geologic record offers important evidence about the rst half of earth s history What are the three basic types of meteorites What do they consist of p 244 Stony meteorites Rocky composition stony like rock pieces of the earth s crust Iron meteorites Metallic composition Iron earth s core Stonyiron meteorites Mixture of rocky and metallic Proxy for core composition Stony iron formed from the impact of a stony meteorite and an iron meteorite Most date around 46 billion years ago thought to be the reminisce of matter around the solar system that never turned into planets What is the redshift How is it used to calculate the age ofthe universe p 245 Redshift the further light travels the redder it becomes a concept used to calculate the age of the big bang The evidence that the universe is expanding and makes it possible to estimate its age an increase in the wavelengths of light waves traveling through space a shift toward the end of the spectrum of wavelength where visible light is red The farther these light waves have travel through space the greater the redshift they have ungone Calculations based on redshifts indicated that about 137 billion years ago all the galaxies would have been at one spot the site of the big bang Expanding universe 7 Galaxies move apart Redshift 7 Originally concentrated into a single point Big Bang 7 15 billion years ago Age of universe Early Earth s surface was most likely a magma ocean p 248 How did the Moon form p 248 Moon formed from impact collision 7 Mantle of impacting body 7 Proportions of Fe and Mg differ from Earth s mantle Moon s maria 7 Originally thought to be seas 7 Craters formed by asteroids 7 Floored by basalts 7 Craters 38746 billion years old Earth also impacted 7 Tilted Earth 235 Moon 45 billion years old depending on craters and moon rocks that have been dated Two topographies lighter colored lunar high lands amp darker parts called Marias Marias are made of basalts formed during the late heavy bombardment period meteorites impacting newly formed planets lunar highland craters being formed The Marias are from after impact melted parts of the moon caused basalts to surface More craters in lunar highlands than in the Marias By counting the amount of craters you have in a certain area you can estimate the age of the moon How did the early atmosphere form p 249 Early atmosphere Early atmosphere Very little free oxygen in the atmosphere because there were no photosynthetic organism 7 Degassing from volcanic emissions 7 CH4 and NH3 abundant 7 Little Oz No photosynthesis How did the oceans form p 249 Earth s oceans 7 Volcanic emissions cooled condensed 7 Salts Carried to sea by rivers and introduced at ridges Approximately constant through time Early oceans come from volcanic emission from the steam At rst the water was not salty the salt came from ions dissolved at the mid ocean ridges places where the plates are spreading apart and water is peculating through rocks and certain elements are being dissolved Rain water weathering the rocks also carried the salt down to the ocean Why were Archean protocontinents small p251 252 Because of earth s hot interior heat from the mantle Continental crust formed during Archean High heat ow required small continents Small continents because of high heat ow during the archean During the Archean heat was 2 to 3 times higher than it is today Plates kept rifting apart and the continents remained small Small Archean fragments High heat ow limited continental thickness Map showing pieces of earth and continent material that found through out the world that are Archean in age They are fairly small pieces compared to the overall size of the continental crust small portions They are distributed throughout all the continents eX Archean fragments on Antarctica Consequence of high heat ow during the Archean maintained the thickness of the continent was very thin compared to today s continental crust Small in size Narrow continental shelves little space for sediment accumulation narrow shallow sea oor not a lot of space to deposit sediment no record of any continents that might of eXisted Many protocontinents bordered by subduction zonesgt narrow continental shelves High heat ow from the mantle was active plate tectonic system so no time to develop large continents What are the oldest materials yet discovered p 251 Certain grains of the mineral zircon are the oldest materials yet discovered that formed within the Earth s crust rather than arriving from outer space Zircon can be dated by means of uranium isotopes and their lead decay products The oldest zircon grains yet dated which eXist in Western Australia are 438 billion years old What evidence is there that photosynthesis was occurring by about 35 billion years ago p 256 Stromatolites 7 35 Billionyears 7 Suggest photosynthesis 7 Biomarkers for cyanobacteria 7 27 Billion years rst evidence for eucrayotes which is found in the biomarkers Where did life originate Which element must have been absent p 259 0 Along mid ocean ridges Midocean ridges 7 High heat 7 Chemosynthetic organisms 7 Atmospheric oxygen is the element that needed to be absent 7 Many kinds of Bacteria and Archaea inhabit the warm water of ridge environments See Figure 12 4 A chloroplast probably evolved from cyanobacteria A mitochondrion probably evolved from bacteria p 269 Photosynthetic Heterotrophs autotrop 5 Animals plants Multl7 cellular P L 1 life W MitochondrionT Protist Chloroplast Cyanobactena Union of 2 prokaryotic cells 7 Mitochondrion Allow cells to derive energy from their food by respiration Evolved from 1 prokaryotic cell 7 Chloroplast Site of photosynthesis Protozoan consumed retained cyanobacterial cell How did they come into being All have a MIT and EUK producers also have Chloroplasts bacteria eventually evolved to be a MIT evidence is MIT has DNA and RNA that s different from the rest of the cell Same thing happened with Protist Eukaryotes that later became plants or algae Bacteria again did not get digested and became Chloroplasts and then eventually became Protist What is the Ediacara Fauna p 273 o Proterozoic Life Nonskeletal fossils 7 Similar to Cnidaria 7 Imprints of soft bodied organisms 7 lt 570 Myears ago Ediacarian fauna 7 Lived before predators 7 Some similar to modern forms 7 The fauna is named for the Ediacara Hills in Australia where it can be found 7 The oldest are leaf shaped forms dating to 570 million years ago that occupied stationary positions on the sea oor and ones that were able to move appear in strata 560 million years old What is remobilization p 281 Remobilization 7 Alter character of preeXisting rocks 7 Reset radiometric clocks Remobilization regional metamorphism and deformation affecting a segment of crust previously altered by similar processes P 281 282 Know that the Canadian Shield is the main part ofthe North American craton and that it was assembled from ve microcontinents The Canadian Shield is the largest Precambrian shield in the world Basically is the center of a larger continent that eXisted in the past called Laurentia7 north america and greenland combined Accreted during the proterozoic The rst stage in the formation of Laurentia before it became part of a supercontinent was the assembly of at least 5 microcontinents into a sizable craton which took place within 100 million years Each of the microcontinents had formed during Archean time Today the microcontinents represent Archean terranes the largest of the terranes is the Superior Province What is the signi cance ofthe Keweenawan basalts p 282 283 Keweenawan basalts are rocksharden lavas that formed within the failed midcontinent rift They are eXposed near the southern border of the Canadian Shield Because these basalts are rich in iron and therefore are very dense their presence is also associated with a feature known as the midcontinental gravity high which is a local increase in Earth s gravitational eld as measured from the surface Know that the Grenville orogeny occurred on the eastern edge ofNorth America during the Proterozoic p 284 Grenville orogency occurred more than 11 billion years ago 9 another step in the accretion of the North American continent Mountain building that took place along the east coast of North America Cyrstalline rocks of Grenville age are best exposed in the Canadian portion of the Grenville Province The Grenville event entailed the collision of eastern North American with a landmass that would later become northern South America where there are remnants of mountain systems that are the same age as the Grenville orogenic belt Know about Rodinia p 284 During proterozoic Supercontinent that formed during this time is called Rodiniai fully assembled about 1 billion years ago Started to break up rift formedi became the paci c ocean 400 million years ago the continets that had separated came back together into the super continent pangea United Laurentia to other land masses Broke up 08707 Billion years ago Created Paci c Ocean Created failed rifts in Western Laurentia Which ocean formed as a result ofRodinia splitting apart p 285 The Paci c Ocean formed as a result of Rodinia splitting apart Read p 285 Did another Neoproterozoic supercontinent form near the end ofthe Proterozoic The large block that separated from Laurentia as the Paci c Ocean formed was eventually to become the eastern segment of Gondwanaland This block and Laurentia continued to separate and the Paci c Ocean continued to grow until their leading edges collided with opposites sides of the newly forming African craton In this was a new supercontinent may have formed with Africa as its center If Laurentia and Baltica had broken away from the supercontinent before African crust was fully assembled then a supercontinent never completely formed near the end of the Proterozoic period P 276 277 Know that cap carbonates may have been formed as a result ofglobal warming and that the cause for this warming may have been due to the release ofmethane hydrates Tillites are a good argument for a glacial period and on top of them we nd carbonate unites called cap carbonates they are depleted of carbon 13 have a lot of carbon 12 Light carbon in the cap carbonates release of methane hydrates Renewed formation of BIFs 7 universal sea ice led to lowoxygen conditions in the waters below but absent during Marinoan Cap carbonates Precipitation of carbonates occur in tropical seas Abrupt shift from glacial to tropical climate The fact that you have tillites that represent cold conditions and then carbonates which can only be deposited in shallow and warm waters indicated that the earth went very quickly from a glacial to a tropical climate A lot of aragonite in cap carbonate means there was a high level of bicarbonate ions means you had a lot of atmospheric carbon dioxide weathering silicate rocks What does the shift 19 billion years ago from Banded Iron Formations to red beds indicate p 278279 Banded Iron Formations ceasing around 19 billions years ago and the appearance of red beds around 2 billion years ago reveals the chemical nature of weathering during the time when the soils formed Banded Iron formations are among the oldest known rocks on Earth The term banded iron formation refers to a bedding con guration in which layers of chert often contaminated by iron that gives them red or brown color alternate with layers of other minerals that are richer in iron than the chert Banded iron formation apparently ceased to form about 19 billion years ago because the concentration of oxygen built up in the waters of the deep ocean re ecting a build up of oxygen in Earth s atmosphere Why did banded iron formations form during the Neoproterozoic glaciations They had stopped forming 19 billion years ago p 277 Proponents of the snowball Earth hypothesis suggest that universal sea ice led to low oxygen conditions in the waters below A criticism of the snowball Earth scenario is that it cannot seem to account for the fact that acritarchs survived in the ocean during the times of widespread glaciation P 243 Notice that during the Cambrian there was a global transgression sea level kept rising What did this mean for continents p 301 P 290 As the seas began to encroach on broadly exposed continents slightly before the beginning of the Cambrian siliciclastic sediments were eroded from the continents and accumulated around the continental margins When the seas encroached farther over most continents during Middle and Late Cambrian times a characteristic sedimentary pattern emerged 9 Siliciclastic sediments along the innermost belt shifted inland Notice that the Cambrian Period and the Phanerozoic Eon starts at 542 million years ago 444 Million years cam ends Cam ends de ned by mass extinction of tribolites not all died there was a radiation during the ORD 488 Million years ORD begins ORD begins by mass extinction by cooling of the planet through a mass of ice sheets in gonwanalan 542 Million years cam begins Cam begins de ned by presence of complex burrows What type ofindex fossil de nes the base ofthe Cambrian p 290 Although the Cambrian Period is famous for the rst appearance of many kinds of animals with skeletons the burrow labeled T reptichnus pedum was formed in many marine sediments before new skeletonized taxa arose and it is an index fossil whose rst occurrence has been designated as marking the base of the Cambrian System Know that monoplacophorans ancestors to mollusks and sponges rst appear in the Tommotian fauna p 291 Tommotian fauna appears abmbtly in the central portion of the Lower Cambrian record It was rst discovered in Siberia but is now recognized on many continents Contains the oldest known members of a few groups that survuve todayi sponges very simple animals monoplacphorans ancestral to present day mollusks and brachiopods When did the trilobites rst appear p 291 Disappearance of Tommotian fauna and appearance of 9 During the nal few million years of the Early Cambrian a new group of animals differing from the Tommotian fauna appeared in two important ways many were much larger and most belonged to phyla that survived to present time Among the new animals were trilobites group survived to the end of the Paleozoic Era Trilobites are popular with fossil collectors because segmented skeletons were heavily calci ed They lacked strong mouthparts for chewing they were deposit feeders Know that Early Cambrian reef builders were archaeocyathids p 295 The oldest organic reefs with skeletal frameworks are low mounds that formed in Early Cambrian time beginning in the Tommotian The main builders of these reefs were archaeocyathids suspension feeders that pumped water through holes in their vase shaped and bowl shaped skeletons Although archaeocyathids were the primary frame builder of Early Cambrian reefs producers of cyanobacterial mats and other taxa of unknown identity contributed a large volume of calcium carbonate to these reefs by encrusting archaeocyathid skeletons and binding them together Reefs Archeocyathids main ones Suspension feeders pump H20 through holes in skeleton Probably sponges Reef builders have changed over time during the CAM main builders were Archeocyathids Change in ocean chemistry Early Cambrian 7 high MgCa ratio Archaeocyathids major reef builders secreted highmagnesium calcite More calcium during the Cambrian which allowed animals to construct shells This shows the Magnesium Calcium ratio throughout Proterozoic PHGH more Magnesium this is at the beginning of the CAM when there wasn t a lot of mid ocean ridge activity LOW more calcium a lot of mid ocean ridge activity 7 after early CAM re ects that the major reed builders in the early CAM were Archaeocyathids sponge that secreted high Magnesium skeletons died off and were replaced by other types of reef builders Conodonts p 297 The earliest vertebrates Teeth which are abundant in the fossil record indicate they were the earliest known vertebrate reveal nothing of their body form but the recent discovery of fossils of their soft bodies has shown them to have been small swimming animals Middle and Late Cambrian 15 Million year duration EXpansion radiation of many groups Trilobites Echinoderns Conodonts Early sh rst evidence of sh Isolated bony external plates found Mass extinction oftrilobites at the end ofthe Cambrian p 298 Trilobites suffered a major extinction at the end of Cambrian time but recovered from this crisis and remained the most abundant members of many arine communities throughout Early Ordovician time Marked the end of the Cambrian Period Trilobite species that inhabited tropical seasismall planktonic formsiwere the ones that suffered in repeated mass extinctions Why did stromatolites decline in the Ordovician p 300 Grazing animals had largely restricted stromatolites to intertidal areas and destroyed their internal layering most of these were thrombolites The types of cyanobacteria that form stromatolites occur widely in modern seas but cyanobacteria proseper well enough to form 1 39 quot only in 39 that are hostile to nearly all animals fringes of land along the ocean that are ooded occasionally when tides are high subtidal channels in which very strong water movements exclude animals and hypersaline lagoons P 304 glaciation associated with Gondwanaland moving over the South Pole during Late Ordovician The ice cap that grew on Gondwanaland was centered near the south pole in what is now northern Africa Evidence of this glacial episode comes in many forms tillites scratches on bedrock and dropstones in marine sediment Near the end of the Ordovician Period a global drop in sea level caused an unconformity to form on top of a shallow water strata throughout the world Sea level fell because the ice cap that grew in Gondwanaland removed a signi cant amount of water from the global water cycle P 304 305 Know the causes of the two step end Ordovician mass extinction EndOrdovician mass extinction First pulse 7 growth of ice sheets cooling planet warm water adapted taxa became eXtinct Second pulse 7 warming climate caused cool wateradapted taxa to become eXtinct First pulse during the ORD a lot of organisms adapted to warm waters and because the growth of the ice sheets cooled the planet these organisms couldn t adapt to new environment and became eXtinct 7 Second ice sheet melted and the planet increased its temperature all the animals use to cool water and die out 7 ORD begins by mass eXtinction by cooling of the planet through a mass of ice sheets in gonwanaland First Eulse As ice sheets eXpanded and waters cooled Tropical taxa that were used to warm water were preferentially eliminated Waters cooled Cool water taxa eXpanded to tropical regions to replace the ones that had died off Taxa living in shallow epicontinental shallow seas on top of contintents seas became eXtinct because as you grow an ice sheet the sea level lowers so the habitats for these organisms living in these shallow water essentially banished 9 became eXtinct Sea level fall Second Eulse Ice sheet melted and the sea waters were warmed organisms adapted for cool waters from the rst pulse that invaded tropical regions became eXtinct Cool water species that had invaded tropical areas died off Warming waters Net result half of genera became eXtinct at endOrdovician Cyanobacterial mats and stromatolites ourished again because they were very abundant in the Proterozoic era as you go into CAM they decreased because the grazers disturbed them At the end of the ORB you have half of these grazers killed and then Stromatolites can ourish again Less grazing EndOrdovician glaciation destroyed many shallow water habitats epicontinental seas because shallow water habitats increased burial of organic matter ice sheets grow lower sea level 9 destroyed shallow water habitats 9 a lot of shallow water organisms eXtinct The Taconic Orogeny is the result of collision between p 305 Ordovician mountain building events in eastern North America are collectively termed the T acom39c orogeny This event was the rst of three orogenic episodes in what is now the Appalachian mountain belt The Taconic orogeny did not result from collision of two large landmasses Rather it entailed collisions between Laurentia and several islands that had occupied the ocean between Laurentia to the north and Baltica and Gondwanaland to the south What kind oftectonic environment did western Laurentia have in the Cambrian Ordovician p 312 Throughout CambroOrdovician time a passive margin bounded western Norh America A stable continental shelf passed diagonally across what is now the southeastern corner of California Coarse poorly sorted sediments derived from shallow water environments accumulated at the base of the steep carbonate platform that formed to continental shelf In many places there are great thicknesses of these limestones composed in part of debris from shallow water thrombolites and invertebrates Deposits that accumulate on deep sea oors beyond the platform include black limey mudstones and limestones


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All subscriptions to StudySoup are paid in full at the time of subscribing. To change your credit card information or to cancel your subscription, go to "Edit Settings". All credit card information will be available there. If you should decide to cancel your subscription, it will continue to be valid until the next payment period, as all payments for the current period were made in advance. For special circumstances, please email


StudySoup has more than 1 million course-specific study resources to help students study smarter. If you’re having trouble finding what you’re looking for, our customer support team can help you find what you need! Feel free to contact them here:

Recurring Subscriptions: If you have canceled your recurring subscription on the day of renewal and have not downloaded any documents, you may request a refund by submitting an email to

Satisfaction Guarantee: If you’re not satisfied with your subscription, you can contact us for further help. Contact must be made within 3 business days of your subscription purchase and your refund request will be subject for review.

Please Note: Refunds can never be provided more than 30 days after the initial purchase date regardless of your activity on the site.