Grand Canyon Geology PDF

included a photographer, a surveyor, and Paleozoic Era and were lithified into the seven life zones and three of the four three topographers. This expedition made...

included a photographer, a surveyor, and Paleozoic Era and were lithified into the seven life zones and three of the four three topographers. This expedition made rock formations that are now exposed in the desert types in North America. detailed topographic and geologic maps of canyon walls (Figure 2). the Grand Canyon area as well as the first Although best known for photographic record of the region. its geology, Grand Canyon Na- The rocks of the Grand Canyon record tional Park is home to a wide more than 1.5 billion years of Earth's history variety of mammals, reptiles, (Figure 4). The Vishnu Schist represents amphibians, birds, fish, and a major mountain-building episode that more than 1,500 known plant occurred during the Precambrian. Follow- species (Figure 5). Its great ing erosion of this mountain range, sedi- biological diversity is attributed ments were deposited in a variety of marine, to the fact that within its coastal, and terrestrial settings during the boundaries are five of the Kaibab Ls Permian Period Toroweap Fm Coconino Ss Hermit Shale Pennsylvanian Period Supai Fm Mississippian Period Redwall Ls Mauv Ls Cambrian Period Bright Angel Shale Colorado Tapeats Ss River Vishnu Schist Precambrian Reed Wicander Fm = Formation Ss = Sandstone Ls = Limestone Figure 4 The rocks of the Grand Canyon preserve more than 1.5 billion years of Earth's history, including periods of moun- Figure 5 White aspen and pinyon pine, shown here in tain building and erosion as well as periods of transgressions DeMotte Campground 28 km north of the North Rim, are and regressions of shallow seas over the area. the typical trees found in the Grand Canyon. The Tippecanoe Sequence much of the midcontinent and resulted from numerous cycles of weathering and erosion of Proterozoic and Cam- As the Sauk Sea regressed from the craton during the Early brian sandstones deposited during the Sauk transgression Ordovician, a landscape of low relief emerged. The exposed ( Figure 10.8). ▼ rocks were predominantly limestones and dolostones depos- The Tippecanoe basal sandstones were followed by ited earlier as part of the Sauk transgression. Because North widespread carbonate deposition (Figure 10.7). The lime- America was still located in a tropical environment when stones were generally the result of deposition by calcium the seas regressed, these carbonates experienced extensive carbonate–secreting organisms such as corals, brachio- erosion at that time ( Figure 10.7). The resulting craton- pods, stromatoporoids, and bryozoans. Besides the lime- ▼ wide unconformity thus marks the boundary between the stones, there were many dolostones that formed as a result Sauk and Tippecanoe sequences. of magnesium replacing calcium in calcite, thus convert- As in the Sauk Sequence, deposition of the Tippeca- ing limestones into dolostones. noe Sequence (Middle Ordovician–Early Devonian) began In the eastern portion of the craton, the carbonates with a major transgression onto the craton. This transgress- grade laterally into shales. These shales mark the farthest ing sea deposited clean and well-sorted quartz sands over extent of detrital sediments derived from weathering and most of the craton. The best known of the Tippecanoe basal erosion of the Taconic Highlands, which resulted from a sandstones is the St. Peter Sandstone, an almost pure quartz tectonic event taking place in the Appalachian mobile belt, sandstone used in manufacturing glass. It occurs throughout and which we will discuss later in the chapter. The Tippecanoe Sequence 201 Copyright 2016 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. ▼ Figure 10.5 Cambrian Rocks of the Grand Canyon West Upper Cambrian East Middle Cambrian Lower Cambrian Muav Limestone No nc on Bright Angel Shale form ity Tapeats Sandstone (a) Block diagram of Cambrian Precambrian igneous and strata exposed in the Grand Canyon, metamorphic basement rocks illustrating the transgressive nature of the three formations. Muav L imeston e Bright Angel Shale Tapea ts San dstone (b) Block diagram of Cambrian rocks exposed along the Bright Angel Trail, Grand Canyon, Arizona. Tippecanoe Reefs and Evaporites barrier reefs, create and maintain a steep seaward front that Organic reefs are limestone structures constructed by living absorbs incoming wave energy (Figure 10.9). As skeletal organisms, some of which contribute skeletal materials to the material breaks off from the reef front, it accumulates as reef framework ( Figure 10.9). Today, corals and calcareous talus along a fore-reef slope. The barrier reef itself is porous ▼ algae are the most prominent reef builders, but in the geologic and composed of many different reef-building organisms. past, other organisms played a major role (see Chapter 12). The lagoon area on the landward side of the reef is a low- Regardless of the organisms dominating reef energy, quiet-water zone where fragile, sediment-trapping communities, reefs appear to have occupied the same organisms thrive. The lagoon area can also become the site ecologic niche in the geologic past that they do today. of evaporite deposits when circulation to the open sea is Because of the ecologic requirements of reef-building restricted or cut off. Modern examples of barrier reefs are organisms, present-day reefs are confined to a narrow the Florida Keys, the Bahamas, and the Great Barrier Reef latitudinal belt between approximately 30 degrees of Australia. north and south of the equator. Corals, the major reef- Reefs have been common features in low latitudes building organisms today, require warm, clear, shallow since the Cambrian and have been built by a variety of water of normal salinity for optimal growth. organisms. The first skeletal builders of reeflike structures The size and shape of a reef are mostly the result of were archaeocyathids. These conical organisms lived dur- interactions among the reef-building organisms, the bot- ing the Cambrian and had double, perforated, calcareous tom topography, wind and wave action, and subsidence shell walls. Archaeocyathids built small mounds that have of the seafloor. Reefs also alter the area around them by been found on every continent except South America (see forming barriers to water circulation or wave action. Figure 12.6). Reefs typically are long, linear masses forming a barrier Beginning in the Middle Ordovician, stromatoporoid- between a shallow platform on one side and a comparatively coral reefs became common in the low latitudes, and deep marine basin on the other side. Such reefs, known as similar reefs remained so throughout the rest of the 202 CHAPTER 10 Early Paleozoic Earth History Copyright 2016 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.  Figure 10.6 Time-Transgressive Cambrian Facies ▼ West Wisconsin Craton Ohio East Margin of Appalachian No mobile belt nc on f or m ity Neoproterozoic basement rock Upper Cambrian Middle Cambrian Lower Cambrian Upper Precambrian (a) Block diagram from the craton interior to the Appalachian mobile belt margin showing the three major Cambrian facies and the time-transgressive nature of the units. Note the progressive development of a carbonate facies stemming from submergence of detrital source James S. Monroe areas by the advancing Sauk Sea. (b) Outcrop of cross-bedded Upper Cambrian sandstone in the Dells area of Wisconsin. Phanerozoic Eon. The burst of reef building seen sequences of rock salt and rock anhydrite are also found in the Late Ordovician through Devonian probably in the Michigan Basin (Figure 10.11). occurred in response to evolutionary changes triggered As the Tippecanoe Sea gradually regressed from the cra- by the appearance of extensive carbonate seafloors and ton during the Late Silurian, precipitation of evaporite miner- platforms beyond the influence of detrital sediments. als occurred in the Appalachian, Ohio, and Michigan basins The Middle Silurian rocks (Tippecanoe Sequence) (Figure 10.1). In the Michigan Basin alone, approximately of the present-day Great Lakes region are world-famous 1,500 m of sediments were deposited, nearly half of which for their reef and evaporite deposits ( Figure 10.10). The are halite and anhydrite. How did such thick sequences of ▼ best-known structure in the region, the Michigan Basin, is evaporites accumulate? One possibility is that when sea level a broad, circular basin surrounded by large barrier reefs. dropped, the tops of the barrier reefs were as high as or above No doubt these reefs contributed to increasingly restricted sea level, thus preventing the influx of new seawater into the circulation and the precipitation of Upper Silurian evapo- basin. Evaporation of the basinal seawater would result in rites within the basin ( Figure 10.11 on page 209). the formation of brine, and as the brine became increasingly ▼ Within the rapidly subsiding interior of the basin, concentrated, the precipitation of salts would occur. A sec- other types of reefs are found. Pinnacle reefs are tall, spin- ond possibility is that the reefs grew upward so close to sea dly structures up to 100 m high. They reflect the rapid level that they formed a sill, or barrier, that eliminated inte- upward growth needed to maintain themselves near sea rior circulation and allowed for the evaporation of the sea- level during subsidence of the basin (Figure 10.11a). water that produced a dense brine that eventually resulted in Besides the pinnacle reefs, bedded carbonates and thick evaporite deposits ( Figure 10.12 on page 210). ▼ The Tippecanoe Sequence 203 Copyright 2016 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.  Figure 10.7 Ordovician ▼ Paleogeography of North America Note that the position of the equator has shifted since the Cambrian, indicating that North America was rotating counterclock- wise at this time. Co rdil leran mobile belt Muddy Craton bottom m s tto nd Carbonate bottom in bo hla pla dy Hig ial Mud v nic Allu T aco t b el bile mo an r i to Land ch ua la pa eq p Mountains a–A leo it Ouach Pa Epeiric sea ttom Deep ocean Muddy bo Oklahoma Figure 10.8 Transgressing Tippeca- ▼ South noe Sea The transgression of the Tippe- canoe Sea resulted in the deposition of Craton the St. Peter Sandstone (Middle Ordovi- cian) over a large area of the craton. Tippecanoe sequence Iowa North Unconformity Lower Ordovician Transgressing Tippecanoe Sea St. Peter Sandstone Sauk Sequence 204 CHAPTER 10 Early Paleozoic Earth History Copyright 2016 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.  Figure 10.9 Organic Reefs ▼ ©John A. Anderson /Shutterstock.com Reef flat Back-reef Reef core Open sea Lagoon Land (a) Present-day reef com- munity showing various Talus reef-building organisms. Fore-reef slope Barrier reef Lagoon (b) Block diagram of a reef showing the different environments within the reef complex. With North America still near the equator during the fingering of the limestone, anhydrite, and halite facies may Silurian Period (Figure 10.2c), temperatures were probably occur, however, because of variations in the amount of sea- high. As circulation to the Michigan Basin was restricted water entering the basin and changing geologic conditions. or ceased altogether, seawater within the basin evaporated Thus, the periodic evaporation of seawater just dis- and began forming brine. Because the brine was heavy, it cussed could account for the observed vertical and lateral concentrated near the bottom, with minerals precipitating distribution of evaporites in the Michigan Basin. Associated on the basin floor and forming evaporite deposits. When with those evaporites, however, are pinnacle reefs, and the seawater flowed back into the Michigan Basin (over the sill organisms constructing those reefs could not have lived in or through channels cut in the barrier reefs), this replen- such a highly saline environment (Figure 10.11). How, then, ishment added new seawater, allowing the process of brine can such contradictory features be explained? Numerous formation and precipitation of evaporites to repeat itself. models have been proposed, ranging from cessation of reef The order and type of salts precipitating from seawa- growth followed by evaporite deposition to alternation of ter depend on their solubility, the original concentration reef growth and evaporite deposition. Although the Michi- of seawater, and local conditions of the basin. In general, gan Basin has been studied extensively for years, no model salts precipitate in a sequential order beginning with the yet proposed completely explains the genesis and relation- least soluble and ending with the most soluble. Therefore, ship of its various reef, carbonate, and evaporite facies. calcium carbonate usually precipitates first, followed by gypsum*, and finally halite. Many lateral shifts and inter- The End of the Tippecanoe Sequence *Recall from Chapter 6 that gypsum (CaSO4 · 2H2O) is the common sulfate precipitated from seawater, but when deeply buried, gypsum loses its water By the Early Devonian, the regressing Tippecanoe Sea had and is converted to anhydrite (CaSO4). retreated to the craton margin, exposing an extensive lowland The Tippecanoe Sequence 205 Copyright 2016 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.  Figure 10.10 Silurian Paleogeography of North America Note the development of reefs in the Michigan, Ohio, ▼ and Indiana–Illinois–Kentucky areas. 206 CHAPTER 10 Early Paleozoic Earth History  Figure 10.11 The Michigan Basin ▼ (a) Generalized block diagram of the northern Michigan Basin during the Silurian Period. From K. J. Mesolella, J. D. Robinson, L. M. McCormick, and A. R. Ormiston, “Cyclic Deposition of Silurian Carbonates and Evaporates in Michigan Basin,” AAPG Bulletin, Vol. 58, No. 1 (Fig. 6, p. 40). Copyright © 1958 AAPG. Reprinted by permission of AAPG, whose permission is required for future use. Laminar stromatoporoid Barrier Anhydrite Halite reef Evaporite Carbonate Pinnacle 0 reef Meters Sue Monroe 100 (b) Limestone from the carbonate facies. Stromatoporoid barrier reef Stromatolites Algal Coral algal Crinoidal Laminar Niagara stromatoporoid Formation Clinton Formation Sue Monroe Sue Monroe (c) Cross section of a stromatoporoid colony from the stromatoporoid (d) Core of rock salt from the evaporite facies. barrier reef facies. was part of the global tectonic regime that sutured the conti- plate boundary), the Appalachian mobile belt was born nents together, forming Pangaea by the end of the Paleozoic. (Figure 10.13b). The resulting Taconic orogeny—named Throughout Sauk time (Neoproterozoic–Early Ordo- after the present-day Taconic Mountains of eastern New vician), the Appalachian region was a broad, passive, York, central Massachusetts, and Vermont—was the first continental margin. Sedimentation was closely balanced of several orogenies to affect the Appalachian region. by subsidence as extensive carbonate deposits succeeded The Appalachian mobile belt can be divided into two thick, shallow marine sands. During this time, move- depositional environments. The first is the extensive ment along a divergent plate boundary was widening the shallow-water carbonate platform that formed the broad Iapetus Ocean ( Figure 10.13a). eastern continental shelf and stretched from Newfoundland ▼ Beginning with the subduction of the Iapetus plate to Alabama (Figure 10.13a). It formed during the trans- beneath Laurentia (an oceanic–continental convergent gression of the Sauk Sea onto the craton when carbonates The Appalachian Mobile Belt and the Taconic Orogeny 207 Copyright 2016 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.  radiometric ages corresponding to the Middle to Late Ordovician. In addition, regional metamorphism coincides with the radiometric dates. The final piece of evidence for the Taconic orogeny is the development of a large clastic wedge, an extensive accu- mulation of mostly detrital sediments deposited adjacent to an uplifted area. These deposits are thickest and coarsest nearest the highland area and become thinner and finer grained away from the source area, eventually grading into the carbonate facies on the craton ( Fig- ▼ ure 10.14). The clastic wedge resulting from the erosion of the Taconic High- lands is referred to as the Queenston Delta. Careful mapping and correlation of its deposits indicate that more than 600,000 km3 of rock were eroded from Evaporation produces the Taconic Highlands. On the basis a dense brine that sinks of this figure, geologists estimate that and forms a thick Inflow of seawater the Taconic Highlands were at least evaporite deposit replenishes water 4,000 m high. Shallow sill impedes lost by evaporation the outflow of dense The Taconic orogeny marked the brine from the basin first pulse of mountain building in the Appalachian mobile belt and was a Figure 10.12 Evaporite Sedimentation Silled basin model for evaporite sedimentation by response to the subduction taking place ▼ direct precipitation from seawater. Vertical scale is greatly exaggerated. beneath the east coast of Laurentia. As the Iapetus Ocean narrowed and closed, were deposited in a vast, shallow sea. Stromatolites, mud another orogeny occurred in Europe during the Silurian. cracks, and other sedimentary structures and fossils are The Caledonian orogeny was essentially a mirror image of evidence of the shallow water depth on the platform. the Taconic and Acadian orogenies (see Chapter 11) and Carbonate deposition ceased along the east coast was part of the global mountain-building episode that took during the Middle Ordovician and was replaced with place during the Paleozoic Era (Figure 10.2c). Even though deepwater deposits characterized by thinly bedded black the Caledonian orogeny occurred during the Tippecanoe shales, graded beds, coarse sandstones, graywackes, Sequence, we discuss it in the next chapter because it was and associated volcanic material. This suite of sedi- intimately related to the Devonian Acadian orogeny. ments marks the onset of mountain building—in this case, the Taconic orogeny. The subduction of the Iape- tus plate beneath Laurentia resulted in volcanism and downwarping of the carbonate platform (Figure 10.13b). Early Paleozoic Mineral Throughout the Appalachian mobile belt, facies patterns, paleocurrents, and sedimentary structures all indicate Resources that these deposits were derived from the east, where the Early Paleozoic-age rocks contain a variety of important Taconic Highlands and associated volcanoes were rising. mineral resources, including sand and gravel for construc- Additional structural, stratigraphic, petrologic, and tion, building stone, and limestone used in the manufacture sedimentologic evidence has provided much information of cement. Important sources of industrial, or silica, sand are on the timing and origin of this orogeny. For example, at the Upper Cambrian Jordan Sandstone of Minnesota and many locations within the Taconic belt, pronounced angu- Wisconsin, the Lower Silurian Tuscarora Sandstone in Penn- lar unconformities occur where steeply dipping Lower sylvania and Virginia, and the Middle Ordovician St. Peter Ordovician rocks are overlain by gently dipping or hori- Sandstone. The latter, the basal sandstone of the Tippecanoe zontal Silurian and younger rocks. Sequence (Figure 10.8), occurs in several states, but the best- Other evidence includes volcanic activity in the known area of production is in La Salle County, Illinois. form of deep sea lava flows, volcanic ash layers, and Silica sand has several uses, including the manufacture intrusive bodies in the area of present-day Georgia to of glass, refractory bricks for blast furnaces, and molds for Newfoundland. These igneous rocks show a clustering of casting iron, aluminum, and copper alloys. Some silica 208 CHAPTER 10 Early Paleozoic Earth History Copyright 2016 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.  Figure 10.13 Neoproterozoic to Late Ordovician Evolution of the Appalachian Mobile Belt ▼ Appalachian carbonate platform Iapetus Ocean Spreading Laurentia ridge (North America) (a) During the Neoproterozoic to the Early Ordovi- cian, the Iapetus Ocean was opening along a diver- gent plate boundary. Both the east coast of Laurentia and the west coast of Baltica were passive continen- tal margins with large carbonate platforms. Passive margin Baltica (Europe) Oceanic–continental Narrowing Taconic plate boundary Iapetus Ocean Caledonian Highlands Highlands (b) Beginning in the Middle Ordovician, the passive margins of Laurentia and Baltica changed to active oceanic–continental plate boundaries, resulting in orogenic activity (Figure 10.2b). Queenston Delta clastic wedge Queenston Delta Epeiric sea Figure 10.14 Reconstruction of the ▼ clastic wedge Taconic Highlands Taconic Highlands and Queenston Delta Clastic Craton Wedge The Queenston Delta clastic wedge, resulting from the erosion of the Taconic High- lands, consists of thick, coarse-grained detrital sediments nearest the highlands that thin later- ally into finely grained sediments in the epeiric seas covering the craton. Un co nf or it y m Upper Ordovician Lower Ordovician Cambrian Early Paleozoic Mineral Resources 209 Copyright 2016 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. sands, called hydraulic fracturing sands, are pumped into Ordovician rocks also contain these metals. These depos- wells to fracture oil or gas-bearing rocks and provide per- its, mined since 1720, have been largely depleted. Now meable passageways for the oil or gas to migrate to the most lead and zinc mined in Missouri comes from Missis- well (see Chapter 11 Perspective). sippian-age sedimentary rocks. Thick deposits of Silurian evaporites, mostly rock salt Elsewhere, most of the gold and copper mined in New (NaCl) and rock gypsum (CaSO4·2H2O) altered to rock South Wales, Australia, comes from Ordovician volcanics anhydrite (CaSO4), underlie parts of Michigan, Ohio, New of the Macquarie Arc. York, and adjacent areas in Ontario, Canada. These rocks The Silurian Clinton Formation crops out from Ala- are important sources of various salts, as well as wallboard. bama north to New York, and equivalent rocks are found In addition, barrier and pinnacle reefs in carbonate rocks in Newfoundland, Canada. This formation has been mined associated with these evaporites are the reservoirs for oil for iron in many places. In the United States, the richest and gas in Michigan and Ohio. ores and most extensive mining occurred near Birming- The host rocks for deposits of lead and zinc in south- ham, Alabama, but only a small amount of ore is currently east Missouri are Cambrian dolostones, although some produced in that area. Summary Table 10.1 summarizes the Early Paleozoic geologic history of Sea covered the craton except for parts of the Canadian the North American craton and mobile belts, as well as global Shield and the Transcontinental Arch, a series of large, events, sea level changes, and major evolutionary events. northeast–southwest trending islands. Continents consist of two major components: (1) a rela- The Tippecanoe Sequence began with deposition of an tively stable craton over which epeiric seas transgressed extensive sand unit over the exposed and eroded Sauk and regressed and (2) a relatively stable craton surrounded landscape and was followed by extensive carbonate by mobile belts in which mountain building took place. deposition. In addition, large barrier reefs surrounded Six major continents and numerous microcontinents many cratonic basins, resulting in evaporite deposition and island arcs existed at the beginning of the Paleozoic within these basins. Era; all of these were dispersed around the globe at low The eastern edge of North America was a stable carbon- latitudes during the Cambrian. ate platform during the Sauk Sequence. During the During the Ordovician and Silurian, plate movements Tippecanoe Sequence, the eastern margin of North resulted in a changing global geography. Gondwana America changed from a passive to an active conti- moved southward and began to cross the South Pole nental margin as an oceanic–continental convergent as indicated by Upper Ordovician tillite deposits; the plate boundary formed. Movement along this oceanic– microcontinent Avalonia separated from Gondwana continental convergent plate boundary resulted in the during the Early Ordovician and collided with Baltica Taconic orogeny, the first of three major orogenies to during the Late Ordovician–Early Silurian; and Baltica, affect the Appalachian mobile belt. along with the newly attached Avalonia, moved north- The newly formed Taconic Highlands shed sediments westward relative to Laurentia and collided with it to into the western epeiric sea, producing a clastic wedge form Laurasia during the Silurian. that geologists call the Queenston Delta. Geologists divide the geologic history of North Early Paleozoic-age rocks contain a variety of mineral America into cratonic sequences that formed as a result resources, including building stone, limestone for ce- of craton-wide transgressions and regressions. ment, silica sand, hydrocarbons, evaporites, and various The Sauk Sequence began with a major marine trans- metallic ores. gression onto the craton. At its maximum, the Sauk Important Terms Appalachian mobile belt, p. 194 Gondwana, p. 195 Sauk Sequence, p. 198 Baltica, p. 195 Iapetus Ocean, p. 207 sequence stratigraphy, p. 198 China, p. 195 Kazakhstania, p. 195 Siberia, p. 195 clastic wedge, p. 208 Laurentia, p. 195 Taconic orogeny, p. 207 Cordilleran mobile belt, p. 194 mobile belt, p. 194 Tippecanoe Sequence, p. 201 craton, p. 193 organic reef, p. 202 Transcontinental Arch, p. 198 cratonic sequence, p. 197 Ouachita mobile belt, p. 194 epeiric sea, p. 194 Queenston Delta, p. 208 210 CHAPTER 10 Early Paleozoic Earth History Copyright 2016 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. Review Questions 1. An elongated area marking the site of mountain build- 6. Discuss how the Cambrian rocks of the Grand Canyon il- ing is a lustrate the sedimentation patterns of a transgressive sea. a. cyclothem; b. mobile belt; c. platform; 7. What evidence in the geologic record indicates that the d. shield; e. craton. Taconic orogeny occurred? 2. A major transgressive–regressive cycle bounded by craton- 8. Discuss why cratonic sequences are a convenient way to wide unconformities is a(n) study the geologic history of the Paleozoic Era. a. biostratigraphic unit; b. cratonic sequence; 9. What are some methods geologists use to determine c. orogeny; d. shallow sea; e. cyclothem. the locations of continents that existed during the 3. The Taconic orogeny resulted from what type of plate Paleozoic Era? boundary activity? 10. According to estimates made from mapping and correla- a. Continental–continental convergent; tion, the Queenston Delta contains more than 600,000 b. Transform; c. Oceanic–oceanic convergent; km3 of rock eroded from the Taconic Highlands. Based d. Divergent; on this figure, geologists estimate that the Taconic High- e. Oceanic–continental convergent. lands were at least 4,000 m high. They also estimate 4. The relatively stable and immobile parts of continents, that the Catskill Delta (see Chapter 11) contains three which form the foundation on which Phanerozoic sedi- times as much sediment as the Queenston Delta. From ments were deposited, make up the what you know about the geographic distribution of a. shield; b. platform; c. mobile belt; the Taconic Highlands, estimate how high the Acadian d. craton; e. none of the previous answers. Highlands might have been. 5. The eastern margin of Laurentia changed from a pas- sive plate margin to an active plate margin during which sequence? a. Zuni; b. Tippecanoe; c. Sauk; d. Kaskaskia; e. Absaroka Important Terms 211 Copyright 2016 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it.  TABLE 10.1 Summary of Early Paleozoic Geologic and Evolutionary Events Relative Cordilleran Craton Ouachita Appalachian Major Events Major Sequence Geologic Changes Mobile Mobile Mobile Belt Outside Evolutionary Period in Sea Level Belt Belt North Events America Rising Falling 416 Acadian First jawed orogeny fish evolve Extensive barrier Caledonian Silurian Early land reefs and orogeny plants— evaporites seedless common vascular plants 444 Tippecanoe Extinction of Queenston many marine Delta clastic invertebrates wedge Continental near end of Taconic glaciation in Ordovician orogeny Southern Hemisphere Age (millions of years) Present sea Plants move Ordovician level to land? Transgression of Tippecanoe Sea Regression Major adaptive exposing large radiation of all areas to erosion invertebrate groups 488 Many Canadian Shield trilobites and Transcon- become Sauk tinental Arch extinct near only areas end of above sea level Cambrian Cambrian Earliest vertebrates— jawless fish Transgression evolve of Sauk Sea 542 212 CHAPTER 10 Early Paleozoic Earth History Copyright 2016 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. H. Mark Weidman Photography/Alamy The coal being mined in this aerial view of an open-pit coal mine northeast of Somerset, Pennsylvania, is Pennsylvanian in age. It formed 11 as a result of tremendous accumulations of plant material deposited in a swampy environment as part of a cyclothem, or repetitive sequence of marine and nonmarine cycles of deposition. Notice the dragline (digging machine) on top of the coal deposit for scale. Late Paleozoic Earth History OUTLINE The Absaroka Sequence Introduction What Are Cyclothems and Why Are They Important? Cratonic Uplift—The Ancestral Rockies Late Paleozoic Paleogeography The Middle Absaroka—More Evaporite Deposits and Reefs The Devonian Period The Carboniferous Period History of the Late Paleozoic Mobile Belts The Permian Period Cordilleran Mobile Belt Ouachita Mobile Belt Late Paleozoic Evolution of North America Appalachian Mobile Belt The Kaskaskia Sequence What Role Did Microplates and Terranes Play in the Formation Reef Development in Western Canada of Pangaea? Black Shales Late Paleozoic Mineral Resources Glaciation Summary The Late Kaskaskia—A Return to Extensive Carbonate Deposition PERSPECTIVE Hydraulic Fracturing: Pros and Cons 213 Copyright 2016 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. CHAPTER OBJECTIVES Today, coal is used primarily to generate electricity. In At the end of this chapter, you will have learned that the United States, coal-fired power plants provided 37.5% of the electricity generated in 2012, down from 50% in Movement of the six major continents resulted in the formation 2007 as many utilities began changing over to lower-cost of the supercontinent Pangaea at the end of the Paleozoic. natural gas. Other uses of coal are for iron and steel pro- In addition to the large-scale plate interactions during the duction; liquefaction, in which coal is converted into liq- Paleozoic, microplate and terrane activity also played an important uid fuels such as diesel and gasoline; home heating; and role in forming Pangaea. any industrial application requiring large amounts of heat, Most of the Kaskaskia Sequence is dominated by carbonates such as in cement manufacturing. and associated evaporites. Coal is generally mined in two ways, and the method used depends on the geology of the coal deposit. In under- Transgressions and regressions over the low-lying craton during ground mining, shafts are drilled into the coal seam (a the Absaroka Sequence resulted in cyclothems and the formation layer or bed of coal) and the seam is then followed until as of coals. much of the coal that can be extracted is removed. Under- During the Late Paleozoic Era, mountain-building activity took ground mining currently accounts for about 60% of the place in the Appalachian, Ouachita, and Cordilleran mobile belts. world’s coal production. The Caledonian, Acadian, and Hercynian (Variscan)–Alleghenian When the coal is close to the surface, and of wide- orogenies were all part of the global tectonic activity resulting spread extent, open-pit, or surface, mining is used. This from the assembly of Pangaea. method involves removing the surface rocks and expos- ing the coal seam, where it can be drilled or blasted and Late Paleozoic-age rocks contain a variety of mineral resources, in- cluding petroleum, coal, evaporites, and various metallic deposits. loaded onto trucks or conveyers (see chapter opening photo). One type of surface mining, called mountaintop removal mining, literally involves removing the top of a mountain and filling in the adjacent valleys with the over- burden. This method of mining is highly controversial Introduction because of the damage done to the surrounding environ- ment as a result of the denudation of the surface. Coal. The name conjures up various images. For some, it is In 2012, world production of coal amounted to what helped fuel the Industrial Revolution in England dur- 7,865 million tons. The top producer in 2012 (and one of ing the 18th and 19th centuries. For others, it brings to mind its largest consumers) was China, which mined 3,650 million the many hazards associated with underground coal mining tons. The United States is a distant second, having mined and the denudation of the landscape caused by open-pit sur- 922 million tons, followed by India, the European Union, face mining. Coal has also been closely linked with global Australia, and Indonesia. As impressive as these numbers warming as a result of its use in industry and power plants. are, it is estimated that based on current production levels, Coal is a biochemical sedimentary rock composed of the United States alone has recoverable reserves of coal to the partially altered, compressed remains of land plants last more than 200 years. (see Figure 2.16b). It forms in anaerobic swamps and Despite its abundance and contribution to the world’s bogs, where decomposition of plant matter is interrupted energy supply, coal has disadvantages. The extraction and and the accumulating vegetation is altered into peat (par- burning of coal releases sulfur dioxide, nitrogen oxide, and tially decayed organic matter). If the peat is later covered many heavy metals into the environment that are harmful and buried by sediments, it can be converted into coal. to human health and have been linked to acid rain (see Much of the world’s coal formed during the Late Car- Epilogue). Furthermore, the burning of coal, especially in boniferous (Pennsylvanian Period), when widespread power plants, releases large quantities of carbon dioxide, swampy conditions provided the ideal conditions for coal which cause climate change and global warming. But until formation. The coal mined from these Carboniferous cleaner sources or renewable sources of energy become deposits has fueled the economies of many of the world’s economically feasible to use, coal will continue to play a nations. But coal did not become an important commodity major role in the world’s energy landscape. until it was needed in quantity to power the steam engines and furnaces of factories during the Industrial Revolution. Recall that William Smith, an English civil engineer who was involved in surveying and building canals in southern Late Paleozoic England and who published the world’s first geologic map, got his start mapping various coal mines. He soon turned Paleogeography his attention to finding the most efficient canal routes for The Late Paleozoic was marked by continental collisions, bringing coal to market. In fact, coal production in England mountain building, fluctuating sea levels, and varied cli- increased from 2.7 million tons in 1700 to 50 million tons