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58-671: The name of the range derives from the St. Francis River , which originates in the St. Francois Mountains. The origin of the river's name, which also was originally spelled "François" in the French manner , is unclear. The area, as part of the Louisiana district of New France , is near some of the earliest French settlements in Missouri, where many French place names survive. Some sources conjecture that

116-622: A cataclysm known as " The Great Dying ", the third and most severe Phanerozoic mass extinction. The early Cambrian climate was probably moderate at first, becoming warmer over the course of the Cambrian, as the second-greatest sustained sea level rise in the Phanerozoic got underway. However, as if to offset this trend, Gondwana moved south, so that, in Ordovician time, most of West Gondwana (Africa and South America) lay directly over

174-642: A clear stream into a slow and silt -laden muddy river as it enters the flat lands of the Mississippi embayment . In its lower course the river parallels Crowleys Ridge and is part of a navigation and flood-control project that encompasses a network of diversion channels and ditches along it and the Castor and Little rivers. Below the mouth of the Little River in Poinsett County, Arkansas ,

232-445: A foothold on land. These early plants were the forerunners of all plant life on land. During this time, there were four continents: Gondwana (Africa, South America, Australia, Antarctica, Siberia), Laurentia (North America), Baltica (Northern Europe), and Avalonia (Western Europe). The recent rise in sea levels allowed many new species to thrive in water. The Devonian spanned from 419–359 million years ago. Also known as "The Age of

290-764: A good example of columnar jointing in igneous rhyolite , the same process that formed Devils Tower in Wyoming and the Giant's Causeway in Ireland . The columnar jointing in this area is called the Devil's Honeycomb . Mountains in this range include; Taum Sauk Mountain , Bell Mountain , Buford Mountain , Proffit Mountain , Pilot Knob , Hughes Mountain , Goggin Mountain and Lead Hill Mountain. The elevations range from 500 to 1,772 feet (152 to 540 meters). Taum Sauk Mountain

348-450: A wide range of sediments and environments, which aids correlation between different sites around the world. Trace fossils reflect the complexity of the body plan of the organism that made them. Ediacaran trace fossils are simple, sub-horizontal feeding traces. As more complex organisms evolved, their more complex behaviour was reflected in greater diversity and complexity of the trace fossils they left behind. After two decades of deliberation,

406-743: Is a tributary of the Mississippi River , about 426 miles (686 km) long, in southeastern Missouri and northeastern Arkansas in the United States . The river drains a mostly rural area and forms part of the Missouri-Arkansas state line along the western side of the Missouri Bootheel . The river rises in a region of granite mountains in Iron County, Missouri , and flows generally southwardly through

464-663: Is considered the first Phanerozoic mass extinction event, and the second deadliest. The Silurian spanned from 444–419 million years ago. The Silurian saw the rejuvenation of life as the Earth recovered from the previous glaciation. This period saw the mass evolution of fish, as jawless fish became more numerous, jawed fish evolved, and the first freshwater fish evolved, though arthropods, such as sea scorpions , were still apex predators . Fully terrestrial life evolved, including early arachnids, fungi, and centipedes. The evolution of vascular plants ( Cooksonia ) allowed plants to gain

522-476: Is consistent with emplacement within resurgent calderas . The exposed igneous rocks of the St. Francois are surrounded at depth by the slightly younger (~100 my) widely distributed igneous Spavinaw terrane . The Spavinaw rocks are intersected in drill core across southern Missouri, southern Illinois, northern Arkansas, southern Kansas and northeastern Oklahoma. The Spavinaw rocks occur in outcrop only near Spavinaw, Oklahoma . The rhyolites and ash flow tuffs of

580-463: Is debated whether the igneous activity was related to a hotspot , like Yellowstone, or whether it was related to an ancient subduction zone . The St. Francois Mountains are the center of the Lead Belt , a mining region yielding lead , iron , baryte , zinc , silver , manganese , cobalt , and nickel ores. Historic Mine La Motte near Fredericktown was the site of lead mining activity by

638-567: Is derived from the Greek palaiós (παλαιός, "old") and zōḗ (ζωή, "life") meaning "ancient life". The Paleozoic was a time of dramatic geological, climatic, and evolutionary change. The Cambrian witnessed the most rapid and widespread diversification of life in Earth's history, known as the Cambrian explosion , in which most modern phyla first appeared. Arthropods , molluscs , fish , amphibians , reptiles , and synapsids all evolved during

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696-683: Is the first of three geological eras of the Phanerozoic Eon. Beginning 538.8 million years ago (Ma), it succeeds the Neoproterozoic (the last era of the Proterozoic Eon) and ends 251.9 Ma at the start of the Mesozoic Era. The Paleozoic is subdivided into six geologic periods (from oldest to youngest), Cambrian , Ordovician , Silurian , Devonian , Carboniferous and Permian . Some geological timescales divide

754-525: Is the highest peak in the range, and the highest point in the state, with an elevation of 1,772 ft (540 m). In the southernmost reaches of the range is Clark's Mountain, elevation 1,450 ft (440 m), with the distinction of being the highest isolated point in the range and in the state; it reaches its top from surrounding terrain of about 900 ft (270 m) in less than two miles (3.2 km). Black Mountain, in Madison County, has

812-575: Is the sudden appearance of nearly all of the invertebrate animal phyla in great abundance at the beginning of the Cambrian. The first vertebrates appeared in the form of primitive fish, which greatly diversified in the Silurian and Devonian Periods. The first animals to venture onto dry land were the arthropods. Some fish had lungs, and powerful bony fins that in the late Devonian, 367.5 million years ago, allowed them to crawl onto land. The bones in their fins eventually evolved into legs and they became

870-550: The Appalachians , Caledonides , Ural Mountains , and mountains of Tasmania . The Cambrian spanned from 539–485 million years ago and is the first period of the Paleozoic Era of the Phanerozoic. The Cambrian marked a boom in evolution in an event known as the Cambrian explosion in which the largest number of creatures evolved in any single period of the history of the Earth. Creatures like algae evolved, but

928-684: The Bell Mountain Wilderness . A section of the Ozark Trail winds through parts of the St. Francois Mountains, including a popular segment that crosses Taum Sauk and Proffit mountains. The St. Francis River in this area is a whitewater stream in the spring when water levels are up, and it has hosted the Missouri Whitewater Championships annually since 1968. See also: U.S. Interior Highlands St. Francis River The St. Francis River

986-531: The Carboniferous Rainforest Collapse . Gondwana was glaciated as much of it was situated around the south pole. The Permian spanned from 299–252 million years ago and was the last period of the Paleozoic Era. At the beginning of this period, all continents joined together to form the supercontinent Pangaea, which was encircled by one ocean called Panthalassa . The land mass was very dry during this time, with harsh seasons, as

1044-645: The Early Palaeozoic Icehouse , culminating in the Hirnantian glaciation, 445  million years ago at the end of the Ordovician. The middle Paleozoic was a time of considerable stability. Sea levels had dropped coincident with the ice age, but slowly recovered over the course of the Silurian and Devonian. The slow merger of Baltica and Laurentia, and the northward movement of bits and pieces of Gondwana created numerous new regions of relatively warm, shallow sea floor. As plants took hold on

1102-536: The French as early as 1720. The area today accounts for over 90% of primary lead production in the United States. Granite has been commercially quarried since 1869 in the vicinity of Elephant Rocks State Park , a tor with huge weathered granite boulders. The red architectural granite quarried in the area has been used in buildings in St. Louis and other areas in the country. It is currently marketed as Missouri Red monument stone . Hughes Mountain contains

1160-722: The Ouachita orogeny to the south. Elevations and strata dips in the Ozark structural dome generally radiate downward and outward away from the Saint Francois mountains. These ancient mountains may be the only area in the Midwestern United States never to have been submerged, (as evidenced by the lack of marine fossils) existing as an island archipelago in the Paleozoic seas. Fossilized coral ,

1218-568: The Ozarks and the St. Francois Mountains near Missouri's highest point Taum Sauk . It forms the Missouri-Arkansas border in the Bootheel and eventually exits the state at Missouri's lowest point in the "toe" at 241 feet (73 m) above sea level. It passes through Lake Wappapello , which is formed by a dam constructed in 1941. Below the dam the river meanders through cane forests and willow wetlands or forested swamp , transitioning from

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1276-571: The South Pole . The early Paleozoic climate was strongly zonal, with the result that the "climate", in an abstract sense, became warmer, but the living space of most organisms of the time – the continental shelf marine environment – became steadily colder. However, Baltica (Northern Europe and Russia) and Laurentia (eastern North America and Greenland) remained in the tropical zone, while China and Australia lay in waters which were at least temperate. The early Paleozoic ended, rather abruptly, with

1334-557: The Appalachians started forming, the St. Francois range was already twice as old as the Appalachians are today. The intrusive rocks of the area are composed of three types: subvolcanic massifs , ring intrusions and central plutons . The subvolcanic intrusives are similar in geochemistry to the associated rhyolite volcanics, which they intrude into. They are granite with granophyric quartz , perthitic potassium feldspar , biotite and magnetite . They are intrusive into

1392-648: The Fish", the Devonian featured a huge diversification of fish, including armored fish like Dunkleosteus and lobe-finned fish which eventually evolved into the first tetrapods. On land, plant groups diversified rapidly in an event known as the Devonian explosion when plants made lignin , leading to taller growth and vascular tissue; the first trees and seeds evolved. These new habitats led to greater arthropod diversification. The first amphibians appeared and fish occupied

1450-649: The ICS chose Fortune Head , Burin Peninsula, Newfoundland as the basal Cambrian Global Stratotype Section and Point (GSSP) at the base of the Treptichnus pedum assemblage of trace fossils and immediately above the last occurrence of the Ediacaran problematica fossils Harlaniella podolica and Palaeopsacichnus . The base of the Phanerozoic, Paleozoic and Cambrian is dated at 538.8+/-0.2 Ma and now lies below both

1508-507: The Jesuit missionary Francis Xavier (1506–1552). The spelling of the river's name shifted from "Francois" to "Francis" in the early 20th century. The St. Francois Mountains were formed by volcanic and intrusive activity 1.485 billion (1.485 x 10) years ago. By comparison, the Appalachians started forming about 460 million years ago, and the Rockies a mere 140 million years ago. When

1566-610: The Middle Carboniferous). An important evolutionary development of the time was the evolution of amniotic eggs , which allowed amphibians to move farther inland and remain the dominant vertebrates for the duration of this period. Also, the first reptiles and synapsids evolved in the swamps. Throughout the Carboniferous, there was a cooling trend, which led to the Permo-Carboniferous glaciation or

1624-629: The Palaeozoic had very few facultatively motile animals that could easily adjust to disturbance, with such creatures composing 1% of its assemblages in contrast to 50% in Cenozoic faunal assemblages. Non-motile animals untethered to the substrate, extremely rare in the Cenozoic, were abundant in the Palaeozoic. Palaeozoic phytoplankton overall were both nutrient-poor themselves and adapted to nutrient-poor environmental conditions. This phytoplankton nutrient poverty has been cited as an explanation for

1682-614: The Paleozoic and Neoproterozoic eras and the Ediacaran and Cambrian periods. When Adam Sedgwick named the Paleozoic in 1835, he defined the base as the first appearance of complex life in the rock record as shown by the presence of trilobite -dominated fauna. Since then evidence of complex life in older rock sequences has increased and by the second half of the 20th century, the first appearance of small shelly fauna (SSF), also known as early skeletal fossils, were considered markers for

1740-560: The Paleozoic informally into early and late sub-eras: the Early Paleozoic consisting of the Cambrian, Ordovician and Silurian; the Late Paleozoic consisting of the Devonian, Carboniferous and Permian. The name Paleozoic was first used by Adam Sedgwick (1785–1873) in 1838 to describe the Cambrian and Ordovician periods. It was redefined by John Phillips (1800–1874) in 1840 to cover the Cambrian to Permian periods. It

1798-410: The Paleozoic. Life began in the ocean but eventually transitioned onto land, and by the late Paleozoic, great forests of primitive plants covered the continents, many of which formed the coal beds of Europe and eastern North America . Towards the end of the era, large, sophisticated synapsids and diapsids were dominant and the first modern plants ( conifers ) appeared. The Paleozoic Era ended with

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1856-529: The Silurian Period, about 420 million years ago, when they began to transition onto dry land. Terrestrial flora reached its climax in the Carboniferous, when towering lycopsid rainforests dominated the tropical belt of Euramerica . Climate change caused the Carboniferous Rainforest Collapse which fragmented this habitat, diminishing the diversity of plant life in the late Carboniferous and Permian periods. A noteworthy feature of Paleozoic life

1914-618: The Spavinaw are essentially identical to the volcanics of the St. Francois mountains (the Washington County volcanics). The Saint Francois Mountains were formed by igneous activity, whereas most of the surrounding Ozarks are developed on Paleozoic sedimentary rocks as a dissected plateau . The localized vertical relief was caused by erosion following uplift during the Pennsylvanian and Permian periods produced by

1972-685: The St. Francis is navigable by barge . It joins the Mississippi River in Phillips County, Arkansas , about 7 miles (11 km) north of Helena . Along its course in Missouri, the river flows through the Mark Twain National Forest and past Sam A. Baker State Park and the towns of Farmington , Greenville and Fisk . In Arkansas it passes the towns of St. Francis , Lake City , Marked Tree and Parkin , and continues through two additional namesakes of

2030-498: The base of the Paleozoic. However, whilst SSF are well preserved in carbonate sediments, the majority of Ediacaran to Cambrian rock sequences are composed of siliciclastic rocks where skeletal fossils are rarely preserved. This led the International Commission on Stratigraphy (ICS) to use trace fossils as an indicator of complex life. Unlike later in the fossil record, Cambrian trace fossils are preserved in

2088-516: The boundary confine its age to a narrow range of 251.902+/-0.024 Ma. The beginning of the Paleozoic Era witnessed the breakup of the supercontinent of Pannotia and ended while the supercontinent Pangaea was assembling. The breakup of Pannotia began with the opening of the Iapetus Ocean and other Cambrian seas and coincided with a dramatic rise in sea level. Paleoclimatic studies and evidence of glaciers indicate that Central Africa

2146-566: The climate of the interior of Pangaea was not regulated by large bodies of water. Diapsids and synapsids flourished in the new dry climate. Creatures such as Dimetrodon and Edaphosaurus ruled the new continent. The first conifers evolved, and dominated the terrestrial landscape. Near the end of the Permian, however, Pangaea grew drier. The interior was desert, and new taxa such as Scutosaurus and Gorgonopsids filled it. Eventually they disappeared, along with 95% of all life on Earth, in

2204-561: The continental margins, oxygen levels increased and carbon dioxide dropped, although much less dramatically. The north–south temperature gradient also seems to have moderated, or metazoan life simply became hardier, or both. At any event, the far southern continental margins of Antarctica and West Gondwana became increasingly less barren. The Devonian ended with a series of turnover pulses which killed off much of middle Paleozoic vertebrate life, without noticeably reducing species diversity overall. There are many unanswered questions about

2262-507: The empty continent of Gondwana. By the end of the Ordovician, Gondwana was at the south pole, early North America had collided with Europe, closing the intervening ocean. Glaciation of Africa resulted in a major drop in sea level, killing off all life that had established along coastal Gondwana. Glaciation may have caused the Ordovician–Silurian extinction events , in which 60% of marine invertebrates and 25% of families became extinct, and

2320-560: The end of the Permian period. In late middle Permian the pareiasaurs originated, successful herbivores and the only sauropsids that could reach sizes comparable to some of the largest synapsids. The Palaeozoic marine fauna was notably lacking in predators relative to the present day. Predators made up about 4% of the fauna in Palaeozoic assemblages while making up 17% of temperate Cenozoic assemblages and 31% of tropical ones. Infaunal animals made up 4% of soft substrate Palaeozoic communities but about 47% of Cenozoic communities. Additionally,

2378-715: The equivalent level is marked by the disappearance of the Permian Dicynodon tetrapods . This means events previously considered to mark the Permian-Triassic boundary, such as the eruption of the Siberian Traps flood basalts , the onset of greenhouse climate, ocean anoxia and acidification and the resulting mass extinction are now regarded as being of latest Permian in age. The GSSP is near Meishan , Zhejiang Province, southern China. Radiometric dating of volcanic clay layers just above and below

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2436-418: The first appearance of trilobites and SSF. The boundary between the Paleozoic and Mesozoic eras and the Permian and Triassic periods is marked by the first occurrence of the conodont Hindeodus parvus . This is the first biostratigraphic event found worldwide that is associated with the beginning of the recovery following the end- Permian mass extinctions and environmental changes. In non-marine strata,

2494-461: The first tetrapods, 390  million years ago , and began to develop lungs. Amphibians were the dominant tetrapods until the mid-Carboniferous, when climate change greatly reduced their diversity, allowing amniotes to take over. Amniotes would split into two clades shortly after their origin in the Carboniferous; the synapsids, which was the dominant group, and the sauropsids . The synapsids continued to prosper and increase in number and variety till

2552-713: The highest rise in elevation from its base, along the St. Francis River (540 feet above sea level) to its summit (1,502 feet above sea level), a rise of just under 1,000 feet in elevation. Five Missouri state parks – Johnson's Shut-Ins , Taum Sauk Mountain , St. Joe , Sam A. Baker and Elephant Rocks – are located in this region. Public lands held by the Missouri Department of Conservation provide access for hiking , backpacking , hunting , fishing , canoeing , and boating . The Mark Twain National Forest contains additional public lands, including

2610-673: The home of Cherokee Indians who attacked a boat on the Tennessee River on June 11, 1794 known as the Muscle Shoals Massacre and had removed to the west. The Spanish authorities allowed the Indian settlement to trade and the area flourished with a population greater than Arkansas Post. The origin of the river's name is unclear. It might refer to St. Francis of Assisi , the founder of the Franciscan order. None of

2668-679: The largest extinction event of the Phanerozoic Eon , the Permian–Triassic extinction event . The effects of this catastrophe were so devastating that it took life on land 30 million years into the Mesozoic Era to recover. Recovery of life in the sea may have been much faster. The base of the Paleozoic is one of the major divisions in geological time representing the divide between the Proterozoic and Phanerozoic eons,

2726-548: The late Paleozoic. The Mississippian (early Carboniferous Period) began with a spike in atmospheric oxygen, while carbon dioxide plummeted to new lows. This destabilized the climate and led to one, and perhaps two, ice ages during the Carboniferous. These were far more severe than the brief Late Ordovician ice age; but, this time, the effects on world biota were inconsequential. By the Cisuralian Epoch, both oxygen and carbon dioxide had recovered to more normal levels. On

2784-603: The most ubiquitous of that period were the armored arthropods, like trilobites. Almost all marine phyla evolved in this period. During this time, the supercontinent Pannotia begins to break up, most of which later became the supercontinent Gondwana. The Ordovician spanned from 485–444 million years ago. The Ordovician was a time in Earth's history in which many of the biological classes still prevalent today evolved, such as primitive fish, cephalopods, and coral. The most common forms of life, however, were trilobites, snails and shellfish. The first arthropods went ashore to colonize

2842-428: The name honors St. Francis of Assisi (1181/1182–1226), the patron saint of the Franciscan order , but none of the region's early explorers were Franciscans. Others propose that Jacques Marquette , a French Jesuit , named the river when he explored its mouth in present-day Arkansas in 1673. Before his voyage down the Mississippi River , Marquette had spent some time at the mission of St. François Xavier, named for

2900-520: The other hand, the assembly of Pangaea created huge arid inland areas subject to temperature extremes. The Lopingian Epoch is associated with falling sea levels, increased carbon dioxide and general climatic deterioration, culminating in the devastation of the Permian extinction. While macroscopic plant life appeared early in the Paleozoic Era and possibly late in the Neoproterozoic Era of the earlier eon, plants mostly remained aquatic until

2958-603: The region stem from the river's name, including St. Francois County and the St. Francois Mountains . The United States Board on Geographic Names settled on "St. Francis River" as the stream's name in 1899. According to the Geographic Names Information System , historical names for the river have included: Paleozoic The Paleozoic ( / ˌ p æ l i . ə ˈ z oʊ . ɪ k , - i . oʊ -, ˌ p eɪ -/ PAL-ee-ə-ZOH-ik , -⁠ee-oh- , PAY- ; or Palaeozoic ) Era

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3016-519: The region's early explorers were Franciscans, however. One possibility is that Jacques Marquette , a Jesuit , named the river when he explored its mouth in 1673. Before his voyage down the Mississippi Marquette had spent some time at the mission of St. François Xavier, named for the Jesuit missionary Francis Xavier . The spelling of the river's name shifted from "François" to "Francis" in the early 20th century. A number of place names in

3074-548: The remains of ancient reefs , can be found among the rocks around the flanks of the mountains. These ancient reef complexes formed the localizing structures for the mineralizing fluids that resulted in the rich ore deposits of the area. The igneous rocks of the Saint Francois Mts. are interpreted to be a series of caldera complexes, similar in scale to the Yellowstone Caldera complex. However, it

3132-976: The rhyolites with development of fine grained granophyre at the contact. At depth they exhibit a coarse-grained rapakivi texture. The subvolcanic granites are the most widespread igneous rocks and were thought to have been covered with extensive volcanics that have been removed by erosion. The ring intrusives are high silica bodies which were intruded along ring faults associated with caldera collapse. Rock types include trachyandesite , trachyte , syenite and amphibole - biotite granite. They are commonly porphyritic . The central plutons are highly evolved two mica (contain both biotite and muscovite ) granites. Distinctive accessory minerals include: fluorite , topaz , apatite , spinel , allanite , sphene and cassiterite . They are enriched in tin , lithium , beryllium , rubidium , barium , yttrium , niobium , uranium , thorium and fluorine and are referred to as "tin granites'. Their circular to oval shape in plan view

3190-619: The river — St. Francis County , and St. Francis Township in northeastern Phillips County — ending its course adjoining the St. Francis National Forest . In addition to the Little River, tributaries of the St. Francis include the Little St. Francis River , which joins it along its upper course in Missouri; the Tyronza River , which joins it in Arkansas; and the L'Anguille River , which joins it just above its mouth. The river became

3248-414: The short, but apparently severe, late Ordovician ice age. This cold spell caused the second-greatest mass extinction of the Phanerozoic Eon. Over time, the warmer weather moved into the Paleozoic Era. The Ordovician and Silurian were warm greenhouse periods, with the highest sea levels of the Paleozoic (200 m above today's); the warm climate was interrupted only by a 30 million year cool period,

3306-492: The top of the food chain. Earth's second Phanerozoic mass extinction event (a group of several smaller extinction events), the Late Devonian extinction , ended 70% of existing species. The Carboniferous is named after the large coal deposits laid down during the period. It spanned from 359–299 million years ago. During this time, average global temperatures were exceedingly high; the early Carboniferous averaged at about 20 degrees Celsius (but cooled to 10 °C during

3364-470: Was most likely in the polar regions during the early Paleozoic. The breakup of Pannotia was followed by the assembly of the huge continent Gondwana ( 510  million years ago ). By the mid-Paleozoic, the collision of North America and Europe produced the Acadian-Caledonian uplifts, and a subducting plate uplifted eastern Australia . By the late Paleozoic, continental collisions formed the supercontinent of Pangaea and created great mountain chains, including

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