Chapter 10 Early Paleozoic Earth History

New York State Most surface rocks are from the Paleozoic

Major mountain-building activity Shallow-water marine transgressions and regressions over the interiors Causes: global changes in sea level plate activity along continental margins glaciation Paleozoic History of North America

Cratons are stable and “immobile” a shield and a platform (granite-gneiss) form the foundation upon which Phanerozoic sediments were deposited Continental Architecture

Areas of mountain building activity – –“orogenic activity” along the margins of continents –sediment are deposits in shallow waters continental shelf –and the deeper waters at the base of the continental slope During plate convergence along margins, the sediments are deformed –intruded by magma –mountain ranges are formed from subduction volcanoes Or continental collision Mobile Belts

The transgressing and regressing shallow seas –common feature of Paleozoic as evidenced by sediments deposited now forming the surface rock in New York State Epeiric Seas Marcellus Shale Devonian Age

Conglomerate Mt. Marion Saugerties NY (exit 20 I-87

Oriskany Sandstone Near Utica NY

How old are the Herkimer “diamond” source rocks?

Geologists use –paleoclimatic data: (glacial, rock types, coal) –paleomagnetic data: (preserved in igneous rocks) tells latitude and magnetic pole directions –paleontologic data: pollens, plants, animals –sedimentologic data: structures, environments –Stratigraphic: data rock relationships and age –tectonic data : evidence of plate boundaries Paleogeographic Maps

At the beginning of the Paleozoic: –1. Baltica - Russia west of the Ural Mountains and the major part of northern Europe –2. Gondwana - Africa, Antarctica, Australia, Florida, India, Madagascar, and parts of the Middle East and southern Europe –3. Laurentia - most of present North America, Greenland, northwestern Ireland, and Scotland Six Major Paleozoic Continents

–4. China - include China, Indochina, and the Malay Peninsula –5. Kazakhstan - a triangular continent centered on Kazakhstan, –6. Siberia - Russia east of the Ural Mountains and Asia north of Kazakhstan and south Mongolia AND numerous small microcontinents and island arcs associated with various microplates Six Major Paleozoic Continents

For the Late Cambrian Period Paleogeography of the World

For the Late Ordovician Period Paleogeography of the World

For the Middle Silurian Period Paleogeography of the World

–epeiric seas transgressed and regressed Over the stable continental interior –mobile belts where mountain building occurred Early Paleozoic Evolution of North America

White areas represent sequences of rocks That are separated by large-scale unconformities shown in brown Cratonic Sequences of N. America Cordillera orogenies Appalachia orogenies

A cratonic sequence is –a large-scale lithostratigraphic unit representing a major transgressive- regressive cycle bounded by cratonwide unconformities Cratonic Sequence Regressing Sea

White areas = sequences of rocks Sauk sequence

Rocks of the Sauk Sequence –Late Proterozoic-Early Ordovician (long, slow process) –first major transgression onto the North American craton Deposition of marine sediments : passive shelf areas of the East and West borders of craton Many of the Sauk carbonates (limestones) contain fragments of organic remain s – bioclastic rock The craton was above sea level –and experiencing extensive weathering & erosion SHALLOW WATER DEPOISITION! The Sauk Sequence

North America was located in a tropical climate at this time –there is no evidence of any terrestrial vegetation, NO plants! –Rapid weathering and erosion of the exposed Precambrian basement rocks = widespread unconformity The Sauk Sequence: Middle Cambrian Period

By the Late Cambrian, –the epeiric seas covered most of North America, Above the sea: a portion of the Canadian Shield and a few large islands “Transcontinental Arch” Highlands: Transcontinental Arch

During this time North America straddled the equator Trans- continental Arch Cambrian Paleogeography of North America Sauk Transgression

Facies are sediments that represent a particular environment During a transgression: the coarse (sandstone), fine (shale) and carbonate (limestone) facies migrate in a landward direction A Transgressive Facies Model

Grand Canyon at western margin of the craton during Sauk time, a passive shelf –most of the craton was still above sea level –deposition of marine sediments was at the margins of the craton on continental shelves and slopes The Cambrian of the Grand Canyon Region

–The Tapeats Sandstone represents the shoreline deposits are clean, well-sorted sands –of the type one would find on a beach today By Middle Cambrian, –muds of the Bright Angle Shale –were deposited over the Tapeats Sandstone By Late Cambrian –carbonates of the Muav Limestone were being deposited over the Bright Angel Shale Evidence of Transgression

Cambrian strata in the Grand Canyon Cambrian Transgression The three formations exposed –along the Bright Angel Trail, Grand Canyon Arizona

–Observe the time transgressive nature of the three formations Cambrian Transgression

The Sauk Sea regressed rocks exposed were predominately –Limestones: deep extensive erosion –North America was still located in a tropical environment – increased weathering The resulting cratonwide unconformity –marks the boundary between the Sauk –and the NEXT Cratonic sequence Tippecanoe Regression and Unconformity

White areas = sequences of rocks Cratonic Sequences of N. America Brown areas = large-scale” uncon-formities Regression Tippecanoe sequence

Paleo- geography of North America –showing change in the position of the the equator The continent –was rotating counter- clockwise Ordovician Period

Resulted in deposition of the St. Peter Sandstone –Middle Ordovician over a large area of the craton Transgression of the Tippecanoe Sea

Outcrop of St. Peter Sandstone in Governor Dodge State Park, Wisconsin St. Peter Sandstone

The Tippecanoe basal sandstones were followed by widespread carbonate deposition The limestones were generally the result of deposition –by calcium carbonate- secreting organisms such as corals, brachiopods, stromatoporoids, and bryozoans The Tippecanoe Sequence

Organic reefs limestone structures constructed by living organisms, Today, corals, and calcareous algae –are the most prominent reef builders, –but in the geologic past other organisms –played a major role in reef building Reefs appear to have occupied –the same ecological niche in the geological past as today Tippecanoe Reefs and Evaporites

Present-day reefs are 30 degrees north and south of the equator Corals require warm, clear, shallow water –of normal salinity for optimal growth

with reef-building organisms Present-Day Reef Community

Block diagram of a reef showing the various environments within the reef complex Reef Environments

significant structure in the region a broad, circular basin surrounded by large barrier reefs reefs contributed to restricted circulation –and the precipitation of Upper Silurian evaporites within the basin –Evaporites form when water evaporates and leaves salts and brines behind halite, gypsum, sylvite Michigan Basin Evaporites

Paleogeography of North America Silurian Period Reefs developed in the Michigan, Ohio, and Indiana-Illinois- Kentucky areas Silurian Period

1.When sea level dropped, the tops of the barrier reefs were as high as or above sea level, 2.Preventing influx of new seawater into the basin Evaporation of the basin seawater would result in the precipitation of salts 2. Alternatively, the reefs grew upward so close to sea level –that they formed a sill or barrier that eliminated interior circulation Origin of Thick Evaporites – 1500 m (Gypsum, Halite)

Silled Basin Model for evaporite sedimentatio n by direct precipitation from seawater Silled Basin Model

Because North America was still near the equator during the Silurian Period, –temperatures were probably high Basin Brines

–Phanerozoic orogeny – mountain building Iapetus Ocean was widening as a divergent plate boundary caused movement Beginning with the subduction of the Iapetus plate beneath Laurentia –which was an oceanic-continent convergent plate boundary the Appalachian mobile belt was born The Appalachian Mobile Belt

The resulting Taconic orogeny, –Today’s Taconic Mountains eastern New York, central Massachusetts, and Vermont –First of 3 to form Appalachians The Taconic Orogeny

Transition to convergence resulted in orogenic activity Appalachian Mobile Belt

Evidence for the Taconic orogeny The remnants of the mountains The remains of a large clastic wedge, detrital sediments adjacent to an uplifted area thinner and finer grained away from the source area, eventually grading into the carbonate cratonic facies The clastic wedge resulting from the erosion of the Taconic Highlands is referred to as the Queenston Delta Queenston Delta Clastic Wedge

Queenston Delta clastic wedge Taconic Highland s –coarse- grained detrital sediments near the highlands –thins laterally into finer- grained sediments on the craton

The Caledonian orogeny was a mirror image of Taconic orogeny Caledonians are similar age in Europe today. Caledonian Orogeny

The transition to convergence resulted in orogenic activity in North America and Europe Caledonian Orogeny –Caledonian Orogeny –was a mirror image of the Taconic Orogeny

Resources of Early Paleozoic Sandstone, Salts, Gypsum, natural gas Igneous minerals during orogeny