Presentation on theme: "Where in Georgia do you find Sediments & Sedimentary Rocks? Coastal Plain Province Valley & Ridge Province* In all provinces, young sediments are associated."— Presentation transcript:
Where in Georgia do you find Sediments & Sedimentary Rocks? Coastal Plain Province Valley & Ridge Province* In all provinces, young sediments are associated with rivers and streams. These are “Quaternary alluvium” - Qal
Sediments & Sedimentary Rocks in Georgia and adjacent states (Modified from Hatcher et al. (1990), Steltenpohl et al. (1995), and Hooper & Hatcher (1988).)
Map on left Adapted from Ga. Geologic Survey state geologic map, 1977 Valley & Ridge Province is composed of Paleozoic Sedimentary rocks
Valley & Ridge* Sandstones Shales Limestones Coal Conglomerate Rocks deposited in a variety of sedimentary environments, shallow marine passive margins, shallow inland sea, delta and tidal flat deposits.
Origin of these sedimentary rocks. Part I - Late Precambrian (700 to 600 m.y.) – Rifting of supercontinent Rodinia, opening of Iapetus Ocean. Passive margins
Low-grade Metamorphosed sedimentary rocks are exposed in the western Blue Ridge Province. These were deposited as rift- related sandstones, conglomerates, and shales.
The shoreline of the Iapetus Ocean might have looked like this – w/o the vegetation
Part II – Periodic coverage of the continent by shallow, inland seas. Tropical to sub-Tropical conditions
Sedimentary rocks of passive margin and shallow inlands seas include sandstone, shale, and limestone.
Silurian limestone from Chattanooga area
Common Paleozoic fossils (photos from Univ. of Calif. Berkeley Museum of Paleontology website) in Ga. include: Trilobites Crinoids Brachiopods
With each of the 3 periods of Appalachian uplift, there was erosion of the rising mountain chain and the deposition of large river delta systems to the NW, draining into the shallow inland sea that covered the continental interior. After the Ordovician Period, most of the Ga. sedimentary rocks were deposited in delta/tidal flat conditions with some incursions of marine conditions during the Mississippian Period.
The first Clastic wedge developed NW of Taconic Highlands, includes Red Mountain Fm. in NW Ga. and Birmingham, AL. 13
When the uplands were eroded and less clastics were reaching the inland seas, marine conditions resumed. The last deposition of Paleozoic limestones in NW Georgia occurred during the Mississippian Period. Fossils include blastoids and horn corals.
The Mississippian St. Genevieve Limestone hosts many of the caverns in TN, AL, and KY.
Typical Pennsylvanian river delta (clastic wedge) related sedimentary rocks.
A close-up of typical fluvial sandstones
The Pottsville Sandstone is one of the clastic wedge units.
Tidal flat deposits, e.g., the Red Mountain Fm., include red sandstones, shales, and siltstones. Photo by P. Bouker
Passive margin Coastal Plain Province With the Triassic and Jurassic rifting of Pangea, a passive margin (continental shelf) developed on the Gulf and Atlantic Coasts
Geologic Time Scale As the continent eroded, the land rose (remember Isostacy?), exposing the Late Cretaceous through Miocene Continental Shelf sediments. The remainder of the Coastal Plain is alluvial and fluvial, except for the coastal barrier islands.
The rising of the SE portion of North America produced an “Emergent Shoreline”
Fall Line – separates crystalline rocks of Piedmont from softer sediments of Coastal Plain. Fall Line Cities – Columbus, Macon, Augusta Marked by waterfalls and rapids. Coastal Plain Piedmont Fall Line
Coastal Plain Province – Late Cretaceous to Holocene (Recent) deposits at shoreline. Age – 100 m.y. - >10,000 yr. Layered sediments, sands, clays, limestones. Late Cretaceous sediments – mostly deltaic, including Providence Sand. Paleocene – Oligocene sediments – mostly marine. Miocene – Holocene – mostly continental deltaic, fluvial and alluvial sediments, except near coast. Aquifers – uniform sediments, a few karst wells.
Aerial view of a Meandering River System on the Gulf Coastal Plain
Eocene Epoch – warm temperatures, high sea level, widespread deposition of shallow-water limestones and much fossil biodiversity. This particular sand dollar (echinoid) is from SE of Perry, Ga.. 25
Residuum of Paleocene Clayton Fm. over deltaic Cretaceous Providence Sand
Excess sand from Providence Canyons erosion produces braided streams in canyon bottom, i.e., too much sand.
Sinkholes can form wherever limestone or marble is at the surface – Coastal Plain, Valley & Ridge, or Blue Ridge – Murphy Marble Belt.
On the Piedmont (and maybe parts of the Blue Ridge), we can find more modern river sediments on flood plains and abandoned channels.
An example of Qal, sand and gravels in a small Piedmont creek.