User:Donald Albury/Trail Ridge

The Trail Ridge is a series of sand hills extending from the Altamaha River in southeastern Georgia to near point at which Alachua, Bradford, Clay and Putnam counties meet in northeastern Florida.

Description
ridge 140 km long, 1 to 2 km wide, in Clay County sand about 20 m thick. laminae of heavy metal rich sand average 6% ilmenite, zircon, rutile, surrounding sand about 1%, including staurolite, sillimanite, and tourmaline, laminae formed as slip faces of aeolian dune complex. Underlying sand is Lignitic Peat, entirely derived from fresh-water plants, some tree stumps still present, vegetation from shrub swamp to cypress forest Peat-sand interface indicates wind deposition, dune overriding swamp, likely dunes dammed in swamp. likely multiples dunes migrating southwest about 65 km inland from coast, elevation about 46 m at north end, rising to 77 m at points in the south. typically 10s of m about adjacent land, very conspicuous, impounds Okeefenokee.

Name
Trail Ridge is named for the Alachua Trail, which ran along part of its crest in Florida. The Alachua Trail was an Indian trail that led from the Altamaha River in Georgia to the "Alachua Country", the area around what is now called Paynes Prairie in Alachua County, Florida, and was used by white Americans in the colonial and Florida Territorial periods. The trail followed the crest of the ridge from east of Maccleney to Kingsley Lake in Florida, where it provided a dry path between flanking wetlands.

Lignite layer
ridge 140 km long, 1 to 2 km wide, in Clay County sand about 20 m thick. laminae of heavy metal rich sand average 6% ilmenite, zircon, rutile, surrounding sand about 1%, including staurolite, sillimanite, and tourmaline, laminae formed as slip faces of aeolian dune complex. Underlying sand is Lignitic Peat, entirely derived from fresh-water plants, some tree stumps still present, vegetation from shrub swamp to cypress forest Peat-sand interface indicates wind deposition, dune overriding swamp, likely dunes dammed in swamp. likely multiples dunes migrating southwest about 65 km inland from coast, elevation about 46 m at north end, rising to 77 m at points in the south. typically 10s of m about adjacent land, very conspicuous, impounds Okeefenokee. peat layer 92% woody, varies with sections of peaty sand and elements of solid wood, intermediate between peat and lignite. pollen and spores indicate shrubs, small trees, sedges (Cyperaceae), ferns (Osmunda) and mosses (Sphagnum), all fresh water, suggesting standing water. lower part of peat consistent with bald cypress swamp, upper part. ti-ti (Cyrilla) common in upper part, pine and oaks present but less common than present-days swamps in area. , pollen indicates post-Miocene, C14 greater than 4.5 x 10↑14 ("dead"), before end Pleistocene,

Trail Ridge relict barrier with lagoon, Okeefenokee Swamp relict of lagoon. abrubt end of barrier at Altamaha River likely caused by River, not original, ancient shoreline relict scarp, slope of ridge north to south likely significant as to which way barrier grew, southern broadens out, changes from relict barrier to karst, solution basins and lakes, relict spits extend north to east of ridge, more northerly seperated from ridge by Black Creek, more southerly by Ates Creek.

Lignitic peat bed underlies heavy-metal bearing sands of Trail Ridge in Bradford and Clay counties. Ridge is linear sand body on Atlantic Coastal Plain from near Altamaha Rover 209 km south to point in Brabford and Clay counties, 43 to 52 m above sea level in Georgia and 51 60 76 m in Florida. primarily indurated quartz sand, minerals include ilmenite, leucoxene, rutile, zircon, tourmaline, kyanite, staurolite present. While it has been proposed that the ridge originated as a barrier spit building south from Georgia, a more favored theory is that it originated as a beach ridge along the shoreline when sea level was higher. In Florida, ridge is approximately aligned with boundary between Baker County to the west and Duval and Nassau counties to the east, and with the boundary between Bradford and Clay counties, extending to approximately the point at which Bradford and Clay counties meet Alachua and Putnam counties. sand on ridge likely reworked from Northern Highlands, west of ridge, as sea eroded ancient terrace deposits. pollen and spores in buried peat of genera and families still common in southeast US. oak and pine not particularly abundant, Cyrilla, Gordonia, Magnolia present, Myrica and Ilex very abundant, Cyrilla and Gordonia decrease with depth, Taxodium increase with depth. Osmuna very abundant near bottom, rapidlt diminishes upward, shrub pollen most common at most levels, some pollen could be from fresh water or brackish water species, but other pollen definitely from fresh-water species, Taxodium pollen not abundant, not likely dominant or even common. oak and pine uncommon, probably not common near the swamp, despite sandy ridge nearby, lower half of peat in one core Taxodium, Ilex, Myrica, Corylus, Myriophyllum, Graminae common, indicate cypress forest, shrubby undergrowth, clear, stranding water. Taxodiumm declined while herbaceous (Cyperaceae, Osmunda, Sphagnum, Woodwardia) more abundant, still later Gordonia and Cyrilla with Ilex, Myrica and Coylus, charcoal layer just be change, maybe from drought and forest fire(s), second core, ferns and scattered shrubs Osmunda, Cyperaceae, Sagittaria, Graminae, Woodwardia, Myrica, Ilex, Corylus) early on, later most declined while Myrica and Corylus increased, shrub dominated swamp. age of swamp and ridge uncertain, ridge age given from Miocene to early Pleistocene. mollusc fossils found in bore holes in ridge in southern Georgia all current shallow-water species, no extinct species, suggesting no older than late Pleistocene. comparison of pollen and spores profiles suggest Pleistocene age for peat, although peat is unlike Pleistocene deposits from Gulf Coast. peat age unclear, but more recent than Miocene.

two cores from South end of ridge, in one at 239 feet elevation, sand layer 63 feet deep, underlying zone of intercalated sand and peaty or sapropelic lens (Sediments with wood and finely divided organic matter) 27 feet deep, second hole, 206 feet elevation, sand 59 feet deep, mixed zone 13 feet cores from Trail Ridge Ore Body. upper five feet of lower zone in core 1 peat, lenses with wood and organic matter at 73 feet to 74 feet, 6 inches, 77 feet to 78 feet, and 80 feet 6 inches to 84 feet 6 inches, core 2 has less woody/organic material but present throughout in lower zone. underneath are post-Hawthorne clastics, mixed layers and lenses of sand, clayey sand, and clay. under that is Hawthorne Formation of middle to late Miocene, sometimes with topped with a shell layer of late Miocene.

Trail Ridge Pleistocene age paleoshoreline of arcuate scarps and sand ridges, up to 70 m above sea level, much higher that any Pleistocene Interglacial sea level. accounted for by isostatic uplift caused by karstic mass loss, lower sea levels exposed Florida Platform to fresh-water, which dissolves limestone

Trail Ridge nearly 80 m above sea level with Quarternary marine fossils, inconsistent with sea levels since early Pleistocene, global isostatic adjustment expected to lower Florida Platform since end of last glaciation, but geomorphic features remain higher than predicted on Florida Platform. Dissolution of carbonate rock underlying Florida reduces weight of rock (dissolved carbonate flows away with water), producing isostatic uplift. Mantle convection may account for part of uplift.

Trail Ridge Ore Body part of Trail Ridge. Drill core in Clay County found three layers of dark woody sediment 10.1 m below surface (under light to dark sand), total 28.5 cm brown coal sediment classified as brown coal, such findings common under Trail Ridge, 1 mm laminations, bottom 5 cm included layers of sands between layers of coal, impressions of leaves, some thick and leathery, others strap like, suggesting grasses or sedges, layers of charcoal. spores and pollen of trees, shrubs and herbaceous plants found, three zones: gtass zone 0-8 cm, Gordonia shrub zone, 8-21 cm, Cyrill Sphagnum grass sedges zone, 21-28 cm, Cyrilla diminished upwards, Salix (willow) present, peak at 21-22 cm, Sphagnum abundant at bottom, dimishes rapidly upwards, Heath pollen in upper levels, more abundant than in modern peats, Gordonia most abundant in middle zone. Cyrilla also abundant in middle zone, Cyrilla and Gordonia commonly grow together, wax myrtle Myrica common throughout, sequence of Cyrilla shrub swamp with Sphagnum and grasses or sedges and closed canopy, to shrub swamp, then to tree/shrub swamp, open canopy, grasses and sedges. community common in southern Georgia northern Florida, adapted to periodic burning, shrubs regrow from roots, trees eliminated, dense shrubs eventually crowd out herbaceous plants. brown coal at site compacted from peat, Rich estimates 84 cm of peat, based on rates observed at Okeefenokee Swamp, could have taken 1400 years to accumulate, eolian dunes overran swamp.