The coastal geomorpholoqy of the 

 Apalachicola reqion is extremeiv complex; 

 major features are developed from wind and 

 current modified beach ridqes (Clewell 

 1977). These formations are complicated 

 by considerable Pleistocene sea-level 

 fluctuations. The northern qulf coastal 

 lowlands are dominated by Pliocene epoch 

 marine sands. The flood plain of Holocene 

 (recent) sediment reaches depths 

 approximating 24.3 m (80 ft) near the 

 river mouth and 13.7 m (45 ft) near 

 Blountstown, Florida (Fiqure 1). These 

 sediments lie directly on Miocene strata 

 because much of the Pliocene and 

 Pleistocene sediments were eroded during 

 periods when sea level was lower and river 

 flow was greater. The sea level 

 approximately 20,000 years ago was over 

 125 m (410 ft) lower than that found 

 today, and the coastline was considerably 

 seaward of its current position. 



The Florida panhandle is an uneven 

 platform of carbonate bedrock (limestone 

 with dolomite) overlain by one or more 

 layers of less consolidated elastics 

 (Fiqure 6, Puri and Vernon 1«564; Clewell 

 1^78). Superficial strata are of Eocene, 

 Oligocene or early Miocene origin. 

 Considerable solution activity has led to 

 the formation of sinks, caves and other 

 karst features (Means 1977). The elastics 

 consist of Fuller's earth (primarily the 

 clays montmoril linite and attapulqite), 

 phosphatic matrix, sand, silt, clay, shell 

 marl, qravel, rock fragments, and fossil 

 remains. The elastics with shell marl are 

 sediments of ancient shallow seas and 

 estuaries. Various clastic strata were 

 deposited during the early Miocene, while 

 others were fluvial and aeolian deoosits 

 or sediments in lake bottoms. These 

 elastics form terraces sloping toward the 

 Gulf. Such terraces are altered by 

 erosion and dissection by streams and 

 rivers. In spite of various 

 post-Pleistocene sea-level fluctuations, 

 elevations in this area have changed less 

 than 10 m as a result o^ erosion, 

 deposition, and sedimentation. Dunes, 

 spits, bars, and beach ridqes became 

 stranded inland as the sea receded. 



Soils and sediments. 



The 



Apalachicola River floodplain lies wholly 

 within the Florida Coastal Plain and is in 

 contact with Tamoa Limestone (early 



Miocene). The river just below the Jim 

 Woodruff Dam flows through the Citronelle 

 formation (Pliocene) that borders the 

 western edge of the Pleistocene bed from 

 16 to 20 km below the dam to Blountstown. 

 The eastern portion of the river is 

 influenced by the Hawthorn formation 

 (Fuller's earth and phosphatic limestone) 

 and Duplin marl (sandy marine and clayey, 

 micaceous shell marl). The clays in 

 particular and fine sands cause 

 considerable turbidity. The river bed is 

 composed primarily of remnants of 

 Pleistocene deposits (sand to coarse 

 gravel) that are covered by fine clay 

 sediments. The lower river valley is 

 composed largely of Plio-Pleistocene 

 marine sands, which lie over the Aucilla 

 Karst Plain, the Jackson Bluff formation, 

 and the lower part of the Citronelle 

 formation. 



Upland soil composition reflects the 

 geological history of the Apalachicola 

 valley. Soils in the titi swamps and 

 savannahs of the Apalachicola National 

 Forest are strongly acidic and low in 

 extractable cations (Mooney and Patrick 

 1915; Coultas 1976, 1C)77, IQRO). Total 

 phosphorus is low in all soils of the 

 basin. Cypress and gum swamps are also 

 highly acidic and low in extractable 

 bases, while more alluvial soils are less 

 acidic. Estuarine marsh soils are rela- 

 tively hiqh in organic matter, especially 

 at the river mouth. These soils are 

 derived largely from the erosion of the 

 northern Piedmont-Appalachian soils, which 

 have been deposited on the sea floor and, 

 at times, have been uplifted above sea 

 level. Floodplain soils are composed of a 

 broad range of textures and colors. They 

 are predominantly clay with some silty 

 clay and minor clay loams (Leitman, 1978). 

 Point bars in the river bed are composed 

 largely of fine and very fine sands. 



Soils in wetlands directly associated 

 with the Apalachicola River have been 

 analyzed. Swamp soils are wet, moderately 

 acidic, high in clay content, and low in 

 salinity (Coultas in press). The princi- 

 pal clay-sized minerals include kaolinite, 

 vermiculite, quartz, and mica. These 

 areas are poorly drained and contain 

 considerable amounts of clay and organic 

 matter. The soils are formed from recent 

 accumulations of sediments deposited in 



