Extensive Late Pleistocene to Mid-Holocene Wetlands along the Tennessee River

A paper about extinct giant beaver (Casteroides sp.) fossil remains in the mid south briefly mentions evidence for the existence of “extensive floodplain lakes and marshes along the middle stretch of the Tennessee River” during the late Pleistocene-mid Holocene.  This intrigues me. Following the end of the Ice Age, increased precipitation in the atmosphere from melting glaciers caused southeastern rivers to meander more than they do today.  Geologists actually refer to these river patterns as supermeanders, and supermeandering rivers were common between ~15,000 BP-~6,000 BP.  Meanders often get cut off from the main river channel, and they become oxbow lakes, a name that describes their curved shape.  Sediment eventually fills oxbow lakes, and during this process they become marshy.  Large oxbow lakes created by this period of supermeanders attracted huge flocks of wintering waterfowl.  Archaeologists found enormous quantities of mallard duck (Anas platyrhyncos) remains dating to the late Pleistocene-early Holocene in Dust Cave and Smith-Bottom Cave, both located in northwestern Alabama.  The ducks were brought inside the caves by early archaic Indians who enjoyed a steady diet of duck during the winter.  70% of the faunal remains in Dust Cave were birds, mostly waterfowl but also including passenger pigeon, bobwhite quail, and prairie chicken.

Diagram showing how oxbow lakes are formed.  There must have been huge oxbow lakes along the Tennessee River during the supermeandering phase of ~15,000 BP-~6,000 BP

Map of Tennessee River.  Abundant remains of ducks and other waterfowl in caves near the river suggest a very extensive wetland occurred along the middle stretch of the river during the Late Pleistocene-to mid Holocene.

Location in Lauderdale County and the state of Alabama

Caves are located  on both sides of the Tennessee River in northwestern Alabama.  They preserve evidence that early Indians ate a lot of duck.

Mallard ducks

Huge flocks of mallard ducks wintered on oxbow lakes and marshes along the Tennessee River during the late Pleistocene-mid Holocene.

Dust Cave was buried by sediment until ~15,000 BP when the nearby Tennessee River changed coarse and eroded through this sediment, exposing the cave entrance.  Indians occupied the cave from ~12,500 BP-5000 BP.  Archaeological evidence shows 5 succeeding cultures utilized the cave. The Indians buried their dead in Dust Cave and left plenty of archaeological evidence such as arrowheads and the impressions of textile weaving on clay.  Toward the end of this time, Indians utilized waterfowl less than their predecessors had and relied more on upland game.  This suggests wetlands and lakes in the region eventually were diminished in extent.

During the time of supermeanders swamp rabbits (Sylvilagus aquaticus) were common.  Flooding helped establish extensive stands of impenetrable bamboo cane (Arundinaria gigantea) known as canebrakes, a favored habitat of swamp rabbits.   Floods killed trees and deposited rich soil.  Bamboo cane thrives on open sunlit ground with well fertilized soil.

Swamp rabbits were abundant here as well.

The deepest lakes offered habitat for the freshwater drum (Aplodonitis grunniens).  This species prefers clear water with sandy or gravel bottoms.  They feed on mussels, insect larva, and small fish.  Freshwater drums, suckerfish, and catfish made up 8% of the faunal remains in Dust Cave.  Fish was an important summer food for Archaic Indians after ducks migrated north.

Freshwaterdrum.png

Indians ate freshwater drum.

The extinct giant beaver occupied the oxbow lakes and marshes created by the supermeandering patterns of the Tennessee River until Indians hunted them to extinction.  (A safe assumption, though no direct evidence of humans hunting giant beavers has ever been found.)  Perhaps, they even persisted here early in the Holocene because the habitat they favored was so extensive.  Remains of giant beavers have been found at 3 sites along the Tennessee River including Ruby Falls, Bell Cave, and ACb-3 Cave.  The latter 2 sites are located in Colbert County, Alabama.  There were at least 2 species of giant beaver–Casteroides ohioensis and Casteroides dilophidusC. ohioensis lived in the Midwest; C. dilophidus lived in Florida and south Georgia.  Scientists aren’t sure which species lived along the Tennessee River because not enough skeletal material was found to distinguish between species.  Giant beavers preferred the same habitat as the modern day muskrat (Onadatra zibethicus) and did not require wooded environments like extant modern beavers (Castor canadensis).

Photo: Giant Beaver, Castoroides ohioensis.

Giant beavers (Casteroides sp.) lived in these wetlands until the Indians overhunted them to extinction.

References:

Parmalee, Paul; and Russell Graham

“Additional Records of the Giant Beaver, Casteroides, from the Mid South: Alabama, Tennessee, and South Carolina”

Tributes to the Career of Clayton Ray, Smithsonian Series of Publications 2002

Pritchard, Erin

TVA Archaeology: 75 Years of Prehistoric Site Records

University of Tennessee Press

 

 

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