Archeological Sites and Archeological Sites and High Probability High Probability

LocationsLocationsAlluvial Fans, Riparian Alluvial Fans, Riparian

Wetlands, Pot Holes, and Wetlands, Pot Holes, and Stream ValleysStream Valleys

The Importance of Topography The Importance of Topography to the Distribution of Cultural to the Distribution of Cultural

ResourcesResources Neither ancient nor modern peoples settled on Neither ancient nor modern peoples settled on

the landscape in a random manner.the landscape in a random manner. Food resources, water resources, Food resources, water resources,

transportation corridors, raw material transportation corridors, raw material availability, defendable positions, good views, availability, defendable positions, good views, and desirable micro-climates all played roles and desirable micro-climates all played roles in concentrating where people settled.in concentrating where people settled.

Our Agency’s responsibility to take cultural Our Agency’s responsibility to take cultural resources into account necessitates that our resources into account necessitates that our field personnel be aware of high probability field personnel be aware of high probability areas where such resources may be areas where such resources may be encountered. encountered.

Low Angle Alluvial FansLow Angle Alluvial Fans

Low angle alluvial fans Low angle alluvial fans are the single most are the single most likely topographic likely topographic feature to contain feature to contain significant cultural significant cultural resources.resources.

They commonly They commonly contain buried sites.contain buried sites.

Field offices shall Field offices shall contact the state contact the state office before working office before working on alluvial fans.on alluvial fans.

How Alluvial Fans FormHow Alluvial Fans Form

Alluvial fans occur Alluvial fans occur where a tributary where a tributary empties into a empties into a larger valley. As larger valley. As the grade becomes the grade becomes less, sediment less, sediment drops out.drops out.

This causes a fan This causes a fan shaped deposit to shaped deposit to form at the mouth form at the mouth of the tributary.of the tributary.

How to Identify an Alluvial How to Identify an Alluvial FanFan

Visually check in the Visually check in the field the mouths of field the mouths of tributaries in larger tributaries in larger valleys.valleys.

Check topographic Check topographic maps, and look for fan maps, and look for fan shaped elevation lines shaped elevation lines at the mouths of at the mouths of tributaries.tributaries.

Check soils maps for Check soils maps for soils designated as soils designated as “local alluvium.”“local alluvium.”

Why Do Fans Have Such a Concentration of Why Do Fans Have Such a Concentration of Significant Cultural Resources?Significant Cultural Resources?

Factors may include the Factors may include the proximity to water, to food proximity to water, to food resources in wetlands, to resources in wetlands, to streams that could be streams that could be canoed, and to flood canoed, and to flood protection from the stream protection from the stream in the main valley.in the main valley.

Spring run-off from the Spring run-off from the tributary would annually tributary would annually bury with sediment the bury with sediment the campsites occupied during campsites occupied during the other seasons, thus the other seasons, thus preserving a stratified record preserving a stratified record valuable to scientists.valuable to scientists.

The large fan shown to the The large fan shown to the left has 4 known prehistoric left has 4 known prehistoric sites, 4 farmsteads (over 50 sites, 4 farmsteads (over 50 years of age), and 1 years of age), and 1 cemetery.cemetery.

Wetlands As a Focus of Cultural Wetlands As a Focus of Cultural ResourcesResources

Our agency’s interest in Our agency’s interest in protecting and restoring protecting and restoring wetlands as valuable wetlands as valuable natural resources, natural resources, necessitates that our necessitates that our field offices understand field offices understand that they will be that they will be working in a cultural working in a cultural resource rich resource rich environment.environment.

We will discuss two We will discuss two types of wetlands, pot types of wetlands, pot holes and riparian holes and riparian wetlandswetlands

Why Are Archeological Sites So Why Are Archeological Sites So Abundant Near Wetlands?Abundant Near Wetlands?

Wetlands are some of the Wetlands are some of the planet’s most biologically planet’s most biologically rich ecosystems.rich ecosystems.

They produce an enormous They produce an enormous quantity of usable plant quantity of usable plant material. Native Americans material. Native Americans camped near these valuable camped near these valuable natural resources.natural resources.

The Ioway, for example, ate The Ioway, for example, ate the root of the cattail, used the root of the cattail, used the leaves of the cattail as a the leaves of the cattail as a salad, and used the stalks salad, and used the stalks to make insulating mats to make insulating mats that covered their lodges. that covered their lodges. They used willow (a wetland They used willow (a wetland plant) saplings to frame plant) saplings to frame their lodges.their lodges.

Wetland Edible Plant Wetland Edible Plant AbundanceAbundance

Edible plants are Edible plants are present in a wide present in a wide variety.variety.

Often, there are stands Often, there are stands of edible plants in of edible plants in wetland zones that wetland zones that approach the approach the monoculture of farm monoculture of farm fields.fields.

This served as a This served as a powerful magnet to powerful magnet to attract ancient attract ancient settlements.settlements.

The Wet Bottom, Dry Bottom The Wet Bottom, Dry Bottom Principle of Site DistributionPrinciple of Site Distribution

Archeological sites tend to fringe wetlands. Archeological sites tend to fringe wetlands. This distribution has been likened to a This distribution has been likened to a “ring around a bathtub.”“ring around a bathtub.”

People like to camp as close as possible to People like to camp as close as possible to the rich natural resources in the wetland, the rich natural resources in the wetland, but don’t want to process these resources but don’t want to process these resources on damp ground.on damp ground.

The goal was to have a wet bottom The goal was to have a wet bottom (topographically speaking) and a dry (topographically speaking) and a dry bottom (anatomically speaking).bottom (anatomically speaking).

Pot Hole WetlandsPot Hole Wetlands

These wetlands are These wetlands are found in areas that have found in areas that have been de-glaciated during been de-glaciated during relatively recent times.relatively recent times.

In Iowa, this area In Iowa, this area corresponds to the Des corresponds to the Des Moines Lobe.Moines Lobe.

Pot holes resulted from Pot holes resulted from uneven topography uneven topography created by glaciations. created by glaciations. Without a well developed Without a well developed drainage system, water drainage system, water collects in the low spots collects in the low spots creating ponds and creating ponds and marshes.marshes.

The Distribution of Archeological The Distribution of Archeological Sites Relative to Pot HolesSites Relative to Pot Holes

Archeological sites tend to Archeological sites tend to be located next to, but not be located next to, but not on hydric soils.on hydric soils.

In the field, the contrast In the field, the contrast between the lighter, better between the lighter, better drained soils and the drained soils and the darker, poorly drained soils darker, poorly drained soils is often dramatic.is often dramatic.

Soils maps can be Soils maps can be examined to locate the examined to locate the boundaries between hydric boundaries between hydric and non-hydric soils.and non-hydric soils.

Topographic maps can be Topographic maps can be used to identify higher and used to identify higher and therefore drier locationstherefore drier locations

Vertical Aspects of Archeological Vertical Aspects of Archeological Sites in Pot Hole EnvironmentsSites in Pot Hole Environments

Most agency ground disturbances in pot holes are Most agency ground disturbances in pot holes are very shallow. For deep disturbances you need to very shallow. For deep disturbances you need to discover what lies below.discover what lies below.

Precipitation fluctuations have caused wetlands to Precipitation fluctuations have caused wetlands to expand or shrink. The contact between hydric and expand or shrink. The contact between hydric and non-hydric soils has shifted over time. In some non-hydric soils has shifted over time. In some cases, archeological sites on non-hydric deposits cases, archeological sites on non-hydric deposits may be buried by hydric deposits.may be buried by hydric deposits.

If deep disturbance is planned, use a soil probe to If deep disturbance is planned, use a soil probe to find out whether there are underlying non-hydric find out whether there are underlying non-hydric deposits which have the potential to have deposits which have the potential to have archeological sites.archeological sites.

Your local soil scientist can be of great help.Your local soil scientist can be of great help. Colluvium may bury archeological sites near the Colluvium may bury archeological sites near the

wetland.wetland.

Riparian WetlandsRiparian Wetlands

Riparian wetlands are Riparian wetlands are found in stream found in stream valleys.valleys.

They have formed in They have formed in abandoned meander abandoned meander scars, on aggrading scars, on aggrading floodplains, in areas floodplains, in areas adjacent to seeps in adjacent to seeps in adjoining valley walls, adjoining valley walls, and in slack-water and in slack-water deposits away from deposits away from the main channel.the main channel.

Archeological Site Distributions Archeological Site Distributions in Riparian Wetlandsin Riparian Wetlands

Damp areas were Damp areas were avoided. Drier areas avoided. Drier areas adjacent to wetlands adjacent to wetlands were selected.were selected.

Drier areas on floodplains Drier areas on floodplains include natural levees, include natural levees, sand dunes, alluvial sand dunes, alluvial terraces, fans, and sandy terraces, fans, and sandy areas. Sediments that areas. Sediments that are elevated or consist of are elevated or consist of larger grain sediments larger grain sediments have a tendency to be have a tendency to be drier.drier.

Sandy Soils and Archeological Sandy Soils and Archeological Site Locations in Riparian Site Locations in Riparian

WetlandsWetlands Sandy deposits bordering Sandy deposits bordering

hydric areas were hydric areas were attractive for ancient attractive for ancient campsites.campsites.

Sand holds less water and Sand holds less water and will potentially drain faster will potentially drain faster than finer grain sediments.than finer grain sediments.

These sandy deposits are These sandy deposits are on sand bars, aeolian on sand bars, aeolian deposits, and natural deposits, and natural levees. They are often levees. They are often slightly higher than slightly higher than surrounding areas.surrounding areas.

Use soil maps and field Use soil maps and field observations to identify observations to identify sandy areas.sandy areas.

Drier Deposits and Archeological Drier Deposits and Archeological Site Locations in Riparian Site Locations in Riparian

WetlandsWetlands People chose the People chose the

best site available. best site available. Although sandy Although sandy areas are probably areas are probably ideal, ancient ideal, ancient campsites are found campsites are found on finer grain on finer grain deposits that have deposits that have low water tables low water tables when sandy deposits when sandy deposits were lacking.were lacking.

Common Ground Disturbing Common Ground Disturbing Actions in WetlandsActions in Wetlands

Shallow Water Shallow Water Excavations for Excavations for Wildlife (SWEW)Wildlife (SWEW)

Water Control Water Control Structure and Dike Structure and Dike ConstructionConstruction

Tile PluggingTile Plugging

Shallow Water Excavations for Shallow Water Excavations for WildlifeWildlife

SWEW’s are shallow areas SWEW’s are shallow areas scooped out by earthmoving scooped out by earthmoving equipmentequipment

Most are made in low spots in Most are made in low spots in the topography. These are the topography. These are mostly meander scars or filled mostly meander scars or filled in potholes.in potholes.

They usually contain hydric They usually contain hydric deposits or post settlement deposits or post settlement alluvium (PSA), which lack alluvium (PSA), which lack significant potential for significant potential for cultural resources.cultural resources.

Cultural resources can be Cultural resources can be found beneath these deposits, found beneath these deposits, so be careful if your SWEW is so be careful if your SWEW is deep or you are on the fringe deep or you are on the fringe of the low spot.of the low spot.

A soil scientist can be very A soil scientist can be very helpful in these situations.helpful in these situations.

Water Control Structures and Water Control Structures and Dike ConstructionDike Construction

Dikes and their water Dikes and their water control structures are control structures are mostly on hydric deposits mostly on hydric deposits or PSA, with little potential or PSA, with little potential for cultural resources.for cultural resources.

However, dikes have to However, dikes have to key into higher locations key into higher locations which are very high which are very high probability areas for probability areas for cultural resources.cultural resources.

The “key in” areas must be The “key in” areas must be very carefully examined. very carefully examined. Shovel test and use Shovel test and use screens if necessary.screens if necessary.

Plugging TilePlugging Tile Many wetlands are drained by Many wetlands are drained by

laying tile.laying tile. The tile needs to be plugged The tile needs to be plugged

or interrupted to restore or interrupted to restore wetlands.wetlands.

When the tile location is When the tile location is known, the tile can be plugged known, the tile can be plugged by digging into already by digging into already disturbed ground. There is no disturbed ground. There is no cultural resource problem.cultural resource problem.

If the tile can be located with If the tile can be located with a tile probe, there is no a tile probe, there is no problem.problem.

A careful investigation must A careful investigation must be done if a long backhoe be done if a long backhoe trench is needed to locate tile trench is needed to locate tile outside the original “footprint” outside the original “footprint” of construction, and outside of construction, and outside hydric or PSA deposits.hydric or PSA deposits.

River Valleys as High Potential River Valleys as High Potential Areas for Cultural ResourcesAreas for Cultural Resources

River valleys have always attracted River valleys have always attracted ancient and modern settlement.ancient and modern settlement.

River valleys provide dependable sources River valleys provide dependable sources of water, transportation corridors, a source of water, transportation corridors, a source of timber in prairie regions, a wide variety of timber in prairie regions, a wide variety of rich environmental resources, and of rich environmental resources, and shelter from the wind.shelter from the wind.

Some of the high potential areas already Some of the high potential areas already discussed (fans and riparian wetlands) are discussed (fans and riparian wetlands) are found in river valleys.found in river valleys.

Topography and Concentrations Topography and Concentrations of Archeological Sites in River of Archeological Sites in River

ValleysValleys Many favored camp Many favored camp

sites were on better sites were on better drained ground (fans, drained ground (fans, stream terraces, stream terraces, natural levees, and natural levees, and dunes) near water dunes) near water (stream channels, (stream channels, oxbows, springs and oxbows, springs and wetlands).wetlands).

Overlooks, especially Overlooks, especially those near springs are those near springs are high probability areas.high probability areas.

Post Settlement Alluvium Post Settlement Alluvium (PSA)(PSA)

PSA is very young PSA is very young over wash. Much over wash. Much of it is the result of of it is the result of modern cultivation.modern cultivation.

PSA is common in PSA is common in river valleys (and river valleys (and sometimes in pot sometimes in pot holes).holes).

PSA has little or no PSA has little or no potential for potential for cultural resources.cultural resources.

How to Identify PSAHow to Identify PSA

PSA may have a PSA may have a poorly developed A poorly developed A horizon, but always horizon, but always lacks a B horizon.lacks a B horizon.

PSA usually shows PSA usually shows alluvial stratification.alluvial stratification.

PSA is at the top of the PSA is at the top of the stratigraphic column stratigraphic column usually overlying a usually overlying a paleosol.paleosol.

Soils descriptions may Soils descriptions may indicate the presence indicate the presence of over wash.of over wash.

Trees as Indicators of PSATrees as Indicators of PSA Trees are a quick way to Trees are a quick way to

spot PSA.spot PSA. Tree trunks spread out Tree trunks spread out

near their base when on a near their base when on a stable surface.stable surface.

Tree trunks that have their Tree trunks that have their basal areas covered by basal areas covered by PSA stick out of the ground PSA stick out of the ground like fence posts.like fence posts.

Scientists have even Scientists have even counted tree rings, then counted tree rings, then measured the depth to the measured the depth to the root spread, and have used root spread, and have used this to estimate when the this to estimate when the PSA began accumulating.PSA began accumulating.

Archeological Sites Are Often Archeological Sites Are Often Associated with Special Associated with Special

Resources Resources Flint outcrops.Flint outcrops. Salt licksSalt licks Rock shelters and Rock shelters and

cavescaves Food rich wetlandsFood rich wetlands SpringsSprings

Things to think aboutThings to think about

Although cultural resources do Although cultural resources do concentrate in certain areas, they can be concentrate in certain areas, they can be found thinly scattered over much of the found thinly scattered over much of the landscape.landscape.

Rare, but sometimes important cultural Rare, but sometimes important cultural resources, such as steamboat wrecks and resources, such as steamboat wrecks and prehistoric fish weirs, are located where prehistoric fish weirs, are located where one would not expect to find a campsite or one would not expect to find a campsite or farmstead.farmstead.

The landscape changes over time. What is The landscape changes over time. What is now dry land may once have been a river now dry land may once have been a river bank or wetland, or some other magnet for bank or wetland, or some other magnet for human settlement.human settlement.