Environmental Data

Introduction

The I-95 project is situated within the Coastal Plain physiographic province, which borders the Delaware River in southeastern Pennsylvania. The boundary of the Piedmont Plateaus province is from two to nine miles west of the river. The Piedmont and Coastal Plain meet at the Fall Zone, which represents a boundary between the two different ecological settings and was likely an attractive location for Native Americans because of the wide variety of resources available. The predominant geologic material on the Coastal Plain consists of Quaternary-age deposits largely dating to the Pleistocene. Younger Holocene landscapes no doubt once existed a quarter mile or more to the southeast beyond the present river shoreline, but these have long since been destroyed or inundated by rising sea level and the marine transgression that has produced the tidal estuary that now exists. Of great importance to Native Americans were the highly productive, interior wetlands associated with local drainageways that typically characterize most undulating Coastal Plain landforms. With the rising tidal transgression these wetlands eventually shifted to marshland.

Drainage

The I-95 project area is located along the Delaware River and within the Delaware estuary, the region surrounding rivers and streams affected by ocean tides. Prior to urban development the project area was in a setting near the Delaware River shoreline, which offered a highly rich and diverse environment to prehistoric inhabitants. In addition, tributary streams once flowed across the landscape between the Delaware and Schuylkill Rivers, making the region the home of productive freshwater swamps and marshes. The I-95 project area was drained by Gunners Run (formerly Tumanaranaming Creek) and Cohocksink Creek, both of which flowed from the Piedmont across the Coastal Plain to the Delaware River. Gunners Run was converted during the nineteenth century into the Aramingo Canal and later reconstructed as a sewer below the present-day Aramingo Avenue. Cohocksink Creek was also incorporated into the city’s sewer system and is below what is now Canal Street.

Prior to 10,000 B.P. the Delaware River was dynamic within a shifting channel that likely destroyed many Paleoindian and Early Archaic sites along its banks. The river stabilized in its present channel sometime between 10,000 and 8000 B.P. 1. As the climate warmed and glaciers melted, sea levels rose, placing the project area in a tidal setting by about the middle of the Holocene. Sea level rise continued through the Middle Woodland and likely drowned some early and middle Holocene sites in low-lying areas of stream valleys. The project area is within the Upper Zone of the Delaware estuary, characterized by tidal freshwater 2.

Stewart 3 posits three major periods of floodplain activity influenced by the rate of sea level rise. During the early and middle Holocene floods were frequent and of moderate to high energy. Alluvial deposits from this period at Area D of the Trenton Archaeological Site Complex are coarse-grained, representing high-energy flooding. From the middle Holocene to ca. 5000 B.P. floodplain accretion slowed and landscape stability increased. After ca. 5000 B.P. there was a dramatic slowing of rate of sea level rise. The intensity and frequency of floods was relatively low and there were periods of prolonged landscape stability. Alluvial deposits from this period at Area D are clayey silts, representing lower energy flooding.

There is considerable evidence of cyclical periods of landscape stability following ca. 5000 B.P. Periods of stability are identified as buried A horizons in alluvial deposits on Delaware River tributaries dating to the Late Archaic, late Middle Woodland, and Late Woodland 4. Upland sites with evidence of colluvium and mass-wasting also indicate variation in landscape stability.

Geology

The Quaternary deposits underlying the project area are classified as Trenton Gravel, the youngest of the Coastal Plain surficial sediments 5. The gravels consist primarily of white and gray quartz and quartzite, gray siltstone and sandstone, minor red siltstone and sandstone, and minor gray chert and gneiss. The deposits were laid down by glacial meltwater from Wisconsinan glaciation approximately 20,000 to 15,000 years ago 6. The deposits form a terrace along the Delaware River with a surface elevation of 15-25 feet above the river. There is a distinctive down-stream fining of the deposits, with coarser gravels in the Trenton, New Jersey, area grading to clayey silt at Philadelphia. Large areas of clayey deposits, referred to as “Philadelphia blue clay” and “Fish House Clay,” occur in the Philadelphia-Camden area 7.

Other nearby glaciofluvial deposits are the older and higher Pennsauken and Bridgeton Formations 8. The Bridgeton Formation forms a narrow band to the west of the Trenton gravels and also occurs on the Coastal Plain in New Jersey. It is comprised mostly of sand, but also includes boulders of shale and quartzite 9. Pennsauken gravels include quartz, quartzite, and chert. However, exposures of the Pennsauken gravels are limited in the vicinity of the project area; exposures are more widespread in the northern Delmarva Peninsula 10.

Soils

Because of the urban development within the project area, no data on undisturbed soils are available modern soil surveys. The I-95 studies indicate that areas of undisturbed natural soils are present in localities unaltered by urban development or preserved below fill.

Geomorphological studies conducted for the project indicate that the natural soils in upland settings are well drained and composed of loamy deposits in which soil formation has reached an advanced stage. Strongly developed subsoil argillic horizons (Bt) with nearly continuous clay films on most ped surfaces indicate a stable and prolonged soil weathering period readily compatible with a timeframe extending into the Pleistocene. Hence, cultural materials in these old Coastal Plain soils would be confined to near-surface levels, principally the original surface horizons (Ap). Some artifacts are also likely to have been mixed into upper subsoil transitional horizons (EB and BE) by natural bioturbation processes, but by the levels where subsoil argillic horizons (Bt) occur, at depths of about 25 to 35 centimeters below the original surfaces, prospects for any cultural materials become increasingly remote.

In contrast, investigations at the Dyottville site revealed both a middle Holocene terrace and fluvial sedimentation on what was originally the active floodplain of the former Gunnars Run. Some lower-lying deposits were also reflective of sea-level transgression and tidal conditions late in the Holocene and into the early Colonial era. The alluvial deposits comprising the former floodplain of Gunnars Run are stratified and exhibit no indications of pedogenic subsoil formation that would testify to any period of appreciable stability. By the late Holocene a lower energy estuarine sedimentary regime was also influencing the floodplain deposits. The floodplain surface during the Late Woodland occupation of the site was likely one foot or more above the normal high tide.

Paleoenvironment

The project area lies near the boundary of the Piedmont and Glaciated Sections of the Oak-Chestnut Forest Region as defined by Braun 11. Extant secondary forests of the region are composed of mesophytic arboreal species such as beech, white and red oak, sugar maple, ash, and walnut. However, the prehistoric forest was not only different from the modern forest in many respects, but was also in a state of gradual change for at least 8,000 years following the retreat of glacial ice.

Pollen data indicate that glacial ice began its final melt and retreat between 14,000 and 15,000 years ago 12. As the glacier retreated, temperatures increased and organic soil horizons developed. Watts 13 suggests that vegetation of this period may have been a mosaic; stands of spruce, dwarf shrubs, and wet meadows would have occupied areas free of permafrost and local areas of tundra would have been found on permanently frozen sites. This environment would have presented little in terms of edible plant resources for human populations. However, large, cold-adapted herbivores such as mastodon, buffalo, and caribou were available as human prey.

Beginning approximately 13,000 B.P., the climate and vegetation of the project area underwent changes as a result of the expansion of species ranges due to increasing temperatures. Webb and Bartlein 14 define the period between 12,000 and 9,000 B.P. as a period of decreasing influence of the ice sheet and increasing influence of summer solar radiation, with atmospheric circulation patterns becoming more like those of the present. Fir, jack pine, paper birch, and white pine were among the earliest immigrants to the area, advancing from glacial-period refugia in the south. Hemlock was present in the study area by 9600 B.P., and oak was also present at a relatively early date. Beech and hickory appear in the pollen record by about 7500 B.P. Chestnut, an exceedingly slow migrant, was not found in the study area until approximately 5,500 B.P. Many of the arboreal species that became established at this time represent food resources such as fruits and nuts, known to have been utilized both by humans and by faunal species hunted by humans, such as deer, elk, bear, and other small mammals 15.

Delcourt and Delcourt 16 show the presence of conifer-hardwood forests in the Mid-Atlantic region at 10,000 B.P. In addition to conifers and oak, these forests included cold-adapted, mesic species such as birch, elm, ash, ironwood, maple, and beech. Deciduous hardwoods and their related understory species likely occupied favorable topographic and edaphic niches and initially occurred as patches within a predominantly coniferous forest. The presence of carbonized grape, plum, and hackberry in a Paleoindian hearth at the Shawnee Minisink Site (36Mr43) on the Delaware River indicates that understory vegetation common in the temperate forest was present by this early period 17.

There is evidence to suggest that the period between 9000 and 5500 B.P. was characterized by a climate warmer and drier than present. Evidence for this Hypsithermal Period is strong in the Midwest where pollen data shows an advance of the prairie eastward into Illinois, reaching its maximum extent at about 7000 B.P. 18. Davis et al. 19 point to an increase in the altitudinal range of hemlock and white pine as evidence of a warmer, drier period between 9000 and 5000 B.P. in New England. Watts 20 in his examination of pollen diagrams in the Middle Atlantic region supports the hypothesis of a warmer, drier climate between 8500 and 5500 B.P.

Additional support comes from aeolian deposits found in the lower Delaware Basin. Evidence indicates a general discontinuity between soils 4000-6000 years in age and those 8000-10,000 years in age, attributed to one or more periods of erosion 21. Erosion could have resulted from reduced vegetation cover overall, or reduced vegetation cover during winter and spring, when cover is generally low. The latter is more likely since pollen data does not show changes that would indicate a dramatic reduction in vegetation.

Effects of the warmer, drier climate included a decrease in the number of low order streams, lower water volume in streams generally, a decrease in biomass on ridges, and a lowering of the water table 22. Evidence provided by correlations of pollen core data with pollen from surface samples from known vegetation types suggests that the overall composition of the vegetation did not change radically 23. However, changes in stream characteristics and wild food productivity would likely have had some effect on the distribution of prehistoric populations. Specifically, upland areas would have become relatively less attractive, whereas major riverine areas such as the Delaware River floodplains and terraces would have been relatively more attractive.

Although there is some disagreement regarding the occurrence of a Hypsithermal climatic optimum in the Northeast, there is still greater disagreement regarding the climate following 5000 B.P. A number of researchers have presented evidence that is interpreted as indicating an environment characterized by severe climatic fluctuations, including a warm, dry, or xerothermic, period between 5000 and 2600 B.P. 24. However, the evidence for a widespread warm, dry climate is not conclusive 25. Although modern levels of temperature and precipitation were likely maintained in the Delaware River Valley, cyclonic storms, as evidenced by flood scouring and the deposition of coarse-grained material on the floodplains, appear to have occurred with greater frequency than in previous periods.

After ca. 5000 B.P. floodplain and terrace soils supported mesophytic species such as beech, oak, tulip tree, ash, sugar maple and walnut 26. Upland soils supported forest communities dominated by chestnut, hickory, and oak, all of which provided edible nuts for Native American populations. Beech, along with other mesophytic species such as tulip, oak, sycamore, mulberry, wild black cherry, and holly, covered ravine slopes. The Late Holocene forest differed from the modern forest primarily in age structure, the Late Holocene vegetation being an all-aged forest containing a mosaic of gaps caused by falls of senescent trees and in various stages of regeneration. These gaps supported a variety of edible resources that grow best in the open, including berries such as blackberries, raspberries, fruits such as persimmon and wild cherry, and a variety of plants with edible tubers.

With rising sea levels and resulting tidal transgressions, wetlands along stream channels shifted to marshland. Freshwater tidal marsh vegetation includes a variety of plant associations whose composition is based on proximity to tidal waters 27. Plants associated with freshwater tidal environments include wild rice, cattail, ferns, and other emergent wetlands vegetation. Wild rice and smartweed, along with a variety of tubers such as cattail, pond lily, pickerelweed, and arrowhead, provided food resources for Native Americans. Plant associations dominated by wild rice occur in the lower reaches of tidal marshes and are most highly developed in quiet waters 28. Tubers were likely an important food source in the spring, when other plant food resources were not in season. In addition, wetland environments were attractive for a variety of mammals and migratory waterfowl.

Over 200 species of fish, including both residents and migrants, currently use the Delaware estuary and would have been available to Native Americans 29. Game fish in streams and rivers include brook trout, sunfish, crappie bass, largemouth bass, yellow perch, common carp, various catfish, and various flounder species. Diadromous fish, which travel between saltwater and freshwater habitats, were also available and provided predictable and highly productive resources as a result of their migratory behavior. Anadromous fish migrate upriver from the ocean between March and June to spawn in freshwater 30. Species include American shad, alewife, blueback herring, striped bass, sea lamprey, and Atlantic sturgeon. Nursery areas are located in shallow marsh fringe areas and mudflats 31. American eel is a catadromous species, which lives in fresh water and migrates to saltwater between August and November 32. Atlantic sturgeon and American shad were identified in small amounts in archaeological contexts within the Abbot Farm National Historic Landmark 33. Freshwater mussels were also available to native populations.

The Delaware River valley also supported a wide range of terrestrial and avian fauna. However, the contemporary fauna do not necessarily represent the full range of species that were available for exploitation by aboriginal populations during the late Pleistocene or Holocene. Late Pleistocene through Recent (12,500 B.P. to Present) faunal remains found in the region indicate that considerably more species would have been available for aboriginal exploitation in the past than are now present, though population densities and distributions would have varied from that seen today 34. White-tailed deer was the most abundant large mammal in the region. The principal small-game included raccoon, opossum, striped skunk, eastern spotted skunk, wood chuck, gray squirrel, muskrat, gray and red fox, eastern cottontail and beaver. Game birds included wild turkey, American woodcock, ruffed grouse and Canadian geese, as well as a large number of ducks that rest and feed on lakes, ponds and rivers during their annual fall/spring migrations.

Lithic Resources

Most of the tools encountered at Native American archaeological sites are fashioned of stone, or lithic, material. The most common lithic materials at sites identified in the I-95 survey were jasper, chert, argillite, quartzite, and quartz. These materials are generally consistent with those recorded at other archaeological sites, where argillite, quartzite, quartz, and jasper are most often reported. Jasper sources are located in the Hardyston Jasper Prehistoric District in the Reading Prong of Lehigh, Berks, and Bucks Counties. Jasper is also present in bedrock found in northern Delaware, where it is known as Iron Hill jasper. Quartzite was also quarried from the Hardyston formation. Chert consisted primarily of gray to black material, likely procured from the Great Valley province, to the north of the Reading Prong. Quartz is widely distributed in the Piedmont Plateau. Argillite outcrops in the Piedmont and in locations along the Susquehanna and Delaware Rivers. In addition, many of the cobbles found along the Delaware River and tributary streams are lithic materials use in tool manufacturing.

Pleistocene Gravel Formations

Trenton gravels, which underlie the project area, are glaciofluvial in origin and consist primarily of white and gray quartz and quartzite, gray siltstone and sandstone, minor red siltstone and sandstone, and minor gray chert and gneiss. The Trenton gravels contain materials from throughout the Delaware Basin, including Lockatong argillite, New York State Onondaga chert, Pennsylvania jasper, and others 35. Wall et al. 36 identified exposures of the Trenton gravels in Abbot’s Brook along the Delaware River and along a stream that had cut through the overlying aeolian deposits and into the gravels. Cobbles of quartz, quartzite, argillite, chert, and feldspar were observed. Chert and jasper cobbles, likely from the Trenton gravels, were identified at the Shady Brook Site, one of the sites comprising the Trenton Archaeological Site Complex 37.

In addition to the Trenton Gravels, chert is found in other Pleistocene deposits in the Lower Delaware Valley, including the Bridgeton and Pensauken Formations 38. The Bridgeton Formation outcrops in the extreme southern and southwestern portions of New Jersey. Lavin 39 reports outcropping of the Pensauken Formation in a belt extending from the Trenton area southwest, but indicates that chert comprises less than 10 percent of the deposit in this area. The chert is reported as black, dark blue, bluish-black, and buff-colored. Lavin 40 reports from personal communications that Hardyston Jasper does not occur in the Pensauken Formation.

Jasper

High-quality jasper occurs within the Hardyston Formation, a Cambrian-age formation that extends in a northeast-southwest direction within the Reading Prong. The Hardyston Jasper Prehistoric District encompasses known prehistoric jasper quarries associated with this formation. The District is bounded on the east and southeast by the Delaware River, on the west and southwest by the Schuylkill River, and on the north by the northern boundary of the Great Valley 41. The boundaries encompass both the zone of known jasper quarries, defined as the Quarry Zone, and the major concentration of non-quarry sites with 50% or more jasper in the lithic assemblage, the Activity Zone.

Ten major prehistoric jasper quarries are known within the Reading Prong, six in Lehigh County, three in Berks County, and one in Bucks County. Because the jasper occurs as float material within the soil, the quarries are represented by pits surrounded by rings of backdirt. The pits at the six sites that have not been destroyed have been mapped 42. The quarry at Macungie was apparently the largest, with as many as 400 craters extant in the late nineteenth century 43. Several geochemical studies of both source and archaeological materials have been done using either X-ray fluorescence or Neutron Activation Analysis 44.

Sites with more than 50% jasper in the Great Valley generally are not found more than 5 miles from a jasper quarry 45. In the Piedmont, however, where other high-quality lithic materials are not present, jasper use extended to greater distances. Overall, Anthony and Roberts conclude that jasper was not subject to any special procurement effort but that lithic use was primarily related to source distance 46.

Both projectile point data at the Vera Cruz jasper quarry 47 and PASS file data on jasper use for District sites 48 indicate that jasper procurement and use was most intensive in the Late Woodland, followed by the Middle Woodland and Late Archaic/Transitional periods. However, these data may instead reflect the limited available diagnostics for the Early Woodland and a general increase in population density over time. Hardyston jasper is also frequently used for fashioning Paleoindian points in southeastern Pennsylvania and adjacent New Jersey 49. Jasper points of this period are found in areas as distant as New England 50 and New York 51.

Chert

Chert occurs in the Cambrian Allentown and Lower Ordovician Beekmantown formations of the Great Valley 52. The Beekmantown group is made up of formations of limestone and dolomite that underlie the Lehigh Valley. The Allentown formation is found along the northern boundary of the Reading Prong. The material is generally black, light gray, or dark gray, and is mostly fine-grained 53. Allentown/Beekmantown chert is also available in secondary deposits along streams, including along the margins of the Little Lehigh Creek 54. Quarry sites like those of Hardyston jasper have not been reported.

The use of chert appears to be less frequent in the Lower Delaware Valley, since non-cobble chert sources are located at some distance. Of 1638 sites in the Pennsylvania Cultural Resources Geographic Information System (CRGIS) that record lithic types present, only 27 percent report the presence of chert. In contrast, 67 percent of sites in the Middle Delaware Valley, where the Allentown and Beekmantown formations outcrop, record the presence of chert.

Quartzite

Quartzite is a common lithic material on sites in the lower Delaware River Valley. The material is found in the Hardyston Formation of the Reading Prong in Bucks, Lehigh, and Berks Counties, Pennsylvania. A number of prehistoric quartzite quarries have been recorded. Sites 36Bk723 and 36Bk724 are located on the slopes of Irish Mountain and Sites 36Bk14 and 36Bk511 are located near the jasper quarries at Lower Longswamp. A quartzite boulder field (36Bk510) is located nearby. The quartzite quarries near Robesonia were investigated as part of the Blue Marsh Lake Project 55.

Quartzite also occurs in cobbles fields along the cuesta, a ridge of the Bridgeton Formation, which separates the Inner and Outer Coastal Plains in New Jersey 56. The cuesta quartzite is a distinctive pale grayish brown, pink, or reddish material. Quartzite boulders occur at or near the surface or eroding from hillsides. Quartzite boulders have been reported as far north and east of the cuesta as Burlington and Monmouth Counties. The material generally occurs as cobbles about 30 centimeters in diameter, but much larger boulders have also been observed. Quartzite is also a component of the Trenton Formation gravels and may have been available in stream channels and along stream banks cutting through the formation.

Quartz

Both white quartz and quartz crystal artifacts were recovered during the field surveys. Quartz is available in surface deposits in scattered locations in the Piedmont physiographic province, having weathered from bedrock. Quartz is also abundant in stream channel gravels.

Argillite

Argillite forms from metamorphism of siltstone at low temperatures and pressures 57. The material is not as hard as cryptocrystalline quartz and patinates quickly. Unpatinated argillite is black to gray in color with a grainy texture. Weathered argillite is lighter gray, green, purple, and variagated and can become soft and porous 58. The material was frequently used for stemmed points and for Koens-Crispin and other broadspears.

Argillite is present within the Lockatong Formation, a Triassic formation found in Montgomery and Bucks Counties, Pennsylvania and Hunterdon County, New Jersey. Sources of argillite are found in the Piedmont and in large outcrops occur along the Delaware River. The outcrops include massive blocks of variable quality and smaller blocks used for stone tool manufacturing 59. The Byram 60 and Lower Blacks Eddy 61 sites are argillite tool manufacturing locations on the New Jersey and Pennsylvania sides of the river, respectively. Both are close to argillite outcrops at Gaddis Run, where quarry pits have been identified 62.

Secondary sources of argillite were also utilized, as evidenced by findings at sites of the Trenton Complex of archaeological sites 63. Argillite cobbles have been found south of the Point Pleasant/Byram area and are also likely to occur along drainages that cut through the Lockatong formation 64. Argillite at these sites was used for bifacial reduction, whereas expedient tools were fashioned from cherts and jasper. Argillite was used as early as the Early Archaic and into the Woodland period before largely giving way to cherts and jasper in the Late Woodland 65.

Steatite

Steatite, or soapstone, is a very soft stone that was used primarily for the production of cooking vessels. It was also used as a temper in early pottery and, less frequently, for decorative items such as beads and pendants. Steatite was widely traded in the Midwest and Southeast, where thousands of steatite vessels were traded through the Poverty Point network. A much more limited trade system was evident in the Susquehanna Valley between 3,000 and 3,800 B.P. 66. Steatite is listed in the CRGIS at only five non-quarry sites in the Lower Delaware Valley. Of the four sites with temporal data, three are multicomponent and one is associated with the Piedmont tradition. On sites where steatite artifacts are found the numbers are generally low, indicating that steatite bowls supplement but did not replace the use of containers made of hide, bark, or other perishable materials.

Steatite occurs in metamorphosed schists, gneisses, or ultramafic intrusives such as the Wissahickon and Peter’s Creek schist geological formations, both of which extend across the Piedmont 67. In Pennsylvania, known quarry complexes occur in the Lower Susquehanna and Lower and Central Delaware valleys. Three steatite quarries (36Ch30, 36Ch31, and 36Ch34) are recorded in the CRGIS in the Lower Delaware Valley. All three are located in Chester County, from 32 to 42 miles west of the I-95 project area.

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