the geomorphology of the pig point site (18an50) landform ......the geomorphology of the pig point...

The Geomorphology of the Pig Point Site (18AN50)Landform Development, Climate Change, and Long-Term Human Occupation

D O N M U L L I S – T E T R A T EC HS T E P H A N I E S P E R L I N G – A N N E A R U N D E L C O U N T Y LO S T TO W N S P R OJ EC T

D R . F R A N K V E N TO - C L A R I O N P E N N S Y LVA N I A U N I V E R S I T YD R . A L LU C K E N BAC H – A N N E A R U N D E L C O U N T Y LO S T TO W N S P R OJ EC TJ A M E S M A R I N E , E D D O L A N – T E T R A T EC H

1

Source: Dr. Al Luckenbach – Anne Arundel County Lost Towns Project

2

Site BackgroundPromontory Bluff

Above 500 Year Floodplain

Jug Bay Western Shore Uplands

Patuxent River, Maryland

Site Background• Site initially recognized in

2008, with field excavations 2009 to 2015

• 149 5-ft square units documented 365 features, 630,000 artifacts, 30 c-14 dates which spanned nearly 10,000 years

• Three distinct areas excavated:• Lower Block• Upper Block• North Block

3

Site Map with Lidar-Derived DEM (ESRI)

Site Background• Lower Block – “Feasting Area”

• Contained Woodland period midden

• Stratified in situ Early, Middle, and Late Archaic cultural deposits

• Cultural deposits extended to over 6 ft (2 m) below grade

• Upper Block – “Habitation Area”• Intact stratigraphy from Late

Woodland to Early Archaic• Thousands post-holes marking

outlines of “wigwams”

• North Block – “Ritual Area”• Rare Adena-influenced mortuary

pits

Lower Block –“Feasting Area”

Upper Block –“Habitation Area”

North Block –“Ritual Area”

4

5Projectile Points – Over 500 Complete No Major Data Gaps

Lower Block – Depth (over 6 ft of Cultural Deposits) – Why?

6

Source: Dr. Al Luckenbach - AA County Lost Towns Project

Early Archaic Kirk

Point

Need for Additional Scientific Disciplines in Geology and Geomorphology

Geomorphological Investigation

Development of a Site Conceptual Model

Desktop Study(Previous Research)

Developed Draft Geologic X-Sections

Visual Observations via Site Visits of

Open Excavations

Hand Auger Soil Sampling (Multiple)

Digital Photography of Sediments

3D Stratigraphic Modeling

Multiple Lines of Evidence

Soil Survey and Soil Profile Analysis

ESRI GIS Mapping (LIDAR)

Coulter-Counter Grain Size Analysis

7

Geology• Patuxent River Valley Terrace

Deposits• Mapped as Pleistocene • Interbedded sand and

gravel• Lesser amounts of Silt/Clay• Quartzose gravel typically

concentrated in lower portion

• Cobbles and boulders of mafic rock

• Limonite conglomerate• Glauconitic Sands

8

Source: MGS – Anne Arundel County Geologic Map

Desktop Study

Site Location

9

Source: Synthesis on Quaternary aeolian research (2015)Markewich, Litwin, Wysocki, Pavich

Desktop Study

Dune Fields- Infilled parabolic- Medium Sands

(0.25-0.50 mm)- NW to SE Trending

Ridge lines

10ESRI GIS Mapping - LIDAR

Regional Map – Source Bordering Dune Aeolian Topography

LIDAR maps confirmed presence of parabolic topographic relief and NW to SE ridge lines

Aeolian Sand Soils in Pig Point and DORR Archeological Areas (NRCS)

Former Sand Quarry

Location

Pig Point(18AN50)

DORR(18AN19)

Infilled Parabolic Dune

Hand AugerLocations

11

Source: Ivester and Leigh (2003)

Relic Aeolian Conditions Determined by Soil Survey Data

20

20

40

40

60

60

40

20 Elevation of Ground Surface(Ft MSL)

0

B’

B

150 ft 300 ft 450 ft 600 ft 750 ft 900 ft 1,050 ft 1,200 ft 1,350 ft0 ft

0 MSL5 MSL

10 MSL

20 MSL

25 MSL

30 MSL

35 MSL

UB

LB

X

X

XX

JC

GroundwaterSprings/Seeps

SC1

Stream Channel

B B’

15 MSL

40 MSL

Marine Clay (Eocene)

Fluvial Terrace Deposits (Gravelly Sand)

Slope Wash (Holocene)

Upper Block

Lower Block

GroundwaterSprings/Seeps

Patuxent River

XX

Early Archaic Artifacts and features

Bt (Argillic Unit)

XNB

North Block

Development of Geologic X-Sections (Local Area)

Mantle of Relic Aeolian Sands

In Field - Data Collection

13

Data collection:• Soil sampling from open

excavations • Hand auger sampling at bottom

of archeological units and in near-by strategic areas

Data Collection – Soil Sampling and Completion of Hand Augers

Typical Digital Photograph of Sediments

Glauconite

14

Typical of Patuxent River Terrace Deposit Sediments

Iron Stained Quartz

Limonite ?

Digital Photography of Sediments

153D Stratigraphic Modeling (Site Specific)

Increased Variability of Gravel within Lower Block

(Adjacent to Swale/Stream Bank)

3D Model of Gravel/Non Gravel InterfacePotential Climate Change Events?

16Soil Profile Analysis Multiple A horizons, A/E transition, series BC horizons, C1/C2 fluvial gravel

Document multiple climate-driven erosional and depositional cycles

17Coulter-Counter Grain Size Analysis – 42 Samples

Highest % in Medium Sand Fractions

Higher % of VF and F Sand Higher % of C and VC Sands

Pleistocene Terrace Deposit Sediments

Relic Late Pleistocene Aeolian Sediments

Mean Grain Size calculated from <2 mm truncated

sample set

Gravel in Sample Bag

18Coulter-Counter Grain Size Analysis – Relic Aeolian vs Fluvial Coarse Gravel

Evidence of Change in Geomorphological Conditions

at Pleistocene/Holocene Contact (Younger Dryas?)

Evidence of Hypsithermal Sediment Accumulation

Changes?

Possible changes during Scandic Time Period

Increased Mass-Wasting during

Pacific/Little Ice Age, Late Woodland, and

Historic Periods

Colluvial Over-Printing and Mass Wasting During

Hypsithermal (5-7 ka)

Development of Anthropogenic “Midden”

during Stable Sub-Atlantic/Scandic/Neo-

Atlantic Early and Middle Woodland Periods Early Holocene

Landform Stabilization

Sediment Accumulation Rates and Climate Change 19

20

8670 815551495310 23252070

C-14 (Avg 2-sigmas YBP)

745 685

655

Hypsithermal(5-7Ka)

Chesapeake Bay

Stabilizes

Possible Erosional Sequence Along Lower Slope of

Swale

Scandic Disconformity

(increased flood frequency and

magnitude)

Warmer and Dryer

(decrease in vegetation

allowing more erosion during rain

events)

Sediment Accumulation Rates and Climate Change

21Climate Change and Long Term Human Occupation

Hypsithermal(5-7Ka)Chesapeake

Bay Stabilizes

22Summary – Correlation Chart

Geomorphic Landform Development of Pig Point(Late Pleistocene)

Northwest Southeast

Prevailing Wind Direction

Exposed Braid-Bars

Active Source-Bordering Dunes

Calvert Formation(Miocene -Marine)

Calvert Formation(Miocene – Marine)

Patuxent River Terrace Deposits (Alluvial)

Marlboro Clay (Eocene – Intertidal)

Paleo River ValleyAquia Formation (Paleocene – Shallow Marine)

Patuxent River Terrace Deposits

(Alluvial)

Braid-plain Sediments (Patuxent River)

Pig Point

Nanjemoy Formation(Eocene- Marginal Shelf)



Aquia Formation (Paleocene – Shallow Marine)

A

(a) Alluvial deposition of basal Pleistocene terrace sand and gravel deposits and Late Pleistocene deposition of active source-bordering aeolian dunes from braid-plain river sediments

23Geomorphic Landform Development

Geomorphic Landform Development of Pig Point(Late Pleistocene/Early Holocene)

Northwest Southeast

Exposed Braid-Bars

Relic Source-Bordering Dunes





Paleo River ValleyAquia Formation (Paleocene – Shallow Marine)


(Alluvial)

Braid-plain Sediments (Patuxent River)





Period of Erosion and Active Slope Wash

B

Pig Point

(b) Terrace scarp erosion during the warm, wet interstadial culminating in the cool and dry Younger Dryas


Geomorphic Landform Development of Pig Point(Early and Middle Holocene)

Northwest Southeast

Relic Source-Bordering Dunes





Paleo River Valley



(Alluvial)

Buried Braid-plain Sediments(Patuxent River)





Continued Slope Wash and Mass

Wasting

Holocene Sands and Silts (Alluvial)

Patuxent River(Beginning of Holocene Silts

and Meandering River)

C

Pig Point

(c) Increased erosion and colluvial over-printing (increased mass wasting) of up-gradient aeolian sands with enhanced activity in the Middle Archaic “hypsithermal”


Geomorphic Landform Development of Pig Point(Late Holocene to Present)

Northwest Southeast





Paleo River ValleyAquia Formation (Paleocene – Shallow Marine) Braid-plain Sediments (Patuxent River)





Holocene Sands and Silts (Alluvial)

Patuxent River(Sediment Laden

and Meandering)

Perched Water

D

Pig Point

(d) Landform stability and development of a cumulic A horizon with anthropogenic enrichment during the stable Sub Atlantic through Neo Atlantic (Early and Middle Woodland periods) and additional colluvial over-printing by accelerated

mass wasting from the Little Ice Age through historic deforestation (Late Woodland and Historic periods)

Cumulic A Horizon Develops


Colluvial Slope Wash and Remnants of Source-

Bordering Dunes


Special Thanks• Stephanie Sperling – Anne Arundel County Lost Towns Project• Dr. Frank Vento - Clarion Pennsylvania University• Dr. Al Luckenbach – Anne Arundel County Lost Towns Project• James marine, Ed Dolan – Tetra tech

the geomorphology of the pig point site (18an50) landform ......the geomorphology of the pig point...

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