1 When Sand, Snails, and Shorelines Mix: Exploring

Home , Assiminea succinea, Gastrocopta contracta, Parvanachis, Polygyra, Truncatella (gastropod), Truncatellidae

WHEN SAND, SNAILS, AND SHORELINES MIX: EXPLORING THE USE OF TRUNCATELLA AS A PROXY FOR RELATIVE SEA LEVEL

CAROLINE A. STEFFY

A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF BACHELOR OF ARTS WITH HONORS IN ANTHROPOLOGY

UNIVERSITY OF FLORIDA

May 2019

 2019 Caroline A. Steffy

ACKNOWLEDGEMENTS

I thank Dr. Ken Sassaman for the initial opportunity to work at the Laboratory of

Southeastern Archaeology (LSA) and for his continued guidance and mentoring. Funding for the

Lower Suwannee Archaeological Survey is provided by the Hyatt and Cici Brown Endowment for Florida Archaeology. Archaeological field work at Clam Beach (8LV66a) was conducted under Archaeological Resources Protection Act (ARPA) permits LSCKNWR022113,

LSCKNWR060614, and LSCKNWR060315 issued by the United States Fish and Wildlife

Service.

The identification of snail taxa was greatly enhanced by the generous assistance of Dr.

John Slapcinsky of the Florida Museum of Natural History.

I am grateful to Anthony Boucher and Terry Barbour for their seemingly endless supply of entertaining stories and witty banter that spiced things up during long hours of sorting at the lab.

A very special gratitude goes out to Julie, Todd, Christie, Lola, and Sookie Steffy: my biggest support system.

Last but certainly not least, I thank Brandon Cooke, Kasthuri Selvakumar, Vincent Trang,

Ensung Kim, Marcos Ramos, Forrest Meyers. Their encouragement and friendships have helped me more than they could ever know.

TABLE OF CONTENTS

Page

ACKNOWLEDGEMENTS...... 3

LIST OF TABLES...... 5

LIST OF FIGURES...... 6

ABSTRACT...... 7

CHAPTER

1 INTRODUCTION...... 8

Background...... 9 Sea Level Rise...... 12

2 MOLLUSK ECOLOGY...... 19

Truncatella Ecology...... 19 Common Mollusk Ecology...... 21

3 EXCAVATION AND LAB METHODS...... 27

Excavation Methods...... 27 Mollusk Analysis Methods...... 29

4 RESULTS OF MOLLUSK ANALYSIS...... 38

5 DISCUSSION...... 45

6 CONCLUSION...... 53

LIST OF REFERENCES...... 55

LIST OF TABLES

Table Page

4-1 Absolute Frequency of Taxa, TU1, 2-mm...... 41

4-2 Standardized Frequency of Taxa, TU1, 2-mm...... 42

4-3 Absolute Frequency of Taxa, TU1, 1-mm...... 43

4-4 Standardized Frequency of Taxa, TU1, 1-mm...... 44

LIST OF FIGURES Figure Page

1-1 Map of the study area of the Lower Suwannee Archaeological Survey showing locations of archaeological sites on record...... 16

1-2 Topographic map of the Cedar Keys, with aerial photo inset of North Key, showing locations of Clam Beach (8LV66a) and two other archaeological sites (Mahar 2019)...... 17

1-3 Timeline comparing climate episodes with sea level estimates...... 18

2-1 Distributions of T. caribaeensis and T. pulchella...... 20

2-2 Photo illustrating Juvenile and Adult Truncatella...... 25

2-3 Illustrating Hawaiia Sp...... 26

2-4 Illustrating Gastrocopta contracta...... 26

3-1 Photographs and scaled drawings of the profiles of the east and south walls of Test Unit 1, Clam Beach...... 32

3-2 Photographs and scaled drawings of the profiles of the west and north walls of Test Unit 1, Clam Beach...... 33

3-3 South Profile of TU1 showing approximate locations of charcoal samples submitted for radiocarbon assays and resultant two-sigma calibrated age ranges...... 34

3-4 Field school student excavating bulk column sample from east wall of TU1 at Clam Beach...... 35

3-5 Process of Sorting a Sample into Distinct Taxa...... 36

3-6 Process of Counting Members of Taxon Hawaiia Sp...... 37

4-1 Comparing Frequencies of Taxa in 2-mm Samples...... 40

5-1 Graph of Standardized Frequency of Truncatella Adults by Sample...... 50

5-2 Graph of Standardized Frequency of Truncatella, Gastrocopta contracta, Hawaiia Sp...... 51

5-3 Schematic of the Present-day shoreline at Clam Beach in relation to TU1...... 52

Abstract of Honors Thesis Presented to the University of Florida College of Liberal Arts and Sciences

WHEN SAND AND SNAILS AND SHORELINES MIX: EXPLORING THE USE OF TRUNCATELLA AS A PROXY FOR RELATIVE SEA LEVEL

Caroline A. Steffy

May 2019

Mentor: Kenneth E. Sassaman Major: Anthropology

This thesis investigates the potential of archaeological shell from snails of the genus

Truncatella as a proxy for changes in sea level over the past 4,000 years. Analysis centers on snail shells from an archaeological site on the northern Gulf Coast of Florida, a region that is highly susceptible to shoreline transgressions. Variations in the frequency of Truncatella shells in stratified deposits at Clam Beach (8LV66a) enable inferences about rising sea after 4,000 years ago that are compared against regional reconstructions of changing sea levels. Additional terrestrial snail taxa provide independent data for evaluating inferences based on Truncatella shell.

Results show that there were two spikes in the frequency of Truncatella: one on a buried surface dating to BC 85-AD 60, and one in the uppermost stratum, dating to around AD 655-770.

Upon comparing the frequency variation of Truncatella with regional reconstructions of sea level, I conclude that this taxon is likely to provide a useful proxy for the relative elevation of sea. However, additional archaeological deposits must be analyzed to substantiate this claim; the results of this pilot study shows this to be a worthwhile prospect for future research.

CHAPTER 1 INTRODUCTION

Since humans first colonized North America over 14,000 years ago, sea level has risen over 100 m, repeatedly drowning coasts vulnerable to shoreline transgression (Donoghue 2011).

The Gulf Coast of North Florida has been and continues to be especially vulnerable to this trend because of its low-gradient terrain. Throughout time, many now-submerged deposits have accumulated, their geological records holding vast stores of information about rising sea.

Underwater archaeological sites provide additional data, but few have been adequately investigated to infer relative sea level from anything other than location (Faught 2004). A third potential data source are the terrestrial archaeological sites along the modern coastline for at least the past 4,500 years, when sea level came to within a few meters of modern levels. These sites hold the records of millennia of human settlement and contain vertebrate and invertebrate fauna, plant remains, sediment, and other proxies for relative sea level. The location and context of these sites is insufficient to infer sea level as they involve human choices beyond proximity to coastlines or availability of near-shore resources. Needed are independent proxies, measures of variation in sea level that are not affected or determined by human activities.

In this thesis I investigate the inferential potential of one such independent proxy, the shells of terrestrial snails of the genus Truncatella. This potential is manifested in its narrow ecological niche, the high tide line of beachfaces, where seaweed and other detritus accumulate.

Although storm surge, human intervention, and other factors may disrupt a direct correlation between sea level and Truncatella accumulations, these minute snails have been proposed as a useful proxy for sea level relative to depth of archaeological deposits (Palmiotto 2015).

The case study of this thesis is a stratified archaeological site on an offshore island near the present-day town of Cedar Key, Florida. Spanning 4,000 years in age, the ~1.5 m of stratified

8 deposits of Clam Beach (8LV66a) contain abundant terrestrial snails. With particular attention to shells of the genus Truncatella, the analysis reported here leads to several inferences about not only changing sea level but also depositional contexts attending changes in shoreline morphology.

Background

The study area of the Lower Suwannee Archaeological Survey (LSAS) is comprised of

42 kilometers of coastline that has largely escaped development in modern times. It is situated along the northern portion of Florida’s Gulf Coast and covers two wildlife refuges with over 110 archaeological sites (Sassaman et al. 2016) (Figure 1-1). One of the thirteen islands off the shore of the modern day town of Cedar Key is North Key, which contains two state-registered sites:

A.B. Midden (8LV65) and Clam Beach (8LV66a) (Mahar 2018). The subject of this thesis project is the assemblage of terrestrial snail shells collected from a 1.5-m-deep column of midden from a 1 x 2-m excavation unit at Clam Beach.

The recorded name of site 8LV66a is North Key Midden, South; however the sheer volume of hard clam shells located on both the beach and in the midden led researchers at the

Laboratory of Southeastern Archaeology (LSA) to unofficially refer to the site as “Clam Beach.”

The midden of Clam Beach extends for 300 meters along the beach and 35 meters inland

(Sassaman et al. 2015).

Clam Beach is an ideal site to compare the presence of mollusks throughout time. This is due in part to the fact that the presence of clam shells on the beach and within the landscape have provided protection to the landform. Other factors are that the site is situated on the eastern side of the island and therefore facing away from open waters of the Gulf of Mexico where many weather events such as hurricanes travel bringing strong winds and waves that have erosive

9 effects on landforms. This protection is also enhanced because the beach is partially sheltered from storm surge and other forces of nature because it is protected by a small land barrier that would act as a wave breaker during harsh storms. The positive effects that these protective forces have had on the preservation of the beach can be observed through the contrast of this island with its neighbors. Although all of the islands are experiencing varying levels of erosion, those with sandier soils and unprotected shorelines that lack the natural benefits Clam Beach enjoys are experiencing more eroded conditions. As the years pass, any cultural context present will be at best disrupted, and at worst destroyed or swept away. The natural protections this site has enable us to be able to use the counts of Truncatella and other mollusks with relative security that they are accurate to the original deposition.

Archaeological testing of Clam Beach began in the summer of 2014 by students of the

Lower Suwannee Archaeological Field School of the LSA. Subsurface excavations began in

2014 with one shovel test pit (STP) and one 1 x 1-meter test unit. The STP excavation ceased at

100-cm below surface (cmbs) without reaching the subsurface of the midden due to wall collapse. Because of this, a second unit was opened nearby to again attempt to reach the base of the midden. The excavation of this test unit (TU1) was left incomplete at the end of the season due to time constraints and excavation resumed the following season in 2015 (Mahar 2018).

Revealed in this effort was a 1.5-m thick, well-stratified deposit with several buried surfaces and accretional shell midden spanning much of the past 4,000 years. A 30 x 30-cm column was removed from the profile of the completed excavation and it was from this sample that terrestrial snails were recovered for the forgoing analysis. Among the shells of numerous terrestrial snail taxa were an abundance of shell from the genus Truncatella.

Truncatella is a genus of terrestrial gastropod belonging to the family Truncatellidae

(World Register of marine Species n.d.). They are commonly called looping snails and they are small in size with a length of approximately 3-6 mm (Burch et al. 1980). What makes them pertinent to this study is their habitat. Their niche is in the wrack zone of a shoreline, which is defined as “the shifting region just above the high-tide line, where seaweed, woody debris, and floating objects of all kinds are deposited by waves” (Wrack Community n.d.).

Because of their unique niche, Truncatella have been useful tools in past archaeological research to assist in approximating sea level. One notable researcher is archaeologist William

Marquardt who studies the Calusa people of southwest Florida (Marquardt and Walker 2013).

Pineland is located in the coastal area of Southwest Florida which is highly susceptible to hurricanes due to its location on the Gulf of Mexico. In his work at Pineland, Marquardt noted that at the Old Mound site, a stratum of the midden was determined to have been deposited due to onshore deposition and wetland episodes because of direct evidence of the high frequency of marine mollusks strengthened with the indirect evidence of the presence of Truncatella.

Truncatella do not wash up with sea grass because they are terrestrial snails, but they are drawn to these rotting grasses after they are deposited, so when you find a high concentration of these snails in an area, you can be sure that a deposit of rotted sea vegetation occurred and that there was likely a storm surge at one time that ended at that spot (Marquardt and Walker 2013).

Another researcher who has made use of the specific environment in which Truncatella thrive is Andrea Palmiotto (2015). The aim of her research was to document variations in faunal utilization through time and space within the Lower Suwannee region and to interpret paleoenvironmental conditions in order to test hypotheses concerning seasonal resource procurement. She did this by finely screening through deposits at eight sites and in many of these

11 sites Truncatella were present. The presence of Truncatella shells suggested to Palmiotto that materials were deposited near high-tide lines or that seaweed was collected from the shore. For instance, she was able to determine that the shoreline was proximate to the western side of a site known as Shell Mound when it was occupied from AD 430 and 660 (Palmiotto 2015). Although her results and those from work at Pineland provide encouragement that Truncatella can indeed provide a useful proxy for relative sea level, additional work is needed to distinguish anthropogenic and storm-surge factors from those of ambient sea-level rise.

Sea Level Rise

As a very general trend over the past 20,000 years, sea levels have been rising at decelerating rates toward the present elevation (Donohue 2011). From Florida’s geologic record including sedimentology, stratigraphy, radiocarbon dating, and paleontology, sea-level rise over the past 20,000 years can be divided into three distinct marine transgression intervals. The first was from the Late Pleistocene to the early Holocene which was between 20,000 and 8,000 years before present (ybp). During this period, sea levels rose around 10 to 20 mm per year leading the coast to respond with submergence, overstep, and widespread shoreline retreat. The second period occurred in the mid-Holocene, 8,000-3,000 ybp when waters rose just 2 mm/year. This was a period when there was a widespread formation of coastal environments, barrier islands, and relatively modest shoreline retreat. The most recent period, is the late-Holocene, which spans the past 3,000 years. During this time sea levels have risen 0.1 to 0.2 mm/year. This has caused a coastal response of aggradation, shoreline stabilization, and progradation (Parkinson et al. 2010).

Occasional overstep events resulting from an imbalance between aggradation and sea-level rise resulted in local transgressions of one or more kilometers. One such event has been inferred from

12 geological coring in the Lower Suwannee region to have occurred around AD 100 (Wright et al.

2005).

Changes in sea level track general changes in global climate. Climatic trends over the past few millennia include a period of warmer climate from ca. BC 350-AD 450/500 deemed the

Roman Warm Period; a period of cooler temperatures from AD 450/500 to AD 850, the so-called

Vandal Minimum; the Medieval Warm Period from AD 850-1200; the Little Ice Age of AD

1200-1850; and finally the Modern Warm Period beginning in 1850 (Marquardt et al. 2013).

These trends have been investigated within the context of the Pineland site once inhabited by the

Calusa people of southwest Florida. The research at Pineland is informed by studies of sea level fluctuations in a raised beach-ridge plain of coastal Denmark. This Danish record is finely resolved in 50-year increments that are used to infer changes in sea level by less detailed records around Florida and the greater North Atlantic Region (Marquardt et al. 2013). The timeline used by Marquardt et al. (2013) comparing sea level with climate episodes can be found below

(Figure 1-2).

Clam Beach is located on a small island about 8 km from mainland of the Lower

Suwannee region, Like much of the of the coastline of the Florida Gulf, Clam Beach consists of low-lying, sandy deposits and is thus extremely vulnerable to changes of sea level. North Key and surrounding islands have eroded with rising sea (Wright et al. 2005) and are expected to eventually disappear with continued sea-level rise. However, due to the accumulation of anthropogenic deposits dominated by bivalves (e.g. oyster, clam) and large gastropods (e.g., lightning whelk, crown conch) locations like Clam Beach are more resistant to erosion than sand and thus preserve records of environmental changes in stratified midden spanning millennia.

Given that sea-level change is driven by global-scale climatic processes, it is reasonable to expect Clam Beach to contain in its stratified deposits evidence for the trends described by the aforementioned research on climate change. However, in seeking such evidence one must be mindful that anthropogenic deposits contain far more than the de facto remains of locally collected taxa; that is, oyster or conch deposited at Clam Beach, for instance, could have been collected kilometers from the site and thus not be terribly useful in inferring relative sea level at this particular location along the coast. Truncatella shells and those of other small terrestrial snails, on the other hand, were not the inedible remains of meals but instead entered into anthropogenic deposits by virtue of proximity to their habitat. Again, Truncatella is especially useful for inferring proximity to the shoreline because of its specific niche. Still, one cannot expect a one-to-one correlation between the frequency of Truncatella shells in anthropogenic deposits and proximity to the shoreline because humans could well have intervened occasionally by displacing wrack from its original context. Likewise, as documented in South Florida,

Truncatella and the wrack debris in which it thrives is subject to displacement by storm surge.

To control for intervening processes such as these I enumerate in this thesis the abundance of terrestrial snail shells from taxa that inhabited niches away from the shoreline. The results suggest that Truncatella generally are a useful proxy for inferring seas level, but that it accumulated under different circumstances and on surfaces with varying morphology and thus varying depositional dynamics. I also conclude that additional research is warranted to corroborate the inferences made possible by Clam Beach snails.

In the chapter that follows I provide a description of the morphology and ecology of

Truncatella, the excavation and laboratory analysis methods employed to collect data, and the stratigraphy and radiocarbon dates of Clam Beach are described in Chapter 3. Chapter 4 provides

14 the results of the mollusk analysis, followed by a discussion of the results and their implications for the height of the sea level relative to the site in Chapter 5. I conclude with a summary of the research reported here and recommendations for further research in Chapter 6.

Figure 1-1. Map of the study area of the Lower Suwannee Archaeological Survey showing locations of archaeological sites on record. North Key and the site of Clam Beach (8LV66a) is location 18, west of the town of Cedar Key (Sassaman et al. 2016).

Figure 1-2 Topographic map of the Cedar Keys, with aerial photo inset of North Key, showing locations of Clam Beach (8LV66a) and two other archaeological sites (Mahar 2019).

Figure 1-3. Timeline comparing climate episodes with sea level estimates, temperatures, and cultures of Southwest Florida (Marquardt et al. 2013)

CHAPTER 2 MOLLUSK ECOLOGY

For the purposes of this research, it is crucial to understand the ecologies of the various mollusk taxa that have been deposited within the matrix of each stratum of TU1 at Clam Beach.

This chapter provides descriptions on the preferred habitats and ecologies of the common mollusks that have been deposited within nearly every sample. In following chapters, the exact frequencies of these mollusks will be provided.

Truncatella Ecology

Few terrestrial snails have an ecological niche as specific as members of the genus

Truncatella. In this chapter I review what is known about the taxonomy and ecology of snails of this genus as a basis for inferring relative sea level.

There are approximately thirty distinct species of Truncatella. These include T. avenacea,

T. bahamensis, T. bairdiana, T. brazieri, T. californica, T. caribaeensis, T. ceylanica, T. clathrus, T. diaphana ,T. ferruginea, T. granum, T. guerinii, T. kiusiuensis, T. marginata, T. obscura, T. pellucida, T. pfeifferi, T. pulchella, T. quadrasi, T. rostrata, T. rustica, T. scalarina,

T. scalaris, T. stimpsonii, T. subcylindrica, T. teres, T. thaanumi, T. truncatula, T. vincentiana, and T. yorkensis (World Register of marine Species, n.d.). Of those, only four are expected in the state of Florida (T. clathrus, T. caribaeensis, T. pulchella, and T. scalaris), and only T. caribaeensis and T. pulchella are expected in the region of the Gulf of Mexico near North Key

(Burch et al. 1980; Clench et al. 1948). Because these species have a common niche, and because it is their niche which is crucial in this research, I will simply refer to the aforementioned taxa as

Truncatella.

Figure 2-1. Distributions of T. caribaeensis and T. pulchella (Burch et al. 1980).

Truncatella are notable for their morphology as the shell is composed of ribbed detachable whorls. As juveniles, those whorls end with an apical point, however as they mature from juvenile to adult, the snail forms a “septum, a rounded and concave plug, in the region of the mid-whorls. Fracture of the early whorls takes place along the outer margin of this septum where it joins the side of the shell” (Clench et al. 1948:157). The apex of their shell breaks off at about the fourth or fifth whorl, leaving a smooth seal for the remainder of the shell (Burch et al.

1980) (Figure 2-2).

This genus is also notable for its locomotion. Species of the genus are commonly called looping snails and they move similarly to an inchworm. Their proboscis first reaches out from the shell and searches for a firm grip. After a stable grip is established, the foot slides up to meet it and thus it is able to travel. Each “step” takes around four seconds and therefore they are able to move around 16 “steps” in a minute and locomoting around 20 -25 mm per minute (Pilsbry et al. 1914).

As noted in Chapter1, Truncatella’s niche is the wrack zone of a shoreline. The American malacologist Leslie Hubricht wrote in his 1985 publication The Distributions of the Native Land

Mollusks of the Eastern United States that Truncatella can be found “in and under seaweed in the strand at or above high-tide” and that there are none to be found “on sandy beaches” (Hubricht

1985:4). They also have a salinity optimum of between 11.0-20.7 parts per thousand (ppt.), which is indicative of “intertidal to marine conditions” (Gaiser et al. 2006:246). These snails do not wash up already dead with the seaweed in the wrack zone, but they seek out that vegetation when it is rotting and the water has receded (Marquardt et al. 2013). This detritus is also how they reproduce and expand the reach of the genus; they lay their egg capsules on supratidal detritus and digest the cellulose (Schmelz et al. 2016). It is because of these unique features that the question is proposed of whether these snails can be used as a relative proxy for sea level.

Common Mollusk Ecology

Twenty-eight discrete taxa were identified in bulk samples from Clam Beach and among those were six taxa that were present in nearly every sample of the column. These common taxa are Truncatella, Oligyra orbiculata, Polygyra septemvolva, Zonitoides arboreus, Melampus bidentatus, Glyphyalinia umbilicata, and Lobosculum pustula. Of those that revealed themselves from a 1-mm screen of each sample, I will discuss Gastrocopta contracta and Hawaiia Sp. in detail as well, because their presence is useful for indicating the qualities of the habitat landward to the wrack zone. They were also the most numerous species that only began appearing in the 1- mm fraction. No other taxon from the finer fraction had an absolute frequency of over 40 in any one sample. The high frequency of Gastrocopta contracta and Hawaiia Sp. indicates that they likely accumulated proximate to their living habitat, notwithstanding the same anthropogenic

21 factors noted for Truncatella. However, storm surge is not a likely depositional factor for these other high-frequency taxa because they do not inhabit the wrack zone like Truncatella.

Oligyra orbiculata, also sometimes called Helicina orbiculata, is a species of snail commonly known as the “Globular Drop” (Turgeon et al. 1998). It is semiarboreal and a calciphile that prefers sunny locations, roadsides, and glens. “It sometimes occurs in woods, but it is not as abundant in such habitats” (Hubricht 1985:3). Its range is the southeastern U.S., including Florida.

The species Polygyra septemvolva is commonly known as the Florida Flatcoil (Turgeon et al. 1998). It is usually found living in a habitat such as sunny coastal regions above the high strand line and on the margins of salt marshes; it enjoys slightly salty areas (Hubricht 1985:36).

It is primarily found on the coastlines of Texas and throughout Florida.

Zonitoides arboreus is another terrestrial snail and its common name is Quick Gloss

(Turgeon et al. 1998). According to Hubricht, it is “usually found on rotting logs and in floodplains, as well as upland woods. It is also found on roadsides and along railroads and is a common urban snail” (Hubricht 1985:32). It is fairly evenly distributed across the United States.

Melampus bidentatus is commonly known as the Common Marsh Snail (Turgeon et al.

1988). According to the Carnegie Museum of Natural History, “this snail is an amphibious saltmarsh dweller of bays and estuaries. It is an air-breather, or pulmonate, that can survive for extended periods upon vegetation above or beyond the water. It consumes rotten vegetation, especially saltmarsh cordgrass” (Virginia Land Snails n.d.). It is distributed along the Eastern

United States.

Glyphyalinia umbilicata is commonly called the Texas Glyph (Turgeon et al. 1998). As its name suggests, it is distributed throughout Texas but also Florida. According to Hubricht, it is

“usually found under logs and leaflitter in the woods bordering streams. Also found on waste ground in urban areas” (Hubricht 1985:25).

Lobosculum pustula is a species whose range is Florida and the coastal regions of

Georgia and South Carolina. Its common name is Grooved Liptooth (Turgeon et al. 1998) and it is “usually found in sandy woods, under logs and dead palm fronds, and in leaf litter” (Hubricht

1985:38).

Gastrocopta contracta is commonly referred to as the Bottleneck Snaggletooth (Turgeon et al. 1998). Its range is in the “United States and Canada, southward to Florida and Vera Cruz,

Mexico; westward to central Kansas and east central Oklahoma. It is an inhabitant of wooded slopes, where it lives under leaf mold, the bark of fallen logs, or stones. It is locally more abundant where loose limestone rock provides cover” (Leonard 1950:30). The preferred habitat of G. contracta is open woodlands and shaded grasslands (John Slapcinsky, personal communication 2019).

Hawaiia Sp. in these samples is a genus whose exact species was unable to be identified

(John Slapcinsky, personal communication 2019). Because of the lack of knowledge of the species, there is no common name. In general, this taxa has a widespread distribution in the

Eastern and Central U.S. and is native to North America. It is commonly found on bare ground or in leaf litter and has been “found crawling on the bare ground on floodplains, meadows, roadsides, along railroads, and on waste ground in urban areas” (Hubricht 1985:29).

It is worth noting again that although Truncatella have a very specific niche that is conducive to inferring the level of sea relative to relict or modern shorelines, live organisms or their shells can be displaced by a number of agents, including humans. As mentioned in Chapter

1, if humans collected seaweed along the shoreline they could displaced Truncatella landward

23 unintentionally (Palmiotto 2015). Likewise, the surge of tropical storms could easily displace these minute creatures and/or their shells landward, as has been inferred in southwest Florida

(Marquardt and Walker 2013). Thus, I do not expect a one-to-one correlation between the frequency of Truncatella shells and proximity to their original habitat. Careful attention to depositional context and associated mollusks are needed to distinguish between Truncatella shells deposited close to their wrack-zone habitat and those that may have been displaced by storms or humans. The archaeological context of Clam Beach, described in the chapter that follows, lends itself to this level of analytical control.

Figure 2-2. Photo illustrating juvenile and adult Truncatella. Top row shows juvenile Truncatella with intact apex and bottom row demonstrating adult Truncatella with a truncated apex.

Figure 2-3 Illustrating Hawaiia Sp.

Figure 2-4 Illustrating Gastrocopta contracta.

CHAPTER 3 EXCAVATION AND LAB METHODS

The archaeological site of Clam Beach (8LV66a) encases a 1.5-m-thick anthropogenic deposit with abundant terrestrial snails amid an array of vertebrate and invertebrate faunal remains. A 1 x 2-m excavation unit at the site was located only a few meters landward of the shoreline at high tide, the wrack zone in which Truncatella accumulate. Since about 4,000 years ago, when Clam Beach was first occupied, accreting midden has elevated the landform beyond its “natural” relief. In fact, an escarpment of over one meter in relief today marks the contact between the beachface and archaeological site. The depositional context of Truncatella shells at

Clam Beach thus deviates from typical beachface erosion, disrupting a direct correlation between

Truncatella and relative sea-level. Truncatella shells deep into the midden are more likely to reflect the conditions under which they accumulate in proximity to shorelines without human intervention.

In this chapter I describe the methods and results of test excavations at Clam Beach and the means by which Truncatella and other snail taxa were recovered in a bulk-sample column. I also review the sorting procedures followed in the lab and the criteria used to identify and quantify the shells of various taxa of terrestrial snails.

Excavation Methods

The purpose of the previous excavations at this site was to investigate cultural and environmental change over time through the diverse array of taxa present, as well as to attempt to close the temporal gap in the timeline of the North Florida Gulf Coast (Mahar 2019). The aforementioned 1 x 1-meter TU1 which was unfinished in the 2014 season was resumed in 2015 by LSA and the 2015 Lower Suwannee Archaeological Field School. It was expanded 1 meter to

27 the north into a 1 x 2-m unit. When the excavation of this test unit was completed, all four profiles were cleaned, photographed, and drawn to scale (Figures 3-1 and 3-2).

There are five macrostratigraphic units in the profile of TU1 with other intervening microstratigraphic units. Detailed stratigraphic information can be found in the technical report by Ginessa Mahar (2019). I am providing a brief description of each stratum to allow for a better understanding of the context of the samples from the bulk-sample column. Figure 3-3 gives a visual representation of the approximate location within the strata from which radiocarbon samples were taken.

Stratum I has a maximum depth of 70 cmbd and is composed of black fine sand with whole and crushed oyster and scallop. A radiocarbon age supplied by Sample 3 dates the matrix to AD 780-985.

Stratum II has a maximum depth of 105 cmbd and can be described as having very dark gray fine sand with mostly whole oyster, hard clam, and gastropods. There is very little sediment. A charcoal sample from the top of the stratum (Sample 5) dates to AD 655-770.

Another charcoal sample from the bottom of the stratum (Sample 9) dates the matrix to AD 255-

415.

Stratum III goes 113 cmbd and is made up of black fine sand with whole and crushed oyster and hard clam. Sample 11 provided a radiocarbon age range of BC 85- AD 60.

Stratum IV extends 141 cmbd and is composed of very dark gray fine sand with some crushed shell and gastropods. From Samples 14 and 16 we gain three radiocarbon dates. Sample

14 located at the top of the stratum dates the matrix to BC 755-405, and Sample 16 provides ages

BC 925-815 and BC 2195-1900.

Stratum V has a maximum depth of 180 cmbd and has light gray fine sand with no shell.

Stratum VI is a pit feature (Feature 3) that originates at the base of the overlying stratum and extends into substrate to a depth of 173 cmbd. It consists of very dark brown and black fine sand with some shell. It is highly organic. A radiocarbon date taken from within the feature dates it to BC 2195-1900.

Stratum VIa is a second pit feature (Feature 1) with a maximum depth of 155 cmbd. It is composed of dark gray and brown fine sand with oyster, scallop, and gastropods.

After profiles were photographed and drawn, a bulk-sample column was removed from the east wall (Figure 3-3). This 30 by 30-cm column was excavated in arbitrary 10-cm levels. All materials were bagged for flotation. Prior to their processing, a small portion of each sample was screened through a 1/8-inch hardware cloth and that sediment was archived for future soil analysis. The remaining portion of the sample was processed using a Dausman Flote-Tech flotation machine. The light fraction was archived for future analysis and the heavy fraction was fractionated into ¼-, 1/8-, and <1/8-inch materials. The ¼- and 1/8-inch materials were sorted and cataloged and the <1/8-inch materials were curated for future analysis (Mahar 2019).

The dried light-fraction of each flotation sample was first passed through a 2-mm geological sieve and then sorted into groups of Truncatella adults, juveniles, and fragments, and other mollusks (Figures 3-5 and 6). Select samples that contained abundant Truncatella shell were further fractionated using a 1-mm geological sieve to isolate taxa that could be used to discriminate among alternative depositional conditions, such as storm surge and human intervention.

Mollusk Analysis Methods.

Specimens were recorded by quantifying the amounts of whole snails for each sample by taxa (Tables 4-1 and 4-3). Truncatella were classified as whole (not fragmented) if their entire

29 shell was fully intact. Juveniles were separated from adults by the presence of an intact spire or apex. As noted in Chapter 2, the spires of Truncatella are “truncated” at maturity, leaving a rounded apex. Truncatella shells missing parts of the whorl were not counted as “whole,” but instead were placed in a category of “Truncatella Fragment,” which was later weighed in grams.

The shells of taxa not given to Truncatella were identified and analyzed with the help of

John Slapcinsky, a malacologist at the Florida Museum of Natural History. Specimens were quantified by counting them as a whole mollusk if their shell was fully intact. These mollusks were classified into the correct taxa and any fragments were labeled as “detritus,” the amount of which was not recorded.

Among the other taxa in the bulk-sample column were substantial quantities of the shells of Glyphyalinia umbilicata, Gastrocopta contracta, and Hawaiia Sp. Moderate quantities of

Polygyra septemvolva and Lobosculum pustula were also present in most samples, followed by traces of Oligyra orbiculata, Zonitoides arboreus, Melampus bidentatus, Strobilops texasiana,

Littoraria irrorata, Euglandina Sp., Bittium varium, Saracioia Sp., Cerithidea Sp., Assiminea

Succinea, Boonea impressa, Boonea seminuda, Gastrocopta pellucida, Chicoreus florifer,

Astyris lunata, Ceritihiopsis Sp., Litiopa melanostoma, Parvanachis ostreicola, Detracia bulloides, Rissoina Sp., and Atys Sp.

Each bulk sample had a unique volume upon arrival at the LSA. That volume was recorded and upon the completion of the quantification of each taxon, the volumetric frequency of the taxa in each sample was divided by the volume of that sample. This yielded what I call the standardized results (Tables 4-2 and 4-4). Each standardized frequency of a given taxon can be compared to those of the same taxon in other samples.

For the counts of Gastrocopta contracta, the juveniles and adults were separated in the initial sort, however for the purpose of this research, it is not important to make this distinction, and their totals have been combined.

It is also important to note that some information for Sample 4 was lost. We have the actual numbers of Truncatella Adults, but none for Juvenile or Fragmented. We do also have the sample volume and the 2-mm counts for the non-Truncatella taxa.

Through the previous excavation and sample collections, it has become possible to ascertain the date ranges of individual samples and the strata where they were deposited. In

Chapter 4, that knowledge will be expanded upon through the computation of absolute and standardized frequencies of the various taxa of mollusks.

Figure 3-1. Photographs and scaled drawings of the profiles of the east and south walls of Test Unit 1, Clam Beach (8LV66a) (Mahar 2018).

Figure 3-2. Photographs and scaled drawings of the profiles of the west and north walls of Test Unit 1, Clam Beach (8LV66a) (Mahar 2018).

Figure 3-3. South Profile of TU1 showing approximate locations of charcoal samples submitted for radiocarbon assays and resultant two-sigma calibrated age ranges. On the left and right side of the image, respectively, are the bulk-sample column identifying numbers and the level at which they were excavated. Figure courtesy of Ken Sassaman (2019).

Figure 3-4. Field school student excavating bulk column sample from east wall of TU1 at Clam Beach (Mahar 2018).

Figure 3-5. Photograph illustrating the process of sorting a sample into its distinct taxa.

Figure 3-6. Photograph illustrating the process of counting members of the taxon Hawaiia Sp.

CHAPTER 4 RESULTS OF MOLLUSK ANALYSIS

The samples of terrestrial snail shells reported in this chapter include all specimens 2-mm or greater in size from each of the 16 bulk samples of the Clam Beach column and a subset of snail shells <2 mm and >1 mm in size from samples with abundant Truncatella shells and one intervening sample with a limited number of Truncatella shells. Aside from fragments and some minute juveniles, Truncatella shells are captured mostly in the 2-mm fraction and are thus reported for all samples of the column. Several taxa of relevance to this research (e.g.,

Gastrocopta spp.) include shells that are smaller than 2 mm but larger than 1 mm. Sorting the finer fractions proved to be time consuming as there were literally thousands of these minute shells in samples chosen.

In addition to Truncatella, nine distinct taxa of terrestrial snails were identified in the 2- mm fraction of bulk samples. These taxa include Oligyra orbiculata, Polygyra septemvolva,

Zonitoides arboreus, Melampus bidentatus, Glyphyalinia umbilicata, Lobosculum pustula,

Strobilops texasiana, and Littoraria irrorata.

After the sorting and identification of the 2-mm fractions were completed, Samples 2, 3,

8, 11, and 12 were passed through a 1-mm geological sieve. Samples 2, 3, 11, and 12 were chosen because they include large numbers of Truncatella shell. Although it contained few

Truncatella shells, Sample 8 was also selected for 1-mm fractionation as an independent control.

The 1-mm fractions include many other taxa that do not appear in the 2-mm fraction and that show up with very limited frequency, some are terrestrial and others are marine. Note that any taxon whose specific species could not be identified does not have a common name. Unless otherwise stated, the common names for each species come from the Turgeon et al. (1998) publication “Common and Scientific Names of Aquatic Invertebrates from the United States and

Canada.” The terrestrial taxa with their common names are: Strobilops texasiana (Southern

Pinecone), Euglandina Sp., and Gastrocopta pellucida (Slim Snaggletooth). The marine varieties are: Littoraria irrorata (Marsh Periwinkle), Bittium varium (Grass Cerith) (Turgeon et al. 1988),

Saracioia Sp., Cerithidea Sp., Assiminea succinea- The Atlantic Assiminea, Boonea impressa

(Impressed Odostome), Boonea seminude (Half-smooth Odostome), Chicoreus florifer (Lace

Murex), Astyris lunata (Lunar Dovesnail), Cerithiopsis Sp., Litiopa melanostoma (Sargassum

Snail), Parvanachis ostreicola (Oyster Dovesnail), Detracia bulloides (Bubble Melampus)

(Turgeon et al. 1988), Rissoina Sp., and Atys Sp.

As seen in Figure 4-3, the frequency distribution of Truncatella follows a similar pattern as the other taxa from the 2-mm fraction. The two groups were separated in the figure due to the fact that number of Truncatella vastly outweigh that of any other taxon and it is impossible to see any patterns when they are alongside each other because the scale of the graph is accommodating to Truncatella and the other taxa are too infrequent to see. There are virtually no individuals present from Samples 13-16, followed by a small spike from around Samples 10-12.

Following that, there is a depression from Samples 6-9 and finally another surge in many taxa in samples 1-5. It appears that the taxon whose trends most closely mirror those of Truncatella is

Polygyra septemvolva; they both exhibit a greater frequencies among the more recent samples than those of the older spike. Implications of these trends will be further discussed in the following section.

Standardized Frequency of Taxa in 2-mm Fraction Excluding Truncatella 9.0 8.0 Oligyra orbiculata 7.0 Polygyra septemvolva 6.0 5.0 Zonitoides arboreus 4.0 Melampus bidentatus 3.0 Glyphyalinia umbilicata 2.0

Standardized Frequency Standardized 1.0 Lobosculum pustula 0.0 Strobilops texasiana 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 Littoraria irrorata Sample Number

350.0 Standardized Frequency of Adult Truncatella in 2-mm Fraction

300.0

250.0

200.0 Truncatella Adult

150.0

Standardized Frequency Standardized 100.0

50.0

0.0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 Sample Number Figure 4-1 Comparing frequencies of Adult Truncatella to that of the other taxa from each sample from the 2-mm fraction.

Table 4-1. Absolute Frequency of Shells by Taxa, TU1, 2-mm fraction

Sample Number Taxon Common Name 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 Total Truncatella Adult Looping Snail 745 3623 1437 1331 908 178 72 159 169 489 1239 282 48 11 10 1 10702 Truncatella Juvenile Looping Snail 22 104 10 56 15 3 6 4 10 18 59 0 0 0 0 307 Truncatella Fragment (g) Looping Snail 0.4 1.6 0.8 0.7 0.1 0.1 0.1 0.1 0.3 1.1 0.8 0 0 0 0 6 Oligyra orbiculata Globular Drop 9 29 9 10 21 10 1 0 2 6 12 7 0 0 0 0 116 Polygyra septemvolva Florida Flatcoil 85 83 42 60 42 8 3 4 8 20 101 19 6 1 3 2 487 Zonitoides arboreus Quick Gloss 6 3 8 11 4 2 0 1 1 4 8 0 0 0 0 1 49 Melampus bidentatus Common Marsh Snail 5 36 10 19 12 0 1 4 8 5 0 6 0 0 0 0 106 Glyphyalinia umbilicata Texas Glyph 43 8 32 44 98 55 12 29 29 79 68 41 5 0 1 0 544 Lobosculum pustula Grooved Liptooth 46 11 10 11 13 8 4 6 15 64 77 15 3 0 3 0 286 Strobilops texasiana Southern Pinecone 5 0 0 1 0 0 0 1 0 0 0 11 0 0 0 0 18 Littoraria irrorata Marsh Periwinkle 1 0 1 0 0 0 0 1 0 0 0 0 0 0 0 0 3 UID 0 0 24 0 7 5 7 16 22 11 0 4 4 4 9 2 115 Total (n) 967 3897 1583 1487 1161 281 103 227 258 688 1523 444 66 16 26 6 12733 Total (g) 0.4 1.6 0.8 0 0.7 0.1 0.1 0.1 0.1 0.3 1.1 0.8 0 0 0 0 6

Table 4-2. Standardized Frequency of Shells by Taxa, TU1, 2-mm fraction

Sample Number Taxon Common Name 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 Total Truncatella Adult Looping Snail 67.7 329.4 159.7 102.4 64.9 12.3 7.2 10.6 14.1 30.6 77.4 47.0 12.0 1.6 1.4 0.1 938.3 Truncatella Juvenile Looping Snail 2.0 9.5 1.1 4.0 1.0 0.3 0.4 0.3 0.6 1.1 9.8 0.0 0.0 0.0 0.0 30.2 Truncatella Fragment (g) Looping Snail 0.0 0.1 0.1 0.1 0.0 0.0 0.0 0.0 0.0 0.1 0.1 0.0 0.0 0.0 0.0 0.5 Oligyra orbiculata Globular Drop 0.8 2.6 1.0 0.8 1.5 0.7 0.1 0.0 0.2 0.4 0.8 1.2 0.0 0.0 0.0 0.0 10.0 Polygyra septemvolva Florida Flatcoil 7.7 7.5 4.7 4.6 3.0 0.6 0.3 0.3 0.7 1.3 6.3 3.2 1.5 0.1 0.4 0.3 42.4 Zonitoides arboreus Quick Gloss 0.5 0.3 0.9 0.8 0.3 0.1 0.0 0.1 0.1 0.3 0.5 0.0 0.0 0.0 0.0 0.1 4.0 Melampus bidentatus Common Marsh Snail 0.5 3.3 1.1 1.5 0.9 0.0 0.1 0.3 0.7 0.3 0.0 1.0 0.0 0.0 0.0 0.0 9.5 Glyphyalinia umbilicata Texas Glyph 3.9 0.7 3.6 3.4 7.0 3.8 1.2 1.9 2.4 4.9 4.3 6.8 1.3 0.0 0.1 0.0 45.3 Lobosculum pustula Grooved Liptooth 4.2 1.0 1.1 0.8 0.9 0.6 0.4 0.4 1.3 4.0 4.8 2.5 0.8 0.0 0.4 0.0 23.2 Strobilops texasiana Southern Pinecone 0.5 0.0 0.0 0.1 0.0 0.0 0.0 0.1 0.0 0.0 0.0 1.8 0.0 0.0 0.0 0.0 2.4 Littoraria irrorata Marsh Periwinkle 0.1 0.0 0.1 0.0 0.0 0.0 0.0 0.1 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.3 UID 0.0 0.0 2.7 0.0 0.5 0.3 0.7 1.1 1.8 0.7 0.0 0.7 1.0 0.6 1.3 0.3 11.6 Total (n) 87.9 354.3 175.9 114.4 82.9 19.4 10.3 15.1 21.5 43.0 95.2 74.0 16.5 2.3 3.7 0.9 1117.2 Total (g) 0.0 0.1 0.1 0.0 0.1 0.0 0.0 0.0 0.0 0.0 0.1 0.1 0.0 0.0 0.0 0.0 0.5

Table 4-3. Absolute Frequency of Shells by Taxa, TU1, 1-mm fraction

Sample Number Taxon Common Name 2 3 8 11 12 Total Truncatella Adult Looping Snail 3793 1473 174 1416 322 7178 Truncatella Juvenile Looping Snail 1020 468 88 530 59 2165 Truncatella Fragments (g) Looping Snail 11.7 4.8 0.4 3.6 0.8 21.3 Oligyra orbiculata Globular Drop 46 17 4 23 7 97 Polygyra septemvolva Florida Flatcoil 122 34 4 101 19 280 Zonitoides arboreus Quick Gloss 16 12 3 9 0 40 Melampus bidentatus Common Marsh Snail 55 13 6 12 6 92 Glyphyalinia umbilicata Texas Glyph 281 121 148 289 41 880 Glyphyalinia Sp. . 12 0 0 0 0 12 Lobosculum pustula Grooved Liptooth 59 41 21 114 15 250 Strobilops texasiana Southern Pinecone 23 18 11 24 11 87 Littoraria irrorata Marsh Periwinkle 0 1 4 0 0 5 Euglandina Sp. . 6 1 1 0 0 8 Bittium varium Grass Cerith 7 0 0 0 0 7 Saracioia Sp. . 1 0 0 0 0 1 Cerithidea Sp. . 5 0 0 0 0 5 Assiminea succinea Atlantic Assiminea 38 0 0 0 0 38 Boonea impressa Impressed Odostome 13 0 0 0 0 13 Boonea seminuda Half-smooth Odostome 1 0 0 0 0 1 Gastrocopta pellucida Slim Snaggletooth 11 0 0 0 0 11 Gastrocopta contracta Bottleneck Snaggletooth 613 318 128 1286 265 2610 Chicoreus florifer Lace Murex 2 0 0 0 0 2 Astyris lunata Lunar Doveshell 10 0 0 0 1 11 Cerithiopsis Sp. . 2 0 0 0 0 2 Litiopa melanostoma Brown Sargassum 1 0 0 0 0 1 Hawaiia Sp. . 2189 2074 1059 2599 309 8230 Parvanachis ostreicole Oyster Dovesnail 1 0 0 0 0 1 Detracia bulloides Bubble melampus 1 0 0 0 0 1 Rissoina Sp. . 2 0 0 0 0 2 Atys Sp. . 1 0 0 0 0 1 UID 0 16 0 6 0 22 Total (n) 8331 4607 1651 6409 1055 22053 Total (g) 11.7 4.8 0.4 3.6 0.8 21.3

Table 4-4. Standardized Frequency of Shells by Taxa, TU1, 1-mm fraction

Sample Number Taxon Common Name 2 3 8 11 12 Total Truncatella Adult Looping Snail 344.8 163.7 11.6 88.5 53.7 662.3 Truncatella Juvenile Looping Snail 92.7 52.0 5.9 33.1 9.8 193.6 Truncatella Fragments (g) Looping Snail 1.1 0.5 0.0 0.2 0.1 1.9 Oligyra orbiculata Globular Drop 4.2 1.9 0.3 1.4 1.2 8.9 Polygyra septemvolva Florida Flatcoil 11.1 3.8 0.3 6.3 3.2 24.6 Zonitoides arboreus Quick Gloss 1.5 1.3 0.2 0.6 0.0 3.6 Melampus bidentatus Common Marsh Snail 5.0 1.4 0.4 0.8 1.0 8.6 Glyphyalinia umbilicata Texas Glyph 25.5 13.4 9.9 18.1 6.8 73.8 Glyphyalinia Sp. . 1.1 0.0 0.0 0.0 0.0 1.1 Lobosculum pustula Grooved Liptooth 5.4 4.6 1.4 7.1 2.5 20.9 Strobilops texasiana Southern Pinecone 2.1 2.0 0.7 1.5 1.8 8.2 Littoraria irrorata Marsh Periwinkle 0.0 0.1 0.3 0.0 0.0 0.4 Euglandina Sp. . 0.5 0.1 0.1 0.0 0.0 0.7 Bittium varium Grass Cerith 0.6 0.0 0.0 0.0 0.0 0.6 Saracioia Sp. . 0.1 0.0 0.0 0.0 0.0 0.1 Cerithidea Sp. . 0.5 0.0 0.0 0.0 0.0 0.5 Assiminea succinea Atlantic Assiminea 3.5 0.0 0.0 0.0 0.0 3.5 Boonea impressa Impressed Odostome 1.2 0.0 0.0 0.0 0.0 1.2 Boonea seminuda . 0.1 0.0 0.0 0.0 0.0 0.1 Gastrocopta pellucida Slim Snaggletooth 1.0 0.0 0.0 0.0 0.0 1.0 Gastrocopta contracta Bottleneck Snaggletooth 55.7 35.3 8.5 80.4 44.2 224.1 Chicoreus florifer Flowery Lace Murex 0.2 0.0 0.0 0.0 0.0 0.2 Astyris lunata Lunar Doveshell 0.9 0.0 0.0 0.0 0.2 1.1 Cerithiopsis Sp. . 0.2 0.0 0.0 0.0 0.0 0.2 Litiopa melanostoma Brown Sargassum 0.1 0.0 0.0 0.0 0.0 0.1 Hawaiia Sp. . 199.0 230.4 70.6 162.4 51.5 714.0 Parvanachis ostreicole Oyster Dovesnail 0.1 0.0 0.0 0.0 0.0 0.1 Detracia bulloides Bubble melampus 0.1 0.0 0.0 0.0 0.0 0.1 Rissoina Sp. . 0.2 0.0 0.0 0.0 0.0 0.2 Atys Sp. . 0.1 0.0 0.0 0.0 0.0 0.1 UID 0.0 1.8 0.0 0.4 0.0 2.2 Total (n) 757.4 511.9 110.1 400.6 175.8 1956.1 Total (g) 1.1 0.5 0.0 0.2 0.1 1.9

CHAPTER 5 DISCUSSION

With the chronological control enabled by radiocarbon dates, stratified samples from

Clam Beach can be sequenced to the climatic periods established from independent data (i.e.,

Roman Warm Period, Vandal Minimum, Medieval Warm Period, Little Ice age, and Modern

Warm Period) to infer the relative level of sea at various points in the occupational span of Clam

Beach.

The basal stratigraphic unit in TU1, Stratum IV, formed over Pleistocene sands (Stratum

V) at a time when sea level was considerably lower than at present. Dating from BC 2195-1900 to BC 755-405, this stratum is composed of very dark gray fine sand with some crushed shell and gastropods, but virtually no Truncatella. The standardized totals of adult Truncatella from

Sample 16 to Sample 14 are 0.1, 1.4, and 1.6, respectively. It is not possible to estimate how far lower sea level was during this time but the area was not a suitable habitat for Truncatella— meaning it was far removed from the wrack zone.

Truncatella shells appear in appreciable numbers in Stratum III, represented by Samples

10, 11, and 12 (Figure 5-1). This stratum represents a buried living surface on which of organic matter decomposed, leaving a dark humic soil, as well as the crushed shell that is a part of the fill. A radiocarbon date from Sample 11 suggests that the time frame of the deposit of this stratum was around BC 85-AD 60. This time period coincides with the middle of the Roman

Warm Period, which spanned BC 350-AD 450/500. As expected, increasing temperatures brought the sea level up, bringing the area of TU1 proximate to the shoreline and a wrack zone.

It bears noting that Stratum III is currently about 1 m below the present ground surface, so if the relationship of this stratum to the shoreline is comparable to the current ground surface, sea must have been about 1 m below present level. It is also important to note that counts of Truncatella,

Gastrocopta contracta, and Hawaiia Sp. were all increasing (Figure 5-2). This may indicate that the habitat was more suitable for species other than Truncatella and/or that humans intervened by moving Truncatella along with wrack material from its original context to this locus of anthropogenic deposition. Current data do not allow discrimination between these two scenarios but given the high frequency of shells from taxa that do not inhabit the shoreline, storm surge is not likely to have been the cause of high concentrations of Truncatella on the surface at this location.

Stratum II is composed of Samples 5-9. During the time it was deposited, Stratum II attracted far fewer snails than the surface on which it accumulated, arguably a function of rapid accumulation. Radiocarbon dates from Samples 5 and 9 show that the deposit was made between

AD 255-415 and AD 655-770. This was a period of cooling; entering the period of the Vandal

Minimum which began at about AD 450/500. During the approximately 400 years that this stratum was deposited, about 60-cm of oyster midden accumulated. Given the lack of soil development within this stratum, it is unlikely that this shell midden accumulated gradually.

Rather, it likely formed in one or a few discrete events, most likely at the outset of the period bracketed by radiocarbon assays, thus close to AD 255. It follows that the low frequency of snails in this stratum is a function of human activity rather than environmental conditions. That is, terrestrial snails did not have much opportunity to colonize and inhabit a surface that was subject to rapid deposition. An alternative inference is that the sea level had dropped enough during this cooling event and the habitat was no longer suitable for Truncatella or the other taxa.

When the height of the stratum reached around 50 cmbd at Sample 5, right at the transition between Stratum II and I, the number of snails, especially Truncatella and Hawaiia Sp. began to dramatically increase.

Stratum I is made up of Samples 1-4. The counts of Truncatella and Hawaiia Sp. rose a significant amount until approximately Sample 3 when the count of Hawaiia Sp. began to recede.

That decline seems to coincide with the transition from Stratum II to I. Based on observations from Marquardt et al. (2013), temperatures would have likely sharply declined during the time period of about AD 800-850 and then rose again beginning at the start of the Medieval Warm

Period at ca. AD 850. The accumulated midden of the shift of Stratum II to I. Stratum II consists of a very dark gray fine sand with mostly whole oyster and very little sediment. Stratum I consists of a black fine sand with whole and crushed oyster and scallop. It would appear that as temperatures increased to the levels they are today, the sea rose again and the location of TU1 was again proximate to the shoreline. Likewise, due to higher temperatures, weather events such as hurricanes and other storms were likely to have been more frequent than in the prior period.

The deposition of especially large amounts of Truncatella in this stratum might be due to storm surges that lifted material from the wrack zone up over the shoreline bank and on to the midden.

This could explain the decrease of Hawaiia Sp. in this stratum as they may have been washed away with the same force that caused the deposition of Truncatella. Another possible explanation is that people began gathering that material from other places and incorporating different types of the fill. For instance, a possibility is that more materials have come from seaweed and other matter from the high tide zone and then it was deposited on the pre-existing midden. That would also explain the increase in Truncatella and simultaneous decrease in

Hawaiia Sp.

Throughout the different strata, the levels of Gastrocopta contracta remained relatively constant compared to the frequencies of both Truncatella and Hawaiia Sp. One notable exception is Sample 12, where the frequency of Gastrocopta contracta is especially high. For

47 example, they make up a much higher percentage of that sample than they do in Sample 2: 25% vs. 7%, respectively. The preferred habitat of this taxon is open woodlands and shaded grasslands. The decrease in this taxon over time may indicate that the landform in this location grew increasingly less favorable as the shoreline retreated, although it could also be due to anthropogenic interferences.

Of the mollusk taxa that were common throughout the samples, Polygyra septemvolva shares a similar trend in frequencies with Truncatella. This species displays higher frequencies within the same samples (10-12 and 1-4). This taxon assists with the association of the strata with the proximity to a tidal zone because “it is usually found living in a habitat such as sunny coastal regions above the high strand line and on the margins of salt marshes; it enjoys slightly salty areas” (Hubricht 1985:36).

In summary, the varying frequencies of terrestrial snails within the strata of TU1 at Clam

Beach indicate both changes in sea level and a changing landscape through time. As Figure (5-3) illustrates in schematic form, the high tide and therefore the habitat of the Truncatella today lies around 5 meters away the elevated ground surface into which TU1 was excavated. Because of the topographic relief of 1.5 m of midden, the elevated surface of TU1 most likely received

Truncatella from overwash events that displaced wrack material from the beach. The precise location of the shoreline during the time the upper stratum of TU1 accumulated is not known, but given the elevation of the midden, either overwash events or human intervention is implicated.

The diminished frequency of Hawaiia Sp. in this upper stratum lends support to the former cause and suggests that sea level at the time of deposition was effectively the same as today.

The older and deeper context for the deposition of abundant Truncatella, Stratum III, was a buried surface about 1 meter below the ground surface today. If the shoreline morphology of

48 that time was identical to what it is today, we would expected tosee about the same ratios of snail taxa that we see in the upper stratum, but we do not. Because this is not the case, it is reasonable to conclude that shoreline morphology has evolved over time. When Stratum III was the ground surface, the shoreline would likely not have looked like it does today with its an escarpment from the elevated and erosion-resistant midden. Rather,the slope of the shoreline was most likely more gentle with a broader tidal range. This could mean that the location of Stratum III was actually situated within the wrack zone during that time, explaining why the levels of the gastropod taxa found today are not identical. It could be that the deposits naturally occurring there instead of due to overwash events would mean that the other taxa would have remained there instead of being swept away, explaining why the frequency of the snails are closer together in stratum III than they are today. Considering all the possibilities, the results of analysis of Truncatella and other snail taxa from TU1 at Clam Beach indicate that more than sea-level rise must be taken into account to expanin variation in both the frequency of Truncatella through time, as well as changes in the ratio of this taxon with those of taxa indicative of other environmental conditions.

350.0 Standardized Frequency of Adult Truncatella in 2-mm Fraction

300.0

250.0

200.0

150.0 Adult Truncatella Standardized Frequency Standardized

100.0

50.0

0.0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 Sample Number Figure 5-1. Standardized Frequency of Truncatella Adults by Sample from TU1, Clam Beach (8LV66a).

Standardized Frequency of Adult Truncatella, Hawaiia Sp., and Gastrocopta contracta in 1- mm Fraction 400.0

350.0

300.0

250.0

200.0 Adult Truncatella Gastrocopta contracta 150.0 Hawaiia Sp.

Standardized Frequency 100.0

50.0

0.0 2 3 8 11 12 Sample Number

Figure 5-2. Standardized Frequency of Adult Truncatella, Gastrocopta contracta, and Hawaiia Sp.1-mm from Samples 2, 3, 8, 11, and 12 from TU1, Clam Beach (8LV66a).

Figure 5-3. Schematic of the present-day shoreline at Clam Beach in relation to TU1. Curtesy of Ken Sassaman (2019).

CHAPTER 6 CONCLUSION

The results of this study verify that the shells of snails Truncatella in datable archaeological contexts are useful proxies for the level of sea but that the relation between the sea level and Truncatella frequency is not direct. Test Unit 1 (TU1) at Clam Beach (8LV66a) contained an abundant amount of snail shells from many different taxa. Shells of Truncatella appear in moderate frequency after about the first century BC. Given the specific niche of members of this genus, the appearance of Truncatella at this time signals the rise of sea levels in conjunction with the climatic period known as the Roman Warm Period (BC 350-AD 450/500).

Given that midden had yet to accumulate very high above the natural ground surface of the area of TU1, shells of Truncatella are likely to have accumulated on the surface in proximity to the wrack zone. Because of the depth of this surface, it is reasonable to infer that sea level was at least 1m below modern levels. Human intervention cannot be ruled out, but if storm surge delivered Truncatella shells to this lovation, sea level was likely to be even lower than inferred based on depth alone. The high frequency of Gastrocopta contracta shells on this buried surface tends to support this inference. It is not possible given current data to infer more precisely the elevation of sea or position of the wrack relative to TU1.

The lower frequency of Truncatella within the thick oyster midden overlying this buried surface is likely a function of human intervention. The deposits overlying the thick oyster stratum contain abundant Truncatella shells, as well as those of many other taxa. The deposition of Truncatella during this interval is most likely a function of storm surge that overwashed the elevated oyster midden, displacing materials from the wrack zone both upward and landward.

To conclude, Truncatella is a useful proxy for relative sea level as far as their ability to demote aspects of shoreline morphology. Whereas the high frequency of Truncatella in the upper

53 stratum of TU1 signals proximity to the shoreline, the anthropogenic deposits of accreted midden negates any direct relationship between sea level and frequency of Truncatella. The high frequency of this taxon in the buried surface of TU1 dating to roughly the first century BC supports the assumption that the sea level was down at least one meter. More precise estimates of sea level are not possible although the high frequency of Gastrocopta shells on this surface suggest that sea level may have been a bit lower, low enough to allow the location of TU1 to support snail taca that cannot tolerate regular inundation by sea eater. Again, the results of this study indicate that changes in shoreline morphology, as well as sea level, will influence the accumulation of Truncatella and other taxa.

The results of this research should encourage further studies on the usefulness of

Truncatella for inferring changes in sea level. Snails from two other test units near the area of

Clam Beach are available for immediate study: one on North Key (8LV65) and one on the adjacent island of Seahorse Key (8LV68). These and other sites in the study area of the Lower

Suwannee Archaeological Survey offer the opportunity to examine the frequencies of

Truncatella shells under variable shoreline conditions and elevations. These other sites also contain the shells of other terrestrial snails that enable comparisons with Truncatella frequencies to infer difference in vegetative cover and surface stability. Combined with the analysis of these other taxa and control over shoreline morphology, the utility of Truncatella for inferring sea level rise is promising.

LIST OF REFERENCES

Burch, J. B., & Van Devender, A. S. (1980). Identification of eastern North American land snails: The Prosobranchia, Opisthobranchia and Pulmonata (Actophila). Ann Arbor, MI: Museum of Zoology and Dept. of Ecology and Evolutionary Biology, The University of Michigan.

Clench W.J. & Turner R.D. (1948). A catalogue of the family Truncatellidae with notes and descriptions of new species. Occasional Papers on Mollusks 1(13): 157-212, 4 plates.

Donoghue, J. F. (2011) Sea level history of the northern Gulf of Mexico coast and sea level rise scenarios for the near future. Climatic Change 107:17-34.

Faught, M. K. (2004) The underwater archaeology of paleolandscapes, Apalachee Bay, Florida. American Antiquity 69:275–289.

Gaiser, E., Evelyn & Zafiris, Angelikie & Ruiz, Pablo & Tobias, Franco and Ross, Mike. (2006). Tracking rates of ecotone migration due to salt-water encroachment using fossil mollusks in coastal South Florida. Hydrobiologia 569. 237-257. 10.1007/s10750-006-0135-y.

Glyphyalinia umbilicata - (Cockerell, 1893). (n.d.). Retrieved from http://explorer.natureserve.org/servlet/NatureServe?searchName=Glyphyalinia umbilicata

Hubricht, L. (1985). The distributions of the native land mollusks of the Eastern United States. Chicago, IL: Field Museum of Natural History.

Leonard, A. B. (1950). A Yarmouthian molluscan fauna in the midcontinent region of the United States. Lawrence, Kan.: University of Kansas Publications.

Marquardt, W. & Walker, K. (2013). The Pineland Site Complex: An Environmental and Cultural History. (need full citation here)

Palmiotto, A. (2015) Effective seasons and mobility practices in the Lower Suwannee Region, Florida: A zooarchaeological study. (Doctoral dissertation, University of Florida). Retrieved from http://ufdcimages.uflib.ufl.edu/UF/E0/04/94/07/00001/PALMIOTTO_A.pdf

Parkinson, Randall and Donoghue, J.F.. (2010). Bursting the Bubble of Doom and Adapting to Sea Level Rise. Shoreline (need volume number)12-20.

Pilsbry, H., and Brown, A. (1914). The Method of Progression in Truncatella. Proceedings of the Academy of Natural Sciences of Philadelphia 66(2), 426-428. Retrieved from http://www.jstor.org/stable/4063643

Sassaman, K. E., Barbour II, T. E., Blessing, M. E., Boucher, A, Donop, M. C., Duke, C. T., Goodwin, J.M., Jenkins, J.A., Mahar, G.J., and Monés, M. P. (2019). Lower Suwannee Archaeological Survey 2014-2016: Shell Mound and Cedar Key Tracts. Technical Report 24.

Sassaman, K. E., Krigbaum, J. S., Mahar, G. J., and Palmiotto, A. (2015). Archaeological Investigations at McClamory Key (8LV288), Levy County, Florida. Technical Report 22.

Sassaman, K. E., Mahar, G. J., Donop, M. C., Jenkins, J. A., Boucher, A., Oliveira, C. I., and Goodwin, J. M. (2015). Lower Suwannee Archaeological Survey 2013-2014: Shell Mound and Cedar Key Tracts. Technical Report 21.

Sassaman, K., Wallis, N., McFadden, P. S., Mahar, G.J., Jenkins, J. A., Donop, M.C., Monés, M.P., Palmiotto, A., Boucher, A., Goodwin, J.M., and Oliveira, C.I. (2016). Keeping Pace With Rising Sea: The First 6 Years of the Lower Suwannee Archaeological Survey, Gulf Coastal Florida. Journal of Island and Coastal Archaeology 1-27. 10.1080/15564894.2016.1163758.

Schmelz, G. W., Portell, R. W. (2016). Three new species of Neogene Truncatella Risso, 1840 (Gastropoda: Truncatellidae) from Florida, USA. The Nautilus 130(1):13-16.

Turgeon, D.D., Bogan, A.E., Coan, E.V., Emerson, W.K., Lyons, W.G., Pratt, W., Roper, C.F.E, Scheltema, A., Thompson, F.G, and Williams, J.D. (1988). Common and scientific names of aquatic invertebrates from the United States and Canada: mollusks. American Fisheries Society Special Publication 16. vii + 277.

Turgeon, D.D., Quinn, J.F., Bogan, A.E., Coan, E.V., Hochberg, F.G., Lyons, W.G., Mikkelsen, P.M., Neves, R.J., Roper, C.F.E., Rosenberg, G., Roth, B., Scheltema, A., Thompson, F.G., Vecchione, M., and Williams, J.D. (1998). Common and scientific names of aquatic invertebrates from the United States and Canada: Mollusks, 2nd ed. American Fisheries Society Special Publication 26. 526.

Virginia Land Snails. (n.d.). Retrieved from https://www.carnegiemnh.org/science/mollusks/va_melampus_bidentatus.html

Wang, T., Surge, D., and Walker, K. J. (2013). Seasonal climate change across the Roman Warm Period/Vandal Minimum transition using isotope sclerochronology in archaeological shells and otoliths, southwest Florida, USA. Quaternary International 308-309, 230-241. doi:10.1016/j.quaint.2012.11.013

World Register of marine Species. (n.d.). Retrieved from http://www.marinespecies.org/aphia.php?p=taxdetails&id=138600

Wrack Community│ Explore Beaches (n.d.). Retrieved from http://explorebeaches.msi.ucsb.edu/sandy-beach-life/wrack-community

Wright, E. E., Hine, A. C., Goodbred JR, S. L., and Locker, S. D. (2005). The Effect of Sea-Level and Climate Change on the Development of a Mixed Siliciclastic-Carbonate, Deltaic Coastline: Suwannee River, Florida, U.S.A. Journal of Sedimentary Research 75:621-635.