Eric S. Collins

Records of prehistoric hurricanes on the South Carolina coast based on micropaleontological and sedimentological evidence, with comparison to other Atlantic Coast records

Singleton Swash on the South Carolina coast provides an extended record of storm events for this coast. We used experience gained by looking at storm traces detected as layers of offshore foraminifera intercalated with marsh sediments from a known storm in the area ( Hugo, which occurred in 1989) to detect storm horizons from the sediments that have been accumulating in Singleton Swash since 5700 yr B.P. We suggest here that the most intense storm activity occurred in the 0–1000 yr B.P. interval (six storms); only three occurred in the 1000–2000 yr B.P. interval and two in the 2000–3000 yr B.P. time interval (calibrated radiocarbon years). There was one giant storm in the pre–5000 yr B.P. interval; a sea-level oscillation in the 3500–5000 yr B.P. interval appears to have destroyed most records during that period. Previous work suggests that the position of the Bermuda (or Azores) High influences the direction of general storm paths for major North Atlantic hurricanes: a position of the Bermuda High farther to the south tends to force storms into the Gulf of Mexico, whereas a northern position allows them to track up the Atlantic Coast. Results here combined with results of other workers on the Gulf Coast suggest a more southern position for the Bermuda High, causing more storms on the Gulf Coast in the interval of 1000–3400 yr B.P. Conversely, a more northern position during the past 1000 yr is suggested to have contributed to higher frequencies of storms on the Atlantic Coast in that period. To test this hypothesis, modern records of the movement of the North Atlantic Oscillation (NAO, which controls the position of the Bermuda High) have been compared with historical records of hurricane tracks over the twentieth century. There does appear to be a strong correlation between the position of the NAO and the track the storms have pursued in modern times.

A Comparison of Postglacial Arcellacean (Thecamoebian) and Pollen Succession in Atlantic Canada, Illustrating the Potential of Arcellaceans for Paleoclimatic Reconstruction

Cores dating back to deglaciation were taken from three lakes in Atlantic Canada and analyzed for arcellaceans and pollen. Paleotemperatures and paleo-precipitation were calculated from the pollen data using transfer functions. A sudden warming is recorded by the pollen around 10,000 years B.P., followed by a general warming to the mid Holocene Hypsithermal, then by a decrease in temperature and increase in effective precipitation to the present. The three lakes, two in western Newfoundland and one in eastern Nova Scotia, contain similar late glacial (13-10 ka), early Holocene (10-8 ka), mid Holocene (8-4 ka), and late Holocene (4-0 ka) arcellacean assemblages. Immediately following retreat of the ice sheets, Centropyxis aculeata, Centropyxis constricta, Difflugia oblonga, Difflugia urceolata, and Difflugia corona were common. The latter part of the late glacial is characterized by sparse assemblages dominated by C. aculeata. The arcellacean record thus suggests a climatic reversal in Atlantic Canada between 11,500 and 10,000 years B.P., analogous to the Younger Dryas, although this is not recorded by the pollen. Species diversity increased sharply at the beginning of the Holocene, and D. oblonga is the dominant taxon in early Holocene sediments. Difflugia oblonga remained common through the mid Holocene, but percentages of C. aculeata were very low, and Pontigulasia compressa and Difflugia bacillifera peaked in abundance during the Hypsithermal. The late Holocene is characterized by a resurgence in C. aculeata at the expense of other taxa. The increase in Heleopera sphagni and Nebella collaris since 5,000 years B.P. at the two sites in southwestern Newfoundland reflects paludification in response to increased precipitation since the Hypsithermal. Because the changes in arcellacean assemblages are regionally synchronous in all three lakes and coincide with climatically driven vegetational successions indicated by the pollen record, arcellaceans appear to respond to climatic change, and thus may be useful paleoecological and paleolimnological indicators. With their quicker generation time, these protists may be better suited than pollen to recording short-lived phenomena, like the mid-Holocene Hypsithermal and the Younger Dryas reversal.

Hurricane records on the South Carolina coast: Can they be detected in the sediment record?

Abstract More than 40 short cores were collected from 10 localities in the Myrtle Beach to McClellandville coastline of South Carolina. The localities were selected on the basis of whether or not they should have a well preserved record of recent hurricanes, most notably Hugo , which occurred in September, 1989. Of the 40 cores collected, results from two sites are presented here as examples — Price’s Inlet, a non-tidal intra-beach ridge area, which was directly in the path of the eyewall of Hugo , and Sandpiper Pond which is a coastal non-tidal pond near Murrells Inlet, about 50–75 km north of where the main landfall of hurricane Hugo but still in the area of high storm surge. These cores were analyzed for percentage organic carbon, visual observations, X-rays, and microfossils. The microfossils were used to differentiate marine/non-marine sequences in the non-tidal inlets and identify reworked sediments by means of displaced benthic foraminifera. Cores were dated using Pb-210 techniques that provide resolution for the last 100 yr. In Price’s Inlet the Hugo effect was most pronounced with an 8 cm thick sand layer containing many nearshore foraminifera, showing transport from offshore. In Sandpiper Pond we could see the trace of Hugo from the offshore foraminifera contained in sediments sandwiched between the freshwater intervals both before and after Hugo , however, there was little detectable trace in the X-rays or sedimentology of this core to indicate a storm event. Hence, we can recognize a range of responses for hurricanes in the form of different types of sediment layers and microfossil assemblages in these non-tidal areas depending on where the impact point is on the coast. Here we are able to distinguish at least two types of signals from the same storm which has significant implications for detecting these events in the pre-historic record and determining their paleo-periodicity.

Relationship of Foraminifera and thecamoebian distributions to sediments contaminated by pulp mill effluent: Saguenay Fiord, Quebec, Canada

Gravity cores and grab samples collected in the Saguenay Fiord between 1976 and 1988 contain the record of a 20th century benthic marine environment contaminated primarily by organic matter discharges from several local pulp and paper mills.Spiroplectammina biformis is the dominant arenaceous species. Its living percent abundance decreases between 1982 and 1988 as a consequence of the apparent recolonization of the upper reaches of the fiord by several arenaceous taxa, the most important beingTextularia earlandi. Cassidulina reniforme, the dominant living calcareous species, shows about a three fold increase in relative abundance over the six year interval. Grab sample observations also suggest a recolonization of some formerly barren benthic environments near the head of the fiord by foraminiferal species between 1982 and 1988. This recolonization may reflect the combined effect of government regulations imposed on local industrial polluters in the early 1970s and the capping of a large area of contaminated sediment by a layer of clay that was transported to the basin at the head of the fiord as the result of a catastrophic landslide in 1971. X-radiographs of core sections from a basin at the head of the fiord show sharp laminations that reflect both the absence of bioturbators and the seasonal variation of fluvial depositional processes. Organic waste deposition from pulp and paper mill outfalls first increased around 1910 and shows a first order inverse relationship to benthonic foraminiferal assemblage diversity. The presence of only allochthonous thecamoebian and reworked planktonic Foraminifera tests in many benthonic Foraminifera-barren core intervals supports the idea that common indigenous estuarine species such asSpiroplectammina biformis were excluded from these areas at certain times as a consequence of pollution “stress” rather than having been removed from the sediment record as a result of post-depositional diagenetic effects. However, future studies of estuarine pollution history based on proxy foraminiferal data from cores must give greater emphasis to distinguishing ecological stress responses from diagenetic process (i.e. test dissolution effects) since both mechanisms can be reflected in the proxy pollution “signal” in a similar way.

Middle Holocene Sea-Level Rise and Highstand at +2 M, Central Texas Coast

New data suggest a revised picture of middle Holocene sea-level change for the Texas Gulf of Mexico coast, and suggest reevaluation of coastal evolution. First, brackish marsh facies with calibrated radiocarbon ages of 7.7 to 7.8 ka have been recovered from depths of −8.5 to −9 m in a core from the ancestral Colorado River delta, and are interpreted to represent a sea-level pinning point. Second, a series of ridges along the Copano Bay margin farther south consist of shelly mud and fine sand with subtidal foram assemblages, occur at elevations of 1.95 m above the modern intertidal zone, and have produced calibrated radiocarbon ages on foram tests of ca. 6.8 to 4.8 ka. These ridges are interpreted to represent relict shallow subtidal to intertidal spits that provide minimum sea-level positions for the middle Holocene, and are now emergent because of later sea-level fall. In aggregate, these data show rates of sea-level rise during this time period that are very comparable to, or even lower than, published eustatic rates, and suggest a middle Holocene sea-level highstand for this non-uplifting, non-rebounding, and very slowly subsiding part of the North American coastline.

Fossil Thecamoebians: Present Status and Prospects for the Future

Some basic facts concerning the biology, ecology and taxonomic problems of thecamoebians are reviewed and summarized on the assumption that this information is useful for the palaeontological applications of this group.

INFAUNAL BENTHIC FORAMINIFERA IN SOME NORTH AMERICAN MARSHES AND THEIR INFLUENCE ON FOSSIL ASSEMBLAGES

We have looked at a series of living and total assemblages of foraminifera in cores from two well-studied salt marshes (Chezzetcook Inlet, Canada, and North Inlet, South Carolina) and replotted data from a marsh in Nanaimo, British Columbia. The data from the three sites indicate that: 1) the infaunal living specimens appear to have little impact on the total assemblages at depth; 2) there is little evidence of test breakdown except for the well-known dissolution of calcareous tests that occurs in these acidic marsh sediments, although there is an inexplicable taphonomic breakdown of specimens in the southeastern USA; 3) the upper 1-cm slice of sediment provides a representative assemblage to use as a modern analogue for fossil benthic foraminiferal assemblages (as opposed to larger segments); and 4) foraminifera do not migrate vertically in the sediment to escape seasonal ice. We also include a taxonomic discussion of the most common Trochammina species, since some new names have been assigned to various formae of Trochammina macrescens.

Biogeographic Distribution of Modern Thecamoebians in a Transect Along the Eastern North American Coast

Thecamoebians in general, and the superfamily Arcellacea in particular, seem ideally suited as paleolimnological tools. The scarcity of baseline biogeographical studies, however, severely limits their value as modern analogs for paleoecological reconstructions. A comparison of the modern arcellacean fauna studied from four lakes from Baffin Island (63°N), Nova Scotia (45°N), Virginia (38°N) and southern Florida (27°N) with the information available in the literature shows how several trends in arcellacean distribution exist in eastern North America.

Model estimates hurricane wind speed probabilities

In the United States, intense hurricanes (category 3, 4, and 5 on the Saffir/Simpson scale) with winds greater than 50 m s −1 have caused more damage than any other natural disaster [Pielke and Pielke, 1997]. Accurate estimates of wind speed exceedance probabilities (WSEP) due to intense hurricanes are therefore of great interest to (re)insurers, emergency planners, government officials, and populations in vulnerable coastal areas. The historical record of U.S. hurricane landfall is relatively complete only from about 1900, and most model estimates of WSEP are derived from this record. During the 1899–1998 period, only two category-5 and 16 category-4 hurricanes made landfall in the United States. The historical record therefore provides only a limited sample of the most intense hurricanes.

Late mid-Holocene sea-level oscillation: A possible cause

Abstract Sea level oscillated between 5500 and 3500 years ago at Murrells Inlet, South Carolina, Chezzetcook and Baie Verte, Nova Scotia and Montmagny, Quebec. The oscillation is well constrained by foraminiferal marsh zonations in three locations and by diatoms in the fourth one. The implications are: (1) there was a eustatic sea-level oscillation of about 2–10 m in the late mid-Holocene on the southeast coast of North America (South Carolina to Quebec) that is not predicted by present geophysical models of relative sea-level change; (2) this oscillation coincides with oceanographic cooling on the east coast of Canada that we associate with melting ice; and (3) this sea- level oscillation/climatic event coincides exactly with the end of pyramid building in Egypt which is suggested to have resulted from a climate change (i.e. drought, cooling). This sea-level/climatic change is a prime example of feedback where climatic warming in the mid-Holocene promoted ice melt in the Arctic which subsequently caused climatic cooling by opening up Arctic channels releasing cold water into the Inner Labrador Current that continued to intensify until 4000 years ago. This sea-level event may also be the best way of measuring when the final ice melted since most estimates of the ages of the last melting are based on end moraine dates in the Arctic which may not coincide with when the last ice actually melted out, since there is no way of dating the final ice positions.