Hunting Paleo-Fires in Jamaica

 

by Dana MacDonald

Students learning how to identify macro charcoal.

The University of the West Indies (UWI) – Mona Campus Kingston Jamaica hosted a two-day workshop on identifying and analyzing macro-charcoal from sediments to characterize past fire regimes on May 3rd and 4th, 2017. Two days were devoted to exploring techniques and research tools from past efforts to reconstruct paleo-fires in New England and Florida, and explored future research possibilities in the Caribbean.

WHOI’s Coastal Systems Group research associate, Dana MacDonald, demonstrates how to subsample a sediment core for charcoal analysis.

The workshop was co-taught by Dr. Michael Burn, Lecturer in Climatology, Department of Geography and Geology, UWI and Dana MacDonald, Research Associate Woods Hole Oceanographic Institution and Research Fellow, Department of Geosciences, University of Massachusetts – Amherst.

The event was attended by about 20 graduate and undergraduate students, faculty, and staff. Lectures and discussions were integrated with lab periods to subsample sediments for charcoal, extraction of samples with sieving,

Students practice their new skills by identifying macro charcoal.

and identifying macro-charcoal and other macro-fossils in sediment samples using
stereo light microscopy. Examples of past research were discussed in the context of their climates, landscapes and sediment records, and students uploaded, troubleshot, and ran a test data set with CharAnalysis, a macro-charcoal analysis software.

 

The field team carries seismic gear down the beach to survey subbottom sediments in Manatee Bay, Jamaica.

Sediment cores from one of the example sites, a lagoon adjacent to Manatee Bay, St. Catherine Parish, were scanned to identify the utility of using macro-charcoal in these saline back-barrier beach lagoons. These cores may hold a fire record for one of Jamaica’s rarest dry sub-tropical forest types, and additional paleo-ecological records for one of the largest areas of undisturbed sub-tropical dry forest in the Caribbean. The workshop was followed by field work originating from the Port Royal Marine Laboratory UWI to several lagoons at Manatee Bay, scouting for areas to conduct seismic sediment profiling, and reconnaissance of the dry forest of the Hellshire Hills.

Seismic surveying of St. George’s Lake, Jamaica. Dana makes it look easy, even as he holds the instrument off the side of the boat.

Additionally, seismic sediment profiling was undertaken at St. George’s Lake, St. Ann Parish, exploring for a Pleistocene length paleo-climate record for the north-coast of Jamaica to compliment sediment records taken from nearby Discovery Bay and Shark Pond in 2016.

The workshop and field research was supported by the Department of Geography and Geology, UWI – Mona Campus, and the Port Royal Marine Laboratory with the gracious help of Drs. Michael Burn and Suzanne Palmer. Additional support was also provided by the University of Massachusetts – Amherst 2017 Research Support Fund, Associate Dean Sally Powers, and Dr. Jeffery Donnelly of the Coastal Systems Group, Woods Hole Oceanographic Institution. Photos: Dr. Michael Burn, Lecturer in Climatology and Dr. Suzanne Palmer, Lecturer Coral Reef Ecology, University of The West Indies – Mona

In The Trenches

Stephanie Madsen and Aleja Ortiz note stratigraphic changes on Eneko Island in the central Pacific.

Sure, acoustic sub-surface imagery and ground penetrating radar are great. Resistivity sensors and magnetometers can tell us so much. We can learn a lot from X-Ray Diffraction scans and radiography. But often the best way to understand the Earth beneath our feet is just to dig a hole. The digging of holes and trenches is a common practice in field work (as is taking advantage of existing holes and trenches that have been conveniently dug within our research area).

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Andrea Hawkes along with Argentine colleagues select sea shells for C-14 dating from a trench wall located over 2km inland of the present day shore line in small coastal town on San Blas Argentina.

A hole lets us analyze the stratigraphy insitu, while a trench lets us track the stratigraphic layers left and right as well as up and down. Seeing how the stratigraphy changes along a trench wall provides increased confidence regarding the conclusions drawn from the interpretation. In a trench, we can record and sample the stratigraphy without concern that it was somehow disturbed by the coring process. Trenches and holes negate the issue of sediment compaction that can result from driving the core barrel into the ground and cause layers to appear deeper and thinner than they actually are.  A simple measuring tape can provide precise depth information with a high degree of confidence (just remember… 0 is the top and we measure down).  A shovel or even bare hands can reveal much of the geologic past.

Digging-Chris

Chris Maio clears out a drainage ditch for sampling in the Marshall Islands.

We just don’t recommend going in head first…

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Jeff Donnelly goes in for a closer look.

A Family Affair

Whether exploring remote wilds, asking questions in our own backyards, or helping out in the lab you’ll find the Donnelly’s are hard at work.

In 2010 Jeff Donnelly’s father, Pat, was fortunate enough to accompany the team to Good News Bay in Alaska as part of a project investigating high latitude barrier beach development

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Jeff and his father arrive in Good News Bay

Naturally Jeff’s own children have been getting involved with science and discovery.  Amelia has been spotted in the lab while Nate’s been known to bring home a sediment core or two.

Nate and Aemilia

Aemilia seiving on the left and Nate and Emmy label cores on the right

Skippy Pond_Nate coring)

Nate helps his dad get a core here on Cape Cod

Unalaskan Rodeo

The problem, in the deep and narrow confines of Naginak Bay on Unalaska Island in the Aelutians, was that the anchors kept slipping. A successful coring operation requires that the coring platform stays still and does not drift off station. While high-tech solutions such as dynamic positioning can be used on larger and more expensively equipped vessels, the go-to solution for station keeping is to set three anchors such that the coring platform comes to rest firmly between them. If not set correctly the anchors may slip, the boat may drift, and coring becomes impossible. This was the problem faced by WHOI scientists Dr. Jeff Donnelly, Dr. Andrea Hawkes, and tech Richard Sullivan in Naginak during their 2011 expedition; the third anchor kept slipping. After numerous failed attempts a new plan was devised… lassoing a pinnacle.

Richard ties a very large bowline

Richard ties a very large bowline

Once the stationkeeping problem was resolved (and after Richard got his rowing and rock climbing work out for the day) the team managed to recover numerous 9m long cores from the base of the bay. These cores contained a high resolution storm record that can help us better understand how frequently high energy storm events in the North Pacific have occurred over the past several thousand years.

Everything Should Be Waterproof

Majetto_Kayak

On a recent field expedition to the remote western end of Kwajalein Atoll in the central Pacific, the team encountered a different sort of problem than what they’re used to.  There was no safe place for the boat to land.  The shallow reef flat and heavy surf prevented the 50′ boat supplied by the US Army base on Kwajalein from getting close to shore or dropping anchor.  This problem, while unusual for a group used to operating off of shallow draft vessels in protected coastal waters, had been anticipated.  The gear was loaded into water tight Pelican cases, dry bags, wrapped in plastic bags, and strapped to a kayak.  The team then donned masks, snorkels, and flippers and swam in through the surf towing the gear behind them.

Fortunately the gear (and personnel) all made it ashore intact, and after taking a few minutes to dry off and collect themselves, it was time for the team to get to work.

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Jimmy Bramante (center) and Richard Sullivan (left) tow the ground penetrating radar across Ebadon Island at the extreme Western end of Kwajalein Atoll. Mollie McDowell (right) maps the topography with the high precision differential GPS. Photo credit: Charlotte Wiman

Hole in One

hole-in-oneWHOI geologist Jeff Donnelly and research assistant Richard Sullivan recently joined Texas A&M University at Galveston (TAMUG) geologist Pete van Hengstum and undergraduate student Tyler Winkler in collecting cores from Thatchpoint Bluehole. It is thought that blueholes form when rising seas flood a sinkhole, formed when limestone bedrock is dissolved from below by groundwater and collapses. The team collected a continuous, nine-meter (30-foot) sediment core from the bluehole as part of their efforts to construct a record of the frequency and intensity of tropical cyclones in the western Atlantic. (Photo courtesy of Pete van Hengstum, Texas A&M University)

Climate Time Machine

time-machineJimmy Bramante, a graduate student in the MIT-WHOI Joint Program, collected a core sample from an Atlantic white cedar tree in Cape Cod National Seashore recently. Tree growth is often affected by variations in climate, including precipitation and temperature, which is recorded in recorded in the width and composition of tree rings in many species, particularly Atlantic white cedar. Bramante was part of a team helping fellow graduate student Jessie Pearl collect the core samples as part of Pearl’s work to construct a climate history of the Northeast. (Photo by Jessie Pearl,Woods Hole Oceanographic Institution)

A Stormy Past

stormy-pastnew study led by WHOI scientist Jeff Donnelly found that intense hurricanes frequently pounded Cape Cod during the first millennium. Donnelly (in orange shirt), accompanied by Stephanie Madsen (left), Richard Sullivan (center), and Brecia Douglas (right) collected sediment cores from Salt Pond in Falmouth, Mass. Analysis of the cores showed evidence of 23 severe hurricanes that hit New England between the years 250 and 1150—the equivalent of a severe storm about once every 40 years on average. (Photo courtesy of Richard Sullivan, Woods Hole Oceanographic Institution)

Surf’s Up

surfs-upThe storm surge from the Great New England Hurricane of 1938, which made landfall as a category 3 storm on Long Island battered the shore of Woods Hole, Mass. In addition to destroying infrastructure and threatening lives, large waves from hurricanes can erode shorelines and transport coastal sediment into nearby ponds and marshes, preserving a record of the storms. Led by WHOI scientist Jeff Donnelly, a new study of sediment cores from Salt Pond in Falmouth, Mass., revealed historically unprecedented hurricane activity along the northern East Coast. The findings could help scientists better predict the frequency and intensity of future hurricanes. (Photo courtesy of Woods Hole Oceanographic Institution Archives)