Hatching

1
Covering Pits Once the egg chamber is
back-filled, the turtle enters a covering
behavior characterized by front flipper sweeps
(Hailman and Elowson, 19xx) pushing and throwing
sand backwards and propelling the turtle forward.
As the turtle moves forward with successive
flipper sweeps, she almost always rotates 180
degrees either clockwise of counterclockwise and
then exits the covering pit to crawl back to the
ocean. The resultant sedimentary structure is a
thin bioturbated layer (20-30 cm thick) covering
the egg chamber and body pit .The structure
exhibits an elliptical shape approximately 3.0 m
long and 1.5 m wide bounded by flipper scarps,
with an uneven surface, trails of loose, thrown
sand, connected to entrance and exit crawlways.
The covering pit and crawlways are exceedingly
ephemeral structures on the surface, rapidly
erased by wind, rain, and tides.

ACKNOWLEDGMENTS This research has been
generously supported by The Georgia Eisenhower
Higher Education Program (now Improving Teacher
Quality), The St. Catherines Island Foundation,
Inc., The Turner Foundation, The JST Foundation,
The Georgia Department of Natural Resources,
Georgia Southern University, and the Museum of
Geology and Paleontology, South Dakota School of
Miners and Technology. The Limon, CO map is
provided by Radar Acquisitions and the Cretaceous
paleogeographis map is from USGS Professional
Paper 1561.
Loggerhead covering pit on top of a dune
McQueens Inlet, South Beach, St. Catherines
Island..
Loggerhead body and covering pit on washover fan
(a sand angel) Seaside Spit, North Beach, St.
Catherines Island, Georgia. Scale 10 cm.
Loggerhead during flipper sweep in covering
behavior.
Hatching After approximately sixty days of
incubation in the solar-heated sand, the eggs
will hatch and the hatchling turtles will emerge
from their egg shell. The hatchlings begin to dig
themselves out by a crawling motion of flippers,
loosening the sand around and above them which
falls through the mass of hatchlings under the
influence of gravity, often forming a "stope" or
air chamber above the mass of wiggling little
turtles. This mining activity continues as long
as the hatchlings are in cool sand beneath the
surface. When they near the surface with its
solar-heated hot sand, the hatchlings stop their
activity and become lethargic, until the sand
cools during the night when activity is renewed
and the hatchlings emerge from their nest and
scamper toward the sea, forming hatchling
crawlways. Near the surface the sand is dry and
not cohesive, so the surface layer may fall into
the stope forming a surface "dimple" announcing a
imminent emergence. The final emergence often is
en masse, although multiple emerges on successive
nights is the norm. Synchronous emergence of
large numbers of hatchlings often forms an
emergence crater as the surface sand collapses
into the void left by the hatchlings. Upon
emergence at night the hatchlings head to the sea
(downhill, away from the island silhouette, and
toward the light and noise of the sea) forming a
pie-shaped arc of anatomizing crawlways
broadening the sea. Reading these crawlways often
allows the documentation of interactions with
predators on the beach and an estimate of the
number of emergent hatchlings. These are
exceedingly ephemeral traces easily destroyed by
wind, rain, and tide.
Table 1 Potential traces of sea turtle nesting
and documentation (in red) of identified
structures in Fox Hills Sandstone, elbert County,
Colorado.
Loggerhead hatchlings during a rare daytime
emergence.
Loggerhead hatchling crawling across the beach.
Loggerhead hatchling crossing a heavy mineral
sand.
Up-side-down loggerhead hatchling producing an
unusual trace as it tries to right itself on dune
surface. Scale 4 in (10 cm).
The Fossil Record Because sea turtles nest in a
dynamic environment with a low probability of
preservation and their modern traces are largely
unknown to most geologists and paleontologists,
their ichnoloy still remains poorly known.
However, by using modern sea turtle traces it is
possible to predict what analogous trace fossils
will look like when preserved in sedimentary
rocks of Cretaceous to Holocene age. The
abundance of body fossils of sea turtles attests
to heir presence in many regions from Early
Cretaceous to present and indicates that they
nested on sandy beaches in those regions during
the same interval. Even though the preservation
potential of back beach sediments is low, the
very number of sea turtles and their multiple
nesting behavior would be expected to produce a
high potential for preservation where back beach
sediments are preserved. This hypothesis was
promulgated at the annual meeting of the Rocky
Mountain Association of the Geological Society of
America (Marsh and Bishop, 1986) by bringing
modern loggerheadsedimentary nesting structures
to the attention of western geologists who might
have seen, or be expected to see, analogous
fossil structures in the Cretaceous of the
Western Interior. During a consult with E. I.
DuPont on ghost Shrimp burrows
Recent Analog
ec
cp
bp
cw
ec
Recent flipper marks in sea turtle crawlway (cw)
in backbeach facies South Beach, St. Catherines
Island, Georgia. Scale 10 cm.
Collapsed Recent egg chamber in sea turtle nest
(ec) in backbeach facies South Beach, St.
Catherines Island, Georgia. Scale 10 cm.
Trenched Recent sea turtle nest in backbeach
facies South Beach, St. Catherines Island,
Georgia showing covering pit (CP), Body pit
(BP), and egg chamber (ec ). Scale 10 cm.
Fossil Example
bp
cw
B
C
Fossilized sea turtle egg molds (arrow) in bottom
of egg chamber Fox Hills Sandstone Elbert
County, Colorado. Hammer 40 cm.
Fossilized sea turtle body pit (bp) incised into
backbeach facies Fox Hills Sandstone Elbert
County, Colorado. Scale 10 cm.
Fossilized flipper marks in sea turtle crawlway
(cw) in backbeach facies Fox Hills Sandstone
Elbert County, Colorado. Scale 10 cm.
Selected References Bishop, G.A., N. B. Marsh, J.
Barron, F. L. Pirkle, R. S. U. Smith. 1997. A
Cretaceous sea turtle nest, Fox Hills Formation,
Elbert Co., CO. Geological Society of America,
Abstracts with Programs 29(6) A104. Brannen, N.
A., and G. A. Bishop. 1993. Nesting traces of the
loggerhead sea turtle (Caretta caretta Linne),
St. Catherines Island, Georgia Implications for
the fossil record. In K. M. Farrell, C. W.
Hoffman, and V. J. Henry, JR. (eds.)
Geomorphology and facies relationships of
quarternary barrier island complexes near St.
Marys, Georgia. Ga. Geol. Soc. Guidebooks 13(1)
30-36. Frey, R. W. and S. G. Pemberton. 1987.
The Psilonichnus ichnoconose, and its
relationship to adjacent marine and nonmarine
ichnocoenoses along the Georgia coast. Bull.
Canadian Petrol. Geol. 35(3) 333-357. Hailman,
J. P. and A. M. Elowson. 1992.Ethogram of the
nesting female loggerhead (Caretta caretta).
Herpetologica 48(1) 1-30. Radar Acquisitions.
lthttp//www.radar.ab.ca/heavy_minerals.htmlgt. Robe
rts, L.N.R. and M.A. Kirschbaum. 1995.
Paleogeography of the Late Cretaceous of the
Western Interior of Middle North America---Coal
Distribution and Sediment Accumulation. U.S. Geol
Survey Professional Paper 1561 115
p. Witherington, Blair. 1992. Crawl
identification for Florida Index Beach Surveys.
Archie Carr Center for Sea Turtle Research,
University of Florida, 5 p.
A
Back beach facies tract in Cretaceous Fox Hills
Sandstone near Limon, Elbert County, Colorado
Showing forebeach (A) and backbeach (B), and
collapsed sea turtle nest structure(C) Scale
10 cm.
Back beach facies tract in Cretaceous Fox Hills
Sandstone near Limon, Elbert County, Colorado
Showing forebeach (A), backbeach (B), washover
fan (C ), and festooned dunes (DE),. Scale 1
m.