What are speleothems and annual
Speleothems are depositional formations found in caves,
the most common of which are stalactites and stalagmites.
These structures are created by water that contains calcium
carbonate percolating down from the surface and dripping
through fissures in the cave.
They are made up of over 70 different minerals, and since
the makeup is influenced by the climate, spleleothems are
prime candidates for inferring information about paleo-
The banding/laminae within the speleothem, much like
tree rings, are used as a chronological tool and the analysis
of the material that constitutes each annual lamina tells us
about what type of climate created it on a year by year
Laminae must be annual
In order to use laminae of a speleothem as a paleoclimate
proxy, it must be determined using other methods of
dating (ex. uranium-thorium) for comparison that the
banding is annual.
Also, (1) the laminae must be easily recognizable and
distinguishable, (2) any intra-annual bands must be
located and excluded from the study of annual bands, and
(3) there should not be an abundance of missing laminae
(hiatuses) in the speleothem.
If the surrounding climate is highly seasonal, it is a good
indication that the speleothem laminae will be annual.
4 main types of laminae:
Fluorescent: observed by using a mercury light source to produce
UV excitation - formed by the yearly fluxes of dissolved organic
matter that generally contain humic or fulvic acids (humic
Visible: alternates between Dark Compact Calcite (DCC) and
White Porous Calcite (WPC) – formed due to seasonal
differences in drip rate and seasonal changes in the relative
humidity and carbon dioxide levels of the cave, or both.
Calcite-aragonite couplets: may be formed by several factors
including temperature variations, drip rate, and concentrations
of dissolved magnesium; however, the processes generating this
type are not understood to a great degree
Trace element: located world-wide because they are, in essence,
a collection of features and conditions that are responsible for
the creation of fluorescent or visible laminae within speleothems
35 mm long stalagmite from NW Scotland
with Fluorescent lamination
1087 bands were counted
(900 AD to present) and
comparison to Carbon-14
and Uranium series dating
confirms their annual
Growth rate was compared
to regional mean annual
precipitation data and
luminescence trends were
The two analyses show the
same thing: the growth
rate of the banding is
increased in warmer, drier
This can be explained by
the fact that the overlying
peat produces carbon
dioxide much more quickly
in warm, dry periods than
in wet, cold periods.
1 meter long aragonitic stalagmite with
visible lamination from NE South Africa
uranium series dating
confirms laminae are
found to correspond
to band width (2 yr
correlates to intensity
of the color of the
bands (no lag).
40 cm long stalagmite with calcite-aragonite
couplets from Drotsky’s Cave in NW Botswana
1500 yrs worth of annual deposition as confirmed by radiocarbon
Thickness of calcite bands correlate to annual rainfall; while thickness
of aragonite bands correspond to average high summer temperatures
Since we know the ages of the layers, we can infer information about
paleoclimate from analyzing the layer thickness and its correlation
with the amount of rainfall or the average temperature.
1 meter long stalagmite from Cold Air Cave
in South Africa (same sample as used for
previous visible laminae analysis)
The trace element bands were determined to be annual in
nature and two chips 14 and 17 millimeters long were taken
from the base of the speleothem for Secondary Ion Mass
Spectrometry (SIMS) analysis.
SIMS is a method in which a beam of ions is accelerated and
projected onto the sample surface and the emitted secondary
ions are analyzed using mass spectrometry.
The first chip was found to have significant and regular
variability of both Sr/Ca and Ba/Ca where the wavelengths
and amplitude appear to coincide.
The second chip also possesses similar coincidence of
elemental variation. These results suggest that there is a
common, cyclical environmental factor that has caused the
trace element variations.
What about comparison to other types of records
that go much farther back in time than
In Mato Grosso do Sul State, Brazil, a 44 centimeter long stalagmite
was extracted from João Arruda Cave. The bands were determined
to be annual and have relatively uninterrupted growth for the past
3800 years using the usual procedure of Uranium series dating.
The stalagmite laminae were compared to different paleoclimate
records for the region such as: sediments from Lake Titicaca, cores
from the Sajama Ice Cap, samples from the Lago Taypi Chaka Khota,
and sediments from the Siberia Peat.
Through comparison of speleothem analysis and the
aforementioned records, it was found that the growth profile for the
speleothem matches up with the known climate change of the area
for hundreds to thousands of years.
This validates the method of analyzing stalagmite growth as an
effective tool in making inferences about paleoclimate.
There is great potential for the analyses of stalagmites to
yield accurate information about paleo-environments.
It does not matter what type of lamination the speleothem
contains as long as it can be confirmed as annual and is
able to be compared with known climatic events and
Reconstructing paleoclimate opens doors to a plethora of
new theories and investigations, anywhere from the
production of thousand plus - year climate trends for
furthering climate change research, to learning about
extinct creatures through the type of paleoclimate in which
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