Applications for the Environmental and Earth Sciences, 2009
... The modern African dataset was created by combining regional datasets from Northwest Africa (... more ... The modern African dataset was created by combining regional datasets from Northwest Africa (125 samples; Khelifa, 1989; F. Gasse, unpublished observations), East Africa (167 samples; Gasse, 1986), and Niger (20 samples; Gasse, 1987). ...
The inference of past temperatures from a sedimentary pollen record depends upon the stationarity... more The inference of past temperatures from a sedimentary pollen record depends upon the stationarity of the pollen-climate relationship. However, humans have altered vegetation independent of changes to climate, and consequently modern pollen deposition is a product of landscape disturbance and climate, which is different from the dominance of climate-derived processes in the past. This problem could cause serious signal distortion in pollen-based reconstructions. In the north-central United States, direct human impacts have strongly altered the modern vegetation and hence the pollen rain since Euro-American settlement in the mid-19th century. Using instrumental temperature data from the early 1800s from Fort Snelling (Minnesota), we assessed the signal distortion and bias introduced by using the conventional method of inferring temperature from pollen assemblages in comparison to a calibration set from pre-settlement pollen assemblages and the earliest instrumental climate data. The e...
A high-resolution, independent pollen-inferred paleoclimate record and direct algal seasonality d... more A high-resolution, independent pollen-inferred paleoclimate record and direct algal seasonality data from the actual time of sediment deposition are used to interpret the high-resolution diatom and chrysophyte record of varved Lake Mina, west-central Minnesota, USA during AD 1116—2002. This direct algal seasonality information was obtained by splitting varves into constituent winter-spring and summer lamina, and separately analyzing the siliceous algae
We developed a fast, inexpensive, statistically rigorous method of varve verification that uses p... more We developed a fast, inexpensive, statistically rigorous method of varve verification that uses prospective varve layer-splitting and seasonal pollen deposition. This method can be used on any sediment that contains seasonally deposited pollen, and avoids the need for radio-isotopic, optical, or thermoluminescence dating. The method uses a χ2 test and non-parametric regression, together with recorded plant bloom times from pollen
... Several studies have shown that many scaled-chrysophyte taxa have rea-sonably well-defined en... more ... Several studies have shown that many scaled-chrysophyte taxa have rea-sonably well-defined environmental optima to several important limnological variables, especially lakewater pH (Cumming et al. ... Killams 6.2 0.54 3.7 1.5 6.0 49 Jesse 6.3 1.25 4.9 5.7 4.3 30 ...
Diatom assemblages preserved in sediment cores from closed-basin lakes can provide high-resolutio... more Diatom assemblages preserved in sediment cores from closed-basin lakes can provide high-resolution records of past hydrologic and climatic conditions, including long-term patterns in the intensity, duration, and frequency of droughts. At Moon Lake, a closed-basin lake in eastern North Dakota, a comparison of diatom-inferred salinity and the precipitation-based Bhalme-Mooley Drought Index (BMDI) over the last 100 years was highly significant,
Applications for the Environmental and Earth Sciences, 2009
... The modern African dataset was created by combining regional datasets from Northwest Africa (... more ... The modern African dataset was created by combining regional datasets from Northwest Africa (125 samples; Khelifa, 1989; F. Gasse, unpublished observations), East Africa (167 samples; Gasse, 1986), and Niger (20 samples; Gasse, 1987). ...
The inference of past temperatures from a sedimentary pollen record depends upon the stationarity... more The inference of past temperatures from a sedimentary pollen record depends upon the stationarity of the pollen-climate relationship. However, humans have altered vegetation independent of changes to climate, and consequently modern pollen deposition is a product of landscape disturbance and climate, which is different from the dominance of climate-derived processes in the past. This problem could cause serious signal distortion in pollen-based reconstructions. In the north-central United States, direct human impacts have strongly altered the modern vegetation and hence the pollen rain since Euro-American settlement in the mid-19th century. Using instrumental temperature data from the early 1800s from Fort Snelling (Minnesota), we assessed the signal distortion and bias introduced by using the conventional method of inferring temperature from pollen assemblages in comparison to a calibration set from pre-settlement pollen assemblages and the earliest instrumental climate data. The e...
A high-resolution, independent pollen-inferred paleoclimate record and direct algal seasonality d... more A high-resolution, independent pollen-inferred paleoclimate record and direct algal seasonality data from the actual time of sediment deposition are used to interpret the high-resolution diatom and chrysophyte record of varved Lake Mina, west-central Minnesota, USA during AD 1116—2002. This direct algal seasonality information was obtained by splitting varves into constituent winter-spring and summer lamina, and separately analyzing the siliceous algae
We developed a fast, inexpensive, statistically rigorous method of varve verification that uses p... more We developed a fast, inexpensive, statistically rigorous method of varve verification that uses prospective varve layer-splitting and seasonal pollen deposition. This method can be used on any sediment that contains seasonally deposited pollen, and avoids the need for radio-isotopic, optical, or thermoluminescence dating. The method uses a χ2 test and non-parametric regression, together with recorded plant bloom times from pollen
... Several studies have shown that many scaled-chrysophyte taxa have rea-sonably well-defined en... more ... Several studies have shown that many scaled-chrysophyte taxa have rea-sonably well-defined environmental optima to several important limnological variables, especially lakewater pH (Cumming et al. ... Killams 6.2 0.54 3.7 1.5 6.0 49 Jesse 6.3 1.25 4.9 5.7 4.3 30 ...
Diatom assemblages preserved in sediment cores from closed-basin lakes can provide high-resolutio... more Diatom assemblages preserved in sediment cores from closed-basin lakes can provide high-resolution records of past hydrologic and climatic conditions, including long-term patterns in the intensity, duration, and frequency of droughts. At Moon Lake, a closed-basin lake in eastern North Dakota, a comparison of diatom-inferred salinity and the precipitation-based Bhalme-Mooley Drought Index (BMDI) over the last 100 years was highly significant,
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