Palaeoclimatology and Palaeoceanography from Laminated Sediments

Palaeoclimatology and Palaeoceanography from Laminated Sediments
Author: Alan E. S. Kemp
Publisher: Geological Society of London
Total Pages: 278
Release: 1996
Genre: Nature
ISBN: 9781897799673

The magnitude and causes of decadal to century-scale changes in climate are major issues of global concern. The separation of anthropogenically driven change from natural 'baseline' variability within the atmosphere/ocean system is a prerequisite to identifying human impact on global climate. An understanding of past climate variability is therefore a key to predicting future climate change. The sedimentary record of the oceans, seas and lakes is produced by a series of depositional events that occur on seasonal timescales but can rarely be resolved due to mixing of the sediment by bottomdwelling organisms. Where they are preserved, laminated sediments act like tree rings to record these seasonal-scale processes, such as plankton blooms and floods, and provide a uniquely high-resolution record of environmental change. In addition, annually laminated or 'varved' sediment sequences act as geochronometers against which other timescales can be tested. Laminated sediments may therefore be used to develop records of interannual and decadal-scale variability which serve to test models of climate change. The authors cover a range of topics that include strategies for study and techniques of analysis. A series of case studies, dealing with a variety of lacustrine and marine records, illustrates the wide potential of laminated sediments as palaeoclimatic and palaeoceanographic indicators.

Laminated Lake Sediments and their Impact on Paleoclimatology

Laminated Lake Sediments and their Impact on Paleoclimatology
Author: Eric Petermann
Publisher: GRIN Verlag
Total Pages: 22
Release: 2010-01-18
Genre: Science
ISBN: 3640513959

Seminar paper from the year 2008 in the subject Geography / Earth Science - Geology, Mineralogy, Soil Science, grade: 1,0, University of Canterbury (Department of Geology), course: Paleoecology and Paleolimnology, language: English, abstract: Zolitschka (1998) defined varves as laminated sediments occurring in stationary water bodies. Their striking feature is a seasonal, rhythmical build-up of thin, horizontal layers with a changing composition. Since the early 20th century, this type of sediment has been used for establishing exact geochronologies. In the course of the climate change debate, and the subsequent demand for high-resolution paleoclimatic data, they have come back into the focus of earth scientists. A crucial advantage of varved sediments is that they provide two different kinds of information on a sediment profile: an absolute chronology and high-resolution paleoclimatic information. Combining these two attributes offers an absolute dated time series of paleoclimatic proxy-data. Furthermore, additional analyses of the same profile can be dated. Varved sediments can be found in recent lakes as well as in paleolakes. However, their occurrence is limited to only a few sites as a consequence of the special circumstances necessary for their generation. Varved sediments in recent lakes are especially found in lakes, which are small and deep. These preconditions are often met by maars, where a lot of investigations are done (Brauer et al. 1999a, 1999b; Litt et al. 2001). Additionally, varved sediments are even found in ancient proglacial lakes (Moscariello et al. 2000) to give an example.