Geological record

The Weyburn site was selected because, during 44 years of oil exploration, Saskatchewan required oil companies to keep extensive geological records. Core samples from 1,200 bore holes allowed an extensive look at subsurface conditions and a way to track the movement of oil and gases. 

Fig. 9.8 Stratigraphic presentation of 813C values for organic material extracted from the Arundal clay formation, Maryland. Error bars reflect the standard deviation for three replicate analyses. The dashed line represents the boundary between the early and middle Aptian eras ( 125 to 112 megayears BP) established from the geological record. The gray arrow highlights the isotope shift of interest (Reprinted from Jahren, A. H. et al., Earth Planet. Sci. Lett. 236, 691, (2005), Copyright 2005, with permission from Elsevier)...

Past climates leave their imprint in the geologic record in many ways. For temperature reconstructions, the most widely nsed geochemical method is the measurement of stable isotope ratios. Samples for climate reconstrnction have in common that their isotope composition depends in a sensitive way on the temperature at the time of their formation. 

The application of biomarker research in the geologic record has dealt with the derivative hydrocarbons as found in petroleum, coals, and sedimentary rocks. Reports on biomarkers in discrete fossils compared to the host rocks are sparse because (1) previous studies focused on the highly degraded geoterpenoids, i.e. saturated and aromatic hydrocarbons, and (2) the preservation potential of polar compounds (natural product bioterpenoids ) was believed to be low. Flowever, recent investigations of conifer fossils demonstrated that unaltered natural product terpenoids can be preserved in resin material.This will be illustrated here with an example. 

Radioactive isotopes have thus enabled scientists to reconstruct the history of the Earth and its environs over billions of years. But stable isotopes are also an indispensable part of the geoscientist s inventory. In particular, their measurement in the geological record has revolutionized our perception of how the planet s climate system works and how it has changed over time. 

Similar changes are seen in other terrestrial and marine geological records from the North Atlantic region, but not from the Antarctic. Circulation changes in the North Atlantic Ocean are conjectured to be the driving force for the climate changes. 

Geological records indicate that many ice ages were initiated by periods of unusually warm weather. How can warm weather precipitate an ice age ... 

Dickens (1999) cautions that in modem times a similar reoccurrence is prevented by deeper oceans than in ancient times. However, the importance of the LPTM perturbation is that it is the only analog available in the geological record for understanding how the global carbon cycle and other systems is related to a rapid, massive input of fossil fuel such as that which may be occurring in modern industrial times. 

Fig. 1.5. Phylogeny of the deuterostomes indicating position of oldest fossil taxa against the geological record. All neodermatans parasitize vertebrates and, if present, host associations represent historical associations the Neodermata must have parasitized the stem group Gnathostomata between the Cambrian and Ordovician. Tree redrawn from Rowe (2004).

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