Assessment of the suitability of Tasmanites and cryptospores for Palynomorph Darkness Index (PDI) determination

Details

The measurement of vitrinite reflectance is the standard oil industry method for assessing the thermal maturity of sedimentary rocks. However, this method can’t be applied to pre-Devonian rocks, as these lack vitrinite, a derivative of the woody tissues of vascular plants which was not produced in significant quantities until Devonian time. Palynomorph Darkness Index (PDI) is an alternative, fully-quantitative method for estimating maturity, based on measurement of the darkness of palynomorphs in transmitted light. Palynomorphs progressively and irreversibly darken with increasing temperature and many palynomorph groups such as acritarchs, Tasmanites (prasinophytes), cryptospores and chitinozoa occur in abundance in Lower Palaeozoic rocks.

This project will focus on the measurement of PDI of Tasmanites, cryptospores and chitinozoa, which has not been previously attempted in any detail. The PDI results obtained will be correlated to PDI results from other groups of palynomorphs such as acritarchs that have already proved suitable for maturity studies. It is anticipated that the new groups investigated will prove more useful than acritarchs in studies of rocks of low maturity, where measurement of the PDI of the latter is technically difficult due to their very thin walls. Samples from various collections will be used for the project with additional outcrop sampling being completed where necessary.