Geochronology: Relative dating and biostratigraphy 4.2.1
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|(a)||the geochronological principles used to place geological events in relative time sequences in outcrops, photographs, maps and cross-sections to interpret geological histories
||To include: superposition, original horizontality, way-up criteria, cross-cutting relationships, included fragments and unconformities.
|(b)||the critical application of lithostratigraphic correlation (lateral variation, diachronous beds)||To include sequences of beds, thickness and composition.|
|(c)||the application and limitations of relative dating|
|(d)||biostratigraphic correlation using first appearance of macro fossils, stratigraphic range, extinction and fossil assemblages.||To include zone fossils.|
Learners may begin this topic with a general appreciation of geological time and the idea that geochronology is all about putting events into a sequence, learners develop these ideas to consider lithostratigraphic and biostartigraphic correlation techniques and can use the evidence to practice skills. Learners consider how the idea of geochronology has evolved and that by current research advances continue to be made. Learners can appreciate how identifying fossils is a useful skill when assemblages are used in biostratigraphy.
Common misconceptions or difficulties students may have:
The greatest challenge within this section is likely to be a true understanding of the relationship between beds in a delta setting where diachronous beds form. Learners considering how lateral variations in the environment can be preserved in the vertical rock record may be difficult for some to visualise. The basic setting needs to be understood first maybe by modelling in the classroom with different materials, once this is understood the model can become more sophisticated and the detailed characteristics of each part of the delta along with the effect of changing sea levels.
Conceptual links to other areas of the specification – useful ways to approach this topic to set students up for topics later in the course:
Unit 7 further develops the idea of lateral migration of environments by looking at Walther’s law. Connections are made in module 7 where local stratigraphic changes can be linked to global cyclical changes. Module 7 includes a detailed view of how fossils evolved which develops the connection between sedimentary products and processes. The economic side of the sedimentary environment is developed further in 7.2.2 oil and gas basins.
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