Sedimentary rocks are important because
- they make up much of the surface of the crust
- they contain information about the history of the earth – the conditions of deposition
- they provide raw materials for industry, building etc
What does the classification of sedimentary rocks tell you about their mode of formation?
Write a 12-word description of clastic sedimentary rocks which says how they formed and how they were formed.
Write a 12-word description of calcareous sedimentary rocks which says how they formed and how they were formed.
Write a 12-word description of evaporite deposits which says how they formed and how they were formed.
Compile a chart which compares the typical features of sedimentary rocks compared with igneous and metamorphic rocks.
How would you recognise a sedimentary rock
- in the field?
- on a geology map?
The igneous structures usually included in exam questions are: plutons, dykes, sills, lavas. They may feature in the written exams, but also in mapwork questions.
a. How can you recognise each of these in the field or on a map, and distinguish between them? Use
- grain size
- massive or sheet-like
- nature of the contact between the igneous rock with the country rock
- relationship between the structure of the igneous feature and the bedding of the country rock.
Make up a chart which summarises these points.
The fossil parts of the A2 papers GL4 (OCR) and F795 (WJEC) concentrate on the development, or evolution, of life. It is assumed that you already know the morphological terms, and you need to know these in order to answer these more complex synoptic questions.
Terms that you must know:
- Fauna – animals
- Flora – plants
- Phanerozoic – “visible life”; the time since the beginning of the Cambrian to the present day; the time during which fossils are well-seen in the rocks.
- Sepkoski’s curves – write a brief description (and make sure you know how the interpret the curves);
- Milankovitch cycles – write a brief description