GL4 E1  Key Idea 2  SEDIMENTARY ROCKS  The mineralogy and texture of sedimentary rocks are controlled by processes of weathering, erosion and deposition

GL4 E1 KI2 a  Immature sedimentary rocks are characterised by a wide range of mineral compositions and/or lithic clasts;  Mature sedimentary rocks have restricted mineralogies dominated by mineral species resistant to weathering and erosional processes

Breccia  Sedimentary (fragmental)  Immature (wide range of fragments)  Angular fragments (little transport)  Fragments range in size consider energy current (landslide?) Credit: British Geological Society

Immature/Mature  Immature rocks - contain easily weathered minerals (eg. first formed minerals from Bowen’s Reaction Series)  Immature rocks – normally very little transport (hence angular fragments), poorly sorted  Mature rocks – mainly quartz (low temperature minerals from Bowen’s Reaction Series)  Mature rocks - fragments often rounded due to long history of weathering and erosion to remove majority of minerals, well sorted

Fragment size/shape  Longer transport will reduce fragment size and will round fragment shape  Geoscience page 88 figure 5.21 (b) and (c) COPY

We need to look more closely at Mature sedimentary rocks  Why?  In order to think of the processes which destroy minerals!