Download Sedimentary Rocks 1

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!