Geoscience Reference
In-Depth Information
6
Figure 6.1
An example of a small part of a section of sedimentary
strata from which a lot of information about the depositional processes can
be gained. The image shows cross-stratifi cation produced by the migration
of wave-formed ripples indicating that the sediments were deposited within
wave base (less than tens of metres depth) by waves. Some of the ripples
near the middle of the image are climbing, indicating high sedimentation
rates. The image shows colour variation that is likely to refl ect grain and/
or compositional changes, which may relate to changing energy or
sediment source. There are also several trace fossils indicating animal
activity. Carboniferous-age strata exposed near Berwick-upon-Tweed, UK.
(Angela L. Coe, The Open University, UK.)
understanding of where sedimentary rock types are situated
in time and space, and how they vary vertically and
laterally, enables the main reservoir rocks, seals and source
rocks to be mapped out and fully exploited.
•
Reconstruct past periods of environmental change,
particularly climate and sea-level change.
Fine-grained
marine sedimentary deposits contain the most laterally
extensive, complete and intact record of the changing
chemistry of the Earth's oceans. Because of the interaction
between the oceans and atmosphere, and that the oceans
act like a large mixing pot, marine deposits are fundamental
to understanding the Earth system in the past. The
sedimentary deposits in caves and lakes also form a key
part in the understanding of palaeoenvironmental change
over about the past 2 Ma. Reconstructing sea-level change
relies on examining and correlating both proximal and
distal marine successions and looking for both gradual and
abrupt changes in the type of sedimentary deposit.
