Chapter 2
Introduction to Sedimentology
Sediment Transport and Sedimentary Environments
Knut Bjørlykke
Sedimentology is the study of sedimentary rocks and
their formation. The subject covers processes which
produce sediments, such as weathering and erosion,
transport and deposition by water or air, and also the
changes which take place in sediments after their
deposition (diagenesis). Diagenesis includes mechanical sediment compaction and mineral reactions as a
function of temperature during burial. Changes in sedimentary rocks at temperatures of over 200–250
C are
called metamorphic processes and are not dealt with
here. In this chapter we shall discuss primarily transport and deposition of clastic sediments and sedimentary environments. These processes determine the
distribution and geometry of reservoir rocks in a sedimentary basin and also the changes in rock properties
during burial. Accumulation of organic-rich sediments
which may become source rocks is also an integral
part of sedimentological models. Since both source
rocks and reservoir rocks normally are sedimentary
rocks, sedimentology is a very important subject for
petroleum exploration and production. Sedimentological research is to large extent funded by the petroleum
industry.
Like all natural sciences, sedimentology has an
important descriptive component. In order to be able
to describe sedimentary rocks, or to understand such
descriptions, it is necessary to familiarise oneself with
quite an extensive nomenclature. There are specialised
names for types of sedimentary structures, grain-size
distributions and mineralogical composition of
sediments. We also have a genetic nomenclature,
which names rock types according to the particular
way in which we think they have formed. Examples of
these are fluvial sediments (which are deposited by
rivers) and aeolian (air-borne) sediments. The descriptive nomenclature is used as a basis for an interpretation of how the rock was formed. When we are
reasonably confident about their origin we may use
the genetic nomenclature.
Sedimentology covers studies of both recent (modern) sediments and older sedimentary rocks. By studying how sediments form today we can understand the
conditions under which various sedimentological processes take place. From such observations we may be
able to recognise older sediments which have been
formed in the same way. This is called using the
principle of uniformitarianism, which has been of
great importance in all geological disciplines since
its proposal by James Hutton (1726–1797).
Conditions on the surface of the Earth have
fluctuated widely throughout geological history and
the principle of uniformitarianism cannot be applied
without reservation. One important aspect of sedimentological research is attempting to reconstruct changes
in environments on the Earth’s surface throughout
geological time. This applies particularly to climate,
vegetation and the composition of the atmosphere and
the oceans.
Palaeontology is important to sedimentology, not
only for dating beds, but also because organisms are an
important component of many sedimentary rocks (particularly limestones), and organic processes contribute
to weathering processes and the precipitation of
dissolved ions in seawater. Many organisms make
very specific demands of their environment, and
K. Bjørlykke (*)
Department of Geosciences, University of Oslo, Oslo, Norway
e-mail: knut.bjorlykke@geo.uio.no
K. Bjørlykke (ed.), Petroleum Geoscience: From Sedimentary Environments to Rock Physics,
DOI 10.1007/978-3-642-34132-8_2, # Springer-Verlag Berlin Heidelberg 2015
31
Introduction to Sedimentology
Sediment Transport and Sedimentary Environments
Knut Bjørlykke
Sedimentology is the study of sedimentary rocks and
their formation. The subject covers processes which
produce sediments, such as weathering and erosion,
transport and deposition by water or air, and also the
changes which take place in sediments after their
deposition (diagenesis). Diagenesis includes mechanical sediment compaction and mineral reactions as a
function of temperature during burial. Changes in sedimentary rocks at temperatures of over 200–250
C are
called metamorphic processes and are not dealt with
here. In this chapter we shall discuss primarily transport and deposition of clastic sediments and sedimentary environments. These processes determine the
distribution and geometry of reservoir rocks in a sedimentary basin and also the changes in rock properties
during burial. Accumulation of organic-rich sediments
which may become source rocks is also an integral
part of sedimentological models. Since both source
rocks and reservoir rocks normally are sedimentary
rocks, sedimentology is a very important subject for
petroleum exploration and production. Sedimentological research is to large extent funded by the petroleum
industry.
Like all natural sciences, sedimentology has an
important descriptive component. In order to be able
to describe sedimentary rocks, or to understand such
descriptions, it is necessary to familiarise oneself with
quite an extensive nomenclature. There are specialised
names for types of sedimentary structures, grain-size
distributions and mineralogical composition of
sediments. We also have a genetic nomenclature,
which names rock types according to the particular
way in which we think they have formed. Examples of
these are fluvial sediments (which are deposited by
rivers) and aeolian (air-borne) sediments. The descriptive nomenclature is used as a basis for an interpretation of how the rock was formed. When we are
reasonably confident about their origin we may use
the genetic nomenclature.
Sedimentology covers studies of both recent (modern) sediments and older sedimentary rocks. By studying how sediments form today we can understand the
conditions under which various sedimentological processes take place. From such observations we may be
able to recognise older sediments which have been
formed in the same way. This is called using the
principle of uniformitarianism, which has been of
great importance in all geological disciplines since
its proposal by James Hutton (1726–1797).
Conditions on the surface of the Earth have
fluctuated widely throughout geological history and
the principle of uniformitarianism cannot be applied
without reservation. One important aspect of sedimentological research is attempting to reconstruct changes
in environments on the Earth’s surface throughout
geological time. This applies particularly to climate,
vegetation and the composition of the atmosphere and
the oceans.
Palaeontology is important to sedimentology, not
only for dating beds, but also because organisms are an
important component of many sedimentary rocks (particularly limestones), and organic processes contribute
to weathering processes and the precipitation of
dissolved ions in seawater. Many organisms make
very specific demands of their environment, and
K. Bjørlykke (*)
Department of Geosciences, University of Oslo, Oslo, Norway
e-mail: knut.bjorlykke@geo.uio.no
K. Bjørlykke (ed.), Petroleum Geoscience: From Sedimentary Environments to Rock Physics,
DOI 10.1007/978-3-642-34132-8_2, # Springer-Verlag Berlin Heidelberg 2015
31