A parasequence is a fundamental concept of sequence stratigraphy. Parasequences are not directly related to sequences.
A parasequence is defined as a genetically related succession of bedsets that is bounded by marine flooding surfaces (or their correlative surfaces) on top and at the bottom. [1] The succession is supposed to be relatively conformable in the sense that breaks in deposition within the parasequence are much shorter than the time of deposition of the parasequence itself. [2] [1] Most parasequences show a shallowing upward, [3] which is sometimes also included into the definition. [4]
Since parasequences are relatively conformable, so Walther's law applies within a parasequence. This is not necessarily the case for transitions from one parasequence to another. They are also typically of the size of one up to tens of meters. [3]
Stratigraphy is a branch of geology concerned with the study of rock layers (strata) and layering (stratification). It is primarily used in the study of sedimentary and layered volcanic rocks. Stratigraphy has three related subfields: lithostratigraphy, biostratigraphy, and chronostratigraphy.
Stratigraphy is a key concept to modern archaeological theory and practice. Modern excavation techniques are based on stratigraphic principles. The concept derives from the geological use of the idea that sedimentation takes place according to uniform principles. When archaeological finds are below the surface of the ground, the identification of the context of each find is vital in enabling the archaeologist to draw conclusions about the site and about the nature and date of its occupation. It is the archaeologist's role to attempt to discover what contexts exist and how they came to be created. Archaeological stratification or sequence is the dynamic superimposition of single units of stratigraphy, or contexts.
In geology, a facies is a body of rock with distinctive characteristics. The characteristics can be any observable attribute of rocks and the changes that may occur in those attributes over a geographic area. A facies encompasses all the characteristics of a rock including its chemical, physical, and biological features that distinguish it from adjacent rock.
The eustatic sea level is the distance from the center of the Earth to the sea surface. An increase of the eustatic sea level can be generated by decreasing glaciation, increasing spreading rates of the mid-ocean ridges or increasing the number of mid-oceanic ridges. Conversely, increasing glaciation, decreasing spreading rates or fewer mid-ocean ridges can lead to a fall in the eustatic sea level.
Sequence stratigraphy is a branch of geology, specifically a branch of stratigraphy, that attempts to discern and understand historic geology through time by subdividing and linking sedimentary deposits into unconformity bounded units on a variety of scales. The essence of the method is mapping of strata based on identification of surfaces which are assumed to represent time lines, thereby placing stratigraphy in chronostratigraphic framework allowing understanding of the evolution of the Earth's surface in a particular region through time. Sequence stratigraphy is a useful alternative to a purely lithostratigraphic approach, which emphasizes solely based on the compositional similarity of the lithology of rock units rather than time significance. Unconformities are particularly important in understanding geologic history because they represent erosional surfaces where there is a clear gap in the record. Conversely within a sequence the geologic record should be relatively continuous and complete record that is genetically related.
Lithostratigraphy is a sub-discipline of stratigraphy, the geological science associated with the study of strata or rock layers. Major focuses include geochronology, comparative geology, and petrology.
In geology, a sequence is a stratigraphic unit which is bounded by an unconformity at the top and at the bottom.
In geology, a bed is a layer of sediment, sedimentary rock, or volcanic rock "bounded above and below by more or less well-defined bedding surfaces". Specifically in sedimentology, a bed can be defined in one of two major ways. First, Campbell and Reineck and Singh use the term bed to refer to a thickness-independent layer comprising a coherent layer of sedimentary rock, sediment, or pyroclastic material bounded above and below by surfaces known as bedding planes. By this definition of bed, laminae are small beds that constitute the smallest (visible) layers of a hierarchical succession and often, but not always, internally comprise a bed.
Cyclic sediments are sequences of sedimentary rocks that are characterised by repetitive patterns of different rock types (strata) or facies within the sequence. Processes that generate sedimentary cyclicity can be either autocyclic or allocyclic, and can result in piles of sedimentary cycles hundreds or even thousands of metres thick. The study of sequence stratigraphy was developed from controversies over the causes of cyclic sedimentation.
The Simla Formation is a stratigraphic unit of Late Devonian age. It is present on the western edge of the Western Canada Sedimentary Basin in the Rocky Mountains and foothills of west-central Alberta and east-central British Columbia. It consists primarily of carbonate rocks and siltstone, and was named for Mount Simla in northern Jasper National Park by D. J. McLaren and E. W. Mountjoy in 1962.
A geological contact is a boundary which separates one rock body from another. A contact can be formed during deposition, by the intrusion of magma, or through faulting or other deformation of rock beds that brings distinct rock bodies into contact.
Marine flooding surfaces are a fundamental concept in sequence stratigraphy, where they form the limiting surfaces of parasequences.
Accommodation is a fundamental concept in sequence stratigraphy, a subdiscipline of geology. It is defined as the space that is available for the deposition of sediments. Accommodation space can be pictured as the volume between the actual surface and the theoretical equilibrium surface where deposition and erosion are in balance at every point. In marine environments, this equilibrium level is sea level.
In geology, range offset is the time difference between the last fossil occurrence of a taxon and the actual disappearance of this taxon. Range offset can be used as a measure of biostratigraphic precision and determines among others how much information about extinctions can be derived from fossil occurrences.
In sequence stratigraphy, a maximum flooding surface is the surface that marks the transition from a transgression to a regression. Maximum flooding surfaces are abbreviated by mfs, synonyms for them include final transgressive surface, surface of maximum transgression and maximum transgressive surface.
In geology, a subaerial unconformity is a surface that displays signs of erosion by processes that commonly occur on the surface. These processes generating the subaerial unconformity can include wind degradation, pedogenesis, dissolution processes such as karstification as well as fluvial processes such as fluvial erosion, bypass and river rejuvenation.
Relative sea level is defined as the sea level that is observed with respect to a land-based reference frame. It is often contrasted with eustatic sea level, which is a measure of the total mass or volume of the oceans. Relative sea level can change by the processes changing eustatic sea level, but also by changes on land such as subsidence and isostatic rebound.
Steven M. Holland is an American paleontologist and geologist at the University of Georgia. His research focuses on stratigraphic paleobiology, the application of event and sequence stratigraphy to a paleobiological understanding of the fossil record. With Mark Patzkowsky, he coauthored the book Stratigraphic Paleobiology.
In sequence stratigraphy, a sub discipline of geology, type 1 sequences and type 2 sequences are special sequences that are defined by having distinct types of sequence boundaries. In modern literature, the distinction in type 1 sequences and type 2 sequences was abandoned.
Stratigraphic paleobiology is a branch of geology that is closely related to paleobiology, sequence stratigraphy and sedimentology. Stratigraphic paleobiology studies how the fossil record is altered by sedimentological processes and how this affects biostratigraphy and paleobiological interpretations of the fossil record.
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