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geology Geology () is a branch of natural science concerned with Earth and other Astronomical object, astronomical objects, the features or rock (geology), rocks of which it is composed, and the processes by which they change over time. Modern geology ...
, tectonostratigraphy is
stratigraphy 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: lithost ...
that refers either to rock sequences in which large-scale layering is caused by the stacking of thrust sheets, or nappes, in areas of thrust tectonics or to the effects of tectonics on lithostratigraphy.


Tectonically formed stratigraphy

One example of such a tectonostratigraphy is the Scandinavian Caledonides. Within the entire exposed 1800 km length of this
orogenic belt An orogenic belt, or orogen, is a zone of Earth's crust affected by orogeny. An orogenic belt develops when a continental plate crumples and is uplifted to form one or more mountain ranges; this involves a series of geological processes collec ...
the following sequence is recognised from the base upwards: * Autochthon : undisturbed foreland of the
Baltic plate The Baltic Plate was an ancient tectonic plate that existed from the Cambrian Period to the Carboniferous Period. The Baltic Plate collided against Siberia, to form the Ural Mountains about 280 million years ago. The Baltic Plate, however, fused on ...
* Parautochthon : thrust sheets that have moved only a short distance (up to 10s of km) from their original position * Lower
allochthon upright=1.6, Schematic overview of a thrust system. The hanging wall block is (when it has reasonable proportions) called a nappe. If an erosional hole is created in the nappe that is called a window (geology)">window. A klippe is a solitary ou ...
: far travelled thrust sheets derived from the Baltic plate passive margin, mainly sediments associated with the break-up of
Rodinia Rodinia (from the Russian родина, ''rodina'', meaning "motherland, birthplace") was a Mesoproterozoic and Neoproterozoic supercontinent that assembled 1.26–0.90 billion years ago and broke up 750–633 million years ago. were prob ...
* Middle allochthon : also derived from the margin of the Baltic plate,
Proterozoic The Proterozoic () is a geological eon spanning the time interval from 2500 to 538.8million years ago. It is the most recent part of the Precambrian "supereon". It is also the longest eon of the Earth's geologic time scale, and it is subdivided i ...
basement and its psammitic cover * Upper allochthon : thrust sheets including
island arc Island arcs are long chains of active volcanoes with intense seismic activity found along convergent tectonic plate boundaries. Most island arcs originate on oceanic crust and have resulted from the descent of the lithosphere into the mantle alon ...
and
ophiolitic An ophiolite is a section of Earth's oceanic crust and the underlying upper mantle that has been uplifted and exposed above sea level and often emplaced onto continental crustal rocks. The Greek word ὄφις, ''ophis'' (''snake'') is found i ...
sequences * Uppermost allochthon : thrust sheets containing sediments with fossil assemblages indicating an origin on the margin of the Laurentian plate This vertically stacked sequence thus represents the passive margins of Baltica and Laurentia and intervening island arcs and
back-arc basin A back-arc basin is a type of geologic basin, found at some convergent plate boundaries. Presently all back-arc basins are submarine features associated with island arcs and subduction zones, with many found in the western Pacific Ocean. Most o ...
s telescoped together and emplaced on top of the
Baltic Shield The Baltic Shield (or Fennoscandian Shield) is a segment of the Earth's crust belonging to the East European Craton, representing a large part of Fennoscandia, northwestern Russia and the northern Baltic Sea. It is composed mostly of Archean an ...
, involving hundreds of km of shortening. Within this overall stratigraphy the individual layers have their own tectonostratigraphy of stacked thrust sheets.


Effects of active tectonics on lithostratigraphy

Tectonic events are typically recorded in sediments being deposited at the same time. In the case of a rift, for instance, the sedimentary sequence is normally broken down into three parts:Jackson, C A L ,Gawthorpe, R L, Leppard, C W , Sharp, I R 2006. Rift-initiation development of normal fault blocks: insights from the Hammam Faraun fault block, Suez Rift, Egypt. Journal of the Geological Society, 163, 165–18

/ref> * The ''pre-rift'' includes a sequence deposited before the onset of rifting, recognised by the lack of thickness and sedimentary Facies (geology), facies changes across the rift faults. * The ''syn-rift'' includes a sequence deposited during active rifting, typically showing facies and thickness changes across the active faults, unconformities on the fault footwalls may pass laterally into continuous conformable sequences in the hanging walls. * The ''post-rift'' includes a sequence deposited after the rifting has finished, it may still show thickness and facies changes around the rift faults due to the effects of differential compaction and remnant rift topography, particularly in the earliest part of the sequence. This relatively straightforward nomenclature may become difficult to use, however, in the case of multiphase rifting with the post-rift from one event being the pre-rift to a later event.


See also

*
Biostratigraphy Biostratigraphy is the branch of stratigraphy which focuses on correlating and assigning relative ages of rock strata by using the fossil assemblages contained within them.Hine, Robert. “Biostratigraphy.” ''Oxford Reference: Dictionary of ...
*
Chronostratigraphy Chronostratigraphy is the branch of stratigraphy that studies the ages of rock strata in relation to time. The ultimate aim of chronostratigraphy is to arrange the sequence of deposition and the time of deposition of all rocks within a geologic ...
*
Terrane In geology, a terrane (; in full, a tectonostratigraphic terrane) is a crust fragment formed on a tectonic plate (or broken off from it) and accreted or " sutured" to crust lying on another plate. The crustal block or fragment preserves its ow ...


References

{{reflist Stratigraphy Tectonics