View source for Spreite

[[Image:Tuscarora Formation Diplocraterion.jpg|thumb|right|Example of spreite in a ''[[Diplocraterion]]'' burrow (at left) from the [[Silurian]] [[Tuscarora Formation]] in Pennsylvania.]]
[[Image:Spreite.jpg|thumb|right|Diagram showing the differences between meniscate and spreiten burrows. Modified from Chamberlain (1978).<ref name="chamberlain1978" />]]
'''Spreite''' ({{IPA|de|ˈʃpʁaɪ̯tə|lang|De-spreite.ogg}}), meaning [[Lamina (leaf)|leaf-blade]] in German (or '''spreiten''' ({{IPA|de|ˈʃpʁaɪ̯tn̩|pron|De-spreiten.ogg}}), the plural form in [[German language|German]]) is a stacked, curved, layered structure that is characteristic of certain [[trace fossils]]. They are formed by invertebrate organisms tunneling back and forth through sediment in search of food. The organism moves perpendicularly just enough at the start of each back-and-forth pass so that it avoids reworking a previously tunneled area, thereby ensuring that it only makes feeding passes through fresh, unworked sediment.<ref name="bromley1996" /><ref name="buatois2011b" />
Two types of spreiten are generally recognized. Protrusive spreiten result from movement of the organism away from its [[burrow]] entrance (i.e., a downward movement in vertical burrows), whereas retrusive spreiten result from movement towards the burrow entrance (i.e., an upward movement in vertical burrows).<ref name="buatois2011b" /> Vertical burrows with retrusive spreiten are also referred to as "escape burrows", as they represent attempts by the organism during periods of high sedimentation to prevent the burrow entrance from being buried, and at the same time keep the bottom of the burrow at the same distance from the sediment-water interface.<ref name="frey1984" /><ref name="buatois2011a" /> In essence, the organism "escapes" from being buried too deeply by progressively tunneling upward, thereby leaving behind it a stacked vertical succession of concave-side-up spreite. ''[[Diplocraterion]]'' is the classic example of a vertical burrow with spreite,<ref name="richter1926" /><ref name="fursich1974a" /> whereas ''[[Rhizocorallium]]'' is an example of a horizontal burrow with spreite.<ref name="fursich1974b" />
Spreiten differ from menisci, which are flat to slightly curved, back-filling structures found in some tubular burrows. Menisci are formed when the organism packs sediment, and sometimes fecal material as well, behind itself as it moves through the burrow.<ref name="chamberlain1978" /> Because spreiten and menisci represent different behaviors, the distinction between spreiten and meniscate burrows is an important criterion for the identification of certain [[ichnotaxon|ichnotaxa]].<ref name="howard&frey1984" /> For example, generally parallel-sided, elongate, horizontal burrows with menisci are typically assigned to the ''[[Muensteria]]'' [[ichnospecies]], whereas similar burrows with spreite will generally be assigned to the ''[[Rhizocorallium]]'' ichnogenus.<ref name="fursich1974b" /><ref name="howard&frey1984" />
==See also==
* [[Trace fossil]]
* [[Ichnology]]
==References==
{{reflist | refs=
.<ref name="bromley1996">{{cite book |author=Bromley, R.G. |year=1996 |title=Trace Fossils: biology, taphonomy and applications |publisher=Chapman & Hall |location=London |pages=11–12|edition=2nd }}</ref>
<ref name="buatois2011a">{{cite book |author1=Buatois, L.A.  |author2=Mángano, M.G.  |name-list-style=amp |year=2011 |title=Ichnology: Organism-Substrate Interactions in Space and Time |publisher=Cambridge University Press |location=New York |pages=22–23 |isbn=9781139500647 |url=https://books.google.com/books?id=kztUtwymPIMC&pg=PA22}}</ref>
<ref name="buatois2011b">{{cite book |author1=Buatois, L.A.  |author2=Mángano, M.G.  |name-list-style=amp |year=2011 |title=Ichnology: Organism-Substrate Interactions in Space and Time |publisher=Cambridge University Press |location=New York |pages=31–33 |isbn=9781139500647 |url=https://books.google.com/books?id=kztUtwymPIMC&pg=PA31}}</ref>
<ref name="chamberlain1978">{{cite book |author=Chamberlain, C.K. |year=1978 |chapter=Recognition of trace fossils in cores  |editor=Basan, P.N. |title=Trace Fossil Concepts - SEPM Short Course No. 5 |publisher=Society of Economic Paleontologists and Mineralogists |location=Oklahoma City |pages=133–162}}</ref>
<ref name="frey1984">{{cite book |author1=Frey, R.W.  |author2=Pemberton, S.G  |name-list-style=amp |year=1984 |chapter=Trace fossil facies models |editor=Walker, R. |title=Facies Models |publisher=Geological Association of Canada |location=Toronto, Ontario |pages=189–207}}</ref>
<ref name="howard&frey1984">{{cite journal |author1=Howard. J.D.  |author2=Frey, R.W.  |name-list-style=amp |year=1984 |title=Characteristic trace fossils in nearshore to offshore sequences, Upper Cretaceous of east-central Utah |journal=Canadian Journal of Earth Sciences |volume=21 |issue=2 |pages=200–219 |doi=10.1139/e84-022}}</ref>
<ref name="fursich1974a">{{cite journal |author= Fursich, F.T. |journal= Journal of Paleontology |volume= 48 |issue= 5 |title=On ''Diplocraterion'' Torell 1870 and the significance of morphological features in vertical, spreiten-bearing, U-shaped trace fossils  |pages = 952–962 |year = 1974 |jstor=1303293}}</ref>
<ref name="fursich1974b">{{cite journal |author=Fursich, F.T. |year=1974 |title=Ichnogenus Rhizocorallium |journal=Paläontologische Zeitschrift |volume=48 |issue=1–2 |pages=16–28 |doi=10.1007/bf02986987}}</ref>
<ref name="richter1926">{{cite journal |author=Richter, Rudolf |year=1926 |title=Flachseebeobachtungen zur Paläontologie und Geologie. XII-XIV |journal=Senckenbergiana |volume=8 |pages=200–224 }}</ref>
}}
{{Commons category|Trace fossils}}
[[Category:Burrow fossils]]
[[Category:Invertebrate paleozoology]]