A rhythmite consists of layers of sediment or sedimentary rock which are laid down with an obvious periodicity and regularity. They may be created by annual processes such as seasonally varying deposits reflecting variations in the runoff cycle, by shorter term processes such as tides, or by longer term processes such as periodic floods.
Rhythmites serve a significant role in unraveling prehistoric events, providing insights into sea level change, glaciation change, and Earth's orbital variations which serve to answer questions about climate change.
Annually-laminated deposits (varves) are rhythmites with annual periodicity: annual layers of sediment or sedimentary rock are laid down through seasonal variations that result from precipitation, or from temperature, which influences precipitation rates and debris loads in runoff. Of the many rhythmites found in the geological record, varves are among the most important and illuminating to studies of past climate change. Varves are amongst the finest resolution events easily recognised in stratigraphy.[1]
Rhythmites may be deposited with periodicities other than annual. The geologic record captures both more frequent events (e.g., tides) and less frequent events (glacial floods).
Tidal rhythmitesedit
Geologic tidal rhythmites display layered Carboniferous Period beds which record tidal cyclical events such as semi-diurnal, diurnal or neap tide, spring tide cycle that demonstrate marine influence in sediments that were previously interpreted as purely continental.[2][3] The geologic record captures layered beds comparable to those found currently in sediments in the Bay of Fundy in Canada and the Bay of Mont Saint-Michel in France.[4] The Storm Mountain area of Big Cottonwood Canyon, Utah, has rhythmites which record sea-level sedimentary deposit fluctuations consistent with the cycle of the tides. Tidal rhythmites are also known from other geological periods and times, such as the late Precambrian.[5]
Proglacial rhythmitesedit
One common mechanism is the episodic flooding which results from glacial dam bursts. In one such example geologists estimate that the Missoula Floods cycle of flooding and reformation of the lake took an average of 55 years and that the floods occurred approximately 40 times over the 2,000-year period between 15,000 and 13,000 years ago. Distinct rhythmites with an approximately 55-year periodicity have been observed.[6][7]
Glacial epicycle rhythmitesedit
Sea-level changes which correspond to the glacial periods also show up as extremely long-term rhythmites. As an example, the ice surge in the Quaternary resulted in changes in sea level of 127 meters to 163 meters. The regression and transgression of the sea level from waxing and waning glaciers have been identified in the rhythmites of the Pennsylvanian and Permian periods.[8]
See alsoedit
The Wikibook Historical Geology has a page on the topic of: Tidal rhythmites and dating
^Hambrey, M. J.; Harland, Walter Brian (1997). Earth's pre-Pleistocene glacial record. Cambridge earth science series. ISBN978-0-521-22860-2. Retrieved 7 September 2009.
^Kuecher, Gerald J.; Woodland, Bertram G.; Broadhurst, Frederick M. (1 September 1990). "Evidence of deposition from individual tides and of tidal cycles from the Francis Creek Shale (host rock to the Mazon Creek Biota), Westphalian D (Pennsylvanian), northeastern Illinois". Sedimentary Geology. 68 (3): 211–221. doi:10.1016/0037-0738(90)90113-8. ISSN 0037-0738.
^Archer, Allen W; Kuecher, Gerald J; Kvale, Erik P (1995). "The Role of Tidal-Velocity Asymmetries in the Deposition of Silty Tidal Rhythmites (Carboniferous, Eastern Interior Coal Basin, U.S.A.)". SEPM Journal of Sedimentary Research. 65: 408–416. doi:10.1306/d42680d6-2b26-11d7-8648000102c1865d.
^B.W. Flemming and A. Bartholoma (1995). Tidal signatures in modern and ancient sediments. Blackwell Science, Oxford. ISBN9780865429789.
^Williams, G. E. (January 1989). "Late Precambrian tidal rhythmites in South Australia and the history of the Earth's rotation". Journal of the Geological Society. 146 (1): 97–111. doi:10.1144/gsjgs.146.1.0097.
^Bjornstad, Bruce (2006). On the Trail of the Ice Age Floods: A Geological Guide to the Mid-Columbia Basin. Keokee Books; San Point, Idaho. ISBN978-1-879628-27-4.
^Washburn, Albert Lincoln (1997). Plugs and Plug Circles: A Basic Form of Patterned Ground, Cornwallis Island, Arctic Canada - Origin and Implications. Geological Society of America, Incorporated. ISBN978-0-8137-1190-4. Retrieved 7 September 2009.
April 12, 2024
rhythmite, rhythmite, consists, layers, sediment, sedimentary, rock, which, laid, down, with, obvious, periodicity, regularity, they, created, annual, processes, such, seasonally, varying, deposits, reflecting, variations, runoff, cycle, shorter, term, process. A rhythmite consists of layers of sediment or sedimentary rock which are laid down with an obvious periodicity and regularity They may be created by annual processes such as seasonally varying deposits reflecting variations in the runoff cycle by shorter term processes such as tides or by longer term processes such as periodic floods Pleistocene age varves at Scarborough Bluffs Toronto Ontario Canada The thickest varves are close to 2 cm thick Rhythmites serve a significant role in unraveling prehistoric events providing insights into sea level change glaciation change and Earth s orbital variations which serve to answer questions about climate change Contents 1 Annually laminated rhythmites 2 Periodically laminated rhythmites 2 1 Tidal rhythmites 2 2 Proglacial rhythmites 2 3 Glacial epicycle rhythmites 3 See also 4 ReferencesAnnually laminated rhythmites editAnnually laminated deposits varves are rhythmites with annual periodicity annual layers of sediment or sedimentary rock are laid down through seasonal variations that result from precipitation or from temperature which influences precipitation rates and debris loads in runoff Of the many rhythmites found in the geological record varves are among the most important and illuminating to studies of past climate change Varves are amongst the finest resolution events easily recognised in stratigraphy 1 Periodically laminated rhythmites edit nbsp Distinct layers of Touchet beds in the Little Grand Canyon near Lowden Washington in the Walla Walla valleyRhythmites may be deposited with periodicities other than annual The geologic record captures both more frequent events e g tides and less frequent events glacial floods Tidal rhythmites edit Geologic tidal rhythmites display layered Carboniferous Period beds which record tidal cyclical events such as semi diurnal diurnal or neap tide spring tide cycle that demonstrate marine influence in sediments that were previously interpreted as purely continental 2 3 The geologic record captures layered beds comparable to those found currently in sediments in the Bay of Fundy in Canada and the Bay of Mont Saint Michel in France 4 The Storm Mountain area of Big Cottonwood Canyon Utah has rhythmites which record sea level sedimentary deposit fluctuations consistent with the cycle of the tides Tidal rhythmites are also known from other geological periods and times such as the late Precambrian 5 Proglacial rhythmites edit One common mechanism is the episodic flooding which results from glacial dam bursts In one such example geologists estimate that the Missoula Floods cycle of flooding and reformation of the lake took an average of 55 years and that the floods occurred approximately 40 times over the 2 000 year period between 15 000 and 13 000 years ago Distinct rhythmites with an approximately 55 year periodicity have been observed 6 7 Glacial epicycle rhythmites edit Sea level changes which correspond to the glacial periods also show up as extremely long term rhythmites As an example the ice surge in the Quaternary resulted in changes in sea level of 127 meters to 163 meters The regression and transgression of the sea level from waxing and waning glaciers have been identified in the rhythmites of the Pennsylvanian and Permian periods 8 See also edit nbsp The Wikibook Historical Geology has a page on the topic of Tidal rhythmites and dating Dendrochronology Dendroclimatology Touchet FormationReferences edit Hambrey M J Harland Walter Brian 1997 Earth s pre Pleistocene glacial record Cambridge earth science series ISBN 978 0 521 22860 2 Retrieved 7 September 2009 Kuecher Gerald J Woodland Bertram G Broadhurst Frederick M 1 September 1990 Evidence of deposition from individual tides and of tidal cycles from the Francis Creek Shale host rock to the Mazon Creek Biota Westphalian D Pennsylvanian northeastern Illinois Sedimentary Geology 68 3 211 221 doi 10 1016 0037 0738 90 90113 8 ISSN 0037 0738 Archer Allen W Kuecher Gerald J Kvale Erik P 1995 The Role of Tidal Velocity Asymmetries in the Deposition of Silty Tidal Rhythmites Carboniferous Eastern Interior Coal Basin U S A SEPM Journal of Sedimentary Research 65 408 416 doi 10 1306 d42680d6 2b26 11d7 8648000102c1865d B W Flemming and A Bartholoma 1995 Tidal signatures in modern and ancient sediments Blackwell Science Oxford ISBN 9780865429789 Williams G E January 1989 Late Precambrian tidal rhythmites in South Australia and the history of the Earth s rotation Journal of the Geological Society 146 1 97 111 doi 10 1144 gsjgs 146 1 0097 Walla Walla Level 1 Watershed Assessment PDF WRIA 32 Watershed Plan Walla Walla Watershed Management Partnership Retrieved 1 September 2009 Bjornstad Bruce 2006 On the Trail of the Ice Age Floods A Geological Guide to the Mid Columbia Basin Keokee Books San Point Idaho ISBN 978 1 879628 27 4 Washburn Albert Lincoln 1997 Plugs and Plug Circles A Basic Form of Patterned Ground Cornwallis Island Arctic Canada Origin and Implications Geological Society of America Incorporated ISBN 978 0 8137 1190 4 Retrieved 7 September 2009 Retrieved from https en wikipedia org w index php title Rhythmite amp oldid 1208881254 Tidal rhythmites, wikipedia, wiki, book, books, library,
