http:// edstruct/hires/wedgebedding.jpg sedimentary structures sedimentary structures: features of...

•http://www.depauw.edu/acad/geosciences/tcope/SedStruct/HiRes/WedgeBedding.jpg

Sedimentary Sedimentary StructuresStructures

Sedimentary structures:Sedimentary structures:•Features of sed rocks recording Features of sed rocks recording processes occurring during deposition or processes occurring during deposition or between deposition and lithification. between deposition and lithification. •Important for interpreting depositional Important for interpreting depositional processes, and reconstructing processes, and reconstructing depositional environments and geological depositional environments and geological historyhistory


Importance of Importance of Sedimentary StructuresSedimentary Structures

• Geopetal Geopetal structures:structures: indicators of top-indicators of top-bottombottom

• Directional Directional structures:structures: indicators of current indicators of current direction & direction & transport agenttransport agent


Types of Sed StructuresTypes of Sed Structures

• Primary sedimentary Primary sedimentary structures:structures: occur in clastic occur in clastic sediments & generated by same sediments & generated by same processes (currents, etc.) that processes (currents, etc.) that caused deposition. caused deposition.

• Secondary sedimentary Secondary sedimentary structures:structures: caused by post- caused by post-depositional processes, including depositional processes, including biogenic, chemical, and mechanical biogenic, chemical, and mechanical disruption of sediment. disruption of sediment.


Depositional Sed Depositional Sed StructuresStructures

• Most fundamental sed structures Most fundamental sed structures are beds and laminaeare beds and laminae

• Usually formed by Usually formed by – Suspension sedimentationSuspension sedimentation– Accumulation of bed loadAccumulation of bed load

• Beds identified through changes Beds identified through changes in in – grain size, grain size, – compositioncomposition

• Bedding planes result from period Bedding planes result from period on non-deposition or from erosionon non-deposition or from erosion

• Beds form within hrs/daysBeds form within hrs/days• Laminations form almost Laminations form almost

instantaneously or over yearsinstantaneously or over years

Schulumberger


bb

Sedimentary beds near Del Rio, TX Sedimentary beds near Del Rio, TX


Laminations, Moenkopi Fm, Laminations, Moenkopi Fm, Lake Mead Lake Mead newterra.chemeketa.edu/.../sedrocktype.htm


Laminations, Monterey Laminations, Monterey FormationFormation

• Kurt A. Grimm (1), Kurt A. Grimm (1), Daniel L. OrangeDaniel L. OrangeJournal of Journal of Sedimentary Sedimentary ResearchResearchVolume 67 (1997)Volume 67 (1997)


Laminations composed of Laminations composed of lighter sand and darker lighter sand and darker

heavier minerals, Chinnai, heavier minerals, Chinnai, India, India, New World EncylopediaNew World Encylopedia


Wedge bedding.Wedge bedding. Successive stack of erosive-based channels Successive stack of erosive-based channels creates wedge-shape beddingcreates wedge-shape bedding cross-sections. cross-sections. higuai Formation, higuai Formation, Inner Mongolia, China.Inner Mongolia, China.


Graded bedding. Graded bedding results from a rapid decrease in flow velocity that causes sediment to drop out of suspension. Larger particles settle fastest, therefore they accumulate at the bottom of the bed. Houcheng Formation, Jurassic, Hebei Province, China

http://www.indiana.edu/~geol105/images/gaia_chapter_5/sedimentary_structures.htm


Tabular cross-bedding.Tabular cross-bedding. These steep foresets are typical of eolian deposition. These steep foresets are typical of eolian deposition. Late Jurassic, Liaoning Province, China.Late Jurassic, Liaoning Province, China.


Ripple MorphologyRipple Morphology


Bed Response to Steady-state, Bed Response to Steady-state, Unidirectional, Water FlowUnidirectional, Water Flow

• FLOW REGIME CONCEPTFLOW REGIME CONCEPT– Consider variation in:Consider variation in: Flow Velocity Flow Velocity

onlyonly• Flume Experiments (med sand & 20 cm Flume Experiments (med sand & 20 cm

flow depth)flow depth)

– A particular flow velocity (after critical A particular flow velocity (after critical velocity of entrainment) produces velocity of entrainment) produces

– a particular bed configuration (Bed a particular bed configuration (Bed form) which in turnform) which in turn

– produces a particular internal produces a particular internal sedimentary structure.sedimentary structure.

www.geology.wmich.edu/barnes/geos435/4b_G435.pps

Cross bed formationUSGSHeller—U. Wyoming


Bed Response to Steady-state, Bed Response to Steady-state, Unidirectional, Water FlowUnidirectional, Water Flow

• Consider Variation in Grain Size & Increasing Flow VelocityConsider Variation in Grain Size & Increasing Flow Velocity– for sand <~0.2mm:for sand <~0.2mm: No Large Ripples/DunesNo Large Ripples/Dunes– for sand ~0.2 to 0.8mmfor sand ~0.2 to 0.8mm Idealized Flow Regime Sequence Idealized Flow Regime Sequence

of Bed formsof Bed forms– for sand > 0.8:for sand > 0.8: No ripples, Have Lower Plane Bed bedNo ripples, Have Lower Plane Bed bed

www.geology.wmich.edu/barnes/geos435/4b_G435.pps


Toroweap Formation. The cross beds are sedimentary structures that represent the slip faces of ancient sand dunes. Thus, this specific layer in the Toroweap likely represents a sand dune. The Toroweap underlies the Kaibab Formation and is also late Early Permian in age (roughly 275 to 270 Ma).


Wave Ripples.Wave Ripples. Cross-sectional view of ripple cross-laminated sandstone, showing bi-directional Cross-sectional view of ripple cross-laminated sandstone, showing bi-directional cross laminae indicative of a wave origin. cross laminae indicative of a wave origin. Entrada Formation, Jurassic, San Rafael Swell, UtahEntrada Formation, Jurassic, San Rafael Swell, Utah


Ripple Marks.Ripple Marks. A pile of eroded, rippled beds that all contain gorgeous ripple marks. If you click on nothing else, click A pile of eroded, rippled beds that all contain gorgeous ripple marks. If you click on nothing else, click to enlarge this one! to enlarge this one! Carmel Formation, Utah.Carmel Formation, Utah.


• Ripple Marks. Ripple Marks. Casts of wave ripples on the base of Casts of wave ripples on the base of a sandstone bed. a sandstone bed. Cretaceous, Hebei Province, ChinaCretaceous, Hebei Province, China


• Linguloid Ripples.Linguloid Ripples. These mud-draped ripples are These mud-draped ripples are linguloid in form, indicating shallow, rapid flow within linguloid in form, indicating shallow, rapid flow within the ripple stability field.the ripple stability field. Permian, Inner Mongolia, China Permian, Inner Mongolia, China


• Herrigbone cross-stratification. Herrigbone cross-stratification. Bi-directional cross beds such as these Bi-directional cross beds such as these are indicative of a tidal origin. are indicative of a tidal origin. Curtis Formation, Jurassic, UtahCurtis Formation, Jurassic, Utah


Climbing current ripples. Climbing current ripples. Ripple foresets that "climb" on the backs of their predecessors are Ripple foresets that "climb" on the backs of their predecessors are indicative of waning flow conditions and rapid sediment fallout, such that sediment drops out of indicative of waning flow conditions and rapid sediment fallout, such that sediment drops out of suspension as fast as it can be molded into a bedform. suspension as fast as it can be molded into a bedform. Entrada Formation, Jurassic, Utah.Entrada Formation, Jurassic, Utah.


Soft Sediment Soft Sediment DeformationDeformation


Climbing current ripples and convolute lamination. Climbing current ripples and convolute lamination. The result The result of rapid sediment fallout is often instability due to liquefaction, of rapid sediment fallout is often instability due to liquefaction, leading to disruption of laminae by water escape. Such disruption is leading to disruption of laminae by water escape. Such disruption is termed convolute lamination. termed convolute lamination. Modern Colorado River, Utah.Modern Colorado River, Utah.


• beds, flame structures. beds, flame structures. Rapid sediment fallout from suspension often loads underlying fine-Rapid sediment fallout from suspension often loads underlying fine-grained sediment to the point of failure, causing foundering of the overlying sediment and grained sediment to the point of failure, causing foundering of the overlying sediment and formation of structures termed flames (for obvious reasons!). formation of structures termed flames (for obvious reasons!). Permian, Inyo County, California.Permian, Inyo County, California.

http://zsylvester.blogspot.com/2007/09/flame-structures.html


Sole/Bedding Plane Sole/Bedding Plane MarkingsMarkings


Flute casts. Flute casts. Flutes are caused by erosional eddies at the base of a turbulent Flutes are caused by erosional eddies at the base of a turbulent flow. The deepest scour is on the upstream end of the flute, and the scours widen flow. The deepest scour is on the upstream end of the flute, and the scours widen and become shallower downflow. and become shallower downflow. Shiguai Formation, Inner Mongolia, China.Shiguai Formation, Inner Mongolia, China.


Flute casts in Austin Glen turbidites, near Flute casts in Austin Glen turbidites, near Hannacroix, NYHannacroix, NY


Groove Casts, base of a turbidite

sandstone, Laga Basin, Italy

http://en.wikipedia.org/wiki/Sole_markings


MudcracksMudcracksDessication cracks. Dessication cracks. Mudcracks can become very large, which may Mudcracks can become very large, which may

make them difficult to recognize in small outcrops. Person for make them difficult to recognize in small outcrops. Person for scale. scale. Jixian Formation, Proterozoic, China.Jixian Formation, Proterozoic, China.


Erosioanl Structure --Erosioanl Structure --ScoursScours

Pigeon Point Formation: An Upper Cretaceous Shoreline Succession, Central California CoastJohn H. Tyler Journal of Sedimentary ResearchVolume 42 (1972)


Biogenic Biogenic StructuresStructures

Crossbedded and rippled sandstone with burrows at Point Lobos, California. Copyright © Bruce Molnia, Terra Photographics

Feeding trails and burrows as trace fossils in rock.Copyright © Bruce Molnia, Terra Photographics

http://www.earthscienceworld.org/images/index.html


Tubidite SequenceTubidite Sequence

faculty.gg.uwyo.edu/


Coarser Turbidite units Coarser Turbidite units dissappear with greater dissappear with greater

distance downflow distance downflow

http://faculty.gg.uwyo.edu/heller/Sed%20Strat%20Class/SedStrat%208/Lecture%208.html


• http://faculty.gg.uwyo.edu/heller/Sed%20Strat%20Class/SedStrat%208/McBride.html


TurbiditeTurbiditess

Bouma sequence in Santa Paula. A Bouma Sequence is a succession consisting of five intervals, each characterized by a particluar sedimentary structure, which forms a turbidite. Copyright © Dr. Roger Slatt, University of Oklahoma

http://www.earthscienceworld.org/images/index.html


More Turbidites. Identify Sequence More Turbidites. Identify Sequence and Flow Regimeand Flow Regime

http://sepmstrata.org/MARINESEDIMENTS/ClasticSlope/bouma.htmhttp://sepmstrata.org/MARINESEDIMENTS/ClasticSlope/bouma.htm

bouma-© 1998 by Hugo Ortner.jpg BOUMA-SEQUENCE (SCHLUMBERGER)


Video SourcesVideo Sources• Sediment entrainment• • http://video.google.com/videoplay?docid=7337603086088337038&q=sediment+tr

ansport&total=6&start=0&num=10&so=0&type=search&plindex=3• • • Turbulent flow

http://video.google.com/videoplay?docid=1827702182265329855&q=turbulent+flow&total=20&start=0&num=10&so=0&type=search&plindex=3

• • Turbulent flow 2

http://video.google.com/videoplay?docid=-1208859987391360223&q=turbulent+flow&total=20&start=0&num=10&so=0&type=search&plindex=0

• • Debris Flow• • http://video.google.com/videoplay?docid=6882150896935629121&q=debris+flow

&total=58&start=0&num=10&so=0&type=search&plindex=1• • Debris flow• • http://video.google.com/videoplay?docid=-6671777048715938531&q=debris+flow

&total=58&start=0&num=10&so=0&type=search&plindex=2• • http://video.google.com/videoplay?docid=-981077879322061890&q=debris+flow&

total=58&start=0&num=10&so=0&type=search&plindex=5•


• Turbidity Currents • http://images.google.com/imgres?imgurl=http://serc.carleton.edu/images/

NAGTWorkshops/visualize04/turbidite_movie.gif&imgrefurl=http://serc.carleton.edu/NAGTWorkshops/visualization/collections/turbid.html&h=264&w=329&sz=21&hl=en&start=2&tbnid=5AgwUroYAb9s_M:&tbnh=95&tbnw=119&prev=/images%3Fq%3Dturbidity%2Bcurrent%26svnum%3D10%26hl%3Den

• • Photos• Tubidites• © 1998 by Hugo Ortner• http://faculty.gg.uwyo.edu/heller/Sed%20Strat%20Class/SedStrat%208/Lecture%208.html• Inverse grading • http://www-odp.tamu.edu/publications/180_IR/chap_09/9_f20.htm• • Crossbeds• http://www.youtube.com/watch?v=cJo0fTpJypg&NR=1 • http://www.youtube.com/watch?v=KYvWwbEi0A0 • http://www.youtube.com/watch?v=rSzGOCo4JEk• http://faculty.gg.uwyo.edu/heller/sed_video_downloads.htm#ClimbRips%20anchor• • http://walrus.wr.usgs.gov/seds/bedforms/2d/2d.html•

http:// edstruct/hires/wedgebedding.jpg sedimentary structures sedimentary structures: features of...

Documents