Sedimentary structures: Shallow marine

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Tidal channel crossbeds

A look at intertidal through subtidal deposits in outcrop

This is part of the How To…series  on describing sedimentary rocks – outcrops of shallow marine deposits and their sedimentary structures.
Here are some annotated, close-up outcrop images showing details of sedimentary structures – mostly bedforms from ancient shoreface, tidal flat and channel, and shallow shelf environments. The two guides to crossbed nomenclature have been borrowed from a previous post on crossbed terminology (link below). Most of these images have been cropped from originals featured in the Atlas of shelf deposits, and Atlas of beach-lagoon-bar-estuary-tidal flat deposits. The Atlases also show examples of modern analogues to these structures.

 

Related links in this series on outcrop descriptions

Sedimentary structures: Alluvial fans

Sedimentary structures: coarse-grained fluvial

Sedimentary structures: Fine-grained fluvial

Sedimentary structures: Mass Transport Deposits

Sedimentary structures: Turbidites

Sedimentary structures: Stromatolites

Volcanics in outcrop: Lava flows

Volcanics in outcrop: Secondary volcaniclastics

Volcanics in outcrop: Pyroclastic fall deposits

 

 

Other useful links

Sediment transport: Bedload and suspension load

The hydraulics of sedimentation: Flow regime

Fluid flow: Froude and Reynolds numbers

Crossbedding – some common terminology

Describing sedimentary rocks; some basics

Analysis of sediment grain size distributions

Measuring a stratigraphic section

 

Click on an image to zoom in, then back arrow to return to this page

The first four diagrams show some basic sediment descriptors and terminology, and a typical stratigraphic column drawn from outcrop data. These are your starting points for describing and interpreting sedimentary rocks and sedimentary structures in outcrop, hand specimen, and core.

 

 

crossbed terminology

 

Ripple formation and terminology

 

 

Cross-section view of symmetric and asymmetric ripples

 

 

Reactivation surfaces, preserved lee and stoss slope, and herringbone crossbed in tidal deposit

 

 

 

Lenticular and flaser bedding in Pleistocene tidal flat deposit

 

 

Estuarine lenticular bedding and mud flasers, Eocene

 

 

Interference ripples and incipient mud cracks, Paleoproterozoic tidal flat deposit

 

 

Desiccation cracks, up-turned mudcrack polygons, and (event bed) storm rip up clasts

 

 

Back flow ripples on shallow shelf sandy bedform, Pliocene, NZ

 

 

HCS Hummocky cross stratification, Jurassic Bowser Basin

 

Tidal bundles in crossbed foresets, Paleocene shelf sandwaves

 

A few references on published sedimentary structure atlases and glossaries

J.C. Harms, 2003. Primary Sedimentary Structures. Annual Review of Earth and Planetary Sciences v. 7(1):227-248

A.W. Martinius and J.H. Van den Berg. 2011. Atlas Of Sedimentary Structures In Estuarine and Tidally-Influenced River Deposits of the Rhine-Meuse-Scheldt System. Their Application to the Interpretation of Analogous Outcrop and Subsurface Depositional Systems EAGE Publications. Available for download

F.J. Pettijohn and P.E. Potter. 1964. Atlas and Glossary of Primary Sedimentary Structures. Springer.A classic.

H.-E. Reineck and I.B. Singh.1980.  Depositional Sedimentary Environments. Springer.

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