Sedimentary structures

src: 3.bp.blogspot.com

Sedimentary structures are structures formed during sediment deposition.

Sedimentary structures such as cross beds, bunk beds and ripple markers are used in stratigraphic studies to show the original position of strata in complex geological fields and understand the sediment deposition environment.

Video Sedimentary structures

Flow structure

There are two kinds of flow structures: two directions (various directions, back and forth) and direction. The flow regime in a single direction (usually fluvial) flow, which at different speeds and velocities produces different structures, called bedforms. In the lower flow regime , the natural progression is from flat beds, to some sedimentary movement (salt etc.), to ripples, to slightly larger hills. Dunes has a vortex on the left side of the sand dunes. As a form of upper stream , the dunes become flat, and then produce antidunes. At higher speeds, antidunes are flattened and most settlements stop, as erosion takes over as a dominant process.

Maps Sedimentary structures

Bedforms vs. flow

Unique uniform bedforms represent certain flow velocities, assuming typical sediments (sand and mud) and water depth, and the graphs below can be used to interpret the sedimentary environment, with increasing water velocity down the graph.

src: acad.depauw.edu

Ripple Mark

Ripple marks are usually formed in conditions with running water, at the bottom of the Lower Flow Regime. There are two types of ripple signs:

Symmetrical rippet mark: Often found on shore, they are made by a two-way stream, such as the waves on the shore (rocking and backflow). It creates ripple marks with spiky peaks and round troughs, which do not tend to be more in certain directions. Three common sedimentary structures made by this process are herringbone cross stratification, flaser bedding, and interference ripple.
Asymmetric ripple mark: This is made by one-way flow, for example in a river, or wind in the desert. It creates ripple marks with rising peaks and round troughs, but which tend to be stronger in the direction of currents. For this reason, they can be used as palaeocurrent indicators.

Sedimentary structures ~ Learning Geology

src: 4.bp.blogspot.com

Antidunes

Antidunes are bedform sediments created by shallow fast water streams with Froude amounts greater than 1. Antidunes are formed beneath water standing waves that periodically steep, migrate, and then break upstream. Bedform antidun is characterized by shallow foresets, which dip upstream at an angle of about ten degrees that can reach up to five feet in length. They can be identified with their low angle foresets. For the most part, bedform antidunes are destroyed during downhill flow, and therefore cross bedding formed by antidunes will not be maintained.

the road to Oz is paved with limestone: Sedimentary structures and ...

src: 2.bp.blogspot.com

Biological structure

A number of biologically created sedimentary structures exist, called traces of fossils. Examples include burrows and various bioturbation expressions. Ichnofacies is a trail fossil group that together helps provide information about deposition environments. In general, because the deeper burrows (becoming sediments) become more common, the shallower the water. Because complex traces of the surface become more common, water becomes deeper.

The microbes can also interact with the sediment to form an induced microbial sediment structure.

Lecture 7 Sediments and Sedimentary Rocks. Lecture Outline ...

src: images.slideplayer.com

Soft sediment deformation structure

The structure of soft-sediment deformation or SSD, is a consequence of loading wet sediments as the burial continues after deposition. The heavier sediments "squeeze" the water from the underlying sediments because of their own weight. There are three common variants of SSD:

load structure or load cast (as well as a single sign) is a clot formed when a dense solid deposit degrades downward and into the less dense sediment below.
pseudonodule or ball-and-cushion structure, is a pinched load structure; this can also be formed by the energy of the earthquake and is called a seismit.
fire structure, "finger" of mud protruding into sedimentary rock.
Clastic dike is a layer of sediment material that crosses the sediment layer.

Geochronology Stock Photos & Geochronology Stock Images - Alamy

src: c8.alamy.com

Bedside structure

Bedding Field Structure is usually used as a paleocurrent indicator. They are formed when the precipitate has been stored and then reworked and rebuilt. They include:

Single signs are formed when an object scratches the surface of the sediment layer; this groove is then maintained as a cast when filled by the above layers. They include:
- The flute roller is a scour dug into a soft, delicate sediment usually filled by a base on it. Measuring the long axis of the flute cast gives the direction of the flow, with the spoon-shaped end pointing toward the rising current and the pointed end pointing down at this moment (paleoflow direction). Flexibility of the flute cast also shows downward stratigraphy.
- The tool sign is a type of single sign formed by the curvature left in the bed by the object dragged by the current. This average direction can be assumed to be the flow direction axis.
Mud forms when mud is drained, shrinks, and leaves a gap. It tells you that the mud is filled with water and then exposed to the air. The mud curve rolls upward, so it can be used as a geopetal structure. The form of cracked sineresis in the same way, with the exception that they have never been exposed to air, is not caused by changes in the salinity of the surrounding water.
Raindropping is formed on sediments exposed to rain impacts.
The separating line is a finely synced mineral formed at the bottom of the Upper Flow Regime in the plane's base plane.

Sedimentary Rocks - Textures - Structures - YouTube

src: i.ytimg.com

In the bed structure

This structure is in sedimentary layers and can help with interpretation of the deposition environment and the current paleo direction. They are formed when the precipitate is deposited.

Cross-bedding: This can include ripples and dunes, or cross stratification caused by currents. The "cross" refers to the angle between the flat bed and the sloping bed of the cross bed, usually about 34 degrees. Paleocurrents are best found from cross beds that showcase 3D architecture so you can measure the axis of the trough from the cross bed.
Hummocky cross-stratification: This stratification consists of a collection of wavy crucifixes that are concave (sengkedah) and convex (hummock). These cross-beds gently cut each other with curved erosion surfaces. They are formed in shallow waters, storm-dominated environments. Strong storm wave action erodes the seafloor into low hummocks and swales that have no special orientation.
Imbrication: This structure is formed by the clustering of larger clusters in the direction of flow.
Normal-floor bed: This structure occurs when the current velocity change and the grain decreases from the current. The most common place to find this is a turbidite deposit. It can also be reversed, called an inverted upstairs bed, and common in debris currents.
Bioturbation: Biological stirring of sediments (ie digging); typical of shallow water, fine-grained sediments.
Tidal package: Layer thickness variation in tidal environment caused by spring and sea change.

Refresher Lecture 1A Sedimentary Rocks, Facies, and Stacking ...

src: slideplayer.com

Secondary sedimentary structure

Secondary sedimentary structures are formed after the primary deposition occurs or, in some cases, during the diagenesis of sedimentary rocks. The common secondary structure includes all forms of bioturbation, soft-sediment deformation, teepee structure, traces, and soil spots. Lyingegang rings, cone-in-cone structures, raindrop impressions, and vegetation induced sedimentary structures will also be considered secondary structures.