How do Flute marks form?

Flute marks are made by strong eddies (vortices) in the current. These scour the underlying mud deeply at first, but then weaken and widen as they move on down current. In which direction was the current flowing which left these flute casts? (A. from left to right).

What do Flute marks suggest?

flute mark A tongue-shaped scour cut into mud by a turbulent flow of water. The tongue is deepest at the up-current end and the flute can thus be used as a palaeocurrent indicator. If the flute is infilled by sediment a flute cast will be preserved in the base of the overlying bed.

What is flute mark in geology?

Flute casts or sole marks are the preserved remnants of water flowing over and eroding sediments. To be preserved, softer sediment must wash over the surface and fill in the structures eroded by the water. The water scours a small depression that is steep on the upstream side and a lower angle on the downstream side.

How are groove marks formed?

Groove or striation marks result from the continuous contact with the muddy bed. Skip or prod marks come from objects that bounce along the surface of the muddy bed. And roll marks result from objects rolling along the muddy bed.

Where are flute casts found?

Quote from video:This specimen shows a type of sole structure that is a structure that formed at the base web and this particular structure is called a flute cast. The sedimentary structure was formed by a turbidity

How do mud cracks form?

Formation of mudcrack



Naturally forming mudcracks start as wet, muddy sediment dries up and contracts. A strain is developed because the top layer shrinks while the material below stays the same size. When this strain becomes large enough, channel cracks form in the dried-up surface to relieve the strain.

How do rip up clasts form?

Rip-up clasts are gravel-size pieces of clay or mud created when an erosive current flows over a bed of clay or mud and removes pieces of clayey sediment, and transports them some distance.

What causes cross bedding?

Cross-bedding is formed by the downstream migration of bedforms such as ripples or dunes in a flowing fluid. The fluid flow causes sand grains to saltate up the stoss (upstream) side of the bedform and collect at the peak until the angle of repose is reached.

What is the principle of inclusions?

The principle of inclusions states that any rock fragments that are included in rock must be older than the rock in which they are included. For example, a xenolith in an igneous rock or a clast in sedimentary rock must be older than the rock that includes it (Figure 8.6).

How does sedimentary rock usually form?

Pieces of rock are loosened by weathering, then transported to some basin or depression where sediment is trapped. If the sediment is buried deeply, it becomes compacted and cemented, forming sedimentary rock.

What is the rule of cross cutting?

Described by Scotsman James Hutton (1726 – 1997), the Law of Crosscutting Relationships stated that if a fault or other body of rock cuts through another body of rock then it must be younger in age than the rock through which it cuts and displaces.

What stratigraphy involves?

Stratigraphy is a branch of geology concerned with the study of rock layers (strata) and layering (stratification). It is primarily used in the study of sedimentary and layered volcanic rocks.

What is a stratigraphic formation?

A formation consists of a certain number of rock strata that have a comparable lithology, facies or other similar properties. Formations are not defined on the thickness of the rock strata they consist of and the thickness of different formations can therefore vary widely.

How does stratigraphy help archaeologists?

Stratigraphic studies of archaeological sites are designed to define objectively and categorize the sediments and soils, the contact units between them, and the amount of time they represent, as well as their relationship to the surrounding sediment history.

What is stratigraphy in geography?

stratigraphy, scientific discipline concerned with the description of rock successions and their interpretation in terms of a general time scale. It provides a basis for historical geology, and its principles and methods have found application in such fields as petroleum geology and archaeology.

How is stratigraphy done?

Simply put: Where one layer overlies another, the lower layer was deposited first. When an archaeological unit is done being excavated, the walls of the unit reveal the different layers of stratigraphy. Archaeologists are then able to tell which of these layers happened before or after layers.

Is the father of stratigraphy?

The man credited as the “father of stratigraphy,” however, was the English engineer and geologist William Smith (1769-1839). In 1815 Smith produced the first modern geologic map, showing rock strata in England and Wales.

How stratified rocks are formed?

Sedimentary rock, also called stratified rock, is formed over time by wind, rain and glacial formations. These rocks may be formed by erosion, compression or dissolution. Sedimentary rock may range from green to gray, or red to brown, depending on iron content and is usually softer than igneous rock.

How igneous rocks are formed?

Igneous rocks (from the Latin word for fire) form when hot, molten rock crystallizes and solidifies. The melt originates deep within the Earth near active plate boundaries or hot spots, then rises toward the surface.

How are metamorphic rocks formed?

Metamorphic rocks form when rocks are subjected to high heat, high pressure, hot mineral-rich fluids or, more commonly, some combination of these factors. Conditions like these are found deep within the Earth or where tectonic plates meet.

What rock is formed by cooling?

igneous rock

igneous rock, any of various crystalline or glassy rocks formed by the cooling and solidification of molten earth material. Igneous rocks constitute one of the three principal classes of rocks, the others being metamorphic and sedimentary.

Does obsidian exist?

obsidian, igneous rock occurring as a natural glass formed by the rapid cooling of viscous lava from volcanoes. Obsidian is extremely rich in silica (about 65 to 80 percent), is low in water, and has a chemical composition similar to rhyolite. Obsidian has a glassy lustre and is slightly harder than window glass.

What rocks are formed by lava?

When lava reaches the surface of the Earth through volcanoes or through great fissures the rocks that are formed from the lava cooling and hardening are called extrusive igneous rocks. Some of the more common types of extrusive igneous rocks are lava rocks, cinders, pumice, obsidian, and volcanic ash and dust.