Where does Flaser bedding occur?
Flaser beds are a sedimentary, bi-directional, bedding pattern created when a sediment is exposed to intermittent flows, leading to alternating sand and mud layers. While flaser beds typically form in tidal environments, they can (rarely) form in fluvial conditions – on point bars or in ephemeral streams.
What are starved ripples?
Starved ripples. Current ripples migrate by the removal of sand from the stoss (upstream) side of the ripple and deposition on the lee side (downstream).
What is the structure of sedimentary rocks?
Sedimentary structures are the larger, generally three-dimensional physical features of sedimentary rocks; they are best seen in outcrop or in large hand specimens rather than through a microscope. Sedimentary structures include features like bedding, ripple marks, fossil tracks and trails, and mud cracks.
What is convolute bedding?
Convolute bedding forms when complex folding and crumpling of beds or laminations occur. This type of deformation is found in fine or silty sands, and is usually confined to one rock layer. Convolute laminations are found in flood plain, delta, point-bar, and intertidal-flat deposits.
What are bedforms in geology?
A bedform is a feature that develops at the interface of fluid and a moveable bed, the result of bed material being moved by fluid flow. Examples include ripples and dunes on the bed of a river. Bedforms are often preserved in the rock record as a result of being present in a depositional setting.
How sedimentary rocks are formed?
Sedimentary rocks are formed from deposits of pre-existing rocks or pieces of once-living organism that accumulate on the Earth’s surface. If sediment is buried deeply, it becomes compacted and cemented, forming sedimentary rock.
How are cross bed formed?
Cross beds form from running water. As the water flows, it creates bedforms, such as ripples or dunes, on the floor of the channel. Sediment deposited on the downcurrent side of these bedforms is deposited at an angle–not horizontally.
How do you identify a cross bed?
The cross-beds reflect the steep faces of ripples and dunes. These steep faces tilt down-current and thus indicate current flow direction. Cross-beds are commonly curved at the base; this gives a handy way of determining right-side up in complexly deformed rocks.
What is convolute lamination?
Convolute lamination is a common fold structure within turbidite beds, attributed to the deformation of sediment during or soon after deposition of the host bed. Despite the prevalence of this feature, the formational processes are still not well understood.
What are metamorphic rocks made of?
Metamorphic rocks result when existing rocks are changed by heat, pressure, or reactive fluids, such as hot, mineral-laden water. Most rocks are made of minerals containing silicon and oxygen, the most abundant elements in the Earth’s crust.
What are the Cretaceous rocks in Minnesota?
The Cretaceous rocks in northeastern Minnesota consist of conglomerate, sandstone, and shale assigned to the Coleraine Formation. The Coleraine Formation was deposited in a nearshore-marine and nonmarine environment, locally covering the irregular surface of the Precambrian bedrock in and around the Mesabi Range.
What type of rock is the Carlile Shale?
Drill core example of the Carlile Shale from a site in Rock County, Minnesota. The Cretaceous rocks in northeastern Minnesota consist of conglomerate, sandstone, and shale assigned to the Coleraine Formation.
What are the three main types of rocks?
There are three kinds of rock: igneous, sedimentary, and metamorphic. Igneous rocks form when molten rock (magma or lava) cools and solidifies. Sedimentary rocks originate when particles settle out of water or air, or by precipitation of minerals from water. They accumulate in layers.