Question

why is the river bed soft discuss on its equality and also discuss on terry?​

Answer 1

Answer form in sediment as it is being deposited. These structures are typically an indication of what the sedimentary environment was like. Sedimentary structures can often be identified by observable patterns in the sedimentary bedding or distinct shapes within the sediment. Basically, if the sedimentary rock doesn’t look uniform or has a distinctive feature, there’s a good chance it’s a sedimentary structure.

Exercise 4.1 – Observing Sedimentary Structures

Part A

For this exercise, your instructor will provide you with a set of sedimentary structures. Look at the samples closely and use a hand lens if necessary. Create a sketch of each sedimentary structure in the blank space below, focusing on what you think are the most important characteristics of the sample. Then, in full sentences, describe the structure you just sketched. If it helps, pretend you are describing what the structure looks like to someone who can not see it.

Structure #1 Sketch:

Description:

Structure #2 Sketch:

Description:

Structure #3 Sketch:

Description:

Structure #4 Sketch:

Description:

Structure #5 Sketch:

Description:

Part B

Now put your observational and descriptive skills to the test. Read your descriptions to your classmates and see if they can identify which samples you are talking about.

4.2 Types of Sedimentary Structures

The simplest sedimentary structure is stratification, which is layering that can be observed in sedimentary rocks (Figure 4.1). Layers of sediment that are thicker than 1 cm are called beds and layers thinner than 1 cm are called laminations. Laminations are typically composed of fine-grained silt and clay-sized sediment. Structures can be more complex like the wavy pattern seen in ripple marks (Figure 4.2) or chaotic looking patterns in cross-bedding (Figure 4.3).

This image shows slightly tilted layering in sedimentary rock downward to the right.

Figure 4.1 – Titled sedimentary beds from Morro Solar near Lima, Peru. Thicker layers are most likely sandstone, and thinner layers are shale. Layering tilts down to the right. I