The key difference between chemical and detrital sedimentary rocks is that the formation of chemical sedimentary rocks does not involve direct mechanical weathering, whereas the formation of detrital sedimentary rocks involves direct mechanical weathering.
Sedimentary rock is formed from pre-existing rocks or pieces of once-living organisms. These rocks form through the depositions that get accumulated on the Earth’s surface and often have distinctive layering or bedding. There are two types of chemical and sedimentary rocks known as clastic and chemical sedimentary rocks.
CONTENTS
1. Overview and Key Difference
2. What are Chemical Sedimentary Rocks
3. What are Detrital Sedimentary Rocks
4. Side by Side Comparison – Chemical vs Detrital Sedimentary Rocks in Tabular Form
5. Summary
What are Chemical Sedimentary Rocks?
Chemical sedimentary rocks are a type of sedimentary rocks formed from processes that do not directly involve mechanical weathering and erosion. However, chemical weathering can contribute to dissolved materials in water, which can cause the formation of this type of rocks. The most common type of chemical sedimentary rock is limestone, which contains the mineral calcite. These rocks form through biochemical processes that take place in shallow seawater.
Limestone frequently gets converted into dolomite or dolostones during stages of compaction, dewatering, and lithification of limestone. This process is known as dolomitization. This process involves the removal of calcium from limestone by magnesium-containing solutions, and this involves the replacement of calcium with magnesium.
Figure 01: A Large Sedimentary Rock
Another type of chemical sedimentary rock is cherts. This is a hard and glassy sedimentary rock containing silica that precipitates from water. This rock is formed in pockets or voids that contain gas or organic matter that has been removed or decomposed with time. In addition, this rock type can occur as continuous layers in sedimentary rocks.
What are Detrital Sedimentary Rocks?
Detrital sedimentary rocks are a type of sedimentary rocks containing pre-existing sediment pieces that come from weathered bedrock. These are also known as clastic rocks. Most sediments in these rocks are mechanically weathered sediments. However, some detrital sedimentary rocks are pieces of chemical sedimentary rocks.
Figure 02: Detrital Sedimentary Rock
We can classify and name a few groups of detrital rocks depending on the grain size. Here, the grains are graded from large to a small size on the Wentworth scale.
What is the Difference Between Chemical and Detrital Sedimentary Rocks?
Sedimentary rock is formed from pre-existing rocks or pieces of once-living organisms. These rocks form through the depositions that get accumulated on the Earth’s surface. The key difference between chemical and detrital sedimentary rocks is that the formation of chemical sedimentary rocks does not involve direct mechanical weathering, whereas the formation of detrital sedimentary rocks involves direct mechanical weathering. In other words, the difference between chemical and detrital sedimentary rocks is that the chemical sedimentary rocks are formed through chemical methods while detrital sedimentary rocks are formed through mechanical methods. Limestone, dolomite, chert, etc. are examples of chemical sedimentary rocks while sand and gravel are examples of detrital sedimentary rocks.
Below is a summary of the difference between chemical and detrital sedimentary rocks in tabular form.
Summary – Chemical vs Detrital Sedimentary Rocks
There are two major types of sedimentary rocks as chemical and detrital or clastic sedimentary rocks. The key difference between chemical and detrital sedimentary rocks is that the formation of chemical sedimentary rocks does not involve e direct mechanical weathering, whereas the formation of detrital sedimentary rocks involves direct mechanical weathering.
Reference:
1. “5.3: Sedimentary rocks.” Libretext, Available here.
2. “Sedimentary Rock.” Wikipedia, Wikimedia Foundation, 16 Mar. 2021, Available here.
Image Courtesy:
1. “Triassic Utah” By Wilson44691 at English Wikipedia – Photograph taken by Mark A. Wilson (Department of Geology, The College of Wooster).[1] (Public Domain) via Commons Wikimedia
2. “Chalus road – ninara 02” By Ninara – (CC BY 2.0) via Commons Wikimedia