Marl
Marl is a sedimentary rock consisting of clay, claystone and limestone. Marl is a transition phase from shale to limestone. The demarcation of this rock type is not very accurate, but in The Netherlands, one speaks of marl when 25%-75% of the rock is made up of chalk. Due to the platy and weakened structure this rock erodes very easily and is very vulnerable to weathering.
Lithology
Sandy, shell-fragmental and ooidal ferruginous limestone interbedded with ferruginous calcareous sandstone, and generally subordinate ferruginous mudstone beds. Locally any of these lithologies may pass by increase in iron content into generally ooidal ironstone, and in places any of these may dominate. The iron content (as ooids, altered shell material or in the groundmass) is berthierine (dark green iron-rich layered silicate formed in low-oxygen marine conditions), altering to siderite. Fossil content variable throughout but locally abundant especially in limestone beds.[1]
Marly limestone
A rock is called a marly limestone when a greater part of argillaceous material is present. Like it is shown in the graph at the top of this page.
Marly sand
A soil is called a marly sand when marl as a lacustrine sediment is present in a sandy soil. This happens in post-glacial lake-bed sediments, often found underlying peat bogs.
Formation
It is a rock containing clay and calcium carbonate. It is formed from the erosion of other rocks during weathering; as rocks erode, small sedimentary particles–sand, silt, and clay–pile up on top of each other. Eventually, these sedimentary particles become compacted together to form a new rock. The type of new rock that is formed depends on the original rock that was eroded and on the nature of the erosion. If the new rock contains predominantly clay and calcium carbonate, it is called marl.[2]
References
Marl
| Group | Organic sedimentary rock |
| Texture | Conchoidal fracture |
| Clasts | <0.02mm |
| Hardness | Weak |
| Color | Green, brown, beige and gray – grayish white |
| Minerals | Calcite, clay minerals, dolomite, gypsum, micas, pyrite, quartz |
| Touch | Smooth |
| Image | Marlstone |
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