Burial
The fats, carbohydrates, and proteins of the plants and animals deposited must be protected from decay due to exposure to oxygen, and from being destroyed by aerobic (free oxygenconsuming) organisms. This protection can occur when the organic material is deposited in a mixture with finely divided clastic sediments, such as clays and silts (Fig PRESERVATION OF ORGANIC MATTER IN SEDIMENT)
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| PRESERVATION OF ORGANIC MATTER IN SEDIMENT |
In general, the more finely graded the sediment is, the more organic matter is preserved, but there must be a significant amount of organic carbon content to start with. At least 5% Total Organic Carbon (TOC) is considered the minimum for a good source rock. The sediments will usually be clays and shale’s, but in some areas, carbonates can be source rocks as well. Microscopic examination of source rocks can show visible bands or layers of dark brown or black organic matter, representing seasonal deposition cycles.