| In contrast, the many shale layers seem to be poor in macrofossils largely because they were deposited at depth below the photic zone as indicated by benthic foraminifera. |
| Seasonal highs that pushed this euxinic layer into the photic zone would then lead to the greatly increased preservation and the TOC maxima. |
| Stromatolites were built by photosynthesizing organisms occupying shallow-water environments within the photic zone. |
| The bottommost, or aphotic, zone is the region of perpetual darkness that lies beneath the photic zone and includes most of the ocean waters. |
| The depth is recognized as that of the lower photic zone, the reproductive depth for planktonic foraminifera. |
| Twilight Zone: The area of the ocean below the sunlit photic zone and above the zone of total darkness. |
