Siderite and hematite are two iron-bearing minerals that can form in lacustrine sediments under different redox conditions. Siderite (FeCO3) is a carbonate mineral that precipitates in reducing environments with low oxygen and high organic matter content (1). Hematite (Fe2O3) is an oxide mineral that forms in oxidizing environments with high oxygen and low organic matter content (2). The presence and abundance of siderite and hematite in lacustrine sediments can indicate the past redox conditions of the lake water and the sedimentary environment, as well as the influence of hydrothermal or magmatic activities. Siderite and hematite can also affect the magnetic properties and geochemical composition of lacustrine sediments (3).

(1) Hydrothermal indications of Early Cretaceous red beds in lacustrine .... https://www.sciencedirect.com/science/article/pii/S0264817217303641.

(2) Iron speciation in modern sediment from Erhai Lake, southwestern .... https://www.sciencedirect.com/science/article/pii/S0883292701000166.

(3) Towards the identification of siderite, rhodochrosite, and vivianite in .... https://www.sciencedirect.com/science/article/pii/S1474706503001219.

Thank you Lyudmil Antonov. I will check out the references for more details.