Gonna dump a bunch of links here, Amazonas and it's disappeared civilization, black soil and such:
https://www.newscientist.com/article/mg24132130-300-long-lost-cities-in-the-amazon-were-once-home-to-millions-of-people/
https://soundsandcolours.com/subjects/books/in-the-footsteps-of-orellana-and-carvajal-22336/
http://www.css.cornell.edu/faculty/lehmann/research/terra%20preta/terrapretamain.html
https://academic.oup.com/mbe/article/35/11/2719/5086311
https://www.nature.com/articles/s41467-018-03510-7
https://science.sciencemag.org/content/321/5893/1214
https://www.jstor.org/stable/2563351?seq=1#page_scan_tab_contents
https://www.sciencedirect.com/science/article/pii/S2352409X15301632
https://www.nature.com/articles/s41559-017-0322-4