  We examine the observed properties of the Nili Fossae olivine-clay-carbonate
lithology from orbital data and in situ by the Mars 2020 rover at the
S\'e\'itah unit in Jezero crater, including: 1) composition (Liu, 2022) 2)
grain size (Tice, 2022) 3) inferred viscosity (calculated based on geochemistry
collected by SuperCam (Wiens, 2022)). Based on the low viscosity and
distribution of the unit we postulate a flood lava origin for the
olivine-clay-carbonate at S\'e\'itah. We include a new CRISM map of the clay
2.38 {\mu}m band and use in situ data to show that the clay in the olivine
cumulate in the S\'e\'itah formation is consistent with talc or serpentine from
Mars 2020 SuperCam LIBS and VISIR and MastCam-Z observations. We discuss two
intertwining aspects of the history of the lithology: 1) the emplacement and
properties of the cumulate layer within a lava lake, based on terrestrial
analogs in the Pilbara, Western Australia, and using previously published
models of flood lavas and lava lakes, and 2) the limited extent of post
emplacement alteration, including clay and carbonate alteration (Clave, 2022;
Mandon, 2022).
