@article{fdi:010091056,
  title = {{C}onstraints on hopanes and br{GDGT}s as p{H} proxies in peat},
  author = {{S}chaaff, {V}alentine and {G}rossi, {V}. and {M}akou, {M}. and {G}arcin, {Y}annick and {D}eschamps, {P}ierre and {S}ebag, {D}. and {N}gatcha, {B}. {N}. and {M}{\'e}not, {G}.},
  editor = {},
  language = {{ENG}},
  abstract = {p{H} is one of the major parameters governing peat functioning, and p{H} variations in modern peatlands affect carbon and methane production and consumption. {P}aleo-p{H} reconstructions have been limited thus far, but they could help to better understand peat functioning in variety of settings and also serve as an indirect proxy for climatic and environmental variations such as precipitation. {B}acterial hopanes and branched {G}lycerol {D}ialkyl {G}lycerol {T}etraethers (br{GDGT}s) were investigated in a 10-ka peat record from {N}orth-{E}ast {C}ameroon ({NG}aoundaba, {W}estern {C}entral {A}frica). {R}ecently developed p{H} proxies using the hopane beta beta/(alpha beta + beta beta) ratio and the br{GDGT} cyclization ratio ({CBT}peat) were applied and compared with previously published bulk organic data from the same core. {D}ifferent hypotheses are usually proposed to explain the high abundance of the "thermally mature" {C}31 alpha beta hopane in peats: acid-catalyzed isomerization of beta beta to alpha beta isomers with or without biological mediation or the direct input of {C}31 alpha beta hopanes by bacteria. {I}n the {NG}aoundaba peat deposit, the opposite variation in the beta beta/(alpha beta + beta beta) ratio of {C}30 and {C}31 hopanes and the carbon isotopic composition of {C}31 beta beta and alpha beta hopanes suggest that an eventual transformation of {C}31 beta beta to alpha beta isomers is not possible without biological mediation. {A} linear correlation between hopane- and br{GDGT}-reconstructed p{H} is observed, suggesting a similar response to environmental changes for these two independent proxies. {A} large increase in reconstructed p{H} values coincides with changes in vegetation and precipitation at the end of the {A}frican {H}umid {P}eriod ({AHP}). {L}ower p{H} values are observed during the {AHP}, coinciding with a period of increased precipitation and consistent with bulk organic data and slightly higher {C}31 beta beta hopane delta 13{C} values compared to middle and late {H}olocene. {B}ulk organic data indicate an interruption of the {AHP} by a drier intermission that coincides with a decrease in reconstructed p{H} values, probably reflecting a decrease in evapotranspiration. {V}ariations in p{H} values could be interpreted in terms of preservation of peat organic matter and might reflect past changes in methane cycling in the investigated peatland. {T}he present study reinforces the idea that reconstruction of p{H} in peat deposits represents a promising proxy of environmental change, enabling a better understanding of changes in peat functioning over large timescales and various locations.},
  keywords = {{L}ipid biomarkers ; {H}opane isomer ratios ; 13 {C} composition ; p{H} ; reconstruction ; {A}frican {H}umid {P}eriod ; {CAMEROUN}},
  booktitle = {},
  journal = {{G}eochimica et {C}osmochimica {A}cta},
  volume = {373},
  numero = {},
  pages = {342--354},
  ISSN = {0016-7037},
  year = {2024},
  DOI = {10.1016/j.gca.2024.03.034},
  URL = {https://www.documentation.ird.fr/hor/fdi:010091056},
}