@article{fdi:010077409,
  title = {{T}he sedimentary origin of black and white banded cherts of the {B}uck {R}eef, {B}arberton, {S}outh {A}frica},
  author = {{L}edevin, {M}. and {A}rndt, {N}. and {C}hauvel, {C}. and {J}aillard, {E}tienne and {S}imionovici, {A}.},
  editor = {},
  language = {{ENG}},
  abstract = {{T}he {B}uck {R}eef is a 250-400 m thick sequence of banded black and white ({B}&{W}) cherts deposited ca. 3416 {M}a ago in a shallow basin. {W}e provide field, petrological and geochemical constraints on the chert-forming process and the origin of the banding. {W}hite layers consist of nearly pure microquartz, while black layers are mixed with detrital carbonaceous matter, quartz grains and carbonaceous microlaminae, interpreted as remnants of microbial mats. {T}he circulation of {S}i-rich fluid is recorded by abundant chert veins and pervasive silicification. {H}owever, the high purity of the white layers, their lack of internal structures and extremely low {A}l, {T}i and high-field-strength elements preclude an origin by silicification of sedimentary or volcanic precursors. {M}oreover, their reworking at the surface into slab conglomerates, and sediment-like contacts with black layers rule out a diagenetic origin. {W}e propose a new model whereby the white layers were periodically deposited as precipitates of pure silica; and the micro-layering within the black layers formed by annual temperature fluctuations, favouring microbial activity in summer and inorganic silica precipitation in winter. {O}utcrop-scale alternation of {B}&{W} layers was associated with major, thousand-year-long climate events: white cherts represent massive silica precipitation resulting from changes in ocean circulation and temperature during cold intervals.},
  keywords = {chert ; {A}rchean ; {B}uck {R}eef ; sediment ; geochemistry ; climate ; {AFRIQUE} {DU} {SUD} ; {BARBERTON}},
  booktitle = {},
  journal = {{G}eosciences},
  volume = {9},
  numero = {10},
  pages = {art. 424 [36 p.]},
  year = {2019},
  DOI = {10.3390/geosciences9100424},
  URL = {https://www.documentation.ird.fr/hor/fdi:010077409},
}