FN Archimer Export Format
PT J
TI Microbialites on the northern shelf of Lake Van, eastern Türkiye: Morphology, texture, stable isotope geochemistry and age
BT 
AF Çağatay, M. Namik
   Damci, Emre
   Bayon, Germain
   Sari, Mustafa
AS 1:1;2:1;3:2;4:3;
FF 1:;2:;3:PDG-REM-GEOOCEAN-ASTRE;4:;
C1 İstanbul Teknik Üniversitesi, EMCOL Research Centre, Maslak, Faculty of Mining, 34469 Maslak, İstanbul ,Türkiye
   IFREMER, Marine Geosciences Research Unit, 29280 Plouzané ,France
   Bandırma Onyedi Eylül Üniversitesi, Maritime Faculty, 10200 Bandırma, Balıkesir ,Türkiye
C2 UNIV ISTANBUL, TÜRKIYE
   IFREMER, FRANCE
   UNIV BANDIRMA ONYEDI EYLUL, TÜRKIYE
SI BREST
SE PDG-REM-GEOOCEAN-ASTRE
UM GEO-OCEAN
IF 3.5
TC 0
UR https://archimer.ifremer.fr/doc/00859/97072/105853.pdf
   https://archimer.ifremer.fr/doc/00859/97072/105854.pdf
   https://archimer.ifremer.fr/doc/00859/97072/105855.pdf
   https://archimer.ifremer.fr/doc/00859/97072/105856.docx
   https://archimer.ifremer.fr/doc/00859/97072/105857.mp4
LA English
DT Article
DE ;Lake Van;microbialite;mineral and isotopic compositions;morphology;textures;Türkiye;U-Th ages
AB Lake Van, the world's largest alkaline lake, hosts some of the largest microbialite towers worldwide, which are considered as modern analogues of ancient stromatolites. This study investigates the links between microbialite evolution, geology, climate and hydrology, and the role of biotic and abiotic processes in microbialite growth and morphology. For these objectives, the northern shelf of Lake Van was surveyed by subbottom seismic profiling and diving, and two 9 m and 15 m high microbialite chimneys were sampled at 25 m water depth. Samples were analysed for stable oxygen and carbon isotopes, X‐ray diffractometry, scanning electron microscopy and U/Th age dating. Lake Van microbialites precipitate wherever focused Ca‐rich groundwater flows to the lake floor to mix with alkaline lake water. Variable columnar, conical and branching morphologies of the microbialites indicate various processes of formation by groundwater channelling within the chimneys. Collectively, our data suggest that the microbialite chimneys have formed within the last millennium, most likely during the warm and humid Medieval Climate Anomaly (ca AD 800–1300), when lake level rose approximately to the present level due to enhanced Inputs of riverine Ca‐rich freshwater and groundwater. Our new scanning electron microscopy observations indicate that the internal structure of the microbialites below the outer cyanobacteria‐covered crust is constructed by calcified filaments, globular aggregates and nanocrystals of algal, cyanobacterial and heterobacterial origins and inorganically precipitated prismatic calcite crystals. These textural features, together with dive observations, clearly demonstrate the important role of inorganic carbonate precipitation at sites of groundwater discharge, followed by cyanobacteria and algal mucilage deposition and microbially meditated calcification in the photic zone in the rapid growth of the microbialite chimneys. Considering the close similarities of some textures with those of ancient stromatolites and meteorites, the results of this study provide new insights into the environmental conditions associated with stromatolite formation and extra‐terrestrial life evolution. 
PY 2024
PD MAR
SO Sedimentology
SN 0037-0746
PU Wiley
VL 71
IS 3
BP 850
EP 870
DI 10.1111/sed.13153
ID 97072
ER

EF