L6 - Biomarkers to proxies Flashcards
(19 cards)
What is AOM and what microbes are involved
Anaerobic Oxidation of Methane
involves a consortium of sulphate-reducing bacteria (SRB) and methanotrophic archaea
what isotopic signal is typical of AOM
AOM results in highly depleted δ13C values due to the use of methane as a carbon source
where is a large amount of methane stored in the marine environment
in marine gas hydrates
especially sub-sea permafrost regions like the East Siberian Arctic shelf
What is the PETM and why is it important
The Paleocene-Eocene Thermal Maximum (55.5Ma)
one of the most dramatic rapid global warming events
marked by large δ13C depletions and increased GHG
what biomarker shifts were observed during the PETM
depleted δ13C values in GDGTs and higher plant HMW n-alkanes
what is Paq and what does it indicate
Paq is a ratio based proxy using n-alkane distributions
Paq 0 = dry conditions
Paq 1 = wet conditions
what does Pwax indicate
0 = wet
1 = dry
used in paleohydrology
what is sphagnums role in n-alkane signals
its a major contributor to remobilise terrestrial organic matter and influences Paq values
what biomarkers come from purple and green sulphur bacteria
okenane
chlorbactane
isorenieratene
how does green sulphur bacteria perform photosynthesis
uses H2S instead of water
H2S+CO2 -> SO42- + organic compounds
what evidence supports photic zone euxinia in Earth history
black sea - largest anoxic basin
kimmeridge clay formation = enhanced preservation under these conditions
what are sapropels and where are they found
organic-rich sediment layers found in the Mediterranean sea = past anoxic events
what causes sapropel formation
intensified monsoons -> more precipitation, runoff, nutrient -> phytoplankton bloom -> anoxia -> sapropel
what is IP25 and what is it used for
highly branched isoprenoid produced by Arctic sea ice diatoms
used as a proxy for past Arctic sea ice extent
where has IP25 been observed and where not
Arctic but not Antarctic
what does the presence of IP25 indicate
formation of fresh sea ice extent in the NH and allows reconstruction of ice edge dynamics overtime
what process do anammox bacteria carry out
anaerobic oxidation of ammounium : NH4+ + NO2- -> N2 + 2H2O
what unique lipids are found in anammox bacteria
ladderanes - highly packed membrane lipids formung the dense anammoxosome
where has anammoc activity been found
black sea water column and arabian sea sediments over the last 140,000 years
