Transcript How Does Our Understanding of Modern Critical

How Does Our Understanding
of Modern Critical Zone
Processes and Earth Systems
Help Us Understand the
Geologic Record?
Steven G. Driese, Department of Geology, Baylor
University
*[email protected]
Jennifer Roberts, Department
of Geology, University of Kansas
[email protected]
What would a paleo-Critical Zone look
like in past geologic times?
Can we get our students to think about terrestrial rocks
as records of ancient Critical Zones?
The present is
the key to the
past; and the
record of the past
may help predict
the future!
Terrestrial ecosystem context is critical!
Paleosols Record Ancient Critical Zones
NSF (2012) Transitions document
Reconstructing
biogeochemical
properties of 65
m.y. old Paleosol
P33, Big Bend
Nordt et al., 2012, GCA
Field Trip: Examining Triassic (215
m.y.) Paleo-Vertisols, Chinle Fm., AZ
Red, well-drained
Vertisol mudstone
Gleyed, poorly drained
Vertisol mudstone
When, Where, What to Introduce
this Concept?
• After introduction of
modern Critical Zone
Concept (obviously)
• Go with local rock
sections? Literature?
• Focus on specific Critical
periods of climate or
faunal changes
(extinctions, PETM,
Pleistocene-Holocene,
e.g.?
• In what course context?
• Advanced Historical
Geology?
• StratigraphySedimentology course?
• Earth System Science ?
• Hydrology?
• Soils?
• Other?
Nordt and Driese (2010) AJS
Colloidal Properties of PaleoVertisols
Estimated using modern Vertisol – based “pedotransfer functions”
Nordt and Driese
(2010) AJS
Coefficient of Linear
Extensibility (cm/cm)
Bulk Density
(g/cm3)
Cation Exchange
Capacity (cmolc/kg)
Cation Exchange
Capacity/Clay
CaCO3 (%)
pH (H2O)
Fe Dithioniteextractable (Fed, %)
Oxalate-extractable
Fe (Feo, %)
0.17
1.12
52
0.75
0
7.2
94
15
5
1.2
~0.1
A2
1760
71
42
0.59
0.17
1.10
52
0.73
0
7.3
94
14
4
1.2
~0.1
Bss1
6086
71
43
0.61
0.18
1.07
53
0.74
0
7.2
94
15
5
1.7
~0.1
Bss2
86104
68
37
0.54
0.18
1.03
63
0.92
0
7.5
97
13
4
2.1
~0.1
Bk
104135
67
33
0.49
0.10
n.d.
40
0.59
5
7.7
100
16
6
1.9
~0.1
Electrical
Conductivity (ds/m)
Fine Clay/Total
Clay
0.59
Exchangeable
Sodium Percent (%)
Fine Clay (%)
41
Base Saturation (%)
Clay (%)
69
Depth
(cm)
017
Paleosol Horizon
A1
Reconstructing (and Direct Measure) of
Colloidal Properties of Paleosols
Microbial contributions to early
diagenesis
• Organic carbon degradation
– Transformed to CO2 and CH4
– <1% of original OC buried in sediment remains in organic geochemical record.
• Nitrogen
– C:N ratio decreases as amino acids are stripped in first 10 cm
– C:N ratio then increases as NH4+ is assimilated into the microbial population.
•
Phosphorous
– C:P ratio balanced by stripping of P v. assimilation of P in microbial cells.
– Balance between precipitation of fluorapatite, adsorption, biological uptake vs.
surface mixing and diffusive losses to overlying water column
• Cementation
• Porosity enhancement
Microbial
interactions
in CaCO3
cementation
in marine
intertidal
stromatolites
Konhauser, 2007
Konhauser, 2007
Konhauser, 2007
Storrie-Lonmbardi et al. 2004
Konhauser, 2007
Limitation and
Competition
• Microbial metabolism
can create
environmental niches
• They may also
experience
competition that
effectively decreases
their influence in a
given environment.
Riding and Liang, 2005