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 *Steven_Driese@baylor.edu Jennifer Roberts, Department of Geology, University of Kansas jenrob@ku.edu

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 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 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? Stratigraphy-Sedimentology course? Earth System Science ? Hydrology? Soils? Other?

Nordt and Driese (2010) AJS

Colloidal Properties of PaleoVertisols Nordt and Driese (2010) AJS Estimated using modern Vertisol – based “pedotransfer functions” Paleosol Horizon Depth (cm) Clay (%) Fine Clay (%) Fine Clay/Total Clay Coefficient of Linear Extensibility (cm/cm) Bulk Density (g/cm3) Cation Exchange Capacity (cmolc/kg) Cation Exchange Capacity/Clay CaCO3 (%) pH (H2O) Base Saturation (%) Exchangeable Sodium Percent (%) Electrical Conductivity (ds/m) Fe Dithionite-extractable (Fed, %) Oxalate-extractable Fe (Feo, %) A1 0- 17 69 41 0.59 0.17 1.12 52 0.75 7.2 94 15 5 1.2 ~0.1 A2 17- 60 71 42 1.10 0.73 7.3 14 4 Bss1 60- 86 43 0.61 0.18 1.07 53 0.74 1.7 Bss2 86- 104 68 37 0.54 1.03 63 0.92 7.5 97 13 2.1 Bk 104- 135 67 33 0.49 0.10 n.d. 40 7.7 100 16 6 1.9

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 Overall increase in N and P ratios

Inorganic byproducts of chemoheterotrophy do not accumulate longterm Inorganic byproducts of chemoheterotrophy do not accumulate longterm. They react with mineral phases and precipitate or diffuse upward to seafloor where they are used by chemolithoautotrophs. Mineralogy also becomes zoned Depth and spacing depends on carbon loading, available electron acceptors, flow.

Microbial interactions in CaCO3 cementation in marine intertidal stromatolites Cyanos produce no net CaCO3 CaCO3 produced by heterotrophic activity Offset by autotrophs New paper by Meister et al., 2013 says that SRBs are ineffective at precipitating large quantities of carbonate mineral due to decrease in pH induced by metabolic pathway Konhauser, 2007

As burial proceeds pore water geochemistry changes resulting in dissolution and precipiation. Formation of concretions Konhauser, 2007

Konhauser, 2007 Carbon isotopic signatures Talk about Isua—stable isotopes used to suggest biogenic origin of graphite apatite with a significant isotopic enrichment in the light stable isotope 12C was found in a banded iron formation in Greenland. , later data suggests metasomatism as source of graphite. We suggest that the isotopic composition of graphite in supracrustal rocks subjected to high-grade metamorphism does not in general, serve as a reli- able biomarker, since epigenetic processes may yield graphite with isotopic characteristics that overlap with isotopic signatures of metamorphosed organism remains. Konhauser, 2007

Storrie-Lonmbardi et al. 2004 Some microorganisms create extensive biofilms or mats that may produce distinct sedimentary structures--such as the stromatolite above.

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