Publications

@article{Tune2023,

title = {Deep root activity overprints weathering of petrogenic organic carbon in shale},

author = {AK Tune and JL Druhan and CR Lawrence and DM Rempe},

editor = {A Jacobson},

doi = {https://doi.org/10.1016/j.epsl.2023.118048},

year  = {2023},

date = {2023-04-01},

urldate = {2023-04-01},

journal = {Earth and Planetary Science Letters},

volume = {607},

number = {118048},

keywords = {ERCZO, root zone, Weathering},

pubstate = {published},

tppubtype = {article}

}

@article{Pedrazas2021,

title = {The Relationship Between Topography, Bedrock Weathering, and Water Storage Across a Sequence of Ridges and Valleys},

author = {Michelle A. Pedrazas and W. Jesse Hahm and Mong-Han Huang and David Dralle and Mariel D. Nelson and Rachel E. Breunig and Kristen E. Fauria and Alexander B. Bryk and William E. Dietrich and Daniella M. Rempe},

url = {https://angelo.berkeley.edu/jgr-earth-surface-2021-pedrazas-the-relationship-between-topography-bedrock-weathering-and-water-storage-across-a-1/},

doi = {10.1029/2020JF005848},

year  = {2021},

date = {2021-03-23},

urldate = {2021-03-23},

journal = {JGR Earth Surface},

volume = {126},

number = {4},

abstract = {Bedrock weathering regulates nutrient mobilization, water storage, and soil production. Relative to the mobile soil layer, little is known about the relationship between topography and bedrock weathering. Here, we identify a common pattern of weathering and water storage across a sequence of three ridges and valleys in the sedimentary Great Valley Sequence in Northern California that share a tectonic and climate history. Deep drilling, downhole logging, and characterization of chemistry and porosity reveal two weathering fronts. The shallower front is ∼7 m deep at the ridge of all three hillslopes, and marks the extent of pervasive fracturing and oxidation of pyrite and organic carbon. A deeper weathering front marks the extent of open fractures and discoloration. This front is 11 m deep under two ridges of similar ridge-valley spacing, but 17.5 m deep under a ridge with nearly twice the ridge-valley spacing. Hence, at ridge tops, the fraction of the hillslope relief that is weathered scales with hillslope length. In all three hillslopes, below this second weathering front, closed fractures and unweathered bedrock extend about one-half the hilltop elevation above the adjacent channels. Neutron probe surveys reveal that seasonally dynamic moisture is stored to approximately the same depth as the shallow weathering front. Under the channels that bound our study hillslopes, the two weathering fronts coincide and occur within centimeters of the ground surface. Our findings provide evidence for feedbacks between erosion and weathering in mountainous landscapes that result in systematic subsurface structuring and water routing.},

keywords = {bedrock weathering, Critical Zone, ERCZO, hillslope, unsaturated zone, water storage, Weathering},

pubstate = {published},

tppubtype = {article}

}

@article{Stock2005,

title = {Field measurements of incision rates following bedrock exposure: Implications for process controls on the long profiles of valleys cut by rivers and debris flows},

author = {J. D. Stock and D. R. Montgomery and B. D. Collins and W. E. Dietrich},

url = {https://angelo.berkeley.edu/wp-content/uploads/sites/59/Stock_2005_GSABulletin.pdf},

doi = {10.1130/B25560.1},

year  = {2005},

date = {2005-01-01},

journal = {GSA Bulletin},

volume = {117},

number = {1-2},

pages = {174-194},

abstract = {Until recently, published rates of incision of bedrock valleys came from indirect dating of incised surfaces. A small but growing literature based on direct measurement reports short-term bedrock lowering at geologically unsustainable rates. We report observations of bedrock lowering from erosion pins monitored over 1–7 yr in 10 valleys that cut indurated volcanic and sedimentary rocks in Washington, Oregon, California, and Taiwan. Most of these channels have historically been stripped of sediment. Their bedrock is exposed to bed-load abrasion, plucking, and seasonal wetting and drying that comminutes hard, intact rock into plates or equant fragments that are removed by higher flows. Consequent incision rates are proportional to the square of rock tensile strength, in agreement with experimental results of others. Measured rates up to centimeters per year far exceed regional long-term erosion-rate estimates, even for apparently minor sediment-transport rates. Cultural artifacts on adjoining strath terraces in Washington and Taiwan indicate at least several decades of lowering at these extreme rates. Lacking sediment cover, lithologies at these sites lower at rates that far exceed long-term rock-uplift rates. This rate disparity makes it unlikely that the long profiles of these rivers are directly adjusted to either bedrock hardness or rock-uplift rate in the manner predicted by the stream power law, despite the observation that their profiles are well fit by power-law plots of drainage area vs. slope. We hypothesize that the threshold of motion of a thin sediment mantle, rather than bedrock hardness or rock-uplift rate, controls channel slope in weak bedrock lithologies with tensile strengths below ∼3–5 MPa. To illustrate this hypothesis and to provide an alternative interpretation for power-law plots of area vs. slope, we combine Shields' threshold transport concept with measured hydraulic relationships and downstream fining rates. In contrast to fluvial reaches, none of the hundreds of erosion pins we installed in steep valleys recently scoured to bedrock by debris flows indicate any postevent fluvial lowering. These results are consistent with episodic debris flows as the primary agent of bedrock lowering in the steepest parts of the channel network above ∼0.03–0.10 slope.},

keywords = {erosion, geomorphology, neotectonics, rivers, Weathering},

pubstate = {published},

tppubtype = {article}

}

@article{Finlay2003,

title = {Controls of streamwater dissolved inorganic carbon dynamics in a forested watershed},

author = {Jacques C. Finlay},

url = {https://angelo.berkeley.edu/wp-content/uploads/sites/59/Controls-of-streamwater-dissolved-inorganic-carbon-dynamics-in-a-forested-watershed_Finlay_2002.pdf},

doi = {10.1023/A:1021183023963},

issn = {1573-515X},

year  = {2003},

date = {2003-03-01},

journal = {Biogeochemistry},

volume = {62},

number = {3},

pages = {231-252},

abstract = {I investigated controls of stream dissolved inorganic carbon (DIC) sources andcycling along a stream size and productivity gradient in a temperate forestedwatershed in northern California. Dissolved CO2 (CO2(aq))dynamics in heavily shaded streams contrasted strongly with those of larger,open canopied sites. In streams with canopy cover > 97%, CO2 (aq)was highest during baseflow periods (up to 540 μM) and wasnegatively related to discharge. Effects of algal photosynthesis on CO2(aq) were minimal and stream CO2 (aq) was primarily controlledby groundwater CO2 (aq) inputs and degassing losses to theatmosphere. In contrast to the small streams, CO2 (aq) in larger,open-canopied streams was often below atmospheric levels at midday duringbaseflow and was positively related to discharge. Here, stream CO2(aq) was strongly influenced by the balance between autotrophic andheterotrophic processes. Dynamics of HCO3 − werelesscomplex. HCO3 − and Ca2+ were positivelycorrelated, negatively related to discharge, and showed no pattern with streamsize. Stable carbon isotope ratios of DIC (i.e. δ13C DIC)increased with stream size and discharge, indicating contrasting sources of DICto streams and rivers. During summer baseflows, δ13C DIC were13C-depleted in the smallest streams (minimum of−17.7‰) due to the influence of CO2 (aq) derived frommicrobialrespiration and HCO3 − derived from carbonateweathering. δ13C DIC were higher (up to −6.6‰)inthe larger streams and rivers due to invasion of atmospheric CO2enhanced by algal CO2 (aq) uptake. While small streams wereinfluenced by groundwater inputs, patterns in CO2 (aq) and evidencefrom stable isotopes demonstrate the strong influence of stream metabolism andCO2 exchange with the atmosphere on stream and river carbon cycles.},

keywords = {CO2, Dissolved inorganic carbon, Metabolism, Stable carbon isotopes, streams, Weathering},

pubstate = {published},

tppubtype = {article}

}