Quantifying rock uplift rates using channel steepness and cosmogenic nuclide–determined erosion rates: Examples from northern and southern Italy

Abstract Uplift and erosion rates have been calculated for a large sector of the Campania-Lucania Apennine and Calabrian arc, Italy, using both geomorphological observations (elevations, ages and arrangement of depositional and erosional land surfaces and other morphotectonic markers) and stratigraphical and structural data (sea-level related facies, base levels, fault kinematics, and fault offset estimations). The values of the Quaternary uplift rates of the southern Apennines vary from 0.2 mm/yr to about 1.2–1.3 mm/yr. The erosion rates from key-areas of the southern Apennines, obtained from both quantitative geomorphic analysis and missing volumes calculations, has been estimated at 0.2 mm/yr since the Middle Pleistocene. Since the Late Pleistocene erosion and uplift rates match well, the axial-zone landscape could have reached a flux steady state during that time, although it is more probable that the entire study area may be a transient landscape. Tectonic denudation phenomena — leading to the exhumation of the Mesozoic core of the chain — followed by an impressive regional planation started in the Late Pliocene have to be taken into account for a coherent explanation of the morphological evolution of southern Italy.

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Boulders as a lithologic control on river and landscape response to tectonic forcing at the Mendocino triple junction

Geological Society of America Bulletin ◽

10.1130/b35385.1 ◽

2020 ◽

Author(s):

Charles M. Shobe ◽

Georgina L. Bennett ◽

Gregory E. Tucker ◽

Kevin Roback ◽

Scott R. Miller ◽

...

Keyword(s):

Triple Junction ◽

High Elevation ◽

River Channels ◽

Erosion Rates ◽

Coastal Belt ◽

Sediment Mass ◽

Mendocino Triple Junction ◽

Landscape Response ◽

Channel Steepness ◽

Tectonic Forcing

Constraining Earth’s sediment mass balance over geologic time requires a quantitative understanding of how landscapes respond to transient tectonic perturbations. However, the mechanisms by which bedrock lithology governs landscape response remain poorly understood. Rock type influences the size of sediment delivered to river channels, which controls how efficiently rivers respond to tectonic forcing. The Mendocino triple junction region of northern California, USA, is one landscape in which large boulders, delivered by hillslope failures to channels, may alter the pace of landscape response to a pulse of rock uplift. Boulders frequently delivered by earthflows in one lithology, the Franciscan mélange, have been hypothesized to steepen channels and slow river response to rock uplift, helping to preserve high-elevation, low-relief topography. Channels in other units (the Coastal Belt and the Franciscan schist) may experience little or no erosion inhibition due to boulder delivery. Here we investigate spatial patterns in channel steepness, an indicator of erosion resistance, and how it varies between mélange and non-mélange channels. We then ask whether lithologically controlled boulder delivery to rivers is a possible cause of steepness variations. We find that mélange channels are steeper than Coastal Belt channels but not steeper than schist channels. Though channels in all units steepen with increasing proximity to mapped hillslope failures, absolute steepness values near failures are much higher (∼2×) in the mélange and schist than in Coastal Belt units. This could reflect reduced rock erodibility or increased erosion rates in the mélange and schist, or disproportionate steepening due to enhanced boulder delivery by hillslope failures in those units. To investigate the possible influence of lithology-dependent boulder delivery, we map boulders at failure toes in the three units. We find that boulder size, frequency, and concentration are greatest in mélange channels and that Coastal Belt channels have the lowest concentrations. Using our field data to parameterize a mathematical model for channel slope response to boulder delivery, we find that the modeled influence of boulders in the mélange could be strong enough to account for some observed differences in channel steepness between lithologies. At the landscape scale, we lack the data to fully disentangle boulder-induced steepening from that due to spatially varying erosion rates and in situ rock erodibility. However, our boulder mapping and modeling results suggest that lithology-dependent boulder delivery to channels could retard landscape adjustment to tectonic forcing in the mélange and potentially also in the schist. Boulder delivery may modulate landscape response to tectonics and help preserve high-elevation, low-relief topography at the Mendocino triple junction and elsewhere.

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Uplift history of the Sila Massif, southern Italy, deciphered from cosmogenic10Be erosion rates and river longitudinal profile analysis

Tectonics ◽

10.1029/2011tc003037 ◽

2012 ◽

Vol 31 (3) ◽

pp. n/a-n/a ◽

Cited By ~ 46

Author(s):

Valerio Olivetti ◽

Andrew J. Cyr ◽

Paola Molin ◽

Claudio Faccenna ◽

Darryl E. Granger

Keyword(s):

Southern Italy ◽

Profile Analysis ◽

Longitudinal Profile ◽

Erosion Rates ◽

History Of ◽

Uplift History

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Millennial-scale denudation rates in the Himalaya of Far Western Nepal

10.5194/esurf-2019-7 ◽

2019 ◽

Author(s):

Lujendra Ojha ◽

Ken L. Ferrier ◽

Tank Ojha

Keyword(s):

Stream Power ◽

Denudation Rate ◽

The Past ◽

Cosmogenic Nuclide ◽

Northern India ◽

Denudation Rates ◽

Cosmogenic 10Be ◽

Channel Steepness ◽

The Himalaya ◽

Millennial Scale

Abstract. Over the past two decades, rates and patterns of Himalayan denudation have been documented through numerous cosmogenic nuclide measurements in central and eastern Nepal, Bhutan, and northern India. To date, however, few denudation rates have been measured in Far Western Nepal – a ~ 300-km-wide region near the center of the Himalayan arc – which presents a significant gap in our understanding of Himalayan denudation. Here we report new catchment-averaged millennial-scale denudation rates inferred from cosmogenic 10Be in fluvial quartz at seven sites in Far Western Nepal. The inferred denudation rates range from 385 ± 31 t km−2 yr−1 (0.15 ± 0.01 mm yr −1) to 8737 ± 2908 t km−2 yr−1 (3.3 ± 1.1 mm yr−1), and, in combination with our analyses of channel topography, are broadly consistent with previously published relationships between catchment-averaged denudation rates and normalized channel steepness across the Himalaya. These data show a weak correlation with catchment-averaged specific stream power, consistent with a Himalaya-wide compilation of previously published stream power values. Together, these observations are consistent with a dependence of denudation rate on both tectonic and climatic forcings, and represent a first step toward filling an important gap in denudation rate measurements in Far Western Nepal.

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Differences in channel and hillslope geometry record a migrating uplift wave at the Mendocino triple junction, California, USA

Geology ◽

10.1130/g46939.1 ◽

2019 ◽

Vol 48 (2) ◽

pp. 184-188 ◽

Cited By ~ 1

Author(s):

Fiona J. Clubb ◽

Simon M. Mudd ◽

Martin D. Hurst ◽

Stuart W.D. Grieve

Keyword(s):

Triple Junction ◽

Land Surface ◽

Plate Motion ◽

Topographic Analysis ◽

Channel Response ◽

Mendocino Triple Junction ◽

Uplift Rates ◽

Order Of Magnitude ◽

Landscape Morphology ◽

Channel Steepness

Abstract Tectonic plate motion, and the resulting change in land surface elevation, has been shown to have a fundamental impact on landscape morphology. Changes to uplift rates can drive a response in fluvial channels, which then drives changes to hillslopes. Because hillslopes respond on different time scales than fluvial channels, investigating the geometry of channels and hillslopes in concert provides novel opportunities to examine how uplift rates may have changed through time. Here we perform coupled topographic analysis of channel and hillslope geometry across a series of catchments at the Mendocino triple junction (MTJ) in northern California, USA. These catchments are characterized by an order-of-magnitude difference in uplift rate from north to south. We find that dimensionless hillslope relief closely matches the uplift signal across the area and is positively correlated with channel steepness. Furthermore, the range of uncertainty in hillslope relief is lower than that of channel steepness, suggesting that it may be a more reliable recorder of uplift in the MTJ region. We find that hilltop curvature lags behind relief in its response to uplift, which in turn lags behind channel response. These combined metrics show the northward migration of the MTJ and the corresponding uplift field from topographic data alone.

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Preliminary Results for the Extraction and Measurement of Cosmogenic in Situ 14C from Quartz

Radiocarbon ◽

10.1017/s0033822200039527 ◽

2004 ◽

Vol 46 (1) ◽

pp. 201-206 ◽

Cited By ~ 13

Author(s):

P Naysmith ◽

G T Cook ◽

W M Phillips ◽

N A Lifton ◽

R Anderson

Keyword(s):

Vacuum System ◽

Quartz Sample ◽

Erosion Rates ◽

The Past ◽

Cosmogenic Nuclide ◽

Lithium Metaborate ◽

University Of Arizona ◽

Efficient Extraction ◽

The University

Radiocarbon is produced within minerals at the earth's surface (in situ production) by a number of spallation reactions. Its relatively short half-life of 5730 yr provides us with a unique cosmogenic nuclide tool for the measurement of rapid erosion rates (>10−3 cm yr−1) and events occurring over the past 25 kyr. At SUERC, we have designed and built a vacuum system to extract 14C from quartz which is based on a system developed at the University of Arizona. This system uses resistance heating of samples to a temperature of approximately 1100° in the presence of lithium metaborate (LiBO2) to dissolve the quartz and liberate any carbon present. During extraction, the carbon is oxidized to CO2 in an O2 atmosphere so that it may be collected cryogenically. The CO2 is subsequently purified and converted to graphite for accelerator mass spectrometry (AMS) measurement. One of the biggest problems in measuring in situ 14C is establishing a low and reproducible system blank and efficient extraction of the in situ 14C component. Here, we present initial data for 14C-free CO2, derived from geological carbonate and added to the vacuum system to determine the system blank. Shielded quartz samples (which should be 14C free) and a surface quartz sample routinely analyzed at the University of Arizona were also analyzed at SUERC, and the data compared with values derived from the University of Arizona system.

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Is more better? Sediment production, weathering, and erosion inferred from multiple geochemical proxies and comprehensive field measurements in mountain catchments

10.5194/egusphere-egu2020-13564 ◽

2020 ◽

Author(s):

Clifford S. Riebe ◽

Leonard S. Sklar ◽

Claire E. Lukens

Keyword(s):

Field Measurements ◽

Cosmogenic Nuclides ◽

Spatial Variations ◽

Residence Times ◽

Size Distributions ◽

Erosion Rates ◽

Cosmogenic Nuclide ◽

Sediment Production ◽

Sediment Size ◽

Geochemical Proxies

Weathering in mountain landscapes produces sediment with size distributions that evolve as particles are transported down hillslopes, delivered to channels, and carried downstream. The evolving sizes influence rates of river incision into bedrock, which in turn set sediment residence times on hillslopes, with implications for the sizes of sediment produced by weathering. Hence, variations in sediment size are central to feedbacks that link climate, tectonics, and erosion in mountain landscape evolution. However, few studies have quantified how sediment sizes evolve during transport across catchments, focusing instead on rates of erosion and weathering. Yet recent modeling suggests that spatial variations in sediment size can lead to bias in erosion rates from conventional techniques, further highlighting the importance of understanding how sediment size evolves across landscapes.Here we show how a more complete and unbiased picture of sediment production, weathering, and erosion can be obtained by combining field measurements of sediment size together with conventional geochemical proxies in an integrative model that accounts for spatial variations in erosion, weathering, and sediment mixing, while incorporating effects of both abrasion and fragmentation during transport in channels. Our measurements, from a catchment draining the steep eastern Sierra Nevada, California, include particle size distributions of sediment from widely distributed locations. These measurements represent sediment that is produced on hillslopes and delivered to channels, reflecting the combined effects of the initial sediment size distribution (set by bedrock fracture spacing) and subsequent weathering on slopes. Our measurements also include cosmogenic nuclide concentrations and apatite-helium ages in 11 size classes, from sand to boulders, sampled from the creek. The cosmogenic nuclides reveal residence times of sediment in the catchment, while the apatite-helium ages reveal source elevations of sediment eroded into the stream. When combined together, the cosmogenic nuclide and apatite-helium data can be used to quantify altitudinal variations in erosion rates and sediment size distributions.Our measurements from catchment slopes indicate that hillslope sediment size decreases with decreasing elevation, reflecting altitudinal trends in physical, chemical, and biological weathering and producing downvalley fining in hillslope sediment supply. Cosmogenic nuclides in stream sediment decrease by two-fold with increasing particle size, indicating that erosion rates calculated using traditional techniques are sensitive to the size sampled from the creek. Apatite-helium ages suggest that the smallest and largest sizes sediment sizes in the stream originate from lower elevations, where slopes are gentler and soil-mantled. In contrast, coarse gravel and cobbles appear to originate from higher in the catchment, where slopes are steeper and bare bedrock is exposed. The differences in altitudinal trends in sediment size implied by the apatite-helium data and the direct observations from catchment slopes can be reconciled by accounting for particle fragmentation and abrasion during transport from hillslope sources to the sampling point in the creek. Our analysis indicates that each of the unique sources of information in our study are necessary for a complete and unbiased understanding of spatial variations in the production of sediment across the full range of sizes and their evolution during transport across the catchment.

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Cosmogenic nuclide chronology of pre-last glacial maximum moraines at Lago Buenos Aires, 46�S, Argentina

Quaternary Research ◽

10.1016/j.yqres.2004.12.003 ◽

2005 ◽

Vol 63 (3) ◽

pp. 301-315 ◽

Cited By ~ 86

Author(s):

Michael R. Kaplan ◽

Daniel C. Douglass ◽

Bradley S. Singer ◽

Robert P. Ackert ◽

Marc W. Caffee

Keyword(s):

Northern Hemisphere ◽

Erosion Rate ◽

Buenos Aires ◽

Glacial Cycles ◽

Rate Estimate ◽

Oxygen Isotope Stage ◽

Erosion Rates ◽

Cosmogenic Nuclide ◽

Stage 4 ◽

Glacial Advance

At Lago Buenos Aires, Argentina, 10Be, 26Al, and 40Ar/39Ar ages range from 190,000 to 109,000 yr for two moraines deposited prior to the last glaciation, 23,000�16,000 yr ago. Two approaches, maximum boulder ages assuming no erosion, and the average age of all boulders and an erosion rate of 1.4 mm/103 yr, both yield a common estimate age of 150,000�140,000 yr for the two moraines. The erosion rate estimate derives from 10Be and 26Al concentrations in old erratics, deposited on moraines that are >760,000 yr old on the basis of interbedded 40Ar/39Ar dated lavas. The new cosmogenic ages indicate that a major glaciation during marine oxygen isotope stage 6 occurred in the mid-latitude Andes. The next five youngest moraines correspond to stage 2. There is no preserved record of a glacial advance during stage 4. The distribution of dated boulders and their ages suggest that at least one major glaciation occurred between 760,000 and >200,000 yr ago. The mid-latitude Patagonian glacial record, which is well preserved because of low erosion rates, indicates that during the last two glacial cycles major glaciations in the southern Andes have been in phase with growth and decay of Northern Hemisphere ice sheets, especially at the 100,000 yr periodicity. Thus, glacial maxima are global in nature and are ultimately paced by small changes in Northern Hemisphere insolation.

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