A RECORD OF BASE LEVEL FALL FROM DATA-DRIVEN LINEAR INVERSION OF FLUVIAL TOPOGRAPHY AND ITS COMPARISON TO FAULT SLIP AT THE MOUNTAIN FRONT, NORTHERN APENNINES, ITALY

Abstract Over the past few decades, tectonic geomorphology has been widely implemented to constrain spatial and temporal patterns of fault slip, especially where existing geologic or geodetic data are poor. We apply this practice along the eastern margin of Bull Mountain, Southwest Montana, where 15 transient channels are eroding into the flat, upstream relict landscape in response to an ongoing period of increased base level fall along the Western North Boulder fault. We aim to improve constraints on the spatial and temporal slip rates across the Western North Boulder fault zone by applying channel morphometrics, cosmogenic erosion rates, bedrock characteristics, and calibrated reproductions of the modern river profiles using a 1-dimensional stream power incision model that undergoes a change in the rate of base level fall. We perform over 104 base level fall simulations to explore a wide range of fault slip dynamics and stream power parameters. Our best fit simulations suggest that the Western North Boulder fault started as individual fault segments along the middle to southern regions of Bull Mountain that nucleated around 6.2 to 2.5 Ma, respectively. This was followed by the nucleation of fault segments in the northern region around 1.5 to 0.4 Ma. We recreate the evolution of the Western North Boulder fault to show that through time, these individual segments propagate at the fault tips and link together to span over 40 km, with a maximum slip of 462 m in the central portion of the fault. Fault slip rates range from 0.02 to 0.45 mm/yr along strike and are consistent with estimates for other active faults in the region. We find that the timing of fault initiation coincides well with the migration of the Yellowstone hotspot across the nearby Idaho-Montana border and thus attribute the initiation of extension to the crustal bulge from the migrating hotspot. Overall, we provide the first quantitative constraints on fault initiation and evolution of the Western North Boulder fault, perhaps the farthest north basin in the Northern Basin and Range province that such constraints exist. We show that river profiles are powerful tools for documenting the spatial and temporal patterns of normal fault evolution, especially where other geologic/geodetic methods are limited, proving to be a vital tool for accurate tectonic hazard assessments.

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Calibration of Local Magnitude Scale for Colombia

Bulletin of the Seismological Society of America ◽

10.1785/0120190226 ◽

2020 ◽

Vol 110 (4) ◽

pp. 1971-1981

Author(s):

Camilo Muñoz Lopez ◽

Laura Velasquez ◽

Viviana Dionicio

Keyword(s):

Volcanic Activity ◽

Seismic Data ◽

Correction Function ◽

Local Magnitude ◽

Linear Inversion ◽

Hypocentral Distance ◽

International Networks ◽

Base Level ◽

Attenuation Values ◽

Distance Correction

ABSTRACT New calibration for local magnitude (ML) was performed for Colombia. The territory was divided into five zones using reported attenuation values for different areas of the country and correlating this information with the mapped lithologies, the absence or presence of volcanic activity, and patterns in the hypocentral locations of seismicity. Seismic data from the Colombian National Seismic Network—Colombian Geological Survey (RSNC-SGC) were used to obtain a total of 81,232 peak amplitudes from 22,816 earthquakes recorded between January 2015 and August 2017. This set of data was incorporated into a linear inversion to calculate the distance-correction functions for each zone. A new methodology is proposed for calculating the base level of the distance-correction function or parameter c, using the amplitude values for earthquakes with moment magnitudes (Mw) close to 3 measured at stations at distances close to 100 km. The distance-correction logA0 functions obtained in this study for the five zones are: Zone 1:−logA0=1.245×log(r)+0.0024×r−2.051,Zone 2:−logA0=1.056×log(r)+0.0021×r−1.76,Zone 3:−logA0=1.07×log(r)+0.0013×r−1.531,Zone 4:−logA0=1.241×log(r)+0.0015×r−2.178,Zone 5:−logA0=0.711×log(r)+0.0009×r−0.69, in which r is the hypocentral distance in kilometers. The results of this study are in use in the RSNC-SGC since September 2018. Before using the equations presented here, the values of local magnitude were previously underestimated for the entire Colombian territory. This work allows the calculation of the local magnitude using the largest attenuation changes in addition to decreasing discrepancies with other magnitude types such as Mw and those calculated by international networks.

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Linking source to stratigraphy through sediment transport: The importance of spatially variable climate on the evolution of the Argentine Andes

10.5194/egusphere-egu2020-22349 ◽

2020 ◽

Author(s):

Rebekah Harries ◽

Linda Kirstein ◽

Alex Whittaker ◽

Mikael Attal ◽

Boris Gailleton ◽

...

Keyword(s):

Sediment Transport ◽

Geomorphic Mapping ◽

Mountain Ranges ◽

Base Level ◽

Source Regions ◽

Sediment Deposits ◽

Mountain Front ◽

History Of ◽

River Profiles ◽

Sediment Export

Over geological timescales, we often assume the export of sediment, from mountainous source regions to depositional basins, is relatively instantaneous. As such, stratigraphic units are thought to capture erosional trends in their upstream catchment. The export of sediment from mountain basins, however, is a process heavily modified by sediment transport.Here, we exploit a well-constrained field site in the Argentine Andes to demonstrate how the connectivity between hillslopes and mountain rivers modulates long-term sediment export in post glacial landscapes. We map out erosion trends in upstream catchments by combining an analysis of river profiles with geomorphic mapping of sediment deposits. We then use a comprehensive catalogue of clast lithology data to test to what extent upstream erosion trends are recorded downstream.Despite their proximity to each other, we find adjacent catchments supplying sediment to the Iglesia basin have distinctly different degrees of hillslope-river connectivity, evident from the morphology of terraced and fan deposits within the catchments. Catchments with good hillslope-river channel connectivity also have a higher abundance of clasts sourced from the upper cordillera downstream of their mountain front. We place these observations within the context of a strong precipitation gradient across the cordillera and demonstrate the importance of climate and climate-controlled base-level on the spatial distribution of erosion within mountain catchments and fundamentally, on sediment export.This work has implications for those using gravels to reconstruct the history of mountain ranges. Furthermore, it highlights the need to better constrain the potential for a disproportionate increase in sediment export to populated areas under future climate scenarios

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Deriving thrust fault slip rates from geological modeling: Examples from the Marche coastal and offshore contraction belt, Northern Apennines, Italy

Marine and Petroleum Geology ◽

10.1016/j.marpetgeo.2012.10.008 ◽

2013 ◽

Vol 42 ◽

pp. 122-134 ◽

Cited By ~ 26

Author(s):

Francesco Emanuele Maesano ◽

Giovanni Toscani ◽

Pierfrancesco Burrato ◽

Francesco Mirabella ◽

Chiara D'Ambrogi ◽

...

Keyword(s):

Thrust Fault ◽

Fault Slip ◽

Northern Apennines ◽

Geological Modeling ◽

Slip Rates ◽

Fault Slip Rates

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Quantitative Characterization of Architecture Elements and Their Response To Base-Level Change In A Sandy Braided Fluvial System At A Mountain Front

Journal of Sedimentary Research ◽

10.2110/jsr.2015.82 ◽

2015 ◽

Vol 85 (10) ◽

pp. 1258-1274 ◽

Cited By ~ 7

Author(s):

Shunli Li ◽

Xinghe Yu ◽

Bintao Chen ◽

Shengli Li

Keyword(s):

Grain Size ◽

Middle Jurassic ◽

Large Scale ◽

Small Scale ◽

Fluvial System ◽

Architectural Elements ◽

Datong Basin ◽

Base Level ◽

Mountain Front ◽

Bounding Surfaces

Abstract: The Rockcave Member of the Yungang Formation (Middle Jurassic), in the Datong Basin, China, is a multistory sandstone that is interpreted as a sandy braided fluvial deposit based on grain size, lithofacies, and architectural elements. The depositional setting was the mountain front of the Datong Basin, which was tens of kilometers from the shoreline of a lacustrine basin during the Middle Jurassic. The concept of base level is used to analyze the architectural elements of the braided system obtained from photographic mosaics and high-resolution measurement of six outcrop sections from Yungang Rock Cave. Grain size, lithology, and bounding surfaces together with scale and dimension parameters of the sedimentary structures in various architectural elements were used to quantitatively characterize each group of architectural elements and stratigraphic units. Width/thickness values of trough crossbeds were found to be a fundamental component of the hydrodynamic regimes. During base-level rise the braided fluvial system developed large-scale channel units, bar units, and overbank fills. The relatively high proportion of bar units and overbank fills reflect processes operating during positive accommodation. However, during base-level fall there are a high proportion of small-scale channel units that reflect incision-dominated processes such as channels with low W/T values for trough crossbeds and less common overbank fines.

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Polyphase extensional basins: interplay between tectonics and sedimentation in the Neogene Siena-Radicofani Basin (Northern Apennines, Italy)

International Journal of Earth Sciences ◽

10.1007/s00531-021-02038-4 ◽

2021 ◽

Author(s):

Ivan Martini ◽

Elisa Ambrosetti ◽

Andrea Brogi ◽

Mauro Aldinucci ◽

Frank Zwaan ◽

...

Keyword(s):

Northern Apennines ◽

Sediment Supply ◽

Coarse Grained ◽

Normal Faults ◽

Rift Basins ◽

Base Level ◽

Accommodation Space ◽

Sedimentary Evolution ◽

Half Graben

AbstractRift-basins are the shallow effects of lithosphere-scale extensional processes often producing polyphase faulting. Their sedimentary evolution depends on the mutual interplay between tectonics, climate, and eustasy. Estimating the role of each factor is generally a challenging issue. This paper is focused on the tectono-sedimentary evolution of the Neogene Siena-Radicofani Basin, a polyphase structural depression located in the inner Northern Apennines. Since Miocene, this basin developed after prolonged extensional tectonics, first as a bowl-shaped structural depression, later reorganized into a half-graben structure due to the activation of high-angle normal faults in the Zanclean. At that time the basin contained coeval continental and marine settings controlled by the normal faulting that caused the development of local coarse-grained depositional systems. These were investigated to: (i) discriminate between the influences of tectonics and climate on sedimentation patterns, and (ii) provide detailed time constraints on fault activity. The analysed successions were deposited in an interval between 5.08 and 4.52 Ma, when a climate-induced highstand phase occurred throughout the Mediterranean. However, evidence of local relative sea-level drops is registered in the sedimentary record, often associated with increased accommodation space and sediment supply. Such base-level fluctuations are not connected to climate changes, suggesting that the faults generally control sedimentation along the basin margins.

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Rapid Holocene bedrock canyon incision of Beida River, North Qilian Shan, China

10.5194/esurf-2021-48 ◽

2021 ◽

Author(s):

Yiran Wang ◽

Michael E. Oskin ◽

Youli Li ◽

Huiping Zhang

Keyword(s):

Average Rate ◽

Foreland Basin ◽

Uplift Rate ◽

Field Surveys ◽

Base Level ◽

The North ◽

River Incision ◽

Mountain Front ◽

The Relationship ◽

North Qilian

Abstract. Located at the transition between monsoon and westerly dominated climate systems, major rivers draining the western North Qilian Shan incise deep, narrow canyons into latest Quaternary foreland basin sediments of the Hexi Corridor. Field surveys show that the Beida River incised 125 m at the mountain front over the Late Pleistocene and Holocene at an average rate of 6 m/kyr. We hypothesize that a steep knickzone, with 3 % slope, initiated at the mountain front and has since retreated to its present position, 10 km upstream. Terrace dating results suggest this knickzone formed around the mid-Holocene, over a duration of less than 1.5 kyr, during which incision accelerated to at least 25 m/kyr. These incision rates are much larger than the uplift rate across the North Qilian fault, which suggests a climate-related increase in discharge drove rapid incision over the Holocene and formation of the knickzone. Using the relationship between incision rates and the amount of base level drop, we show the maximum duration of knickzone formation to be 700 yr and the minimum incision rate to be 50 m/kyr. This period of increased river incision is the result of increasing excess discharge, which likely corresponds to a pluvial lake-filling event at the terminus of the Beida River and correlates with a wet period driven by strengthening of the Southeast Asian Monsoon.

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