Development and response of a coupled catchment fan system under changing tectonic and climatic forcing

Densmore, Alexander L.; Allen, Philip A.; Simpson, Guy

doi:10.1029/2006jf000474

Cited by 119 publications

(132 citation statements)

References 56 publications

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“…Erosional base-level falls tend to result in temporary thin fans, and tectonic base-level falls tend to result in prolonged accumulation of thick fans (Bull, 1977). There are strong relationships between active orogenic environments and thick accumulations of young fan deposits (Beaty, 1970;Densmore et al, 2007). On the other hand, continued lack of tectonic uplift will change the depositional environment to an erosional environment where pedimentation or flooding events are the main process operating on the landscape (Bull, 1977;Haug et al, 2010).…”

Section: Geographical Setting Of El'gygytgyn Cratermentioning

confidence: 99%

Depositional dynamics in the El'gygytgyn Crater margin: implications for the 3.6 Ma old sediment archive

Schwamborn¹,

Fedorov²,

Ostanin³

et al. 2012

Clim. Past

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Abstract. The combination of permafrost history and dynamics, lake level changes and the tectonical framework is considered to play a crucial role for sediment delivery to El'gygytgyn Crater Lake, NE Russian Arctic. The purpose of this study is to propose a depositional framework based on analyses of the core strata from the lake margin and historical reconstructions from various studies at the site. A sedimentological program has been conducted using frozen core samples from the 141.5 m long El'gygytgyn 5011-3 permafrost well. The drill site is located in sedimentary permafrost west of the lake that partly fills the El'gygytgyn Crater. The total core sequence is interpreted as strata building up a progradational alluvial fan delta. Four macroscopically distinct sedimentary units are identified. Unit 1 (141.5-117.0 m) is comprised of ice-cemented, matrix-supported sandy gravel and intercalated sandy layers. Sandy layers represent sediments which rained out as particles in the deeper part of the water column under highly energetic conditions. Unit 2 (117.0-24.25 m) is dominated by ice-cemented, matrix-supported sandy gravel with individual gravel layers. Most of the Unit 2 diamicton is understood to result from alluvial wash and subsequent gravitational sliding of coarse-grained (sandy gravel) material on the basin slope. Unit 3 (24.25-8.5 m) has icecemented, matrix-supported sandy gravel that is interrupted by sand beds. These sandy beds are associated with flooding events and represent near-shore sandy shoals. Unit 4 (8.5-0.0 m) is ice-cemented, matrix-supported sandy gravel with varying ice content, mostly higher than below. It consists of slope material and creek fill deposits. The uppermost metre is the active layer (i.e. the top layer of soil with seasonal freeze and thaw) into which modern soil organic matter has been incorporated. The nature of the progradational sediment transport taking place from the western and northern crater margins may be related to the complementary occurrence of frequent turbiditic layers in the central lake basin, as is known from the lake sediment record. Slope processes such as gravitational sliding and sheet flooding occur especially during spring melt and promote mass wasting into the basin. Tectonics are inferred to have initiated the fan accumulation in the first place and possibly the off-centre displacement of the crater lake.

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Section: Geographical Setting Of El'gygytgyn Cratermentioning

confidence: 99%

Depositional dynamics in the El'gygytgyn Crater margin: implications for the 3.6 Ma old sediment archive

Schwamborn¹,

Fedorov²,

Ostanin³

et al. 2012

Clim. Past

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“…2b). These values are chosen because they generate response times within the range of observations from normal fault-bounded sedimentary systems that have responded to changes in slip rate (Densmore et al, 2007;Armitage et al, 2011).…”

Section: Erosion By Sediment Transportmentioning

confidence: 99%

Numerical modelling of landscape and sediment flux response to precipitation rate change

et al. 2018

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Abstract. Laboratory-scale experiments of erosion have demonstrated that landscapes have a natural (or intrinsic) response time to a change in precipitation rate. In the last few decades there has been growth in the development of numerical models that attempt to capture landscape evolution over long timescales. However, there is still an uncertainty regarding the validity of the basic assumptions of mass transport that are made in deriving these models. In this contribution we therefore return to a principal assumption of sediment transport within the mass balance for surface processes; we explore the sensitivity of the classic end-member landscape evolution models and the sediment fluxes they produce to a change in precipitation rates. One end-member model takes the mathematical form of a kinetic wave equation and is known as the stream power model, in which sediment is assumed to be transported immediately out of the model domain. The second end-member model is the transport model and it takes the form of a diffusion equation, assuming that the sediment flux is a function of the water flux and slope. We find that both of these end-member models have a response time that has a proportionality to the precipitation rate that follows a negative power law. However, for the stream power model the exponent on the water flux term must be less than one, and for the transport model the exponent must be greater than one, in order to match the observed concavity of natural systems. This difference in exponent means that the transport model generally responds more rapidly to an increase in precipitation rates, on the order of 10 5 years for post-perturbation sediment fluxes to return to within 50 % of their initial values, for theoretical landscapes with a scale of 100 × 100 km. Additionally from the same starting conditions, the amplitude of the sediment flux perturbation in the transport model is greater, with much larger sensitivity to catchment size. An important finding is that both models respond more quickly to a wetting event than a drying event, and we argue that this asymmetry in response time has significant implications for depositional stratigraphies. Finally, we evaluate the extent to which these constraints on response times and sediment fluxes from simple models help us understand the geological record of landscape response to rapid environmental changes in the past, such as the Paleocene-Eocene thermal maximum (PETM). In the Spanish Pyrenees, for instance, a relatively rapid (10 to 50 kyr) duration of the deposition of gravel is observed for a climatic shift that is thought to be towards increased precipitation rates. We suggest that the rapid response observed is more easily explained through a diffusive transport model because (1) the model has a faster response time, which is consistent with the documented stratigraphic data, (2) there is a high-amplitude spike in sediment flux, and (3) the assumption of instantaneous transport is difficult to justify for the transport of large grain sizes as an alluvi...

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“…In other cases, however, a change in climatic forcing may exert the strongest control on fan slope and morphology. Densmore (2007) found that sediment transport efficiency controls the long profile slope of fans rather than the dominance of debris flow or fluvial activity. One uniting observation is that fans have distinct spatial variation.…”

Section: Alluvial Fansmentioning

confidence: 99%

“…The processes that control fan morphology are complex and include interactions between uplift, subsidence, climate, depositional processes, and lithology (Blair and McPherson, 1994; 6 Densmore et al, 2007). Alluvial fans commonly form in regions of active uplift where normalfaulted footwall blocks form catchments and material is deposited onto subsiding down-thrown hanging wall blocks.…”

Section: Alluvial Fansmentioning

confidence: 99%

Climatic and geomorphic interactions on alluvial fans in the Atacama Desert, Chile

et al. 2010

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Alluvial fan surfaces in the Atacama Desert of northern Chile preserve evidence of recent, precipitation-driven, surface flows. Determining the hydrologic characteristics of these flows is important for understanding the effects of rare yet significant storms in the region. Flow reconstruction, runoff analysis, and comparison with climatological data yield surface activation recurrence intervals of ~1-20 years for three small fans and associated catchments proximal to Iquique and Antofagasta. Relatively short-lived and intense precipitation events (1-3 hour, > 4 mm/hr) are required to mobilize and transport the largest surface grains. Modeled discharges provide minimum constraints on the rates of precipitation that yield surface-forming flows in the hyper-arid region. The results of this study aid in understanding the evolution of various surfaces in the region. In particular, results provide a clear indication of the ability of a particular storm event --i.e., precipitation rate to activate a surface.

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Development and response of a coupled catchment fan system under changing tectonic and climatic forcing

Cited by 119 publications

References 56 publications

Depositional dynamics in the El'gygytgyn Crater margin: implications for the 3.6 Ma old sediment archive

Depositional dynamics in the El'gygytgyn Crater margin: implications for the 3.6 Ma old sediment archive

Numerical modelling of landscape and sediment flux response to precipitation rate change

Climatic and geomorphic interactions on alluvial fans in the Atacama Desert, Chile

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