Timing and distribution of alluvial fan sedimentation in response to strengthening of late Holocene ENSO variability in the Sonoran Desert, Southwestern Arizona, USA

2010 ◽  
Vol 73 (3) ◽  
pp. 425-438 ◽  
Author(s):  
Steven N. Bacon ◽  
Eric V. McDonald ◽  
Todd G. Caldwell ◽  
Graham K. Dalldorf
Keyword(s):  
Sonoran Desert ◽  
Late Holocene ◽  
Southern Oscillation ◽  
Climatic Variability ◽  
Alluvial Plain ◽  
Alluvial Fan ◽  
Alluvial Deposits ◽  
Geomorphic Mapping ◽  
Precipitation Record ◽  
Precipitation Records

The integration of geomorphic mapping, soil stratigraphy, and radiocarbon dating of alluvial deposits offers insight to the timing, magnitude, and paleoclimatic context of Holocene fan sedimentation near Yuma, Arizona. Mapping of 3400 km2 indicates about 10% of the area aggraded in the late Holocene and formed regionally extensive alluvial fan and alluvial plain cut-and-fill terraces. Fan deposits have weakly developed gravelly soils and yielded a date of 3200–2950 cal yr BP from carbonized wood. Alluvial plain deposits have weakly developed buried sandy soils and provided a date of 2460–2300 cal yr BP from a terrestrial snail shell. Precipitation records were analyzed to form historical analogues to the late Holocene aggradation and to consider the role of climatic variability and extreme hydrologic events as drivers of the sedimentation. The historical precipitation record indicates numerous above-average events correlated to the Southern Oscillation Index (SOI) in the region, but lacks any significant reactivation of alluvial fan surfaces. The timing of aggradation from 3200 to 2300 cal yr BP correlates well with other paleoclimatic proxy records in the southwestern U.S. and eastern Pacific region, which indicate an intensification of the El Niño-Southern Oscillation (ENSO) climatic pattern and rapid climate change during this period.

Holocene landscape evolution and geoarcheology of low-order streams in the Rio Grande basin, San Juan Mountains, Colorado, USA

2014 ◽  
Vol 82 (2) ◽  
pp. 331-341 ◽  
Author(s):  
Daniel P. Carver ◽  
Jared M. Beeton
Keyword(s):  
Landscape Evolution ◽  
Research Area ◽  
Alluvial Fan ◽  
San Juan ◽  
Drainage Basins ◽  
Alluvial Deposits ◽  
Geomorphic Mapping ◽  
San Juan Mountains ◽  
Rio Grande Basin ◽  
Alluvial Terraces

AbstractThis geoarcheological study investigates soil stratigraphy and geochronology of alluvial deposits to determine Holocene landscape evolution within the Hot Creek, La Jara Creek, and Alamosa River drainage basins in the San Juan Mountains of Colorado. Geomorphic mapping and radiocarbon dating indicate synchronicity in patterns of erosion, deposition, and stability between drainage basins. In all three basins, the maximum age of mapped alluvial terraces and fans is ~ 3300 cal yr BP. A depositional period seen at both Hot Creek and the Alamosa River begins ~ 3300 to 3200 cal yr BP. Based on soil development, short periods of stability followed by alluvial fan aggradation occur in the Alamosa River basin ~ 2200 cal yr BP. A period of landscape stability at Hot Creek before ~ 1100 cal yr BP is followed by a period of rapid aggradation within all three drainages between ~ 1100 and 850 cal yr BP. A final aggradation event occurred between ~ 630 and 520 cal yr BP at La Jara Creek. These patterns of landscape evolution over the past ~ 3300 yr provide the framework for an archeological model that predicts the potential for buried and surficial cultural materials in the research area.

scholarly journals Stochastic alluvial fan and terrace formation triggered by a high-magnitude Holocene landslide in the Klados Gorge, Crete

2021 ◽  
Author(s):  
Elena T. Bruni ◽  
Richard F. Ott ◽  
Vincenzo Picotti ◽  
Negar Haghipour ◽  
Karl W. Wegmann ◽  
...  
Keyword(s):  
Late Holocene ◽  
Alluvial Fan ◽  
Tectonic Activity ◽  
Climate Variations ◽  
Alluvial Deposits ◽  
Small Catchment ◽  
Radiocarbon Dates ◽  
Quaternary Climate ◽  
Stochastic Events

Abstract. Alluvial fan and terrace formation is traditionally interpreted as related to Quaternary climate oscillations under the backdrop of slow and steady tectonic activity. However, several recent studies challenge this conventional wisdom, showing that such landforms can evolve rapidly as a geomorphic system responds to catastrophic and stochastic events, like large magnitude mass-wasting. Here, we contribute to this topic through a detailed field and geochronological investigation of alluvial sequences in the Klados catchment in southwestern Crete, Greece. The Klados River catchment is characterised by well-preserved, alluvial terraces and a set of fans at the river mouth, which do not seem to fit the sediment capacity of a small catchment with a drainage area of ~ 11.5 km2. Previous studies interpreted the formation of the deposits and their development to be of Pleistocene age and controlled by climate variations and the region's long-term tectonic activity. We find that the > 20 m thick intermediate fan buries a paleoshoreline uplifted in AD 365 placing the depositional age of this unit firmly into the Late Holocene. This is supported by seven new radiocarbon dates that infer mid to late Holocene ages for the entire fan and terrace sequence. As sediment source, we identify a landslide scar at the head of the catchment. We document landslide deposits 100 m above the modern stream and utilise landslide runout modelling to reconstruct landslide volumes and validate our hypothesis. We find that a landslide volume of 0.0908 km2 matches the observed distribution of landslide deposits and the landslide scar dimensions. We hypothesise that subsequent aggradation and incision cycles of the alluvial deposits are not linked to long-term tectonic uplift and climate variations but rather stochastic events such as mobilisation of sediment in large earthquakes, storm events, or blockage in the valley's narrow reaches. The Klados case study represents a model-environment for how stochastically-driven events can mimic climate-induced sedimentary archives, and how catchments can become ultrasensitive to external perturbations after catastrophic events.

scholarly journals Stochastic alluvial fan and terrace formation triggered by a high-magnitude Holocene landslide in the Klados Gorge, Crete

2021 ◽  
Vol 9 (4) ◽  
pp. 771-793
Author(s):  
Elena T. Bruni ◽  
Richard F. Ott ◽  
Vincenzo Picotti ◽  
Negar Haghipour ◽  
Karl W. Wegmann ◽  
...  
Keyword(s):  
Late Holocene ◽  
Alluvial Fan ◽  
Tectonic Activity ◽  
System Response ◽  
Alluvial Deposits ◽  
Radiocarbon Dates ◽  
High Magnitude ◽  
Stochastic Events ◽  
Landslide Deposit

Abstract. Alluvial fan and terrace formation is traditionally interpreted as a fluvial system response to Quaternary climate oscillations under the backdrop of slow and steady tectonic activity. However, several recent studies challenge this conventional wisdom, showing that such landforms can evolve rapidly as a geomorphic system responds to catastrophic and stochastic events, like large-magnitude mass wasting. Here, we contribute to this topic through a detailed field, geochronological, and numerical modelling investigation of thick (>50 m) alluvial sequences in the Klados catchment in southwestern Crete, Greece. The Klados River catchment lies in a Mediterranean climate, is largely floored by carbonate bedrock, and is characterised by well-preserved alluvial terraces and inset fans at the river mouth that exceed the volumes of alluvial deposits in neighbouring catchments of similar size. Previous studies interpreted the genesis and evolution of these deposits to result from a combination of Pleistocene sea-level variation and the region's long-term tectonic activity. We show that the >20 m thick lower fan unit, previously thought to be late Pleistocene in age, unconformably buries a paleoshoreline uplifted in the first centuries CE, placing the depositional age of this unit firmly in the late Holocene. The depositional timing is supported by seven new radiocarbon dates that indicate middle to late Holocene ages for the entire fan and terrace sequence. Furthermore, we report new evidence of a previously unidentified valley-filling landslide deposit that is locally 100 m above the modern stream elevation, and based on cross-cutting relationships, it predates the alluvial sequence. Observations indicate the highly erodible landslide deposit as the source of the alluvial fill sediment. We identify the likely landslide detachment area as a large rockfall scar at the steepened head of the catchment. A landslide volume of 9.08×107 m3 is estimated based on volume reconstructions of the mapped landslide deposit and the inferred scar location. We utilise landslide runout modelling to validate the hypothesis that a high-magnitude rockfall would pulverise and send material downstream, filling the valley up to ∼100 m. This partial liquefaction is required for the rockfall to form a landslide body of the extent observed in the valley and is consistent with the sedimentological characteristics of the landslide deposit. Based on the new age control and the identification of the landslide deposit, we hypothesise that the rapid post-landslide aggradation and incision cycles of the alluvial deposits are not linked to long-term tectonic uplift or climate variations but rather stochastic events such as mobilisation of sediment in large earthquakes, storm events, or ephemeral blockage in the valley's narrow reaches. The Klados case study represents a model environment for how stochastically driven events can mimic climate-induced sedimentary archives and lead to deposition of thick alluvial sequences within hundreds to thousands of years, and it illustrates the ultrasensitivity of mountainous catchments to external perturbations after catastrophic events.

scholarly journals Pedosedimentary records of Holocene paleoenvironments in a dryland alluvial fan system in Sonora, NW-Mexico

2018 ◽  
Vol 8 ◽  
Author(s):  
Georgina Ibarra Arzave ◽  
Elizabeth Solleiro-Rebolledo ◽  
Emmanuel Ayala ◽  
Héctor Cabadas ◽  
Rafael López-Martínez
Keyword(s):  
Late Holocene ◽  
Archaeological Site ◽  
Alluvial Fan ◽  
Alluvial Deposits ◽  
Marine Isotopic Stage ◽  
Braided Channel ◽  
Terminal Pleistocene ◽  
Landscape Units ◽  
San Rafael ◽  
Micromorphological Analysis

In this work we present a detailed micromorphological analysis of a sequence of palaeosols and sedimentary units at La Playa archaeological site. This sequence is from the Late Pleistocene (Marine Isotopic Stage 2) to the Late Holocene. Complementing the micromorphological study, a geomorphological analysis is provided, in order to establish the origin of the landscape units. The results show that according to the geomorphology, La Playa constitutes an alluvial fan, formed by a complex, braided channel. The older unit, the San Rafael Palaeosol (SRP) is the most developed and has a set of features associated with the changing paleoenvironmental conditions such as weathering of the primary minerals, clay illuviation (evidencing humid conditions of the Terminal Pleistocene), pedogenic carbonate accumulation in the A horizon (related to dry environments of Altithermal). The SRP is buried by fluvial sediments, which include different facies interpreted as: floodplain, sandbars, and channels. These sedimentation events are associated with the end of the Altithermal period and evidence more active geomorphic processes, probably due to strong storms causing flooding and the migration of the main tributary. Above the sedimentary unit, the Boquillas Palaeosol (BOP), formed during the Late Holocene, is derived from fluvial-alluvial deposits causing a syn-sedimentary soil, with a more incipient development as indicated by micromorphological features.

scholarly journals Late Holocene intensification of the westerly winds at the subantarctic Auckland Islands (51° S), New Zealand

2017 ◽  
Author(s):  
Imogen M. Browne ◽  
Christopher M. Moy ◽  
Christina R. Riesselman ◽  
Helen L. Neil ◽  
Lorelei G. Curtin ◽  
...  
Keyword(s):  
New Zealand ◽  
Late Holocene ◽  
Drainage Basin ◽  
Southern Oscillation ◽  
Southern Annular Mode ◽  
Ice Age ◽  
The Pacific ◽  
Westerly Winds ◽  
Latitudinal Position ◽  
Paleoclimate Records

Abstract. The Southern Hemisphere westerly winds (SHWW) play a major role in controlling wind-driven upwelling of Circumpolar Deep Water (CDW) and outgassing of CO2 in the Southern Ocean on interannual to glacial-interglacial timescales. Despite their significance in the global carbon cycle, our understanding of millennial-scale changes in the strength and latitudinal position of the westerlies during the Holocene (especially since 5000 yr BP) is limited by a scarcity of paleoclimate records from comparable latitudes. Here, we reconstruct middle to late Holocene variability in the SHWW using a fjord sediment core collected from the subantarctic Auckland Islands (51° S, 166° E), located in the modern centre of the westerly wind belt. Drainage basin response to variability in the strength of the SHWW at this latitude is reconstructed from downcore variations in magnetic susceptibility (MS) and bulk organic δ13C and atomic C/N, which monitor influxes of lithogenous and terrestrial vs marine organic matter, respectively. The hydrographic response to SHWW variability is reconstructed using benthic foraminifer δ18O and δ13C, both of which are influenced by the isotopic composition of shelf water masses entering the fjord. Using these data, we provide marine and terrestrial-based evidence for increased wind strength from ~ 1600–900 yr BP at subantarctic latitudes that is broadly consistent with previous studies of vegetation response to climate at the Auckland Islands. Comparison with a SHWW reconstruction using similar proxies from Fiordland suggests a northward migration of the SHWW over New Zealand at the beginning of the Little Ice Age (LIA). Comparison with paleoclimate and paleoceanographic records from southern South America and the western Antarctic Peninsula indicates a late Holocene strengthening of the SHWW after ~ 1600 yr BP that appears to be broadly symmetrical across the Pacific basin, although our reconstruction suggests that this symmetry breaks down during the LIA. Contemporaneous increases in SHWW at localities either side of the Pacific in the late Holocene are likely controlled atmospheric teleconnections between the low and high latitudes and by variability in the Southern Annular Mode (SAM) and El Niño Southern Oscillation (ENSO).

scholarly journals Deflation's soil and technogenic pollutants of the near-highway zones of road Lviv–Krakovets

2017 ◽  
pp. 370-381
Author(s):  
Yuliia Chykailo ◽  
Ivan Voloshyn
Keyword(s):  
Chemical Elements ◽  
Alluvial Plain ◽  
Soil Profiles ◽  
Buried Soils ◽  
Beech Forests ◽  
Alluvial Deposits ◽  
Different Depths ◽  
The Village ◽  
Humus Horizons ◽  
Near Highway

In the article is analyzed the soils’ properties in near-highway road strips of M-10 Lviv- Krakovets with width up to 150 m. Within the near-road strips of the highway, have been established 12 experimental polygons under forest, meadow vegetation and agricultural lands. On each polygons from soils profile samples are selected the most common soils: sod-podzolic, formed on fl uvio-glacial and gray-forest soils formed onloess loam. Completed description of soil profiles to depth of 0-100 cm. Part of experimental soils are formed under hornbeam-beech forests (11, 12 polygons) and oak-hornbeam-pine (4, 6, 7, 8 polygons). The researches revealed that in soil profiles at different depths are lie buried in eolian forms of relief (dunes) with different steepness of slopes. The steepness of the walls of the superficial layers of the dunes varies from 10 to 30°. In the research profiles of near-highway soils on the surface of the dunes, fi nd presence of progumed fragments of strips up wide to 2–3 cm. On the territory of the Nadsyanska moraine-zandrova alluvial plain at a distance of 50 m from the roadway (polygon 2, in the valley of the river Shklo, where the grassland vegetation is predominant, the turfy shallow gluten sandy soils are formed on alluvial deposits) discovered two low-power buried humus horizons who inherited a deflationary relief. Their steepness on the surface of the dunes is about 10 °. In polygon 3, the incision is laid in the micro threshold of the ancient relief, where the vegetation is represented by a spruce forest with oak impurities. In the profile of sod-hidden-podzolic sandy soil, on the surface of buried dunes which have steep walls 10-20°, are observed a humus layers . In the polygon 12, which is laid in the southwestern spurs of Roztochya 1,5 km north of the village of Birky in the hornbeam forest, steepness of the walls superficial layers of dunes of western exposition ranges from 10 to 12°. Soil is a clear-gray forest-loamy on loess loamy. In the soil profi les have been identified the following chemical elements: Pb, Zn, Co, Cu, Ni, Mo, Cr, Mn, V, Ba, Sr, Zr, Fe, Ti, Sn. The researches have established that in the territory of the Nadsyanska moraine-zandrovu alluvial plain, and in the southwestern spurs of Roztochchya, widespread buried dune relief. Based on our research, we propose to consider the issue of the allocation of types (subtypes) in soil legends, to investigate the defilations and inter deflation periods of their formation. Key worlds: near-roads strips, soil profile, deflation forms, buried soils, fragments of humus layers.

Paleoearthquakes on the Húsavík-Flatey Fault in northern Iceland: Where are the large earthquakes?

2021 ◽  
Author(s):  
Remi Matrau ◽  
Yann Klinger ◽  
Jonathan Harrington ◽  
Ulas Avsar ◽  
Esther R. Gudmundsdottir ◽  
...  
Keyword(s):  
Slip Rate ◽  
Late Glacial ◽  
Fault Scarp ◽  
Alluvial Fan ◽  
Tectonic Deformation ◽  
Birch Wood ◽  
Alluvial Deposits ◽  
Slip Rates ◽  
Tephra Layers ◽  
Large Earthquakes

<p>Paleoseismology is key to study earthquake recurrence and fault slip rates during the Late Pleistocene-Holocene. The Húsavík-Flatey Fault (HFF) in northern Iceland is a 100 km-long right-lateral transform fault connecting the onshore Northern Volcanic Zone to the offshore Kolbeinsey Ridge and accommodating, together with the Grímsey Oblique Rift (GOR), ~18 mm/yr of relative motion between the Eurasian and North American plates. Significant earthquakes occurred on the HFF in 1755, 1838 and 1872 with estimated magnitudes of 6.5-7. However, historical information on past earthquakes prior to 1755 is very limited in both timing and size.</p><p>We excavated five trenches in a small basin (Vestari Krubbsskál) located 5.5 km southeast of the town of Húsavík and at 300 m.a.s.l. and one trench in an alluvial fan (Traðargerði) located 0.5 km north of Húsavík and at 50 m.a.s.l. In a cold and wet environment, such as in coastal parts of Iceland, one has to take into account periglacial processes affecting the topsoil to discriminate tectonic from non-tectonic deformation. We used tephra layers in the Vestari Krubbsskál and Traðargerði trenches as well as birch wood samples in Traðargerði to constrain the timing of past earthquakes. Tephra layers Hekla-3 (2971 BP) and Hekla-4 (4331±20 BP) are visible in the top half of all the trenches. In addition, a few younger tephra layers are visible in the top part of the trenches. In Traðargerði several dark layers rich in organic matter are found, including birch wood-rich layers from the Earlier Birch Period (9000-7000 BP) and the Later Birch Period (5000-2500 BP). In Vestari Krubbsskál the lower halves of the trenches display mostly lacustrine deposits whereas in Traðargerði the lower half of the trench shows alluvial deposits overlaying coarser deposits (gravels/pebbles) most likely of late-glacial or early post-glacial origins. In addition, early Holocene tephra layers are observed in some of the trenches at both sites and may correspond to Askja-S (10800 BP), Saksunarvatn (10300 BP) and Vedde (12100 BP). These observations provide good age constraints and suggest that both the Vestari Krubbsskál and Traðargerði trenches cover the entire Holocene.</p><p>Trenches at both sites show significant normal deformation in addition to strike-slip, well correlated with their larger scale topographies (pull-apart basin in Vestari Krubbsskál and 45 m-high fault scarp in Traðargerði). We mapped layers, cracks and faults on all trench walls to build a catalogue of Holocene earthquakes. We identified events based on the upward terminations of the cracks and retrodeformation. Our results yield fewer major earthquakes than expected, suggesting that large earthquakes (around magnitude 7) are probably rare and the more typical HFF earthquakes of magnitude 6-6.5 likely produce limited topsoil deformation.[yk1]  Our interpretation also suggests that the Holocene slip rate [yk2] for the fault section we are studying may be slower than the estimated geodetic slip rate (6 to 9 mm/yr)[yk3]  for the entire onshore HFF, although secondary onshore sub-parallel fault strands could accommodate part of the deformation.</p>

Monitoring Agricultural Drought Using El Niño and Southern Oscillation Data

2005 ◽  
Author(s):  
Lino Naranjo Díaz
Keyword(s):  
El Niño ◽  
El Nino ◽  
Southern Oscillation ◽  
Climatic Variability ◽  
Past Century ◽  
Climatic Data ◽  
Weather Patterns ◽  
El Niño Events ◽  
Ring Analysis ◽  
El Nino Events

Almost all the studies performed during the past century have shown that drought is not the result of a single cause. Instead, it is the result of many factors varying in nature and scales. For this reason, researchers have been focusing their studies on the components of the climate system to explain a link between patterns (regional and global) of climatic variability and drought. Some drought patterns tend to recur frequently, particularly in the tropics. One such pattern is the El Niño and Southern Oscillation (ENSO). This chapter explains the main characteristics of the ENSO and its data forms, and how this phenomenon is related to the occurrence of drought in the world regions. Originally, the name El Niño was coined in the late 1800s by fishermen along the coast of Peru to refer to a seasonal invasion of south-flowing warm currents of the ocean that displaced the north-flowing cold currents in which they normally fished. The invasion of warm water disrupts both the marine food chain and the economies of coastal communities that are based on fishing and related industries. Because the phenomenon peaks around the Christmas season, the fishermen who first observed it named it “El Niño” (“the Christ Child”). In recent decades, scientists have recognized that El Niño is linked with other shifts in global weather patterns (Bjerknes, 1969; Wyrtki, 1975; Alexander, 1992; Trenberth, 1995; Nicholson and Kim, 1997). The recurring period of El Niño varies from two to seven years. The intensity and duration of the event vary too and are hard to predict. Typically, the duration of El Niño ranges from 14 to 22 months, but it can also be much longer or shorter. El Niño often begins early in the year and peaks in the following boreal winter. Although most El Niño events have many features in common, no two events are exactly the same. The presence of El Niño events during historical periods can be detected using climatic data interpreted from the tree ring analysis, sediment or ice cores, coral reef samples, and even historical accounts from early settlers.

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