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

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.

Download Full-text

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

Earth Surface Dynamics ◽

10.5194/esurf-9-771-2021 ◽

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.

Download Full-text

Late Holocene landscape change history related to the Alpine Fault determined from drowned forests in Lake Poerua, Westland, New Zealand

Natural Hazards and Earth System Science ◽

10.5194/nhess-12-2051-2012 ◽

2012 ◽

Vol 12 (6) ◽

pp. 2051-2064 ◽

Cited By ~ 8

Author(s):

R. M. Langridge ◽

R. Basili ◽

L. Basher ◽

A. P. Wells

Keyword(s):

Lake Level ◽

Late Holocene ◽

Alluvial Fan ◽

Time Of Death ◽

Fault Rupture ◽

Radiocarbon Dates ◽

Living Tree ◽

Alpine Fault ◽

History Of ◽

Lowland Forests

Abstract. Lake Poerua is a small, shallow lake that abuts the scarp of the Alpine Fault on the West Coast of New Zealand's South Island. Radiocarbon dates from drowned podocarp trees on the lake floor, a sediment core from a rangefront alluvial fan, and living tree ring ages have been used to deduce the late Holocene history of the lake. Remnant drowned stumps of kahikatea (Dacrycarpus dacrydioides) at 1.7–1.9 m water depth yield a preferred time-of-death age at 1766–1807 AD, while a dryland podocarp and kahikatea stumps at 2.4–2.6 m yield preferred time-of-death ages of ca. 1459–1626 AD. These age ranges are matched to, but offset from, the timings of Alpine Fault rupture events at ca. 1717 AD, and either ca. 1615 or 1430 AD. Alluvial fan detritus dated from a core into the toe of a rangefront alluvial fan, at an equivalent depth to the maximum depth of the modern lake (6.7 m), yields a calibrated age of AD 1223–1413. This age is similar to the timing of an earlier Alpine Fault rupture event at ca. 1230 AD ± 50 yr. Kahikatea trees growing on rangefront fans give ages of up to 270 yr, which is consistent with alluvial fan aggradation following the 1717 AD earthquake. The elevation levels of the lake and fan imply a causal and chronological link between lake-level rise and Alpine Fault rupture. The results of this study suggest that the growth of large, coalescing alluvial fans (Dry and Evans Creek fans) originating from landslides within the rangefront of the Alpine Fault and the rise in the level of Lake Poerua may occur within a decade or so of large Alpine Fault earthquakes that rupture adjacent to this area. These rises have in turn drowned lowland forests that fringed the lake. Radiocarbon chronologies built using OxCal show that a series of massive landscape changes beginning with fault rupture, followed by landsliding, fan sedimentation and lake expansion. However, drowned Kahikatea trees may be poor candidates for intimately dating these events, as they may be able to tolerate water for several decades after metre-scale lake level rises have occurred.

Download Full-text

Fluvial Sedimentology and Paleoecology of Holocene Alluvial Deposits, Red River, Manitoba

Géographie physique et Quaternaire ◽

10.7202/032948ar ◽

2007 ◽

Vol 47 (2) ◽

pp. 193-210 ◽

Cited By ~ 8

Author(s):

Erik Nielsen ◽

W. Brian McKillop ◽

Glen G. Conley

Keyword(s):

Late Holocene ◽

Red River ◽

Present Position ◽

Lake Agassiz ◽

Alluvial Deposits ◽

Radiocarbon Dates ◽

The North ◽

Mollusc Species ◽

History Of ◽

Overbank Sedimentation

ABSTRACT Stratigraphie and paleoecological analyses at five sections, together with age determinations based on 19 previously published and 21 new radiocarbon dates, provide a detailed late Holocene history of the Red River, Manitoba. Ecological information, such as age frequency analysis, relative abundance, diversity and association of species was drawn from 19 mollusc species. These data indicate that the Red and Assiniboine rivers cut the valleys they occupy today within a thousand years of the regression of Lake Agassiz. In the south, up to 14 m of alluvium has accumulated during the last 7000 years. A decrease in the sedimentation rate at 1400 BP is coincident with the shift in the position of the Assiniboine from the valley of the La Salle River to its present position. Overbank sedimentation did not start in the northern part of the area until ca. 5200 BP. Initial rapid sedimentation rates in this area are attributed to increased precipitation and a brief eastward excursion of the Assiniboine River into the Red. In spite of increased precipitation, flood frequencies remained low in the north until 1400 BP. Increased overbank sedimentation after 1400 BP is attributed to the northward shift in the position ot the Assiniboine.

Download Full-text

Late-Holocene coastal depositional environments and climate changes in the Gulf of Corinth, Greece

The Holocene ◽

10.1177/0959683619875793 ◽

2019 ◽

Vol 30 (1) ◽

pp. 77-89 ◽

Cited By ~ 4

Author(s):

Alexandros Emmanouilidis ◽

Ingmar Unkel ◽

Maria Triantaphyllou ◽

Pavlos Avramidis

Keyword(s):

Late Holocene ◽

Eastern Mediterranean ◽

Eastern Mediterranean Region ◽

Depositional Environments ◽

Tectonic Activity ◽

Radiocarbon Dates ◽

X Ray ◽

Salt Pond ◽

Gulf Of Corinth ◽

Holocene Period

Multidisciplinary studies in coastal systems of the eastern Mediterranean region have proven to be excellent tools in understanding paleoenvironmental, paleoecological, and paleoclimatic changes that took place during the Holocene period, and how these changes interacted with urban development and growth. This paper presents sedimentological, high-resolution x-ray fluorescence (XRF scanning), micropaleontological, and x-ray diffraction (XRD) data from three shallow sediment cores that were retrieved from Aliki (ancient Siphai or Tipha) salt pond. The study area is located in a unique, highly tectonic geographical region, at the northeast part of the Gulf of Corinth in Greece. Beachrock deposits that form a barrier between the salt pond and the marine environment seem to play an important role in the evolution of the area. The chronological framework was set at around 3100 cal. BP by four 14C radiocarbon dates, and the evolutionary model that was established indicates four different changes taking place during this period at the study area. From around 3100 to 1600 cal. BP, a transition from a closed to an open lagoonal environment was identified, interrupted by a fluvial terrestrial deposit at around 2500 cal. BP. A shift toward a closed lagoonal system at around 1600 cal. BP and the establishment of a salt pond environment seem to correlate with tectonic activity. The study provides important information about the evolution of coastal landscape in such a tectonic active region and points the interaction between regional human activity and climatic changes during the late-Holocene period.

Download Full-text

Optical dating of alluvial deposits at the orogenic front of the andean precordillera (Mendoza, Argentina)

Geochronometria ◽

10.2478/s13386-011-0050-5 ◽

2012 ◽

Vol 39 (1) ◽

pp. 62-75 ◽

Cited By ~ 7

Author(s):

Silke Schmidt ◽

Sumiko Tsukamoto ◽

Eric Salomon ◽

Manfred Frechen ◽

Ralf Hetzel

Keyword(s):

Debris Flow ◽

Alluvial Fan ◽

Osl Dating ◽

Tectonic Activity ◽

Humid Climate ◽

Alluvial Deposits ◽

Three Samples ◽

Minimum Age ◽

Floodplain Deposits ◽

Depositional Age

AbstractWell constrained numerical ages of alluvial fan sediments are key to understanding the chronology of alluvial episodes and tectonic activity at the front of the Andean Precordillera. We tested the application of radiocarbon and optically stimulated luminescence (OSL) dating in the distal part of an alluvial fan five kilometers north of Mendoza. For OSL dating a large number of aliquots (n > 70) — each composed of ∼50 quartz grains — were measured in order to obtain reliable burial ages despite scattered dose distributions. Owing to a feldspar contamination in all samples, an infrared stimulation was inserted before each OSL measurement, which reduced the feldspar OSL signal successfully. By using the minimum age model we obtained stratigraphically consistent burial ages of alluvial deposits in a depth profile. The uppermost ∼1 m of sediment is composed of debris flow deposits buried 770±76 years ago. Three plant remnants used for radiocarbon dating from the same layer, however, yielded ages younger than 350 years, which are interpreted to underestimate the depositional age. Underneath the debris flow, a major unconformity cuts a series of distal alluvial fan sediments with interstratified floodplain deposits, which are composed of sandy and calciterich silt layers, respectively. Three samples from this unit which were distributed over one meter of sediment thickness yielded statistically concordant OSL ages of 12.3±1.2 ka, 12.3±1.2 ka, and 11.7±1.1 ka. The deposition of these sediments during the latest Pleistocene coincides with a phase of cool and humid climate, which occurred before the alluvial fan propagated farther into the foreland. The overlying debris flow sediments are associated with alluvial fan incision during the arid Late Holocene.

Download Full-text

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

Quaternary Research ◽

10.1016/j.yqres.2010.01.004 ◽

2010 ◽

Vol 73 (3) ◽

pp. 425-438 ◽

Cited By ~ 28

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.

Download Full-text

Using Single-Forcing GCM Simulations to Reconstruct and Interpret Quaternary Climate Change

Journal of Climate ◽

10.1175/jcli-d-15-0329.1 ◽

2015 ◽

Vol 28 (24) ◽

pp. 9746-9767 ◽

Cited By ~ 11

Author(s):

Michael P. Erb ◽

Charles S. Jackson ◽

Anthony J. Broccoli

Keyword(s):

Climate Change ◽

Greenhouse Gases ◽

Ice Sheets ◽

Meridional Overturning Circulation ◽

Climate Response ◽

Climate Variations ◽

Past Climate ◽

Quaternary Climate ◽

Temperature Records

Abstract The long-term climate variations of the Quaternary were primarily influenced by concurrent changes in Earth’s orbit, greenhouse gases, and ice sheets. However, because climate changes over the coming century will largely be driven by changes in greenhouse gases alone, it is important to better understand the separate contributions of each of these forcings in the past. To investigate this, idealized equilibrium simulations are conducted in which the climate is driven by separate changes in obliquity, precession, CO2, and ice sheets. To test the linearity of past climate change, anomalies from these single-forcing experiments are scaled and summed to compute linear reconstructions of past climate, which are then compared to mid-Holocene and last glacial maximum (LGM) snapshot simulations, where all forcings are applied together, as well as proxy climate records. This comparison shows that much of the climate response may be approximated as a linear response to forcings, while some features, such as modeled changes in sea ice and Atlantic meridional overturning circulation (AMOC), appear to be heavily influenced by nonlinearities. In regions where the linear reconstructions replicate the full-forcing experiments well, this analysis can help identify how each forcing contributes to the climate response. Monsoons at the mid-Holocene respond strongly to precession, while LGM monsoons are heavily influenced by the altered greenhouse gases and ice sheets. Contrary to previous studies, ice sheets produce pronounced tropical cooling at the LGM. Compared to proxy temperature records, the linear reconstructions replicate long-term changes well and also show which climate variations are not easily explained as direct responses to long-term forcings.

Download Full-text

37,000 Years and More in Tropical Australia: Investigating Long-Term Archaeological Trends in Cape York Peninsula

Proceedings of the Prehistoric Society ◽

10.1017/s0079497x00002358 ◽

1997 ◽

Vol 63 ◽

pp. 1-23 ◽

Cited By ~ 18

Author(s):

Bruno David ◽

Harry Lourandos

Keyword(s):

Land Use ◽

Late Holocene ◽

Temporal Trends ◽

Temporal Distribution ◽

Radiocarbon Dates ◽

Demographic Processes ◽

Changing Patterns ◽

Cape York ◽

Historical Antecedents

The prehistory of Cape York Peninsula, in tropical northern Australia, has been more intensively investigated than that of most other parts of the continent. As a result, a considerable database now exists by which long-term archaeological trends can be evaluated. In this paper we investigate temporal trends in occupational intensities and patterns of land use during the last 37,000 years by employing: 1, the temporal distribution of all radiocarbon dates obtained for the region; 2, the numbers of sites occupied through time; and 3, rates of establishment of new sites during the course of prehistory. These archaeological trends are then compared with the palaeo-environmental record of the region to determine its potential influence on the trends. We conclude that an initial, long period of regional occupation occurred (c. 37,000–4000 BP) when cultural trends varied in tandem with gross environmental fluctuations. This was followed by a late Holocene period (post 4000 BP) when cultural trajectories diverged significantly from environmental trends. This suggests that more complex Aboriginal demographic processes were set in train during the late Holocene, associated with social structures that were more dynamic than previously. We suggest that while changing patterns of land use may be apparent, their understanding requires an enquiry into periods of emergence — that is, their immediate historical antecedents. These results have broader implications for our understanding of Australian prehistory and the prehistory of other hunter-gatherer societies.

Download Full-text

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

Spanish Journal of Soil Science ◽

10.3232/sjss.2018.v8.n2.09 ◽

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.

Download Full-text

Milankovitch, the father of paleoclimate modeling

Climate of the Past ◽

10.5194/cp-17-1727-2021 ◽

2021 ◽

Vol 17 (4) ◽

pp. 1727-1733 ◽

Cited By ~ 1

Author(s):

Andre Berger

Keyword(s):

Mathematical Model ◽

Solar Radiation ◽

Climate Variations ◽

Paleoclimate Modeling ◽

Quaternary Climate ◽

History Of ◽

Astronomical Theory ◽

Winter Insolation ◽

Long Term Variations

Abstract. The history of the long-term variations in the astronomical elements used in paleoclimate research shows that, contrary to what might be thought, Milutin Milankovitch is not the father of the astronomical theory but he is definitely the father of paleoclimate modeling. He did not calculate these long-term variations himself but used them extensively for calculating the “secular march” of incoming solar radiation. He advanced our understanding of Quaternary climate variations by two important and original contributions fully described in his Canon of insolation. These are the definition and use of caloric seasons and the concept of the “mathematical climate”. How his mathematical model allowed him to give the caloric summer and winter insolation a climatological meaning is illustrated.

Download Full-text