New seismic evidence of the Messinian paleomorphology beneath Lake Maggiore area (Italy)

Cazzini, Ferdinando Franco; Amadori, Chiara; Bosino, Alberto; Fantoni, Roberto

doi:10.3301/ijg.2019.26

Cited by 10 publications

(17 citation statements)

References 21 publications

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“…This is generally in good agreement with observations in other perialpine lakes north of the Alps (e.g., Finckh et al, 1984;Preusser et al, 2010;Fabbri et al, 2018). While the Southern Alpine deep incision (Finckh, 1978) may be caused either by subglacial activity (Winterberg et al, 2020) or by the Messinian drawdown of base level (e.g., Cazzini et al, 2020), overdeepenings north of the Alps are primarily attributed to a glacial origin (Preusser et al, 2010). During the Last Glacial Maximum (LGM), the Rhine Glacier's ice elevation above the Lake Constance area was at ∼1,000 m a.s.l (Bini et al, 2009), indicating an ice thickness of ∼1,500 m. During the Quaternary, several glacial advances coupled with the erosive power in the subglacial domain created overdeepenings and shaped the perialpine realm (Preusser et al, 2010;Reber and Schlunegger, 2016;Magrani et al, 2020).…”

Section: Bedrock Morphology and Overdeepeningsupporting

confidence: 87%

Active Faulting in Lake Constance (Austria, Germany, Switzerland) Unraveled by Multi-Vintage Reflection Seismic Data

et al. 2021

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Probabilistic seismic hazard assessments are primarily based on instrumentally recorded and historically documented earthquakes. For the northern part of the European Alpine Arc, slow crustal deformation results in low earthquake recurrence rates and brings up the necessity to extend our perspective beyond the existing earthquake catalog. The overdeepened basin of Lake Constance (Austria, Germany, and Switzerland), located within the North-Alpine Molasse Basin, is investigated as an ideal (neo-) tectonic archive. The lake is surrounded by major tectonic structures and constrained via the North Alpine Front in the South, the Jura fold-and-thrust belt in the West, and the Hegau-Lake Constance Graben System in the North. Several fault zones reach Lake Constance such as the St. Gallen Fault Zone, a reactivated basement-rooted normal fault, active during several phases from the Permo-Carboniferous to the Mesozoic. To extend the catalog of potentially active fault zones, we compiled an extensive 445 km of multi-channel reflection seismic data in 2017, complementing a moderate-size GI-airgun survey from 2016. The two datasets reveal the complete overdeepened Quaternary trough and its sedimentary infill and the upper part of the Miocene Molasse bedrock. They additionally complement existing seismic vintages that investigated the mass-transport deposit chronology and Mesozoic fault structures. The compilation of 2D seismic data allowed investigating the seismic stratigraphy of the Quaternary infill and its underlying bedrock of Lake Constance, shaped by multiple glaciations. The 2D seismic sections revealed 154 fault indications in the Obersee Basin and 39 fault indications in the Untersee Basin. Their interpretative linkage results in 23 and five major fault planes, respectively. One of the major fault planes, traceable to Cenozoic bedrock, is associated with a prominent offset of the lake bottom on the multibeam bathymetric map. Across this area, high-resolution single channel data was acquired and a transect of five short cores was retrieved displaying significant sediment thickness changes across the seismically mapped fault trace with a surface-rupture related turbidite, all indicating repeated activity of a likely seismogenic strike-slip fault with a normal faulting component. We interpret this fault as northward continuation of the St. Gallen Fault Zone, previously described onshore on 3D seismic data.

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Section: Bedrock Morphology and Overdeepeningsupporting

confidence: 87%

Active Faulting in Lake Constance (Austria, Germany, Switzerland) Unraveled by Multi-Vintage Reflection Seismic Data

et al. 2021

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“…On the northern slope of the Alps a glacial origin was always the prevailing model for valley over-deepening (Hinderer 2001;Wildi 1984). On the southern slope of the Alps, the drawdown of the Mediterranean in the Messinian led to incision of the Po Plain and the interpretation of fluvial over-deepening of valleys into the Alps, hence referred to as Messinian canyons (Bargossi et al 2010;Bini et al 1978;Cazzini et al 2020;Finckh 1978). The observed data for both theories is similar and used to explain the Messinian river incision theory and the Pleistocene glacial over-deepening.…”

Section: Introductionmentioning

confidence: 90%

“…Further studies describe over-deepened valleys on the southern flank of the Alps in the Lake Maggiore and Lake Como area, in the Adda Valley and around Lake Garda (Bini et al 1978;Cazzini et al 2020;Felber et al 1991;Finckh 1978). The depth of the basement-sediment contact at the northern tip of Lake Garda, 50 km within the Alps, is 1100 m below sea level and suggests a V-shaped valley setting.…”

Section: Observations From Drill Holes and Seismic Investigationsmentioning

confidence: 99%

“…Below the Po Plain and at the transition into the Alps, Pliocene marine to fluvial sediments are well described and dated due to intensive oil exploration (Ghielmi et al 2013). Between Lake Maggiore and Lake Garda paleo-valleys below the Po Plain were incised during the Messinian Salinity Crisis (MSC) (Bini et al 1978;Cazzini et al 2020;Finckh 1978), and the seismic character suggests a filling with coarse material such as sandstones and conglomerates (Felber et al 1991). More generally, in the Po Plain and the Adriatic Sea, the Pliocene sediments seal a late Messinian paleo-topography with a drainage network of incised canyons formed during the MSC (e.g.…”

Section: Introductionmentioning

confidence: 99%

“…Pliocene sediments are filling V-shaped valleys at the transition from the Po Plain to the Alps (Amadori et al 2018;Bini et al 1978;Cazzini et al 2020;Felber et al 1991;Finckh 1978). The Messinian valley incision and Pliocene infilling in the Po Plain is widely acknowledged in the literature.…”

Section: Introductionmentioning

confidence: 99%

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Messinian or Pleistocene valley incision within the Southern Alps

2020

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Many of the valleys on the southern slope of the Alps are over-deepened, having bedrock valley floors well below sea level. This has typically been attributed to incision that occurred during the Messinian Salinity Crisis (MSC) when sea level dropped by hundreds of meters, leading to incision of many of the margins of the Mediterranean. We reassess this interpretation by documenting the correct elevation of the valley floor of the Adige river, one of the major valleys draining the Southern Alps, and by estimating the vertical motion of that valley floor since the end of Messinian incision. We re-evaluated the bedrock incision in the Adige valley using existing borehole data and seismic profiles. We estimate the vertical post-Messinian uplift using thermochronometric data that reveal the removed rock mass and then infer the expected isostatic uplift. These data are combined to reconstruct paleo-river gradients and to test viability of incision profiles. We find that the erosive surfaces in the drill holes restore to a paleo-elevation well below estimates of the Messinian Salinity Crisis (MSC) sea level. Restored valley gradients are often reversed compared to todays river gradients, as the uplift correction is higher upstream. A Messinian age of the erosional unconformities within the Alps can therefore be excluded based on the current best estimates of Messinian Mediterranean sea level and post-Messinian rock uplift. Pleistocene glacial erosion left a major signature on the geomorphology of the valleys, which is documented by glacially over-deepended valleys in the northern Alps. These valleys are not influenced by the Messinian sea-level drawdown. Therefore, it is suggested that the over-deepened valleys on the southern slope of the Alps are also glacial in origin.

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Geophysical Investigation and 3D Modeling of Bedrock Morphology in an Urban Sediment-Filled Basin: The Case of Bolzano (Northern Italy)

Giulia,

Corrado,

Giovanni

et al. 2024

Pure Appl. Geophys.

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Bedrock mapping is essential for understanding seismic amplification, particularly in sediment-filled valleys or basins. However, this can be hard in urban environments. We conducted a geophysical investigation of the sediment-filled Bolzano basin in Northern Italy, where three valleys converge. This study uses low-impact, single-station geophysical methods suitable for urban areas to address the challenges of mapping in such environments. A dataset of 574 microtremor and gravity measurements, along with three seismic reflection lines, allows for the inference of the basin’s deep bedrock morphology, even without direct stratigraphic data. The dataset facilitates a detailed analysis of the spatial patterns of resonance frequencies and amplitudes, revealing 1D and 2D characteristics of the resonances. Notably, 2D resonances predominate along the Adige valley, i.e., the deepest part of the basin with depths up to 900 m. These 2D resonances, which cannot be interpreted through simple 1D frequency-depth relationships, are better understood by integrating gravity data to develop a depth model. The study identifies resonance frequencies ranging from 0.27 to over 3 Hz in Bolzano, affecting different building types during earthquakes. Maximum resonance amplitudes occur at lower frequencies, specifically at 2D resonance sites, therefore primarily impacting high structures. The 2D resonances are directional, with the most significant amplification occurring longitudinally along the valley axes. The resulting 3D bedrock model aids in seismic site response modeling, hydrogeological studies, and geothermal exploration and provides insights into the geological history of the basin, highlighting the role of the Adige Valley as a major drainage pathway.

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New seismic evidence of the Messinian paleomorphology beneath Lake Maggiore area (Italy)

Cited by 10 publications

References 21 publications

Active Faulting in Lake Constance (Austria, Germany, Switzerland) Unraveled by Multi-Vintage Reflection Seismic Data

Active Faulting in Lake Constance (Austria, Germany, Switzerland) Unraveled by Multi-Vintage Reflection Seismic Data

Messinian or Pleistocene valley incision within the Southern Alps

Geophysical Investigation and 3D Modeling of Bedrock Morphology in an Urban Sediment-Filled Basin: The Case of Bolzano (Northern Italy)

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