Abstract
Three-dimensional seismic data are increasingly resolving original compositional heterogeneity and structural complexity in evaporitic successions within sedimentary basins. The relationship between basin structure, evaporite composition and its influence on subsequent deformation are investigated here using Messinian examples from the Maghrebian thrust system of Sicily and applied to the adjacent Ionian sea-bed. By integrating outcrop and onshore subsurface data, we demonstrate variations in evaporite stratigraphies deposited across thrust-top basins, and how these variations have controlled subsequent deformation of these basins. Gypsum and carbonate units develop broad single-layer buckle fold trains, with wavelengths reflecting layer thickness. The development of deformation appears limited by bending resistance at fold hinges, which can be overcome by syntectonic erosion. In contrast, the thick halite and K-salt accumulations in growth synclines have deformed with short-wavelength folds and distributed strain. These structures can display rapid lateral variations (on a scale of hundreds of metres). Similar structural styles, with buckle fold trains passing laterally into more homogeneously shortened, short-wavelength folding, are evident on seismic data from the buried Messinian interval beneath the Ionian Sea. Using the Sicilian outcrop as analogues, the structural styles for the Ionian may be used to infer evaporite type in these subsurface examples.
Highlights
By integrating outcrop and onshore subsurface data, we demonstrate variations in evaporite stratigraphies deposited across thrust-top basins, and how these variations have controlled subsequent deformation of these basins
The development of deformation appears limited by bending resistance at fold hinges, which can be overcome by syntectonic erosion
The aim of this paper is to demonstrate lateral variations in evaporite stratigraphies deposited in thrust-top basins and how these variations have controlled subsequent deformation of these basins
Summary
Butler & Grasso 1993; Jones & Grasso 1997; Lickorish et al 1999; Gugliotta 2012) This thrust belt formed the eastern part of the Mahgrebian system that continues through the central Mediterranean into northern Africa. The evaporitic strata and time-equivalent carbonates (the so-called Calcare di Base; Ogniben 1957) are generally sandwiched between fine-grained units (Decima & Wezel 1973; Butler & Grasso 1993). The younger, Second Cycle evaporites are exclusively gypsum and rarely reach bed-set thicknesses in excess of 10–15 m They are interbedded with detrital mud, silt, sandstones and conglomerates that rework earlier Messinian strata. It is in the First Cycle that evaporitic facies show their greatest variations, from Mg- and K-salts with thick halite that are exploited in mines located in specific structural settings, to gypsum and carbonates with bed-by-bed dissolution
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