Megabloques dislocados

Dislocated (allochthonous) megablocks are characteristic of impact structures and are understood to be related to the different stages of impact cratering (excavation, ejection and modification of the transient crater; see Melosh [1989]). Thorough mapping within the Azuara structure (Bärle, 1988; Fiebag, 1988; Gwosdek, 1988; König, 1988; Linneweber, 1988; Waasmaier, 1988; Hunoltstein-Bunjevac, 1989; Müller, 1989; Katschorek, 1990; Mayer, 1991) has revealed a large number of dislocated megablocks. Gravity gliding can in most cases be excluded as an explanation, and the rootless layering of many megablocks has been shown by geophysical measurements (Bärle, 1988, König, 1988). A location map for allochthonous megablocks is given in Fig. 5. UTM coordinates of typical locations are: 6 67 350, 45 47 790¸ 6 70 140, 45 47 790; 6 70 390, 45 47 520; 6 77 660, 45 45 700; 6 88 850, 45 60 000, 6 69 760, 45 45 470.

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Fig. 1. Location map for dislocated megablocks (7) in the Azuara structure. Modified from Ernstson et al. (2002).

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Fig. 2. Megabloque alóctono del Paleozoico de unos 150 m de tamaño (color oscuro) que sobreyace y se indenta en las capas Cretácicas de la Fm. Utrillas (color claro). El Paleozoico esta totalmente aislado y está rodeado por una orla Mesozoica de aproximadamente 4 Km de anchura. Estructura de impacto de Azuara, al SE de Monforte de Moyuela.

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Fig. 3/4. Megabloque alóctono acuñado en calizas del Malm. Estructura de impacto de Azuara; Barranco de Muniesa. La anchura de campo es de unos 100 m.

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Fig. 4.

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Fig. 5. Allochthonous megablock (encircled) of probably Malmian limestone south of Blesa.

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Fig. 6. Detail of the allochthonous megablock in Fig. 5. Photographs S. Linneweber.