02747nas a2200289   4500008004100000245013700041210006900178300001200247490000700259520185800266653002102124653002702145653001502172653001202187653002802199653002002227653001202247653001602259653001002275653002102285653002202306653002602328100001602354700001402370700001802384856005502402       2006                        eng d00aDistinguishing Eustatic and Epeirogenic Controls on Lower-Middle Cambrian Boundary Successions in West Gondwana (Morocco and Iberia)0 aDistinguishing Eustatic and Epeirogenic Controls on LowerMiddle   a899-9180 v543 a<div class="para">
<p>Major eustatic fall has been invoked to explain Lower–Middle Cambrian boundary sandstones and faunal replacements on a number of Cambrian palaeocontinents. This proposal has been tested on the Moroccan and Spanish margins of West Gondwana and found to be inadequate to explain stratigraphical developments. In these regions, sandstone intervals long presumed to be regressive and late Early Cambrian in age are now shown to be early Middle Cambrian, and composed of a lower regressive and an overlying transgressive sandstone separated by a regional unconformity. Only the lower tidalites (i.e. Tazlaft Formation in Morocco and lower Daroca sandstones in Spain) record the Hawke Bay eustatic regression in West Gondwana. The Tazlaft is overlain by a newly recognized, unconformably overlying sandstone (Talelt Formation) that onlapped southern Morocco with reactivation of a pull-apart or transcurrent regime. Up to 150&nbsp;m of erosion on uplifted blocks in the High Atlas range and foundering of the Souss Basin to the south preceded onlap and deposition of the volcanic-rich Tatelt, the correlative and depositional analogue of the upper Daroca and lower Valdemides Formations in northern Spain. With folding and erosion, a type 1 depositional sequence boundary also caps the Tatelt at its contact with an overlying, lower Middle Cambrian mudstone-dominated succession. This unconformity probably occurs in Spain within the Valdemiedes Formation and corresponds to a faunal discontinuity called the ‘Valdemiedes geoevent’. The Iberian ‘Daroca regression’ and Moroccan ‘Asrir regression’ are misnomers, as the sandstones on which they are based are composite units with a lower regressive interval that records eustatic fall and an upper transgressive unit that records epeirogenically driven onlap.</p>
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10aDaroca Sandstone10adepositional sequences10aepeirogeny10aeustasy10aJbel Wawrmast Formation10aMiddle Cambrian10aMorocco10aSouss Basin10aSpain10aTatelt Formation10aTazlaft Formation10aValdemiedes Formation1 aLanding, E.1 aGeyer, G.1 aHeldmaier, W.  uhttp://dx.doi.org/10.1111/j.1365-3091.2006.00780.x