Anne Rutger Fortuin

We present a new lithostratigraphy and chronology for the Miocene on central Crete, in the Aegean forearc. Continuous sedimentation started at ∼10.8 Ma in the E–W trending fluvio‐lacustrine Viannos Basin, formed on the hangingwall of the Cretan detachment, which separates high‐pressure (HP) metamorphic rocks from very low‐grade rocks in its hangingwall. Olistostromes including olistoliths deposited shortly before the Viannos Basin submerged into the marine Skinias Basin between 10.4 and 10.3 Ma testifies to significant nearby uplift. Uplift of the Skinias Basin between 9.7 and 9.6 Ma, followed by fragmentation along N–S and E–W striking normal faults, marks the onset of E–W arc‐parallel stretching superimposed on N–S regional Aegean extension. This process continued between 9.6 and 7.36 Ma, as manifested by tilting and subsidence of fault blocks with subsidence events centred at 9.6, 8.8, and 8.2 Ma. Wholesale subsidence of Crete occurred from 7.36 Ma until ∼5 Ma, followed by Pliocene uplift and emergence. Subsidence of the Viannos Basin from 10.8 to 10.4 Ma was governed by motion along the Cretan detachment. Regional uplift at ∼10.4 Ma, followed by the first reworking of HP rocks (10.4–10.3 Ma) is related to the opening and subsequent isostatic uplift of extensional windows exposing HP rocks. Activity of the Cretan detachment ceased sometime between formation of extensional windows around 10.4 Ma, and high‐angle normal faulting cross‐cutting the detachment at 9.6 Ma. The bulk of exhumation of the Cretan HP‐LT metamorphic rocks occurred between 24 and 12 Ma, before basin subsidence, and was associated with extreme thinning of the hangingwall (by factor ∼10), in line with earlier inferences that the Cretan detachment can only explain a minor part of total exhumation. Previously proposed models of buyoant rise of the Cretan HP rocks along the subducting African slab provide an explanation for extension without basin subsidence.

The Feos Formation of the Nijar Basin comprises sediments deposited during the final stage of the Messinian salinity crisis when the Mediterranean was almost totally isolated. Levels of soft‐sediment deformation structures occur in both conglomeratic alluvial sediments deposited close to faults and the hyposaline Lago Mare facies, a laminated and thin‐bedded succession of whitish chalky marls and intercalated sands alternating with non‐marine coastal plain deposits. Deformation structures in the coarse clastics include funnel‐shaped depressions filled with conglomerate, liquefaction dykes terminating downwards in gravel pockets, soft‐sediment mixing bodies, chaotic intervals and flame structures. Evidence for soft‐sediment deformation in the fine‐grained Lago Mare facies comprises syndepositional faulting and fault‐grading, sandstone dykes, mixed layers, slumping and sliding of sandstone beds, convolute bedding, and pillar and flame structures. The soft‐sediment deformed intervals resemble those ascribed elsewhere to seismic shaking. Moreover, the study area provides the appropriate conditions for the preservation of deformation structures induced by seismicity; such as location in a tectonically active area, variable sediment input to produce heterolithic deposits and an absence of bioturbation. The vertical distribution of soft‐sediment deformation implies frequent seismic shocks, underlining the importance of seismicity in the Betic region during the Late Messinian when the Nijar Basin became separated from the Sorbas Basin to the north. The presence of liquefied gravel injections in the marginal facies indicates strong earthquakes (M ≥ 7). The identification of at least four separate fissured levels within a single Lago Mare interval suggests a recurrence interval for large magnitude earthquakes of the order of millennia, assuming that the cyclicity of the alternating Lago Mare and continental intervals was precession‐controlled. This suggestion is consistent with the present‐day seismic activity in SE Spain.

Reconstruction of the vertical motion history of Crete and Karpathos (southeastern Aegean region, Greece) from the Messinian to Recent revealed a previously poorly documented late Messinian phase of strong subsidence with rates of 50-100 cm/k.y. followed by stasis during the first 250 k.y. of the Pliocene and then by uplift of 500-700 m during the late early to early middle Pliocene. Uplift continued up to Recent albeit at a slower pace and at different rates in different areas. The lower Pliocene in Crete and Karpathos is characterized by widespread occurrences of mass-wasting deposits, which were emplaced over a period of time spanning the first 1.35 m.y. of the Pliocene. The origin of these mass-wasting deposits has long been enigmatic but is here related to uplift which started in Crete as early as ca 5 Ma. It is suggested that the beginning uplift following strong subsidence of various fault blocks until late in the Messinian is related to the onset of south Aegean strike-slip faulting. We postulate that small-scale tilting of fault blocks by transtensional strike-slip faulting and increased seismic activity generated slope failures and subsequent sliding of poorly cemented lower Pliocene and uppermost Messinian Lago Mare sediments overlying the terminal Miocene erosional unconformity. The absence of mass-wasting deposits after 3.98 Ma, while uplift continued, is most likely the result of progressive compaction and cementation of the increasingly deeper buried Lago Mare and lower Pliocene sediments, thereby preventing slope failure to a depth of the terminal Mocene unconformity. Matuses in some places in Crete and on Karpathos, however, indicate that slope failures continued to occur although on a smaller scale and less frequent than before. Connecting the change from subsidence to uplift in the earliest Pliocene with the onset of left-lateral, strike-slip tectonics in the southeastern Aegean arc would make this major strike-slip system much older (by ∼2 m.y.) than the generally accepted age of middle to late Pliocene. A recently postulated scenario of "Subduction Transform Edge Propagator" (STEP) faulting to explain the south Aegean strike-slip system predicts rates, distribution, and amount of uplift as rebound to south-westward retreat of the subducted slab along a transform fault zone that is in line with our findings on Crete and Karpathos and explains the absence of compressional structures associated with the uplift, as well as the ongoing southwestward motion of Crete. © 2008 Geological Society of America