Dear Dr. Göncüoglu,

I would like to wrap up your question pointing to structure and sediments and ocean closure. The final stage in my opinion is reached when along a suture zone sediments evolved which contain proven debris or eroded relics of the oceanic lithosphere which is best represented by critical minerals like chromite associated with heavy minerals typical of basic and ultrabasic provenance. I have renounced to sum up the entire HM suite and the chemical variation of minerals which tend to be enriched in V, Cr and Ni.

Another criterion seems to be the evolution of saprolites along such a suture zone, like Ni laterites, indicative of a subaquatic setting that has turned into a subaerial environment (New Caledonia –Type).

Best regards

Harald G. Dill

Not so much sedimentological as palaeontological - there needs to be a unifying of continent-fringing fossils from both sides of the ocean.  Obviously this will be difficult if there was not a former difference in faunas on opposite sides of the closing ocean

Best wishes

John

Even though we might define an ocean as a marine basin floored by oceanic crust, the final closure of an ocean is arguably not quite related to (i.e. may happen before) processes which lead to preservation of oceanic crust remnants along the suture.

The end of marine sedimentation and disappearance of marine fossils and ichnofossils _throughout_ the supposed former basin area and their replacement by non-marine sedimentation with indications of exposure (dessication cracks, rain drop marks, root horizons, soil formation, haematitic cements etc.) and non-marine biota might be a better criterion for the final closure of an ocean.

Unification of continental or marginal faunas from both sides probably doesn't work as an indicator because the exchange might occur along the margins when the basin has still an oceanic character but is encircled by continent/ cut-off from the main marine realm .

I think the presences of Huge molasses at the flanks of fold -thrust belt indicates the turn over from Aqueous marine Oceanic conditions associated by Folding and thrusting ,over thrusted syructurs in  

Sayın Hocam,

Sanıyorum bir okyanusun kapanmasının son ürünü olan yapısal ve sedimantolojik veriler:1. Okyanusal litosfer üzerindeki piggi back havza ile bindirme öneyindeki molas havzasının aynı zamanı fakat farklı ortam özelliklerini gösteren fosiller bulundurmasıdır. 2. ise kapanma ile gelişen imbrike ters fayların (ekayların) önünde gelişen debris folowlardan sığ denizel ya da kıyı fasiyeslerine kısa mesafelerde geçişler olmasıdır. Asimetrik kıvrımları da bunlara ilave edebiliriz.

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