Gelgit düzlüğü sedimantasyonuna güncel bir örnek: Mont-Saint-Michel Körfezi (Kuzeybatı Fransa)

Fransa'nın kuzeybatısında 500 km2'lik bir alan kaplayan Mont-Saint-Michel (MSM) Körfezi yeryüzündeki en büyük gelgit nedenli günlük deniz seviyesi değişimlerinden birine sahne olması ile bilinir. Bahar aylarında 15 m'yi bulan deniz seviyesi değişimleri sonucu açığa çıkan 250 km2'lik gelgit düzlüğünde gerçekleştirilen bu çalışma sonucunda bölge, üç adet jeomortik birime ayrılmış ve her birinin içerdiği sedimanter tasiyes ve ortamlar irdelenmiştir. Buna göre; körfez sistemi, gelgit kanalları, organik maddece zengin tuzlu bataklıklar ve gelgit düzlüğünün çamurlu-kumiu çevrimlerinden oluşur. Körfezin batısında ve orta kesimlerinde yer alan istridye-midye yığışımları ve solucan resifleri ise, zaman zaman engel adaları oluşturacak kadar gelişmişlerdir. Kuzeydoğudaki kıyı kumul sistemi ise, kuzeybatı rüzgarlarına açık bir alanda gelişmiş olup, kıyı kumulları ve gelgit akıntılarının yarattığı megaripıllardan oluşur. Eldeki veriler ve yapılan gözlemler; her üç sistemin de sadece doğal nedenlerle değil, baraj, yol ve su kanalı yapımı gibi insan müdahalesi nedeni ile de denize doğru ilerlediğini göstermektedir. Bu bağlamda jeomorfik birimlerin ve içerdikleri sedimanter fasiyeslerin oluşum mekanizmalarının tam olarak anlaşılabilmesi sadece jeolojik anlamda değil, çevresel ve ekolojik anlamda da çok önemli hale gelmektedir.

A recent example for tidal flat sedimentation: Mont-Saint-Michel Bay (Northwestern France)

The Mont-Saint-Michel (MSM) Bay covers an area of 500 km2 to the northwest of France and is characterized by exceptional tidal amplitudes (up to 15 m during spring tides). Three geomorphic units together with their sedimentary fades and environments can be described from 250 km2 tidal flat exposed daily. The estuary system is composed of tidal channels, organic rich schorre and mud-sand alternations of the tidal flat. The oyster and mussel accumulations and worm reefs situated to the west and center of the bay often create barrier islands. The dune system to the northeast is developed by strong northwesterly winds and contains coastal dunes and tide influenced megaripples. Available data and observations indicate that all three systems prograde not only because of natural processes but also because of human interventions such as dam, road and irrigation channel constructions. Therefore, a full understanding of the mechanisms that control the development of the geomorphic units and their sedimentary fades is not only important from a geological point of view but also from environmental and ecological perspectives.

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