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2.8 Aalburg Formation

Authors: Legrand, 1961; Legrand in Delmer, 1963; van Adrichem  Boogaert & Kouwe, 1993.

Description: Open marine, grey to dark grey, locally sandy or silty mudstones and marls. Macrofossils (ammonites, molluscs), often pyritised, and siderite nodules can be common.

Boundaries: top: erosive, cut by Mid Cimmerian uncon­formity and covered  by  Upper  Cretaceous  deposits; base : passing inconspicuously into Steen Formation.

Stratotype: Parastratotypes in Belgium: well KB99 Neeroeteren , well KB198 Molenbeersel.

Area: Roer Valley Graben ; removed by erosion from Campine Basin and eastern Brabant Massif . Aalburg and Sleen Formations follow Pangaea break-up and deposi tion in the North Sea - North German Shale basin during the Rhaetian to Hettangian transgression (Ziegler, 1990).

Thickness: ca. 450 m preserved thickness in Molenbeersel (becoming thicker and more  complete  towards the northwest on Dutch territory ).

Age: Lower Jurassic, Hettangian (identified in well KB99) to Pliensbachian (identified in well KB198).