DÜZCE GEOLOGY
ABSTRACT
İn the study area encompassing Düzce, Yığılca, and the Almacık mountain and its
surrounding in the western sector of the Pontides, the units belonging to the western
Pontide zone, Armutlu-Almacık-Arkot mountain zone and Sakarya zone have been
juxtaposed by the tectonic events. İn the region the Yedigöllerformation of
Precambrian age composed of high grade metamorphics such as amphibolite and
gneiss, and the Bolu granitoid of the same age, which cuts, the rocks of the former
unit, form the basement. This units are unconformably overlain by the Paleozoic
Sequence of Istanbul, which starts at the base with the Kocatöngel formation of early
Ordovician age composed of shale, mudstone, and sandstone. The other units of the
sequence are,from bottom to töp, the Kurtköyformation of Early Ordovician age
consisting of sandstone,mudstone and conglomerate; the Ereğli formation of Middle
Ordovician-Early Devonian age composed of shale, sandstone and limestone, and
the Yılanlı formation of Middle Devonian-Early Carbon age made up of limestone,
dolomitic limestone and dolomit. Between the latter two units, in İstanbul and
Çamdağ regions, is the Aydos formation of Early Ordovician age, composed of
Quartzitic sandstone, conglomarate and mudstone, which is not observed in the
study area. The contacts between the units of the Paleozoic Sequence of İstanbul in
the study area are conformable. The Çakraz formation of Permian-Triassic age
composed of terrestrial mudstone, sandstone and conglomerate lies with an angular
unconfornity over the Paleozoic Sequence of İstanbul. The Yemişliçay formation
represented by the products of Upper Cretaceous island-arc volcanism, which is
commonly seen in the Pontides, with the Kapanboğazı member of SantonianCampanian age consisting of pelagic limestone and mudstone, rest angularunconformably over the former units. This unit is transitionallyfollowed by the Akveren
formation of Late Companian Early Eocene age, which is a flysch-type sequence with
limestone, the Sermi limestone member of Maastrichtian-Paleocene age, and the
Çangaza volcanite member. İn the sector of the Almacık mountain of the ArmutluAlmacık-Arkot mountain zone it lies unconformably over the underlying units. The
Çaycuma formation of Early-Middle Eocene age cosisting af the alternation of
sandstone, siltstone and claystone, and the Yığılca formation af the same age
composed of lavas and agiomerates and tuffs are ttransitional with the Akveren
formation; where it is absent they lie unconformabiy over the underiying units. Within
the Armutlu Almacık-Arkot mountain zone the Almacık ophiolitic melange of late
Cretaceous age, the units belonging to the Paleozoic sequence of Istanbul, which
have a tectonic relationship with the former unit, and the Abant formation of late
Campanian-Early Eocene age characterized by an olistostromal-turbiditic sequence,
lie. İn the westward continuation of the Safranbolu basin representing an
intermountains shallow-marine the Doğanlar volcanite member belonging to the
Kışlaköy farmation of late Danian-Tanesian age, and the Safranbolu formation of
Early-Middle Eocene age made up of limestones, which lies conformabiy on the
former unit, crop out. İn the southern sector of the study area the units of the Sakarya
Zone are the Mudurnuformation of Early-Middle Jurassic age with an alternation of
volcanic and sedimentary rocks, the Soğukçam formation of Callovian-Aptian age
composed of limestones, which overlies transitionaliy the former one, the
Yenıpazarformation
ofAlbian-Maastrichtian
age
characterized
by
a
turbiditic
sequence, which iles conformabiy over the former unit, and the Meyildere volcanite of
late Paleocene-Early Eocene age, which cuts the former unit. The Kiraz mountain
volcanite, Ilıcadere volcanite, and the Bakacaktepe volcanite, which are composed of
volcanic rocks, of Early-Middle Miocene age, and the Örencik formation of Pliocene
age, composed of terrestrial clastics, and the deposits of Quaternaıy age are seen as
younger units. İn Pre-late Campanian to Maastrichtian times the Paleozoic sequence
of Istanbul must have been empiaced over the Almacık ophiolitic melange. İn the
region Miocene and post-Miocene neotectonic movements have been continuing
atpresent.