Cretaceous (Albian–Coniacian) dinoflagellate biostratigraphy of the Vomb Trough, southern Sweden

Abstract

ABSTRACT We document diverse and well-preserved dinoflagellate cyst assemblages from Cretaceous successions in the Kullemölla 1 drill core (640.0 m–590.0 m), Vomb Trough, southern Sweden. Palynology reveals a nearshore marine environment. Dinoflagellate index taxa indicate an Albian to Coniacian age, thus spanning the Early–Late Cretaceous boundary. The lower part of the core is Albian, based on the presence of the index dinocyst taxa Pareodinia and Callaiosphaeridium asymmetricum. The First Appearance Datum (FAD) of Oligosphaeridium prolixispinosum, together with the presence of Achomosphaera ramulifera, Heterosphaeridium difficile and Oligosphaeridium pulcherrimum, reveals a Cenomanian age for the interval 635– m–617 m. The Turonian interval is characterized by an increase in the dinocysts Chatangiella spectabilis and Florentinia spp., in combination with the FAD of Senoniasphaera rotundata, whereas the youngest samples are dated to the Coniacian as defined by the appearance of Glaphyrocysta sp. We show that Cenomanian and Turonian strata are indeed represented by a relatively condensed section between 635 m and 612 m in the Kullemölla 1 core showing that the apparent hiatus recorded by calcareous microfossils elsewhere is likely a result of post-depositional dissolution of calcareous tests and limestone, a process that did not affect the organic-walled plankton. This is further supported by the presence of hardgrounds and dissolution features. This updated, detailed biostratigraphical assessment based on dinoflagellates provides a framework for correlation with zonations based on other marine fossil groups, useful, for e.g., correlating aquifers in subsurface successions and, further, provides opportunities for linking marine and continental biotas.