The Middle Jurassic succession in the central sector of the Pieniny Klippen Belt (Sprzycne Creek): implications for the timing of the Czorsztyn Ridge development

Abstract

In this study, we revisit the stratigraphic age and discuss sedimentary characteristics of the lower Middle Jurassic turbidite deposits (“black flysch”) of the Szlachtowa Formation, as well as the under- and overlying members of the Sprzycne Creek section situated in the central sector of the Pieniny Klippen Belt (Poland). We show that the succession captures the lower Middle Jurassic marine sediments of the pre-Late Albian Magura Basin, located to the north of an ancient submarine swell (Czorsztyn Ridge). The turbidite deposits of the Szlachtowa Formation and marly shales of the Opaleniec Formation yield dinoflagellate cysts indicative of the latest Aalenian or learliest Bajocian to Early Bathonian. The character of these deposits, and their location below the overthrusted Subpieniny Nappe show that this succession does not belong to the successions of the Oravicum domain, located on the southern side of the Czorsztyn Ridge. The Szlachtowa Formation is underlain by the Skrzypny Formation, which is reported for the first time outside the Oravicum domain. It suggests that the pre-Late Albian Magura Basin came into existence not earlier than during the latest Aalenian, following the rising of the Czorsztyn Ridge. The marly shales assigned here to the Opaleniec Formation of Late Bajocian-Bathonian age and younger marly deposits of Cretaceous age were distinguished in the past as the so-called “Sprzycne beds” of Cretaceous age. However, the combination of these two rock units into a single lithostratigraphic unit is unsuitable because they represent two separated stratigraphical intervals and their contact is tectonic.

Keywords

• Middle Jurassic
• Pieniny Klippen Belt
• Magura Basin
• “black flysch”
• stratigraphy
• dinoflagellate cysts