Osady morskie interglacjału eemskiego i pozycja stratygraficzna iłów elbląskich (yoldiowych) na podstawie otworów w Pęklewie i Pagórkach (Wzniesienie Elbląskie)

Abstract

W profilach Pąklewa i Pagórków uzyskano jasny i wyraźny obraz pozycji stratygraficznej iłów elbląskich (yoldiowych). Spoczywają one nad morskimi osadami interglacjału eemskiego, od których są oddzielone gliną zwałową zlodowacenia toruńskiego (poziom BII). Potwierdza to wcześniejsze ustalenia współautorki artykułu, że powstały one w interglacjale krastudzkim, młodszym od interglacjalu eemskiego.

Marine deposits of the Eemian interglacial and stratigraphic position of the Elbląg clays (Yoldia) on the base of boreholes in Pęklewo and Pagórki (the Elbląg Elevation)

Works on the sketch and detailed maps performed for several year in the Elbląg Elevation have provided information on geologic structure of the area (A. Makowska, 1978, 1979a, 1987, in print). Besides the surface mapping some boreholes have been drilled through the Quaternary deposits 300 m in thickness to the Tertiary basement. One of the most important results there has been the findings of some independent marine deposits in the Quaternary sediments, manifesting that this area (or its fragments) was transgressed repeatedly in Upper Pleistocene (A. Makowska, 1986). Among these members there are also the Elbląg Clays (Yoldia) known in this area and described by A. Jentzsch (1876). The stratigraphic position of these deposits has been discussed for years due to the fact they occur in highly complicated geological structure caused by large glaciotectonic disturbances in the Pleistocene deposits occurred on the surface. Their age was attributed to various periods of Quaternary, most often recently to the Eemian Interglacial (R. Galon, 1934, 1938; B. Halicki, 1961; B. Halicki, I. Brodniewicz, 1961a, b), they were placed in the beginning or at the end of this period (H. Gross, 1967; P. Woldstedt, 1955, 1958, 1969). Data resulted from new works show the deposits to be younger than the Eemian Interglacial. Their stratigraphic position is shown in profiles of two new boreholes at Pęklewo and Pagórki (A. Makowska, 1987, in print; W. Rabek, in preparation) at the distance of 1,0 and 6,5 km from the known outcrop in Kadyny, where the Elbląg Clays are exploited for building materials (Fig. 1). The boreholes drilled through the Quaternary complex of 246.0 to 299.0 m thick and reached the Tertiary basement (Fig. 2). In the bottom of the Quaternary deposits there is the till of the South Polish Glaciation (layer 1). The till is covered by a higher part of the Quaternary complex including deposits of the Middle Polish Glaciation and the Eemian Interglacial and younger deposits of the Toruń Glaciation, the Krastudy Interglacial and the Vistula Glaciation. The complex consist of two developed intermorainic series (layers 2-10 and 12-16) parted and covered by horizontal till horizons (layer 11 and 19). Based on the surface mapping in the upper part of the complex there have been distinguished theoretically other till horizon - lower than the highest (layer 17) and the highest intermorainic series (layer 18) occurring near by on the surface. Marine deposits occur in two intermorainic series the lower (layers 5 and 8) and the upper (layers 14). They consist of Foraminifera and Molluscs shell fragments. Based on the Molluscs Cardium paucicostatum Sower by and Corbula gibba Olivi, deposits of the lower intermorainic series, after correlation with deposits in the lower Vistula River (A. Makowska, 1979b), where they make the well recognized Lower Vistula Formation, have been determined as Eemian Interglacial (A. Makowska, 1986). Marine deposits of the upper series consist of numerous shells of Portlandia arctica (Gray) what allows to correlate them with the Elbląg Clays (Yoldia) occurring in Kadyny. Of this site, the whole  intermorainic series is determined as the Kadyny Formation. It corresponds to the Gniew Formation - on the Lower Vistula. It was recognized as the interglacial formation (A. Makowska, 1986) sedimented in the period younger than the Eemian Interglacial (Krastudy Interglacial). The Pęklewo and Pagórki profiles in connection with the Kadyny outcrop clearly determine the stratigraphic position of the Elbląg Clays. These deposits occur in the Kadyny Formation, younger than the Eemian Interglacial deposits from which they are separated by a distinct till horizon. They were formed as ascertained before (A. Makowska, 1986) in the Krastudy Interglacial, preceded by the Toruń Glaciation, when the continental glacier stepped over the Baltic Basin and invaded the Lower Powiśle, where reached the Torun area.