Rola procesów tektonicznych oraz eustatycznych w rozwoju sekwencji stratygraficznych utworów neoproterozoiku i kambru basenu lubelsko-podlaskiego
Abstract
Relative role of tectonic and eustatic processes in development of the Neoproterozoic and Cambrian stratigraphic sequences of the Lublin–Podlasie Basin.
S u m m a r y. Sequence stratigraphy approach has been applied for the Neoproterozoic to Cambrian sedimentary fill of the Lublin–Podlasie Basin; the main goal of the study is to discriminate between eustatic and tectonic control of the observed sequence development. The Neoproterozoic and Cambrian sedimentary fill of the Lublin–Podlasie Basin is subdivided here into two second-order depositional sequences, separated by a basin-wide unconformity. The lower sequence A is poorly recognised. It is presumably of the early Neoproterozoic age, and is characterized by continental to costal shallow marine developments. Sequence B comprises the (late?) Neoproterozoic to Middle Cambrian. The lowermost part of the sequence B is composed of a lowstand systems tract (LST). At that time a low relative sea level was controlled by regional thermal doming, followed by rapid clastic and volcanogenic deposition, with rate exceeding that of subsidence of extensional grabens. During the latest Ediacaran, a transgressive systems tract I (TST I) developed. Increase of the rate of relative sea level rise was induced by a transition from syn-rift to post-rift subsidence. During the development of a following highstand systems tract I (HST I), significant sediment supply exceeded the rate of basement subsidence, causing progradation of shoreline. The next higher up-section transgressive system tract (TST II) is characterized by a gradual relative sea level increase and reflects continued thermal sag phase of the Lublin–Podlasie Basin. Development of the TST II was coeval with a global transgression and controlled mainly by eustatic sea level rise. The beginning of the Middle Cambrian corresponds to the development of a HST II, controlled by a low rate of increase of the relative sea level, even if it was coeval in time with the Hawke Bay regression. The HST II is therefore interpreted here as controlled by local tectonic processes, superimposed on continued post-rift thermal subsidence of the passive margin.
S u m m a r y. Sequence stratigraphy approach has been applied for the Neoproterozoic to Cambrian sedimentary fill of the Lublin–Podlasie Basin; the main goal of the study is to discriminate between eustatic and tectonic control of the observed sequence development. The Neoproterozoic and Cambrian sedimentary fill of the Lublin–Podlasie Basin is subdivided here into two second-order depositional sequences, separated by a basin-wide unconformity. The lower sequence A is poorly recognised. It is presumably of the early Neoproterozoic age, and is characterized by continental to costal shallow marine developments. Sequence B comprises the (late?) Neoproterozoic to Middle Cambrian. The lowermost part of the sequence B is composed of a lowstand systems tract (LST). At that time a low relative sea level was controlled by regional thermal doming, followed by rapid clastic and volcanogenic deposition, with rate exceeding that of subsidence of extensional grabens. During the latest Ediacaran, a transgressive systems tract I (TST I) developed. Increase of the rate of relative sea level rise was induced by a transition from syn-rift to post-rift subsidence. During the development of a following highstand systems tract I (HST I), significant sediment supply exceeded the rate of basement subsidence, causing progradation of shoreline. The next higher up-section transgressive system tract (TST II) is characterized by a gradual relative sea level increase and reflects continued thermal sag phase of the Lublin–Podlasie Basin. Development of the TST II was coeval with a global transgression and controlled mainly by eustatic sea level rise. The beginning of the Middle Cambrian corresponds to the development of a HST II, controlled by a low rate of increase of the relative sea level, even if it was coeval in time with the Hawke Bay regression. The HST II is therefore interpreted here as controlled by local tectonic processes, superimposed on continued post-rift thermal subsidence of the passive margin.