Oscar A. Abbink1,
Roel M.C.H. Verreussel1,
Jan Willem Weegink1
(1) LPP, Utrecht, Netherlands
Paralic depositional sequences in the Jurassic of the North Sea form an important economic objective. In these sequences, palynomorphs are the most abundant (micro)fossil group and palynology is increasingly challenged to identify systems tracts and parasequences.
Based on the general ecologies of aquatic palynomorphs and on a recently developed Sporomorph EcoGroup model it can be demonstrated that (1) the interplay of the distribution patterns of brackish-marine, freshwater and terrestrial palynomorphs, and (2) distribution patterns of even solely terrestrial palynomorphs (grouped in six Sporomorph EcoGroups(SEGs), viz. Upland, Lowland, River, Pioneer, Coastal, and Tidally-influenced SEG), can be used for the recognition of sea-level fluctuations in paralic settings
The sea-level changes recognized based on the SEG model allow the identification of discrete palynological sea-level induced units (Sea-level Induced Palynomorph Succession;SIPS). Within the SIPS, four phases can be distinguished: (1) a "wet" Lowland SEG phase, (2) a phase with maximum abundance of Upland, Coastal and/or Tidally-influenced SEGs and a high marine/terrestrial ratio, (3) a Coastal SEG phase, and (4) a "dry" Lowland SEG phase. These phase are considered to correlate to the (1) late LST and TST, (2) MFS, (3) early HST, and (4) late HST. The boundary of between SIPSs reflects the abrupt shift from a regressional to a transgressional regime and is considered to approximately correlate to the SB.
AAPG Search and Discovery Article #90914©2000 AAPG Annual Convention, New Orleans, Louisiana