--> Abstract: Fluvial Depositional Environments in a Non-Marine Cratonic Basin: Stacking Pattern Architecture as a Response to Baselevel Changes, by J. C. Konstanty and W. Ricken; #90942 (1997).

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Abstract: Fluvial Depositional Environments in a Non-Marine Cratonic Basin: Stacking Pattern Architecture as a Response to Baselevel Changes

KONSTANTY, JAN C. and WERNER RICKEN

To better understand the dynamics of fluvial depositional environments and their autocyclic and allocyclic controls, fluvial genetic units in the upper Triassic Stubensandstein Fm., SW Germany, were investigated in an outcrop study (regional stratigraphic unit: km4.2/km4.3).

The high resolution, sequence stratigraphic framework was established by detailed analysis of the micro- and mesoarchitectural sedimentary features, changes in channel connectivity, and hand-held gamma-ray measurements.

Deposits of low-sinuosity bedload braided rivers (multistory sandstones) are believed to be a result of low accommodation to increasing accommodation regimes, whereas the meandering river deposits represent a high accommodation regime. Additionally, it was possible to characterize depositional environments by channel width/depth ratios (ribbon channels vs. sheet sandstones) and maximum channel depths (0.8-5.5 m) within individual braided river genetic units. Within the mixed-load meandering river deposits, excellent preservation of lateral and vertical accretion surfaces in point bar deposits led to distinction of vertically stacked channel groups. To distinguish accommodation cycles, analysis of paleosol maturity and preservation in point bar and floodplain facies served as an important additional tool.

Systematic changes in fluvial depositional environments through five genetic units identified in the study area indicate a combination of strong baselevel control and climatic changes documented in sedimentary structures and channel geometries. The investigated fluvial deposits represent high frequency sequences following a nonmarine sequence stratigraphic concept. This concept establishes a preliminary 4th-order cyclicity for the fluvial deposits of the Upper Stubensandstein Fm as a part of the cratonic Keuper basin fill.

AAPG Search and Discovery Article #90942©1997 AAPG International Conference and Exhibition, Vienna, Austria