Dinoflagellate stratigraphy and its response to sea level change in Cenomanian-Turonian sections of the western Interior of the United States

Journal Article · Thu Feb 01 04:00:00 EST 1996 · Palaios

DOI:https://doi.org/10.2307/3515113· OSTI ID:426073

Li, Huan; Habib, D ^[1]

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1. Graduate School of CUNY, New York (United States)

Detailed palynological analysis of depositional environments in carbonaceous shales and marlstones in the Cenomanian-Turonian (C-T) interval of the Cretaceous Western Interior seaway indicates that: (1) dinoflagellate species diversity, (2) ratio of Spiniferites to Cyclonephelium (S/C ratio), and (3) depositional organic facies are collectively useful for distinguishing cycles of marine transgression and regression. The increase in number of dinoflagellate species and of the S/C ratio within a matrix of abundant amorphous debris is interpreted to have resulted from the expansion of an epeiric seaway during sea level rise. The marked drop in dinoflagellate species diversity in the interval of mixed amorphous debris and detrital inertinite adjacent to the ammonite Sciponoceras gracile-Neocardioceras juddii ammonite zonal boundary, and prior to or at the C-T boundary, indicates two short periods of shoreline progradation. The S/C ratio increases in the offshore direction as well as in the transgressive intervals. The largest number of dinoflagellate species occurs in the lower part of transgressive intervals, and not in peak transgression. The successive decrease in species diversity from the early stage to late stage within transgressive intervals and into the next highstand interval is the result of shoreline progradation. The downlap surface (maximum starvation surface) which delimits the boundary between the transgressive and highstand intervals can be indicated by an inflection in the trend of decreasing species diversity. The position of the inflection point within the C-T transgressive sequence shows the same trend as the position of the condensed interval. It shifts higher in the transgressive sequence in the offshore direction. 65 refs., 12 figs., 2 tabs.

• Sponsoring Organization: USDOE
• OSTI ID: 426073
• Journal Information: Palaios, Journal Name: Palaios Journal Issue: 1 Vol. 11; ISSN PALAEM; ISSN 0883-1351
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
CRETACEOUS PERIOD
DINOFLAGELLATE
PALEOCLIMATOLOGY
POPULATION DYNAMICS
SEA LEVEL
VARIATIONS