--> Abstract: An Alternative Model for the Growth and Evolution of Paleozoic Algal Mounds with Significance to Reservoir Distribution, by Audrey L. Ritter and G. Michael Grammer; #90039 (2005)

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An Alternative Model for the Growth and Evolution of Paleozoic Algal Mounds with Significance to Reservoir Distribution

Audrey L. Ritter and G. Michael Grammer
Western Michigan University, Kalamazoo, MI

During the Late Paleozoic, phylloid algae were common reef builders and are known to form well-developed hydrocarbon reservoirs in many parts of the world. Current dogma on the formation of phylloid algal mounds is that they formed in situ through primarily constructional processes. These processes included sediment baffling and binding by the algae and various other organisms, coupled with pervasive early submarine cementation. Most models suggest deposition along a shelf margin or outer parts of a distally steepened ramp resulting in a generally strike-elongated distribution. Recent evaluation, however, of phylloid algal mounds exposed along the San Juan River in Utah have shown that 10-12m amplitude mounds are distributed in a near sinusoidal pattern suggesting that they may have formed under the influence of wave- or tide-generated ocean currents. In modern environments, tide-generated currents may pile plates of the modern algae Halimeda into dunes or sand waves along the sea floor with a similar near-sinusoidal distribution.

Ascertaining the conditions under which these mounds initiated and grew may have important implications to exploration concepts devised for algal reservoirs. High energy, current-emplaced mounds, for instance, may be areally limited in the subsurface and may trend preferentially along strike (e.g. wave currents) or conversely along dip (e.g. tidal currents). In contrast, constructional mounds may have formed in much broader areas across an entire shelf or platform. Relative percentages of primary matrix mud, which is generally lower in current-influenced mounds, may also affect reservoir quality and should be considered at both exploration and production scales.

AAPG Search and Discovery Article #90039©2005 AAPG Calgary, Alberta, June 16-19, 2005