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K.M. Bohacs1,
J.E. Neal1,
A.R. Carroll2,
D.J. Reynolds1
(1) Exxon Production Research Co, Houston, TX
(2) University of Wisconsin, Madison, WI
Abstract: Lakes are not small oceans! —sequence stratigraphy in lacustrine basins
Contrasts among lake and marine 
systems
make it
inap-propriate to apply one unmodified marine sequence-stratigraphic model to
all lake systems. The sequence-stratigraphic approach— looking at a hierarchy
of rock packages bounded by various types of surfaces— works very well with
lake strata. However, the expression of depositional sequences varies as a
function of lake depositional system — just as shallow marine-carbonate sequences
differ from shallow-marine-siliciclastic sequences. Indeed, one lacustrine
model is not applicable to all lake-basin types.
Lakes differ from oceans in several significant ways, most
notably: 1. Lake levels vary more widely and rapidly than sea level, hence,
shoreline strata are commonly poorly developed and relatively thin. 2. Lake
level and sediment supply are often closely linked in lake systems (most marine
models assume no linkage). These differences strongly influence the expression
of depo-sitional sequences and the occurrence, distribution, and character of
hydrocarbon source, reservoir, and seal play elements. Sequence boundaries vary
by lake-basin type, from non-existent or minimally developed, through extensive
erosion and incised-valley formation, to large basinward shifts and widespread
exposure. Flooding surfaces are enhanced as they are commonly coincident with
decreased sediment supply.
Lowstand systems tracts vary from aggradational stacks of
basin-floor turbidite strata to basin-center evaporites surrounded by extensive
desiccation surfaces. Transgressive systems tracts vary from thick and
coarse-clastic prone to thin and shale prone. Highstand systems tracts
range
from obliquely progradational clastic shoreline parasequences to aggradational
carbonate shoreline parasequences. Recognizing these differences is essential
to successful exploration and exploitation in lake basins.
AAPG Search and Discovery Article #90914©2000 AAPG Annual Convention, New Orleans, Louisiana