GBDS

 
 
     

WELL LOG FACIES DEFINITION AND DEPOSITIONAL INTERPRETATION Gulf of Mexico Basin

REPRESENTATIVE LOG PATTERNS

DEPOSITIONAL SYSTEM AND FACIES ASSOCIATIONS

LITHOFACIES DESCRIPTION

INTERPRETATION

OCCURRENCE IN BASIN

FACIES ASSOCIATION

Fluvial

A. Bedload dominated

B. Mixed-load 
    dominated

C. Suspended-load
     dominated
 

Aggradational facies succession

Sand (A) to mud (C) dominated, heterolithic succession containing discontinuous sand bodies.
 
Sharp basal, variably sharp (A) to transitional, upward-fining (B, C) upper contacts.

Laterally discontinuous lithofacies.
 

Constructional alluvial
plain succession landward
of delta or shore zone
system.
 
Major fluvial systems source
deltaic depocenters. Bed load  systems occur primarily in the N.W. Gulf, Rio Grande
and Burgos basins. Major fluvial systems source
deltaic depocenters. Bed load
systems occur primarily in
the N.W. Gulf, Rio Grande
and Burgos basins.
 

fbl fml fsl  

Delta

Fluvial dominated

A. Platform delta
 
B. Shelf-margin delta
 

Progradational facies succession.

Heterolithic composition.

Upward coarsening, lenticular,
discontinuous sand bodies
overlying prodelta mud.

Digitate, laterally discontinuous
sand bodies.
 

Major delta system
prograding across shelf platform (A) or
directly onto the
continental slope (B).
 
Major fluvial-dominated
deltas are prominent
in the S. Louisiana,
Houston and Macuspana
depocenters.
 

dfp dfsm    

Delta

Wave-dominated

A. Platform delta

B. Shelf-margin delta
 

Progradational facies succession.

Sand rich.

Upward-coarsening to massive delta margin sand bodies overlying
prodelta mud.

Tabular to lobate, laterally
continuous sand bodies.
 

Major delta system
prograding across shelf
platform (A) or directly
onto the continental
slope (B).
 
Major delta system
prograding across shelf
platform (A) or directly
onto the continental
slope (B).
 

dwp dwsm

Shore zone

Wave-dominated
 

Progradational to aggradational
facies successions.

Sand rich.

Upward-coarsening to massive, lenticular to tabular, clean sand
bodies.

Transitional to sharp base;
sharp top.
 

Constructional shorelines
supplied by longshore
reworking from major
deltaic systems and/or
reworking of non-deltaic
coastal plain fringes.
Includes barrier/ lagoon
and strandplain complexes.
 
Thick shore-zone systems
occur in Paleogene through
Middle Miocene depisodes.
 

sz

Shelf

A. Mud-dominated shelf

B. Sandy wave-dominated shelf

C. Carbonate-dominated shelf
Aggradational to progradational blankets and prisms.
 
 

Aggradational to progradational blankets and prisms.

Sharp to transitional vertical boundaries.

Transitional lateral boundaries.

Massive to interstratified lithologies.

Neritic faunas.
 

Constructional shelves
marginal to major
delta systems, fronting
shore-zone systems, or
capping transgressive
coastal successions.
 

Carbonate shelves and
ramps dominate the Florida
and Yucatan margins.
Relatively thick, clastic shelf
systems occur in Paleogene-
Miocene depisodes along
N.W. and N.C. Gulf margins  

sm ss sc  

Slope

Progradational delta-fed apron

A. Sandy

B. Muddy
 

Offlapping succession of sandy to muddy turbidite and debris flow deposits.

Upward-shoaling succession with bathyal faunas.

Discontinuous, sharp to
transitionally bounded sand bodies.

Abundant syndepositional faults.

Capped by delta system facies.
 

Constructional continental
margin primarily supplied
by a superjacent
shelf -margin delta complex.
 
Front major delta
depocenters of N., N.W.
and S.W. Gulf.
 

sbpsd sbpmd  

Slope

Progradational shelf-fed apron

A. Sandy

B. Muddy
 

Offlapping succession of sandy to muddy turbidite and debris flow deposits.

Upward-shoaling succession with bathyal faunas.

Discontinuous, sharp to
transitionally bounded sand bodies.

Capped by shelf system facies.
 

Constructional continental
margin primarily supplied
by a superjacent shelf.
 
Front major shelf and
shore-zone  depositional
system tracts of the N.W.
and N.C. Gulf Paleogene-
Miocene depisodes.
 

sbpss sbpms

Slope

Sandy retrogradational
slope apron
 

Onlapping succession of muddy to sandy turbidite, debris flow and
slump deposits.

Upward-deepening and fining succession with bathyal or mixed faunas.

Heterolithic interbedded, discontinuous facies association.
 

Destructional sandy to
heterolithic continental
margin undergoing
long-term mass wasting.
 
Locally prominent within
OF, PGa, and PAB
depisodes.
 
 

sbras

Slope

Muddy retrogradational
slope apron
 

Onlapping succession of muddy debris flow and slump deposits.

Upward deepening paleobathymetry
 

Destructional muddy 
continental margin
undergoing long-term
mass wasting.
 
Locally prominent within
OF, PGa, and PAB
depisodes.
 

sbram

Slope

Submarine canyon fill
 

Laterally bounded by deeply incised erosion surface.

Dominantly mud fill with
lenticular to lobate turbidite
channel and lobe sand bodies and discontinuous heterolithic slump
and debris flow deposits.

Capped by progradational
upper slope mud and sandy
shelf or deltaic facies.
 

Large-scale focused
mass-wasting and
submarine erosion
creating a canyon,
which subsequently fills 
with onlapping debris
flow and turbidite
deposits capped by an
offlapping succession of
shelf or prodelta sediment.
 
Locally prominent in the
early Paleogene depisodes
of the W., N.W. and C. Gulf
and in the PS depisode of
the N.C. Gulf.
 

sbsc

Slope to basin
 
Megaslide complex
 
Bounded updip at base by slide plane.

Rotated fault blocks to chaotic
debris apron.

Upper progradational facies succession overlies middle muddy unit; turbidite and sandy debris flow deposits and/or disarticulated blocks of upper slope, shelf-margin delta or other shallow facies concentrated in lower part of wedge.

Subregional failure of upper
slope and shelf margin
creating an embayment or
re-entrant in basin margin.
Slide blocks and
incompletely evacuated
debris flow form basal fill.
Turbidites and smaller
debris flows scour and pond
between these. Prograding
muddy slope apron deposits
heal the embayment.
 
Locally prominent within
OF, PGa, PAB and PTA
depisodes.
 

sbms

Basin floor

A. Basinal mud

B. Sand-rich submarine fan
Mud; mud with interbedded sand
and mud units.
 

Transitional to sharp upper
boundary.

Sharp lower boundaries on sand
bodies.

Bathyal faunas.
 

Deposition on basin floor by
low to high density turbidity
currents and fluidal debris
flows.
 
Pentrated only by deep
wells in the N.E. and N.C.
Gulf margin.
 

bsbsf