|
publications >
papers > sequence stratigraphy... > carbonate ramp and bounding siliciclastics > peace river formation > lithostratigraphy
SEQUENCE STRATIGRAPHY OF A SOUTH FLORIDA CARBONATE RAMP AND BOUNDING SILICICLASTICS (LATE MIOCENE-PLIOCENE)
CARBONATE RAMP AND BOUNDING SILICICLASTICS TEMPORAL AND SPATIAL BOUNDARIES
Peace River Formation
Lithostratigraphy
Three depositional sequences (DS1, DS2, and DS3) are newly defined on a regional scale within the Peace River Formation (Fig. 2). Although interpreted to be depositional sequences, DS3 actually may be a parasequence. Much of the lithofacies analysis completed by Reese and Cunningham (2000, in press) for southeastern Florida was limited mostly to DS2 and DS3. Depositional sequence 1 (DS1) was characterized primarily by Weedman et al. (1997) and Edwards et al. (1998). Five lithofacies have been identified by Reese and Cunningham (2000, in press) for the upper part of the Peace River Formation in an area shown in Figure 1: (1) diatomaceous mudstone, (2) terrigenous mudstone, (3) clay-rich quartz sand, (4) quartz sand, and (5) pelecypod-rich quartz sand or sandstone (Table 1).
 |
 |
| Figure 3. Structure contour map of the top of the mudstone contained in condensed section 2 (CS2) within depositional sequence 2 (DS2) of the Peace River Formation in southern Florida. The dashed line shows the mapped limit of CS2. Structure contours show altitude in feet below sea level of top of the mudstone. [larger image] |
Figure 4. Structure contour map of the top of the mudstone contained in condensed section 3 (CS3) within depositional sequence 3 (DS3) of the Peace River Formation in southern Florida. Both mudstones mapped on the southwestern and southeastern parts of Florida were deposited during the early Pliocene, possibly synchronously, as suggested by dating from Missimer (1997) for the W-16523 corehole in Lee County and the biochronology of the mudstones in Palm Beach and Martin Counties. Structure contours show altitude in feet below sea level of top of the mudstone. [larger image] |
|
The diatomaceous mudstone and terrigenous mudstone typically occur as a couplet with the diatomaceous mudstone underlying the terrigenous mudstone. Two mudstone couplets were identified as CS2 and CS3 (Fig. 2). Structure contour maps of the two condensed sections show that the lower condensed section (CS2) extends over about 6,000 square miles of southeastern Florida (Fig. 3); the upper condensed section (CS3) is considerably more limited in areal extent (Fig. 4). The lower condensed section (CS2) thins and pinches out in a paleo-landward or western direction (Figs. 5 and 6). The paleo-seaward lap out of CS2 is near the southern margin and probably near the southeastern margin of the Florida peninsula (Figs. 3 and 6). The updip lap out of CS3 is in a paleo-seaward direction from the updip lap out of CS2, suggesting eastward offlapping progradation of Peace River siliciclastics (Fig. 6).
Above the lower mudstone in much of the study area, the Peace River Formation is composed, from bottom to top, of clay-rich quartz sand, quartz sand, and pelecypod-rich quartz sand and sandstone (Table 1). Some of the clay-bearing facies of the Peace River Formation may grade laterally into mainly quartz sand facies in the western part of the study area.
| Table 1. Lithofacies characteristics of the upper part of the Peace River Formation for the area outlined in Figure 1
[Visual estimation was made for porosity. Hydraulic conductivity was estimated by comparison of corehole from Fish and Stewart (1991, table 6)]
|
|
Characteristic
|
Lithologic description
|
|
Diatomaceous Mudstone Facies
|
|
Depositional textures
|
Diatomaceous mudstone
|
|
Color
|
Mainly yellowish-gray 5Y 7/2 and light-olive-gray 5Y 5/2
|
|
Grain size
|
Mainly terrigenous clay and fine sand-size diatoms; minor silt-size quartz; local very fine sand-size quartz and phosphate grains, and fish scales
|
|
Carbonate grains
|
Local benthic foraminifers
|
|
Accessory grains
|
Common quartz grains and local phosphate grains
|
|
Porosity
|
Minor microporosity
|
|
Hydraulic conductivity
|
Very low (less than 0.1 foot per day)
|
|
Terrigenous Mudstone Facies
|
|
Depositional textures
|
Terrigenous mudstone and claystone
|
|
Color
|
Mainly light-olive-gray 5Y 5/2, yellowish-gray 5Y 7/2, and olive-gray 5Y 4/1, 5Y 3/2
|
|
Grain size
|
Mainly terrigenous clay; minor silt-size quartz; local very fine sand- to granule-size quartz grains and very fine sand- to pebble-size phosphate grains
|
|
Carbonate grains
|
Local benthic foraminifers and pelecypod fragments
|
|
Accessory grains
|
Common quartz grains; local diatoms, phosphate grains, mica, fish scales, shark’s teeth
|
|
Porosity
|
Minor microporosity
|
|
Hydraulic conductivity
|
Very low (less than or equal to 0.1 foot per day)
|
| Clay-Rich Quartz Sand Facies |
|
Depositional textures
|
Terrigenous clay-rich sand
|
|
Color
|
Mainly yellowish-gray 5Y 7/2 and 5Y 8/1, and light-gray-olive 5Y 6/1
|
|
Grain size
|
Mainly very fine quartz grains; minor silt-size quartz grains and terrigenous mud; local micrite, fine sand-size to small pebble-size quartz grains and very fine sand-size to pebble-size phosphate grains
|
|
Carbonate grains
|
Local thin-shelled pelecypods, oysters, Turritella and benthic foraminifers
|
|
Accessory grains
|
Common phosphate grains (trace to 40 percent); minor heavy minerals; trace mica
|
|
Porosity
|
Mainly intergrain; local moldic; ranges from 5 to 20 percent
|
|
Hydraulic conductivity
|
Mainly very low (less than 0.1 foot per day) to low (0.1 to 10 feet per day); ranges from very low (less than 0.1 foot per day) to moderate (10 to 100 feet per day)
|
| Quartz Sand Facies |
|
Depositional textures
|
Quartz sand with less than 10 percent skeletal grain
|
|
Color
|
Mainly yellowish-gray 5Y 8/1 and yellowish-gray 5Y 7/2; locally medium-dark-gray N4 to very light gray N8, light-olive-gray 5Y 5/2, grayish-yellow-green 5GY 7/2, pale-olive 10Y 6/2, very pale orange 10YR 8/2, and pale-yellowish-brown 10YR 6/2
|
|
Grain size
|
Mainly very fine to medium quartz sand; ranges from silt to granule size; carbonate grains range from silt to pebble size; terrigenous clay
|
|
Carbonate grains
|
Pelecypods (local Pecten and Chione), benthic foraminifers, echinoids, and undifferentiated skeletal grains
|
|
Accessory grains
|
Trace to 30 percent phosphate and heavy mineral grains; local minor terrigenous clay; local trace mica; trace to 1 percent plagioclase; trace microcline
|
|
Porosity
|
Intergrain; ranges from 5 to 20 percent
|
|
Hydraulic conductivity
|
Mainly low (0.1 to 10 feet per day) to moderate (10 to 100 feet per day); ranges from very low (less than 0.1 foot per day) to moderate (10 to 100 feet per day)
|
| Pelecypod-Rich Quartz Sand or Sandstone Facies |
|
Depositional textures
|
Quartz sand matrix with pelecypod rudstone framework, or quartz sand supporting skeletal floatstone
|
|
Color
|
Mainly yellowish-gray 5Y 8/1 and 5Y 7/2; locally light-gray N7 to white N9, light-olive-gray 5Y 5/2, light-olive-gray 5Y 6/1, and very pale orange 10YR 8/2
|
|
Grain size
|
Mainly very fine to fine quartz sand; ranges from silt to very coarse quartz sand; carbonate grains range from silt to cobble size; local terrigenous clay and lime mudstone
|
|
Carbonate grains
|
Pelecypods (including Pecten and oysters), undifferentiated skeletal grains, gastropods (including Turritella), bryozoans, serpulids, and echinoids
|
|
Accessory grains
|
Trace to 40 percent phosphate and heavy mineral grains; local minor terrigenous clay and lime mudstone; local trace mica
|
|
Porosity
|
Intergrain and moldic; ranges from 5 to 25 percent; local abundant pelecypod molds contribute to high porosity
|
|
Hydraulic conductivity
|
Mainly low (0.1 to 10 feet per day) to moderate (10 to 100 feet per day); ranges from very low (less than 0.1 foot per day) to high (100 to 1,000 feet per day)
|
|
|
