Field Trip Stop Descriptions
Field trip stops (fig. 8).
Potomac River Sections
Stop 1. Aquia Creek.
Right bank of Aquia Creek, 0.5 mi (0.8 km) above Thorney Point, Stafford County, Va.
| ft | m | ||
|---|---|---|---|
| Sloped and covered by vegetation | 3.0 | 0.9 | |
| Paleocene | |||
| Aquia Formation | |||
| Piscataway Member | |||
| Sand, grayish-orange (10YR 7/4), silty, fine-grained, very | 9.0 | 2.7 | |
| glauconitic, poorly sorted, weathered, and leached; | |||
| some molds and casts | |||
| —Unconformity— | |||
| Brightseat Formation | |||
| Sand, dark-olive-black (5Y 2/1), micaceous, clayey, silty, very fine | 7.0 | 2.1 | |
| grained, well-sorted in the lower half, weathered to grayish-orange in | |||
| the upper half; an 8-in (20-cm)-thick indurated capping present at the | |||
| lower end of the exposure but beveled off at the upper end of the exposure | |||
| —Unconformity— | |||
| Lower Cretaceous | |||
| Patapsco Formation | |||
| Sand, well-consolidated, clayey, silty, light-blue-gray (5B 7/1); | 0.0–1.0 | 0.0–0.3 | |
| burrowed and eroded upper surface | |||
| —Sea Level— |
Below the mouth of Aquia Creek, most of the good exposures are on the Virginia shore for the next 5.0 mi (8.0 km). The bluffs immediately downriver of the mouth of Aquia Creek are the site of the lectostratotype section of the upper Paleocene Aquia Formation. Ward (1985, p. 62) described the section as follows.
Stop 2. Aquia Creek.
Right bank of the Potomac River, 1.5 mi (2.4 km) below the mouth of Aquia Creek, Stafford County, Va.
| ft | m | ||
|---|---|---|---|
| Covered | 5.0 | 1.5 | |
| Eocene | |||
| Nanjemoy Formation | |||
| Sand, yellowish-gray (5Y 8/1), weathered, | 5.0 | 1.5 | |
| moderately glauconitic, fine-grained | |||
| Paleocene | |||
| Marlboro Clay | |||
| Clay, light-gray (N 8), weathered; where this bed is | 0.0–0.75 | 0.0–0.23 | |
| absent there is a distinct line between the Aquia Formation | |||
| and the overlying bed of Nanjemoy Formation | |||
| Aquia Formation | |||
| Paspotansa Member | |||
| Sand, weathered, grayish-orange (10YR 7/4), | 35.0 | 10.7 | |
| glauconitic, fine-grained; contains large number of Turritella | |||
| in lenses, bands, and large indurated masses | |||
| Sand, olive-black (5Y 2/1), fine-grained, well-sorted, silty; | 25.0 | 7.6 | |
| scattered, poorly preserved Turritella | |||
| Sand, olive-black (5Y 2/1), glauconitic, very fine grained, | 1.5 | 0.5 | |
| well-sorted; many Turritella ("Zone 6" of Clark and Martin, 1901) | |||
| — Unconformity— | |||
| Aquia Formation |
|||
| Piscataway Member |
|||
| Sandstone, light-olive-gray (5Y 6/1), indurated, | 2.0 | 0.6 | |
| glauconitic: many molds and casts, some siliceous | |||
| replacements ("Zone 5" of Clark and Martin, 1901) |
|||
| Sand, olive-gray (5Y 4/1), very glauconitic, silty, | 12.0 | 3.7 | |
| clayey, very shelly, poorly sorted; packed with large | |||
| bivalves and Turritella. Appears light-olive-gray | |||
| (5Y 6/1) from a distance because of large numbers of | |||
| mollusks present; preservation, poor to moderate; | |||
| irregularly indurated in beds where Ostrea are concentrated | |||
| — Sea Level— | |||
Stop 3. Belvedere Beach.
Right bank of the Potomac River, 0.3 mi (0.5 km) above Belvedere Beach, King George County, Va.
| ft | m | |||
|---|---|---|---|---|
| Covered | 5.0 | 1.5 | ||
| Paleocene | ||||
| Aquia Formation | ||||
| Paspotansa Member | ||||
| Sand, olive-black (5Y 2/1), fine-grained, well-sorted, silty, | 12.0 | 3.7 | ||
| micaceous, glauconitic; many Turritella, scattered | ||||
| as well as in distinct bands; common Ostrea sinuosa; | ||||
| moderate molluscan diversity | ||||
| —Sea Level— |
Stop 4. Fairview Beach Marina
Right bank of the Potomac River, just 100 yd below the Fairview Beach Marina, King George County, Va. (Ward, 1985, p. 64).
| ft | m | |||
|---|---|---|---|---|
| Sloped and covered | 5.0 | 1.5 | ||
| Eocene | ||||
| Nanjemoy Formation | ||||
| Potapaco Member (Bed A) | ||||
| Sand, grayish-yellow (5Y 8/4), weathered, clayey, fine-grained, |
6.0 | 1.8 | ||
| poorly sorted, glauconitic | ||||
| — Unconformity— | ||||
| Paleocene |
||||
| Marlboro Clay |
||||
| Clay, light-gray (N 7), somewhat weathered, blocky |
6.0 | 1.8 | ||
| Aquia Formation |
||||
| Paspotansa Member | ||||
| Sand, grayish-yellow, silty, very weathered; molds |
2.5 | 0.8 | ||
| of Turritella mortoni | ||||
| — Sea Level— |
Stop 5. Woodstock Member lectostratotype.
Right bank of the Potomac River (high bluffs), 2.0 mi (3.2 km) above Mathias Point, King George County, Va.
| ft |
m |
|||
|---|---|---|---|---|
| Pleistocene |
||||
| Sand, orange, coarse-grained |
5.0 | 1.5 | ||
| Conglomerate, sand, gravel, cobbles, boulders |
3.0 | 0.9 | ||
| — Unconformity— | ||||
| Miocene |
||||
| Calvert Formation |
||||
| Fairhaven Member |
||||
| Clay, yellowish-gray (5Y 8/1), silty, somewhat |
17.0 | 5.2 | ||
| sandy near base, weathered, blocky, diatomaceous, |
||||
| phosphate pebbles and coarse-grained sand along |
||||
| basal contact |
||||
| — Disconformity— | ||||
| Eocene |
||||
| Nanjemoy Formation |
||||
| Woodstock Member |
||||
| Sand, pale-greenish-yellow (10Y 8/2), weathered, | 25.0 | 7.6 | ||
| fine-grained, micaceous; molds and casts; upper surface | ||||
| very eroded and burrowed with as much as 3 ft | ||||
| (0.9 m) of relief | ||||
| Sand, olive-black (5Y 2/1), silty, very fine grained, | 15.0 | 4.6 | ||
| micaceous, glauconitic; small mollusks with | ||||
| moderate preservation | ||||
| — Sea Level— |
Stop 6. Popes Creek.
Left bank of the Potomac River, 0.95 mi (1.5 km) below the mouth of Popes Creek, Charles County, Md.
| ft | m | |||
|---|---|---|---|---|
|
Pleistocene |
||||
| Conglomerate, yellowish-orange, weathered; gravel, sand, | 25.0 | 7.6 | ||
| cobbles, boulders | ||||
| Miocene |
||||
| Calvert Formation |
||||
| Fairhaven Member |
||||
| Clay, light-yellowish-gray (5Y 9/1), blocky, |
10.0 | 3.0 | ||
| diatomaceous |
||||
| Sand, yellowish-gray (5Y 8/1), silty |
2.0 | 0.6 | ||
| — Disconformity— |
||||
| Clay, light-yellowish-gray (5Y 9/1), blocky |
0.5 | 0.2 | ||
| Sand, yellowish-gray (5Y 8/1), silty |
5.0 | 1.5 | ||
| Sand, olive-brown (5Y 4/4), silty, phosphatic,
pebbles |
1.5 | 0.5 | ||
| Sand, yellowish-gray (5Y 7/2), silty |
2.5 | 0.8 | ||
| Sand, olive-brown (5Y 4/4), silty, phosphatic,
pebbles |
2.0 | 0.6 | ||
| — Unconformity— |
||||
| Eocene |
||||
| Nanjemoy Formation(?) The following unit is provisionally placed in
the Woodstock Member. |
||||
| Sand, olive-gray (5Y 4/1), medium-grained, very
glauconitic; |
0.75 | 0.23 | ||
| many molds and casts; unit becoming thicker downstream |
||||
| — Disconformity— | ||||
| Nanjemoy Formation | ||||
| Woodstock Member |
||||
| Sand, olive-black (5Y 2/1), very fine grained,
micaceous, |
5.0 | 1.5 | ||
| silty, glauconitic; many small mollusks, poorly |
||||
| preserved |
||||
| Concretions, olive-gray (5Y 4/1), calcareous, |
5.0 | 1.5 | ||
| sandy, glauconitic, rounded |
||||
| Sand, olive-black (5Y 2/1), very fine grained, micaceous, | 5.0 | 1.5 | ||
| silty, glauconitic; many small mollusks, moderately | ||||
| preserved | ||||
| — Sea Level— |
Chesapeake Bay Section
Stop 7. Randle Cliffs (northern end).
High bluff just south of Chesapeake Beach, Calvert County, Md.
| ft | m | |||
|---|---|---|---|---|
| Soil | 2.0 | 0.6 | ||
| —Unconformity— | ||||
| Miocene | ||||
| Choptank Formation | ||||
| Boston Cliffs Member | ||||
| Silt, sandy, blocky (Bed 19) | 7.0 | 2.1 | ||
| —Unconformity— | ||||
| Drumcliff and St. Leonard Members, undivided | ||||
| Silt, sandy, blocky (Beds 17, 18) | 10.0 | 3.0 | ||
| Calvert Formation | ||||
| Calvert Beach Member | ||||
| Silt, clayey, blocky (Bed 15) | 6.0 | 1.8 | ||
| Sand, silty, shelly (Bed 14) | 17.0 | 5.2 | ||
| Plum Point Member | ||||
| Silt, clayey, blocky (Bed 13) | 6.0 | 1.8 | ||
| Sand, silty; poorly preserved shells (Bed 12) | 3.0 | 0.9 | ||
| Silt, clayey, blocky (Bed 11) | 2.0 | 0.6 | ||
| Sand, silty; very shelly (Bed 10) | 10.0 | 3.0 | ||
| —Unconformity— | ||||
| Sand, silty; many Corbulids concentrated | 35.0 | 10.7 | ||
| in bands (Beds 4–9) | ||||
| Fairhaven Member | ||||
| Silt, clayey, blocky, burrowed (Bed 3) | 2.0 | 0.6 | ||
| —Sea Level— |
Stop 8. Camp Roosevelt.
3.7 mi south of the mouth of Fishing Creek at Chesapeake Beach, Calvert County, Md.
| ft | m | |||
|---|---|---|---|---|
| Soil | 2.0 | 0.6 | ||
| — Unconformity— | ||||
| Miocene | ||||
| Choptank Formation | ||||
| Boston Cliffs Member | ||||
| Silt, sandy, fine-grained, with sand near base (Bed 19) | 14.0 | 4.3 | ||
| Drumcliff Member | ||||
| Sand, silty, clayey; poorly preserved shells (Bed 17) | 1.0 | 0.3 | ||
| — Unconformity— | ||||
| Calvert Formation | ||||
| Calvert Beach Member | ||||
| Silt, clayey, blocky (Bed 15) | 10.0 | 3.0 | ||
| Sand, silty, clayey; poorly preserved shells (Bed 14) | 10.0 | 3.0 | ||
| Plum Point Member | ||||
| Silt, clayey, blocky (Bed 13) | 7.0 | 2.1 | ||
| Sand, silty, shelly (Bed 12) | 4.0 | 1.2 | ||
| — Unconformity— | ||||
| Silt, clayey, blocky (Bed 11) | 4.0 | 1.2 | ||
| Sand, silty; very shelly (Bed 10) | 12.0 | 3.7 | ||
| — Unconformity— |
||||
| Sand, silty; many small Varicorbula | 25.0 | 7.6 | ||
| concentrated in several distinct bands (Beds 4–9) |
Stop 9. Plum Point.
1.0 mi (1.6 km) south of Plum Point, Calvert County, Md.
| ft | m | |||
|---|---|---|---|---|
| Miocene | ||||
| Choptank Formation | ||||
| Boston Cliffs Member | ||||
| Silt, clayey, blocky (Bed 19) | 17.0 | 5.2 | ||
| St. Leonard Member | ||||
| Silt, clayey, blocky (Bed 18) | 9.0 | 2.7 | ||
| Drumcliff Member | ||||
| Sand, silty, clayey; some preserved shells (Bed 17) | 4.0 | 1.2 | ||
| Calvert Formation | ||||
| Calvert Beach Member | ||||
| Silt, clayey, blocky, laminated (Bed 15) | 10.0 | 3.0 | ||
| Sand, silty, clayey; moderately shelly (Bed 14) | 15.0 | 4.6 | ||
| Plum Point Member | ||||
| Silt, clayey, blocky (Bed 13) | 13.5 | 4.1 | ||
| Sand, silty, clayey; poorly preserved mollusks (Bed 12) | 2.5 | 0.8 | ||
| Silt, clayey, blocky (Bed 11) | 10.0 | 3.0 | ||
| Sand, silty; very shelly (Bed 10) |
9.0 | 2.7 | ||
| — Sea Level— |
Stop 10. Parkers Creek.
Just above Scientists Cliffs, Calvert County, Md.
| ft | m | |||
|---|---|---|---|---|
| Covered with vegetation | 1.5 | 0.5 | ||
| Miocene | ||||
| St. Marys Formation | ||||
| Clay, silty | 4.9 | 1.5 | ||
| Choptank Formation | ||||
| Boston Cliffs Member | ||||
| Sand, silty, fine-grained; many mollusks | 13.1 | 4.0 | ||
| St. Leonard Member | ||||
| Sand, clayey, silty, well-burrowed; some molds | 14.7 | 4.5 | ||
| of mollusks |
||||
| Drumcliff Member | ||||
| Sand, very shelly, fine-grained; many large mollusks, | 13.1 | 4.0 | ||
| well-preserved | ||||
| Calvert Formation | ||||
| Calvert Beach Member | ||||
| Sand, silty, fine-grained; scattered, small, | 6.5 | 2.0 | ||
| poorly preserved mollusks | ||||
| Sand, shelly, silty; many mollusks, especially Glossus | 4.9 | 1.5 | ||
| Plum Point Member | ||||
| Clay, blocky, silty | 9.8 | 3.0 | ||
| Sand, shelly, silty; many, poorly preserved mollusks | 0.9 | 0.3 | ||
| Clay, blocky, silty |
4.2 | 1.3 | ||
| — Sea Level— |
Stop 11. Baltimore Gas and Electric Powerplant.
The section given below, now inaccessible, was described from a bluff just upbay from the powerplant, Calvert County, Md. A similar section near Rocky Point, below the plant site, will be visited instead.
| ft | m | |||
|---|---|---|---|---|
| Pleistocene(?) | ||||
| Miocene | ||||
| St. Marys Formation | ||||
| Little Cove Point Member | ||||
| Soil | 1.5 | 0.5 | ||
| Sand, pebbly, coarse-grained | 10.0 | 3.0 | ||
| Sand, silty, fine-grained; molluscan molds | 14.7 | 4.5 | ||
| Sand, fine-grained, burrowed, clean, well-sorted | 3.2 | 1.0 | ||
| Sand, medium-grained, well-sorted | 3.2 | 1.0 | ||
| Shell hash, clayey, sandy; very worn mollusks | 1.9 | 0.6 | ||
| Clay, sandy; scattered, small fragmented mollusks | 4.9 | 1.5 | ||
| Clay, sandy; scattered, small, poorly preserved mollusks | 1.3 | 0.4 | ||
| Clay, sandy; scattered, small shells | 4.9 | 1.5 | ||
| Sand, shelly, fine-grained | 1.5 | 0.5 | ||
| Clay, blocky; molluscan molds | 1.9 | 0.6 | ||
| Sand, clayey, fine-grained | 5.1 | 1.6 | ||
| Clay, blocky; molluscan molds abundant | 5.1 | 1.6 | ||
| along thin horizontal planes | ||||
| Choptank Formation | ||||
| Boston Cliffs Member | ||||
| Sand, shelly, fine-grained; abundant large mollusks, upper | 5.1 | 1.6 | ||
| 1.0 m (3.3 ft) indurated | ||||
| St. Leonard Member | ||||
| Sand, silty, fine-grained, very burrowed; mollusks scarce, | 5.1 | 1.6 | ||
| scattered, poorly preserved | ||||
| Drumcliff Member | ||||
| Sand, shelly, silty, fine-grained; abundant mollusks, | 10.4 | 3.2 | ||
| cetacean remains common |
Stop 12. Little Cove Point.
Bluff, 0.6 mi (1.0 km) downbay from Little Cove Point, Calvert County, Md.
| ft | m | |||
|---|---|---|---|---|
| Pliocene(?) | ||||
| Sand, grayish-orange (10YR 7/4), interbedded with thin | 30.0 | 9.1 | ||
| clay layers, flaser-bedded, ripple-marked | ||||
| Sand, reddish-orange (10YR 5/6) medium- to coarse-grained, | 5.0 | 1.5 | ||
| burrowed, crossbedded, with pebbles and cobbles at base | ||||
| Miocene | ||||
| St. Marys Formation | ||||
| Little Cove Point Member | ||||
| Sand, yellow-orange (10YR 5/6), poorly sorted, burrowed | 13.0 | 4.0 | ||
| Sand, olive-gray (5Y 4/1), fine-grained, silty, | 15.0 | 4.6 | ||
| interbedded with silty clay | ||||
| Sand, olive-gray (5Y 4/1), silty, fine-grained; | 11.0 | 3.4 | ||
| molluscan molds only | ||||
| Sand, olive-gray (5Y 4/1), silty, fine-grained, | 5.0 | 1.5 | ||
| glauconitic; abundant mollusks | ||||
| Sand, olive-gray (5Y 4/1), silty, fine-grained; few mollusks | 6.0 | 1.8 | ||
| Sand, olive-gray (5Y 4/1), fine-grained, very shelly; mollusks | 1.0 | 0.3 | ||
| dominated by Turritella, many worn | ||||
| Sand, grayish-olive-gray (5G 4/1), silty, fine-grained, | 3.0 | 0.9 | ||
| burrowed; small, fragile mollusks |
U.S. Department of the Interior, U.S. Geological Survey
URL: https://
pubsdata.usgs.gov
/pubs/circ/2004/1264/html/trip9/log.html
For more information, contact Lauck Ward
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