What follows is a transcript of parts of Shattuck's description of the zones from the Calvert County volume of the Maryland Geological Survey. It is interesting to compare his descriptions with what you actually can see at Brownie's Beach today. I only include the section on Shattuck's original Calvert formation. The zones continue through the Choptank (16-20) which overlies the Calvert formation unconformably, and the St. Mary's formation (21-24).
More recently, several of Shattuck's zones have been reassigned. Zone 16 has moved from the Choptank to the Calvert formation, and zone 20 has moved from the Choptank to the St. Mary's formation.
Shattuck divided the Calvert formation in two members, the Fairhaven diatomaceous earth and the Plum Point marls, not to be confused with the more recent "members" described in the next section.
[...] The Fairhaven diatomaceous earth has been subdivided into three zones, which may be characterized as follows:
- Zone 1. - At the base of the Calvert formation and lying
uncomformably on the Eocene deposits is a bed of brownish sand carrying
Phacoides (Lucinoma) contractus. This stratum varies somewhat
in thickness from place to place, but does not depart widely from six feet
on the average.
- Zone 2. - Lying immediately above Zone 1 is a thin stratum
of white sand of about one foot in thickness, which is locally indurated
to form sandstone. It contains a large number of fossils, of which the
following are the most important: Ecphora tricostata, Panopea whitfieldi,
P. americana, Corbula elevata, Phacoides (Lucinoma) contractus, Venericardia
granulata, Astarte cuneiformis, A. thomasi, Thracia conradi, Pecten madisonius,
P. humphreysii, Chione latilirata, Cytherea staminea.
- Zone 3. - This stratum when freshly exposed consists of a greenish colored diatomaceous earth which, on weathering, bleaches to a white or buff-colored deposit breaking with a columnar parting and presenting perpendicular surfaces. It is very rich in diatomaceous matter, the mechanical analyses of specimens yielding more than 50 per cent of diatoms. The thickness of this bed varies from place to place, but where it is penetrated at Chesapeake Beach by an artesian well it has a thickness of about 55 feet. At Fairhaven, where it is well exposed, it caries large numbers of Phacoides (Lucinoma) contractus. This zone is best exposed at Popes Creek, Lyons Creek, Fairhaven, and in stream gullies lying along the northern margin of the Miocene beds.
- Zone 4. - (see photo)
At the base of the Plum Point marls and lying conformably
on Zone 3, the uppermost member of the Fairhaven diatomaceous earth is a
six-inch deposit of greenish sandy clay carrying Ostrea percrassa.
This zone first makes its appearance along the Calvert Cliffs at
Chesapeake Beach and continues on down the shore for about 2.5 miles, when
it can be no longer distinguished. Throughout this distance, the zone
does not dip toward the southeast in harmony with the other zones, which
are visible above it, but actually appears to rise slightly against the
dip until it finally vanishes at the point indicated. The eratic behavior
of this zone would seem to indicate a local migration and temporary
occupation of this particular area by Ostrea percrassa. This zone
corresponds to "Zone a" of Harris (Tertiary Geology of Calvert Cliffs,
Maryland. Amer. Jour. Sci., vol. xlv, 1893, pp 21-31).
- Zone 5. - This zone is developed immediately above Zone 4 and at
Chesapeake Beach has a thickness of 7 feet; as it is followed southward,
however, along the Calvert Cliffs, it is found to thin rapidly until at
a distance of about 2.5 miles south of Chesapeake Beach it has a thickness
of only 2 feet and 6 inches. At this point the base actually lies higher
than at Chesapeake Beach, although on account of the thinning the top lies
lower. From this point southward it dips away in harmony with the dip
of the other beds of the Calvert formation. The materials making up this
zone consist of a greenish sandy clay, which carries scattered bands of
Corbula elevata.
- Zone 6. - This zone consists of a greenish sandy clay carrying
large numbers of Corbula elevata which are distributed thickly
throughout the stratum and not separated in scattered bands as in the
zones immediately below and above it. At Chesapeake Beach, where this zone
is best developed, it attains a thickness of eight feet, but thins rapidly
toward the south, like the two preceding zones, until at a point 2.5 miles
south of Chesapeake Beach it has diminished to a thickness of two feet.
From this place it continues at about the same thickness until it finally
disappears beneath the beach at Plum Point.
- Zone 7. - Lying immediately above the last layer is a layer of
greenish sandy clay, resembling very much in appearance Zone 5, and carrying
scattered bands of Corbula elevata.
- Zone 8. - This stratum is lithologically like those immediately
preceding, but varies from them in either being devoid of fossils or
in carrying only a few poorly preserved fossil casts of a Corbula,
which is probably Corbula elevata. It consists of a greenish sandy
clay varying from 9 to 15 feet in thickness. It may be best seen along the
Calvert Cliffs from Chesapeake Beach to Plum Point.
- Zone 9. - This zone consists of greenish and greenish blue
sandy clay carrying scattered layers of Corbula elevata and varying
in thickness from 6 feet at Chesapeake Beach to 2 feet at Plum Point.
- Zone 10. - On account of its great and varied assemblage of
fossils this stratum is the most conspicuous zone in the entire Calvert
formation. It consists of a grayish green or a yellow to brown sandy
clay varying in thickness from 6 to 9 feet, and is continuously exposed
along the Calvert Cliffs from Chesapeake Beach till it drops below tide
two or three miles south of Plum Point Wharf. The following is a partial
list of the fossils found in this zone: Turritella indentata,
Phacoides anodonta, Crassatellites melinus, Astarte cuneiformis, Ostrea
sellaeformis, Pecten madisonius, Macrocallista marylandica, Atrina
harisii, Arca subrostata, Glycymeris parillis, etc. It corresponds
to "Zone b" of Harris.
- Zone 11. - This stratum consists of a greenish blue to a brown
sandy clay changing locally to a sand. It thickens somewhat as it passes
down the dip from 5 feet where it is exposed in the bluffs at Chesapeake
Beach to 13 feet 1.5 miles south of Plum Point Wharf, where it approaches
tide level. It is unfossiliferous or carries a few imperfect fossil casts.
- Zone 12. - When typically developed, this zone consists of a
brownish sandy clay, although at times it changes to a bluish color. In
many of its exposures only imperfect fossil casts can be distinguished,
but in other places it is found to carry Ecphora quadricostata var.
umbilicata, Venus mercenaria, Cytherea staminea, etc. It varies in
thickness from two to four feet and corresponds to "Zone c" of Harris.
- Zone 13. - The materials of this zone consist of a bluish sandy
clay more or less changed in sections to a yellowish or brownish color.
It carries imperfect fossil casts and varies in thickness from 32 feet
at Chesapeake Beach to 10 feet at a point one mile south of Parker Creek,
thus gradually thinning as it passes down the dip.
- Zone 14. - The materials which make up this stratum consist
of a brownish to yellowish sandy clay abundantly supplied with
Isocardia fraterna. It varies in thickness from 2 to 7 feet and
corresponds to "Zone d" of Harris.
- Zone 15. - This zone is the uppermost member of the Calvert
formation and consequently has been considerably eroded so that its
true thickness is not definitely known. It consists of a yellowish sandy
clay grading down locally into yellowish sand in its local portions. At a
point one mile south of Plum Point Wharf this zone shows a greater thickness
than anywhere else along the Calvert Cliffs; at that place it measures
48.5 feet. Sections north and south of this point have either been in great
part replaced by Pleistocene sand or have suffered by the unconformable
overlapping of the Choptank formation.
- Zone 16. - Note: Shattuck placed this zone in the Choptank Formation, but several recent authors have argued that zone 16 is actually the top most layer in the Calvert formation.
Members
More recently, Shattuck's zones have been grouped in to members:
| Member | Zones |
| Fairhaven | (1) 2-3 |
| Plum Point | 4-13 |
| Calvert Beach | 14-16 |
| Drumcliff | 17 |
| St. Leonard | 18 |
| Boston Cliffs | 19 |
| Conoy | 20 |
| Little Cove Point | 21-23 |
| Windmill Point | 24 |