TABLE 6. Discussion of pollen zones depicted in figure 8.
Zone 7
0 - 11 cm

1996 to
< 1963
  • Arboreal taxa stable except for Quercus which increases.
  • Compositae (high and low-spine) and Graminea increase.
  • Coiled microforams increase dramatically.
 Modern zone, defined by an increase in microforam linings (fig. 9H) possibly resulting from the rise in salinity levels after construction of the Mississippi River/ Gulf Outlet Canal in the late 1950's.
Zone 6
11 - 77 cm

< 1963 to
> 1830
  • Arboreal taxa decline, especially TCT.
  • Non-arboreal taxa remain unchanged except Cheno-Am which fluctuates.
  • Compositae (low-spine) rises dramatically, then begins declining.
 Defined by the dramatic decrease in TCT and the large increase in low-spine Compositae. The TCT decline records the historic decline in Taxodium distichum (bald cypress) resulting from intensive logging between 1890 and 1925 and the slightly earlier logging associated with the expansion of New Orleans. Continued increase of low-spine Compositae is the result of logging and/or expanding settlement.
Zone 5
77 - 106 cm

> 1830 to
550 ± 50 yr BP
(1350 - 1450; uncalibrated)
  • Arboreal taxa remain the same except Quercus which declines.
  • Cheno-Am and Compositae (high-spine) remain low.
  • Compositae (low-spine) begins increase.
  • Cyperaceae, Graminea, Sagittaria, and Typha decline.
  • Vigna luteola appears for the first time.
 Most noticeable is the increase in low-spine Compositae (fig. 9F) and the appearance of Vigna luteola (fig. 9G) (cow pea) at 85 cm, an Old World domesticate that probably made its first appearance after colonization of New Orleans in 1717. The increase in the sun-loving, low-spine Compositae supports the hypothesis that Zone 5 reflects the period of colonization and clearing of the New Orleans area.
Zone 4
106 - 214 cm

550 ± 50
(1450 - 1350; uncalibrated) to
>1000 ± 60 yr BP
  • Pinus, Quercus, Salix, and TCT increase.
  • Cheno-Am and Compositae remain low.
  • Cyperaceae and Graminea are abundant.
  • Sagittaria appears for the first time.
  • Typha reaches a peak near the top of this zone.
 The return of wetland taxa such as Salix, Cyperaceae (fig. 9E) and Typha indicates an end to the drier conditions of Zone 3. Although Zone 4 is characterized by a return to wetter conditions, the abundance of Cyperaceae and Graminea, and the appearance of Sagittaria, make this wetland qualitatively different from the wetland of Zone 2. Zone 4 has a stronger marsh character and probably records the beginning of the disintegration of the St. Bernard deltaic plain following its maximum development.
Zone 3
214 - 305 cm

>1000 ± 60 to
2360 ± 60 yr BP
  • Juglans and Piperaceae make their only appearance.
  • Pinus, Quercus, and Compositae (low-spine) are common.
  • Salix and TCT decline.
  • Cheno-Am, Compositae (high-spine), and Typha decline.
  • Cyperaceae and Graminea increase at the initiation of the zone and subsequently disappear and decline, respectively.
 The presence of Juglans (and possibly Piperaceae) indicates a shift to drier, more terrestrial, conditions than those reflected in Zone 2. This conclusion is supported by the decline of Salix, Cheno-Am, and Typha. Following the delta model (Coleman and Roberts, 1989), Zone 3 is composed of the vegetation of the mature delta plain. That is, as the delta prograded further seaward of the core site, the site became more terrestrial in character.
Zone 2
305 - 384 cm

2360 ± 60 to
3180 ± 50 yr BP
  • Pinus and Quercus common.
  • Salix reaches a peak.
  • TCT (Taxodiaceae/Cupressaceae/Thuja) generally increases.
  • Cheno-Am (Chenopodiaceae-Amaranthaceae) fluctuates but maintains a strong presence throughout.
  • Compositae (high-spine), Graminea and Typha increase in the middle of the zone.
  • Compositae (low-spine) and Cyperaceae are present but rare.
 The presence of Quercus, Salix and TCT (fig. 9A) reflects the proximity of floodplain forests. Cheno-Am (fig. 9B) and Typha (fig. 9C) are typical pond or stream-side taxa in fresh to brackish water marshes. The presence of Compositae (high-spine) and Graminea (fig. 9D) is consistent with a marsh environment, perhaps along the delta margin. Zone 2 is synchronous with the developmental phase of the St. Bernard delta.
Zone 1
384 - 396 cm

3180 ± 50 to 8420 ± 60 yr BP
  • Pyrite abundant in sample.
  • Pollen not abundant.
 14C age is old compared to previous work in the area (Frazier, 1967). The date, on decomposed plant fragments in the interdistributary clay, probably reflects older, redeposited, organic material.
Source: U.S. Geological Survey Open-File Report 98-36. Carbon storage and late Holocene chronostratigraphy of a Mississippi River deltaic marsh, St. Bernard Parish, Louisiana (H.W. Markewich, ed.).

Last Updated on 2/5/98
By Gary R. Buell