Samples were selected from the Bethany Beach corehole for palynological analysis based on lithologies that were most likely to yield spores, pollen, or dinocysts. Samples were subjected to standard processing methods, similar to those described in Traverse (1988). Dilute nitric acid was used for oxidation, which removes excess organic debris, but oxidation can lower the recovery of some protoperidinacean dinoflagellates, especially Brigantedinium (Hopkins and McCarthy, 2001; F.M.G. McCarthy, pers. comm., 2002). Relative abundances were determined for most samples between 8.0 and 753.9 ft (2.44 and 229.79 m) based on counts of ~300 specimens (Fig. F9). Relative abundances for samples at 449.9 and 477.9 ft (137.13 and 145.66 m) and from 822.8 to 1467.2 ft (250.79 to 447.20 m) are estimates based on thorough scans of the samples (counts not yet completed). Only the most abundant, clearly identifiable, and stratigraphically important forms are included in Figure F9. Less abundant taxa are not included on the figure because of difficulty in estimating their abundances in the samples that were not counted; however, most are noted in the text.
The pollen assemblages of the Omar Formation reflect a distinct change in climate through the deposition of the unit. Samples from the upper part of the Omar (8.0, 16.4, and 24.5, ft; 2.44, 5.00, and 7.47 m) contain a cool-climate assemblage dominated by Pinus (pine) and Picea (spruce). Other common constituents include Betula (birch), Carya (hickory), Quercus (oak), Sphagnum (moss), Lycopodium (clubmoss), Polypodiaceae (polypod fern family), Gramineae (grass family), and Cyperaceae (sedge family). In contrast, the pollen assemblages in the lower samples (34.4, 40.9, and 45.8 ft; 10.49, 12.47, and 13.96 m) reflect warmer conditions. Pinus and Quercus are the most abundant, with Pinus decreasing downward somewhat as Fagus (beech) becomes more abundant; Picea, Sphagnum, and Betula are absent or uncommon. Dinoflagellates are present in most of the samples from the Omar Formation, indicating estuarine or shallow-marine conditions. Other taxa present include Abies (fir), Alnus (alder), Carpinus (American hornbeam), Castanea (chestnut), Liquidambar (sweetgum), Salix (willow), Tilia (linden), Tsuga (hemlock), Ulmus (elm), TCT (Taxodiaceae-Cupressaceae-Taxaceae, or the bald cypress-cypress-yew families), Ericaceae (heath family), Caryophyllaceae (pink and chickweed family), Cheno-Ams (goosefoot and amaranth families), Ambrosia-group composites (ragweeds), and Aster-type composites (sunflowers and daisies).
All samples examined for palynomorphs in the Beaverdam Formation had very poor recovery or were barren.
Samples from the Bethany formation (117.8, 127.0, 156.1, and 196.1 ft; 35.91, 38.71, 47.58, and 59.77 m) have assemblages dominated by Carya and Quercus, with Quercus most abundant in the upper part of the unit and Carya most abundant in the lower part. Liquidambar (sweet gum) and Pinus are common, but the latter is less abundant than in the Omar Formation. The Bethany formation also includes several stratigraphically significant "exotic" taxa, plants that are extinct in eastern North America. Rare grains of Pterocarya (wing nut) and Engelhardia-type pollen have their highest occurrences at 117.8 ft (35.91 m) in the Bethany formation and are present in all Bethany samples studied. Groot (in Groot et al., 1990) considered the presence of such "exotic" taxa to be indicative of a pre-Pleistocene age. In addition, a single specimen of cf. Dacrydium (Huon Pine) was noted at 156.1 ft (47.58 m); this conifer is currently restricted to Asia, Australasia, and western South America but was recently noted in the Pliocene of Florida by Hansen et al. (2001). A variety of other palynomorphs are present in the Bethany formation: Alnus, Betula, Carpinus, Castanea, Ilex, Salix, TCT, Tilia, Tsuga, Ulmus, Fagus, Juglans, Nyssa, Gramineae, Caryophyllaceae, Cheno-Ams, Ambrosia-group composites, Aster-type composites, and Polypodiaceae. Rare dinoflagellates are present in most samples. Together these occurrences indicate that the Bethany formation is upper Miocene or Pliocene and was deposited under warm temperate conditions in an estuarine or shallow-marine environment.
The Manokin formation samples (224.4, 230.3, 305.5, 317.3, 356.9, 371.8, and 413.9 ft; 68.40, 70.20, 93.12, 96.71, 108.78, 113.33, and 126.16 m) have similar assemblages as the Bethany formation. Quercus and Carya are dominant and Pinus is common. Liquidambar is most abundant in the uppermost sample in the formation and Carya decreases in the lowermost sample (413.9 ft; 126.16 m). Rare exotics are present in most of the samples, with Pterocarya in most of the samples, Engelhardia-type pollen present at 356.9 ft (108.78 m), and Podocarpus (yew pine) pollen at 413.9 ft (126.16 m). Epilobium (willow herb and fireweed) and other Onagraceae are also present. Umbelliferae (carrot family) become a common component of the flora, and Ambrosia-group composites are more abundant than in the overlying formations. Many of the same less common constituents are present as in the Bethany formation, including Alnus, Betula, Carpinus, Castanea, Salix, TCT, Tilia Ulmus, Fagus, Juglans, Gramineae, Caryophyllaceae, Cheno-Ams, Ambrosia-group composites, and Polypodiaceae. Dinoflagellates are rare but present in these samples. Like the Bethany formation, these palynomorphs indicate that the Manokin formation is upper Miocene or Pliocene and was deposited under warm temperate conditions in an estuarine or shallow-marine environment.
Two samples in the upper part of the St. Marys Formation (449.9 and 477.9 ft; 137.13 and 145.66 m) have notably more abundant non-arboreal pollen than is present in the Manokin and Bethany samples. Although Quercus is the most abundant pollen in these samples, pollen from the family Compositae (sunflower family) are also very common. Other non-arboreal types are present, including family Gramineae (grasses) and Umbelliferae (carrot family), along with arboreal types Pinus and Carya.
In the lower sample (524.9 ft; 160.0 m) from the St. Marys Formation, Quercus becomes the dominant form and the abundance of non-arboreal pollen is reduced. Carya and Pinus are present, but the abundance of Carya is lower than in the section above. Exotic taxa present are rare and include Pterocarya, Podocarpus, Symplocos (sweet-leaf), and possible Eucommia (hardy rubber tree). Other pollen in the St. Marys Formation include Alnus, Ilex, Salix, Tilia, Ulmus, Fagus, and Juglans. The pollen assemblage appears to represent a warm-temperate climate based on comparison to previous work by Groot (1997). This sample also contains the highest stratigraphically significant dinoflagellates identified in the cores. The presence of Hystrichosphaeropsis obscura restricts this sample to no higher than the top of upper Miocene dinoflagellate Zone DN9 of de Verteuil and Norris (1996a). Geonettia clinae is common, a form that is restricted to Zone DN8 in the Cape May corehole (de Verteuil, 1997), although it has a longer known stratigraphic range (upper middle Miocene to upper upper Miocene) (de Verteuil and Norris, 1996b). These criteria, although not definitive, suggest that this sample should be placed in Zone DN8, with an age estimate of 8.6 to 11.2 Ma.
Similar pollen assemblages were identified from the uppermost sample from the Choptank Formation (572.0 ft; 174.35 m). Quercus dominates and Carya and Pinus are important components. Exotics are present but rare, including Pterocarya, Podocarpus, Engelhardtia-type, and Symplocos. Dinoflagellates are common, with Polysphaeridium zoharyi the most common. De Verteuil (1997) noted a similar change in dinoflagellate assemblages in the Cape May borehole, with common Geonettia clinae in upper Zone DN8 changing downward to predominantly Polysphaeridium zoharyi in lower Zone DN8. A poor specimen resembling Trinovantedinium glorianum was noted, which, if accurate, would place the sample no lower than mid-Zone DN7 and thus no older than ~12.4 Ma.
Below this, the upper two samples in the Choptank Formation (596.9 and 645 ft; 181.94 and 196.60 m) are dominated by Pinus, with abundant Quercus and common Carya. The assemblage changes in the lower two Choptank samples (701.9 and 753.9 ft; 213.94 and 229.79 m) to dominance by Quercus, with common Pinus and Carya. Of the exotic taxa, Engelhardtia-type pollen becomes significantly more abundant in this interval (notably at 645.0 ft; 196.60 m) than in the samples uphole. Pterocarya and Podocarpus are also present in most of these samples, and Symplocos and possible Manilkara pollen are present in a few samples. Other pollen noted in the Choptank Formation include Alnus, Ilex, Liquidambar, TCT, Tilia, Tsuga, Ulmus, Fagus, and Nyssa. Scattered dinoflagellate occurrences were noted, including a partial form probably attributable to Hystrichosphaeropsis obscura (last abundance datum [LAD] at top of Zone DN9) (de Verteuil and Norris, 1996a).
The assemblages in the Calvert Formation samples studied between 822.8 and 1321.6 ft (250.79 and 402.82 m) are dominated by arboreal forms and are similar to those in the Choptank Formation. Quercus is the most abundant pollen in the Calvert samples studied, with Pinus and Carya generally important in varying proportions downcore. Carya is notably abundant at 985.7 ft (300.44 m), and Pinus is abundant at 1103.0 ft (336.19 m). Exotic taxa are present and tend to be more common than in the overlying formations. Engelhardia is common in most samples, with scattered occurrences of Podocarpus and possible Manilkara. Alnus, Ilex, Liquidambar, TCT, Tilia, and Ulmus are also present, with some Cheno-Ams and Gramineae. These pollen findings are consistent with those reported from the Calvert Formation in central Delaware by Groot (1992), who concluded that these assemblages are dominantly temperate and warm-temperate types but with the consistent presence of subtropical or tropical taxa, reflecting a setting similar to the modern Atlantic coastal plain of Georgia or Florida.
Several stratigraphically significant dinoflagellate occurrences were also noted in the Calvert Formation. Paleocystodinium golzowense is present at 969.7 ft (295.57 m); this species has its LAD at the top of dinoflagellate Zone DN8 (~8.6 Ma) (de Verteuil and Norris, 1996a). Cousteadinium aubryae is present in a number of samples in the Calvert Formation and is common in many. De Verteuil and Norris (1996a) report a range from the base of dinoflagellate Zone DN2 (22.2 Ma) to the top of Zone DN4 (15.2 Ma). Its highest occurrence at 1135.0 ft (345.95 m) and presence through the base of the formation place the lower Calvert (below 1135.0 ft; 345.95 m) in the interval from Zones DN2 to DN4 (22.4-15.2 Ma) (de Verteuil and Norris, 1996a). Polysphaeridium zoharyi is also common in most Calvert samples and is considered to reach its maximum development in warm-water, neritic, or estuarine environments (Wall et al., 1977).
Pollen assemblages in the unnamed glauconitic sediments that underlie the Calvert Formation (samples from 1422.0-1460.8 ft; 433.23-445.25 m) are generally characterized by abundant Quercus, frequent Carya, and common Pinus. Alnus, Tilia, TCT, and Ulmus are also present in this interval. The samples are characterized by abundant clumpy algal amorphous matter that obscures many of the pollen grains. The sample at 1460.8 ft (445.25 m) has many broken, poorly preserved pollen grains and appears to have suffered significant environmental oxidation. The dinoflagellate Cousteadinium aubryae is present at 1435.0 and 1446.6 ft (437.39 and 440.92 m), limiting this interval to a position between the base of Zone DN2 (22.2 Ma) and the top Zone DN4 (15.2 Ma) (de Verteuil and Norris, 1996a).
One sample was analyzed from the lowest unit in the corehole at 1467.2 ft (447.20 m). Like the above sample, abundant algal amorphous matter obscures many of the palynomorphs and many grains are broken. Quercus is the most common, and Carya, Pinus, and Engelhardia-type pollen were also noted. Dinoflagellates are present but not common.
Planktonic foraminifers are generally rare in the Miocene section of the Bethany Beach borehole and are of limited stratigraphic utility. However, they are significantly more abundant in the Oligocene section encountered at the bottom of the hole. The results of the foraminiferal analyses in Table T4 are based on analyses of the >250-µm fraction studied by J.V. Browning from samples taken at 5-ft intervals through the core. The planktonic foraminifers listed in Table T5 were identified by R.N. Benson and P.P. McLaughlin in the >63-µm fraction of samples taken where lithologies appeared most likely to yield good foraminiferal faunas.
The greatest abundances of planktonic foraminifers in the Miocene section are in the St. Marys Formation and indicate a probable late Miocene age. A single specimen of a menardiform globorotalid resembling Globorotalia pseudomiocenica was identified in the sample at 506 ft (152 m). The first-appearance datum (FAD) of G. pseudomiocenica is placed in the Neogloboquadrina humerosa Zone by Bolli and Saunders, suggesting an age younger than the 8.3-Ma FAD of N. humerosa reported by Berggren et al. (1995). Although the FAD of G. pseudomiocenica is not well calibrated, we note that this age is slightly younger than that suggested by the Sr isotopes. Orbulina suturalis was found in samples at 501 and 536 ft (152.70 and 163.37 m). The FAD of O. suturalis defines the base of Zone M6 (Berggren et al., 1995), indicating an age younger than 15.1 Ma. A short section of re-cored material from somewhere between 540 and 550 ft (164.59 and 167.64 m) yielded one juvenile specimen of Globorotalia menardii as well as very rare Globoquadrina dehiscens. The FAD of G. menardii indicates an age no older than its FAD in the middle part of the middle Miocene (~12 Ma). The last appearance datum (LAD) of G. dehiscens is near the top of the Miocene in Zone M14 at 5.8 Ma (Berggren et al., 1995), which provides a youngest possible age for this sample. This recored sample also includes two other forms that have LADs in the Pliocene (based on Bolli and Saunders, 1985), Globigerinoides obliquus obliquus and Globoquadrina altispira.
One of the few stratigraphically significant planktonic foraminifers noted in the Calvert Formation was Globorotalia praescitula at 1103 ft (336.19 m). The FAD of this species is within the lower part of Zone M3 at 18.5 Ma (Berggren et al., 1995), indicating that the section above is no older than 18.5 Ma.
Planktonic foraminifers were recovered in two samples from the sequence between 1430.5 and 1454.5 ft (436.02 and 443.33 m) in the interval referred to as "unnamed glauconitic silt." A sample at 1436.4 ft (437.81 m) contains the planktonic foraminifers Paragloborotalia mayeri, Globigerina ciperoensis ssp., and Globigerina sp., which indicate a lowermost Miocene or upper Oligocene position. The very rare occurrence of Globorotalia kugleri at 1446.6 ft (430.07 m) indicates that this interval is Miocene, with this sample in basal Miocene Zone M1, indicating an age between 21.5 and 23.8 Ma (Berggren et al., 1995). Specimens of Globigerinoides trilobus are found sporadically in samples down to 1446.6 ft (430.07 m), also supporting the placement in the Miocene. No foraminifers were recovered in the one sample examined (1460.9 ft) in the sequence between 1454.5 and 1465.7 ft (443.45 and 446.77 m).
Oligocene planktonic foraminifers are present below the dramatic sequence boundary at 1465.7 ft (446.77 m). The presence at 1467.2 ft (447.20 m) of a Globorotalia opima form transitional between Globorotalia opima opima and Globorotalia opima nana (five chambers, intermediate size), as well as G. opima opima and P. mayeri, suggest this sample lies in Zone P22 based on the ranges defined by Bolli and Saunders (1985). Berggren et al. (1995) provide an estimated age of 23.8 to 27.1 Ma for this zone.
Benthic foraminifers are generally present to common in samples below 376 ft (114.60 m) and were examined to determine approximate water depths. The benthic foraminifers in Table T4 are based on analyses of the >250-µm fraction studied by J.V. Browning from samples taken at 5-ft (1.52 m) intervals through the core. In the 5-ft samples below 1200 ft (365.76 m), specimens were concentrated by floating in tetrachloroethylene. Table T5 includes the benthic foraminifers identified by R.N. Benson in the >63-µm fraction of samples taken where lithologies appeared most likely to yield good foraminiferal faunas. Some of these samples were studied in detail, with relative abundances based on estimated percentages of each species; others (denoted by # above the sample depth) are general estimates based on quick scans of samples during and shortly after drilling.
The benthic biofacies established by Miller et al. (1997) in New Jersey are used to interpret paleodepths:
Elphidium biofacies: the Elphidium-dominated biofacies was defined by Miller et al. (1997) as an indicator of nearshore paleoenvironments with 10 m or less water depth, including lower estuarine, bay, and innermost neritic environments.Hanzawaia biofacies: the Hanzawaia biofacies was defined by Miller et al. (1997) as the Hanzawaia cf. Hanzawaia hughesi biofacies; this (or a similar) form is also referred to as Hanzawaia concentrica in this study. This biofacies is characterized by the presence of the nominate taxon, the common occurrences of Elphidium, and the absence of Pseudononion pizarrensis. It is associated with inner neritic paleodepths from 10 to 25 m (inner neritic).
Pseudononion biofacies: the Pseudononion biofacies is the same as the Nonionellina biofacies described by Miller et al. (1997). Here it is dominated by Pseudononion pizarrensis and commonly includes Nonionella miocenica and Hanzawaia. It is interpreted as reflecting paleodepths of 25-50 m (outer inner to inner middle neritic).Bulimina biofacies: the Bulimina biofacies was defined by Miller at al. (1997) as the Bulimina gracilis biofacies. Bulimina elongata is the same form, or similar, and here is included in this biofacies. It characterizes middle neritic (50-80 m) paleodepths.
Uvigerina biofacies: the Uvigerina biofacies characterizes middle neritic paleodepths (>75 m) and has been associated with MFSs by Miller at el. (1997). As defined, it included Uvigerina modeloensis and Uvigerina juncea, and in this study includes forms identified as Uvigerina subperegrina/auberiana and Uvigerina calvertensis.
The highest stratigraphic occurrences of foraminifers noted in the Bethany Beach borehole are in the Manokin formation at 376 ft (114.60 m), where rare P. pizarrensis were noted. Abundant to common P. pizarrensis at the base of the formation (441-451 ft; 134.42-137.46 m) indicates water depths of 25-50 m (Miller et al., 1997). The presence of Buliminella in samples at the base of the formation (446.0-451.0 ft; 135.94-137.46 m) indicates that the bottom of the formation was deposited in deeper water and that environments shallow upward.
Foraminifers are generally abundant in the St. Marys Formation. The upper sequence in the St. Marys Formation (down to 452.45 ft; 137.91 m) is dominated by P. pizarrensis, indicating water depths between 25 and 50 m. The composition of the fauna changes little through the sequence, although an increase in the number of species downsection may indicate a small amount of deepening. The lower sequence in the St. Marys Formation (523.05-575.2 ft; 159.43-175.32 m) shows deepening downward, with the richest foraminiferal assemblage present near its base. The fauna in the upper part of this sequence is dominated by P. pizarrensis and H. concentrica, indicating water depths of ~25 m on the shallow end of the Pseudononion biofacies. Samples from the lower part (540-555 and 572.0 ft; 164.6-169.2 and 174.35 m) have abundant U. calvertensis, B. elongata, Cassidulina laevigata, Buccella mansfieldi, and Cibicides cravenensis, with Transversigerina lamellata in one sample. These represent a Uvigerina biofacies assemblage indicating water depths reached 75 m or more.
Foraminifers are generally rare in the underlying Choptank Formation. Specimens are found in samples at 596, 596.9, and 601 ft (181.66, 181.97, and 183.18 m), just above a flooding surface at ~607 ft (185.01 m). The sparse fauna contains abundant Hanzawaia in places and less numerous P. pizarrensis, indicating ~25 m paleowater depth.
Immediately above a sequence boundary at ~649.0 ft (197.82 m), a sample from 645.0 ft (196.60 m) yielded Bolivina paula, Buliminella elegantissima, and H. concentrica. This assemblage is suggestive of the inner neritic Hanzawaia biofacies (10-25 m paleodepth). In the underlying sequence (649.0-698.5 ft; 197.81-212.90 m), rare to common Hanzawaia are noted in samples between 671 and 681 ft (204.52 and 207.57 m), also suggesting water depths of 10-25 m. This interval corresponds to the lower HST of the sequence.
Foraminifers are also sporadically present in the sequence between 698.5 ft and 787.1 ft (212.90 and 239.91 m). The uppermost fossiliferous samples (721 and 726 ft; 219.76 and 221.28 m) contain a low diversity Pseudononion biofacies at the shallow end of its depth range, at inner neritic (~30 m?) paleodepths. Just above the maximum flooding surface at 755 ft (230.12 m), a sample at 753.9 ft (229.79 m) contains a more diverse fauna including abundant P. pizarrensis, B. paula, and other small Bolivina species, with common H. concentrica, B. elongata, and B. elegantissima and rare Spiroplectammina mississippiensis and Textularia spp. These taxa likely represent the deep end of the Pseudononion biofacies or shallow end of the Bulimina biofacies, at ~50 m paleodepth. A low diversity Pseudononion biofacies was noted below this (756 and 766 ft; 230.43 and 233.48 m), again indicating inner neritic (~30 m?) paleodepths. The lowermost fossiliferous sample of this formation (771 ft; 235.00 m) contains Hanzawaia without Pseudononion. This indicates shallower water at top and at bottom and deeper water in the middle of the sequence, in agreement with the facies analysis.
The Calvert Formation (819.9-1420.0 ft; 249.91-732.82 m) contains locally abundant foraminifers. P. pizarrensis is the most common foraminifer in this formation, indicating prevailing water depths were generally 25-50 m (Miller et al., 1997). In some places, P. pizarrensis is absent or rare and Hanzawaia is present, suggesting shallower water environments. In other places, P. pizarrensis is commonly present with Lenticulina and Cibicides/Cibicidoides, likely representing slightly deeper environments.
In the uppermost sequence in the Calvert Formation (which extends from 787.1 ft [239.91 m] in the Choptank Formation to 897.7 ft [273.62 m] in the Calvert), the benthic foraminifers generally record deepening downsection, with assemblages of rare Hanzawaia passing downward into more consistently fossiliferous samples with more diverse assemblages that include common to abundant Lenticulina and P. pizarrensis. At 822.8 ft (250.83 m), the assemblage includes B. paula, small Bolivina spp., H. concentrica, Cibicides americanus, and Nonion advenum pustulosum. The richest samples are present near the maximum flooding surface identified at 887.7 ft. At 888.0 ft (270.66 m), the fauna is composed of P. pizarrensis, B. paula, Bolivina spp. (small), Lenticulina americana, H. concentrica, B. elongata, B. elegantissima, S. mississippiensis, and Textularia sp.
Samples from the underlying sequence, from 897.7 to 981.3 ft (273.62 to 299.10 m) and from 981.3 to 1057.95 ft (299.10 to 322.46 m), yielded foraminifers less consistently. Samples from the lower part of each sequence are generally the most diverse and thus represent the deepest water. P. pizarrensis is the most consistently occurring species, and Hanzawaia and Cibicides/Cibicidoides have scattered occurrences, together indicative of the Pseudononion biofacies. The sample at 948.9 ft (289.22 m) also includes frequent B. elegantissima, common B. paula, and very rare Transversigerina transversa. Other forms present with this assemblage include B. elegantissima, Rotorbinella bassleri, and Textularia spp. at 985.7 ft (300.44 m) and Textularia spp. and S. mississippiensis at 1054.3 ft (321.35 m).
Immediately under the sequence boundary at 1057.95 ft (322.46 m), foraminifers are sparse. However, other than in the upper 10-15 ft of this sequence, foraminifers are more common and diverse than in the overlying two sequences. A sample just below the top of the sequence at 1059 ft (322.78 m) yielded fine sand and very rare foraminifers. A sample at 1064 ft (324.31 m) yielded very fine sand, glauconite (<1%), and sparse benthic foraminifers that include striate Uvigerina, H. concentrica, and Bulimina. At 1071 ft (326.44 m), abundance and diversity increase and generally persist through the bottom of the sequence at 1153.0 ft (351.43 m). P. pizarrensis and Lenticulina spp. are abundant to common through this interval. The greatest diversity was noted between 1071 and 1116 ft (326.44 and 340.16 m), with regular occurrences of S. mississippiensis, B. paula, H. concentrica, Cibicides/Cibicidoides sp., Textularia spp., U. subperegrina/auberiana, B. marginata multicostata, and B. elegantissima. Scattered occurrences of B. paula, Gyroidina scalata, B. elongata, and B. curta were also noted with the common P. pizarrensis and Lenticulina in the lower part of the sequence. These assemblages are probably overall referable to the Pseudononion biofacies, but with some aspects of the Bulimina and Uvigerina biofacies. These suggest that most of this part of the Calvert Formation was deposited at middle neritic depths (50-80 m), with the upper part of this sequence representing the shallowest water depths.
Foraminifers are less common in the very thick sequence from 1153.0 to 1421.1 ft (351.43 to 433.15 m). P. pizarrensis is present in most of the samples, but is abundant in only one sample (1217.7 ft; 371.15 m) and rare in most others. Scattered occurrences of H. concentrica, B. elegantissima, Cibicides/Cibicidoides sp., U. subperegrina/auberiana, B. paula, B. marginata multicostata, and Elphidium spp. were also noted, with B. elegantissima common to abundant in several samples. Paleowater depths were probably mostly 25-50 m (Pseudononion biofacies).
In the next sequence down, from 1421.1 to 1430.5 ft (433.15 to 436.02 m), the facies become more glauconitic. P. pizarrensis is abundant in the uppermost sample at 1422.0 ft (433.43 m), and B. elongata, B. curta, and U. subperegrina/auberiana are abundant to frequent. Transversigerina transversa also is in this sample, but it is very rare. This assemblage, like that in the sequence above, is probably best referred to the Pseudononion biofacies, but with some deeper neritic aspects of the B. gracilis and Uvigerina biofacies, suggesting middle neritic depths (~50 m).
A similar fauna, but with some slightly deeper water aspects, characterizes the sequence between 1430.5 and 1454.5 ft (436.02 and 443.33 m) in the interval referred to as "unnamed glauconitic clays and sands." Samples in the upper part of the sequence (1435.0 to 1436.4 ft; 437.39 to 437.81 m) contains common to abundant B. elongata, as well as P. pizarrensis and B. curta. A sample from the middle of the sequence (1443.5 ft; 439.98 m) contains similar benthic foraminifers in addition to common Siphonina cf. tenuicarinata, Lenticulina spp., polymorphinids (Guttulina, Globulina, and Pseudopolymorphina) and assorted lagenids (Marginulinopsis sp., Fissurina sp., Oolina sp., and others). P. pizarrensis and Buliminella curta are also present in the lower part of the sequence (1446.0-1451.0 ft; 440.74-442.26 m) along with T. transversa, Gyroidinoides sp., Rotorbinella bassleri, and B. paula. The overall increase of diversity downward in this sequence suggests deepening from middle neritic depths characteristic of the Bulimina biofacies to deeper middle neritic or even outer neritic depths.
Very rare foraminifers, exclusively B. elongata and Cassidulinoides sp., were recovered in the one sample examined (1460.8 ft; 445.25 m) in the sequence between 1454.5 and 1465.7 ft (443.33 and 446.77 m).
A significant change in foraminiferal faunas takes place across the dramatic sequence boundary at 1465.7 ft (446.75 m). Several uvigerinids are present in this interval that are not present above, including Tiptonina nodifera, Uvigerina tumeyensis, and U.? glabrans. Other forms present include Frondicularia, Guttulina, Gyroidina scalata, Lenticulina spp., B. paula, B. elongata, and Eponides? cocoaensis. Together these taxa suggest an outer neritic paleoenvironment.
The calcareous nannofossil assemblages, although diverse, are extremely difficult to interpret because of the absence or extreme scarcity of markers.
The upper part of the hole does not yield calcareous nannofossils. Samples of the Omar Formation from 36 and 51 ft (10.97 and 15.54 m) are barren, as is the sample from the Bethany formation at 192 ft (58.52 m).
Of the five samples examined from the St. Marys Formation, only one contains nannofossils. The sample at 486 ft (148.13 m) yields long-ranging taxa, but the sample is remarkable because of the presence of reworked Paleogene taxa (Paleocene in particular). Samples from 451, 506, 531, and 561 ft (137.46, 154.23, 161.85, and 170.99 m) are barren.
Stratigraphically useful nannofossils are present in scattered samples from the Calvert Formation. A sample from 876 ft (267.00 m) contains reworked Paleogene coccoliths. The sample from 1071.0 ft (326.44 m) is probably assignable to Zone NN3 and contains rare Sphenolithus belemnos. The sample at 1091 ft (332.54 m) is assigned to Zone NN3 (between the highest occurrence (HO) of Triquetrorhabdulus carinatus and the HO of S. belemnos) based on the absence of T. carinatus. T. carinatus is present in levels below but is very rare. The sample at 1116.0 ft (340.16 m) is placed in the upper part of Zone NN2, 1136 ft (346.25 m) in Zone NN2, and 1311 ft (399.59 m) in the lower part of Zone NN2. Samples from 1286 and 1331 ft (391.97 and 405.69 m) cannot be assigned to a zone, and the sample at 1396 ft (425.50 m) is barren.
One sample from the unnamed glauconitic clays and sands in the lower part of the hole yields nannofossils. The sample at 1426 ft (434.64 m) is possibly assignable to the lowermost Zone NN2.
A completely different assemblage is present in the sample at 1466 ft (446.84 m) than those above. It is most probably uppermost Oligocene, in younger Chron C6Cr (~24.2-24.7 Ma).
Radiolarians are present in nearly all samples between 572.0 and 1446.6 ft (174.35 and 440.92 m), inclusive. Their abundances range from very rare (<100 count) to nearly 5% of the sand fraction (Table T5). Assemblages are dominated by spumelline taxa, mainly actinommids, spongodiscids, coccodiscids, and lithelids. Members of these groups persist in neritic paleoenvironments in the Miocene of the middle Atlantic Coastal Plain (Palmer, 1984, 1986a; Benson, 1998) where oceanic taxa are rare or absent. All identifications were made under low-power and reflected light.
The highest occurrence of biostratigraphically significant radiolarians is the isolated occurrence of Calocycletta costata at 822.8 ft (250.79 m). This species ranges from the base of the Calocycletta costata Zone (RN4) into the lower part of the Dorcadospyris alata Zone (RN5), indicating that the sample should be between 17.03 and ~14 Ma based on the estimated ages of these zones (see Sanfilippo and Nigrini, 1998).
Didymocyrtis mammifera is a stratigraphically useful form that ranges from 822.8 to 948.9 ft (250.79 to 289.22 m). This species is generally considered to appear within the lower Miocene Stichocorys wolffi Zone (RN3) and ranges up into the middle Miocene Dorcadospyris alata Zone (RN5) (Nigrini and Sanfilippo, 2001). The presence of this species below the lowest occurrence of C. costata suggests the samples at 888.0 and 948.9 ft (270.66 and 289.22 m) can be assigned to Zone RN3.
The highest occurrence of the stratigraphically significant radiolarian Spongasteriscus marylandicus is at 1103.0 ft. Palmer (1986b) indicated that Spongasteriscus marylandicus is a useful stratigraphic indicator of the S. wolffi Zone (RN3). Nigrini (1996) identified this species from the uppermost Oligocene Zone RP22 to within lower Miocene Zone RN3 at Ocean Drilling Program (ODP) Sites 902, 903, and 904 on the New Jersey continental slope. Thus, the presence of S. marylandicus suggests that this sample is no younger than somewhere within the Stichocorys wolffi Zone (RN3).
Radiolarians indicative of the lowermost Miocene Cyrtocapsella tetrapera Zone (RN1) are present at 1446.6 ft (440.92 m) with the planktonic foraminifer G. kugleri, which is restricted to the earliest Miocene Zone M1 (23.8-21.5 Ma) (Berggren et al., 1995). The C. tetrapera Zone is defined between the first occurrence (FO) of the nominate taxon (23.62 Ma) and the last occurrence (LO) of Theocyrtis annosa (20.53 Ma) (Sanfilippo and Nigrini, 1998). The former is present in the Bethany Beach borehole in the 1446.6-ft (440.92 m) sample (Table T5); the latter taxon was not found in this preliminary study. The radiolarians at 1446.6 ft (440.92 m), therefore, represent the Cyrtocapsella tetrapera Zone.
Other species found in the sample 1446.6 ft (440.92 m) (Table T5) support this interpretation: (1) the FO of Calocycletta virginis is approximately synchronous with the base of Zone RN1 (Sanfilippo and Nigrini, 1998); (2) the FO of Cyrtocapsella cornuta is present within the zone (Sanfilippo and Nigrini, 1998); (3) Lychnocanoma elongata (the FO defines the base of the latest Oligocene Zone, RP22, named for the taxon) ranges from late Oligocene to late early Miocene (Sanfilippo and Nigrini, 1998); (4) Didymocyrtis prismatica ranges from late Oligocene to late early Miocene (Nigrini and Sanfilippo, 2001); (5) Spongasteriscus marylandicus ranges from the latest Oligocene Zone RP22 to within early Miocene Zone RN3 (Nigrini, 1996); and (6) the FOs of Didymocyrtis violina and D. tubaria are approximately synchronous with the base of the Stichocorys delmontensis Zone, RN2 (Sanfilippo and Nigrini, 1998; Nigrini and Sanfilippo, 2001); their FOs in the Bethany Beach borehole suggest that they are older than the base of Zone RN2.
Diatom frustules from the >63-µm size fraction are present in nearly all samples examined, and in several they reach >5% of the sand fraction (Table T5). The only readily identifiable taxon in this size range under low magnification and reflected light is Actinoptychus heliopelta. Its LO at 985.7 ft (300.44 m) is within the Stichocorys wolffi Zone. Its FO is at 1446.6 ft (440.92 m) in the G. kugleri and Cyrtocapsella tetrapera zones. Its total range defines East Coast Diatom Zone (ECDZ) 1 (Abbott, 1978; Andrews,1988), which encompasses nearly the entire lower Miocene of the middle Atlantic Coastal Plain.