Palaeontographica Abt. B |
213 |
Lfg. 1-3 |
37-87 |
Stuttgart, August 1989 |
FROM THE RICHMOND RIFT BASIN OF
VIRGINIA, U.S.A.
BY
BRUCE CORNET*)
With 9 Plates and 12 Text-figures in the Text
SummaryThe Richmond Basin is a small intracratonic rift basin containing some of the oldest strata in the Newark Supergroup of eastern North America. Recent drilling has established for the first time an accurate picture of its fluvial-lacustrine stratigraphy. Detailed palynological studies of outcrop samples and well cuttings indicate an age range for the bulk of Richmond Basin sediments as early Carnian to late middle Carnian (early Late Triassic).
Seven new genera and thirteen new species are described from the deltaic-lacustrine Vinita Beds of the Richmond Basin, including a new zone fossil for the early-middle Carnian, Placopollis Koobii n. gen. et sp. Six new genera and eleven new species of angiosperm-like pollen are recognized: Dicrinopollis operculatus n. gen. et sp., Monocrinopollis doylei, n. gen. et sp., M. microreticullatus n. sp., M. mulleri n. sp., M. walkeri n. sp., Pentecrinopollis gemmatus n. gen. et sp., P. traversei n. sp., Polycolpopollis magnificus n. gen. et sp., Tricrinopollis minutus n. gen. et sp., P. olsenii n. sp., and Zonacrinopollis anasulcatus n. gen. et sp. Most of the angiosperm-like species are placed in the Crinopolles Group, which is also defined. Steevesipollenites STOVER is emended to include S. hemiplicatus n. sp., which is related to the Crinopolles Group as a possible polyplicate precursor. The stratigraphic record of this group is traced from its first appearance below the Vinita Beds to the migration of M. microreticulatus n. sp. into younger Triassic strata of eastern and western North America. The morphological and evolutionary implications of Triassic angiosperm-like pollen are discussed and reconciled with recent cladistic analyses of angiosperm - seed plant relationships.
Key words: Pollen; angiosperm-like; crinopolles; Late Triassic; rift basin.
Table of Contents
Introduction.......................................................................................... Richmond Basin Geology....................................................…...........…... Richmond Basin Palynology..................................................….…........ Richmond Basin Age...................................................………..……...... Materials and Methods......................................................……..…....... Systematic Palynology....................................................………........… The Crinopolles Group.......................................................…..…....... Pentecrinopollis n. gen..............................................................… Tricrinopollis n. gen. ..................................................…............... Monocrinopollis n. gen................................................…............... Dicrinopollis n. gen....................................................….…........... Zonacrinopollis n. gen...............................................................… Polycolpopollis n. gen………………………….....………................... Steevesipollenites emend……………………….………..................... Placopollis n. gen………………………………………........................ Discussion……………………………………..………………….................... Origin and Evolution of the Crinopolles Group……………...................... Habitat Evolution within the Crinopolles Group…………….................... Morphological Comparisons and Significance …………….................... Phylogenetic Significance ………………………………......................... Conclusions ……………………………………………………...................... Addendum ……………………………………………………........................ Acknowledgements ……………………………………………….................. Literature Cited …………………………………………………….................. Explanation of Plates ……………………………………..…….................... |
3838 41 42 44 45 46 46 49 54 62 64 65 68 69 70 70 73 74 77 80 81 81 81 84 |
Introduction
Over the past eighteen years considerable fossil data have been brought to bear on the problem of angiosperm origin and early evolution. Unlike most investigations into the early history of angiosperms, this investigation began with the discovery of angiosperm-like pollen in rocks at least 100 million years older than previously dated angiosperm pollen (CORNET 1977; 1979). Most investigators concentrated their search in Lower Cretaceous rocks, where they hoped to find an answer to the long standing mystery of angiosperm origin. Out of their search came new evidence for a major mid-Cretaceous radiation of primitive dicots (DOYLE & HICKEY 1978), but as hard as they looked, they could not find any clues to angiosperm ancestry. Instead, their investigations showed that angiosperm pollen precedes the record of angiosperm leaves in the Lower Cretaceous, and that angiosperm fossils become fewer and harder to find with age, until they seem to disappear below the Barremian or upper Hauterivian (DOYLE et al. 1977; DOYLE 1978a; BRENNER 1984; RETALLACK & DILCHER 1981; 1986; BRENNER 1987, Abs.).
Much of the bias in accepted age for the oldest angiosperms stems from the failure of paleobotanists to "convincingly" demonstrate pre-Cretaceous angiosperm megafossils (CORNET 1986, notwithstanding). Yet, the burden of proof for pre-Cretaceous angiosperms has become increasingly more difficult as belief in a Cretaceous origin has gained strength due more to popularity than substance (cf. WALKER & WALKER 1984: p. 516). The "consistent failure of palynologists to find distinctively angiospermous pollen types in Triassic, Jurassic, and earliest Cretaceous strata" (DOYLE 1977: p. 501) has been more a problem of acceptance than a dearth of evidence. Rare accounts of Clavatipollenites hughesii, Liliacidites spp., or reticulate-columellate tricolpates in the Jurassic ( SCHULZ 1967; HOROWITZ 1970; LUND 1977; POCOCK 1978; CORNET 1981) have been dismissed or ignored, but never pursued by others with the intent of testing interpretations of the Cretaceous angiosperm pollen record. BAKKER (1978: p. 661) prematurely remarked that Late Triassic Newark "rift valleys...deep in the interior of the Laurasian supercontinent...seem ideal for trapping remains of...pre-Cretaceous angiosperms... But no trace of angiosperms has been found among Newark pollen or leaf floras." The palynological discoveries reported here may represent the oldest clues to the origin and early evolution of the angiosperms, and are not inconsistent with interpretations, based on recent cladistic analyses, that the Gnetales, Bennettitales, and angiosperms are sister groups, having a possible common origin in the Triassic (DOYLE & DONOGHUE 1986; 1987; CRANE 1985).
Richmond Basin Geology
The amount of information about the geology of the Richmond Basin has increased significantly since drilling began in 1980 for oil and gas in the basin. The author's work on angiosperm-like pollen from the basin was interrupted by his active participation in drilling in the basin. Two deep test wells were drilled in 1981 (Horner No. 1 and Bailey No. 1), proving that the basin was more than twice as deep as previously indicated in the literature (e.g. SHALER & WOODWORTH 1899). To date, at least 17 shallow wells (under 3,000 ft./915 m.) and three deep wells have been drilled in the basin (Text-fig. 1), with four of them reaching basement at 1190 feet/363 meters (Chalkley No. 1); 2,770 feet/844 meters (Adamson No. 1); 4,490 feet/1,369 meters J. R. Hicks No. 1); and 7,140 feet/2,177 meters (Bailey No. 1).
Text-fig. 1
Two types of depositional cycles are recognizable in the Richmond Basin wells: 1) Very large upwards-coarsening cycles of approximately 2,750 feet (838 meters) in thickness, consisting of swamp and shallow lacustrine facies dominated by cryptogam spores in the lowest part, mostly lacustrine facies in the middle, and fluvial-deltaic facies dominated by pollen in the upper part of the cycle (palynofloral sequences a, b, c and d: Text-fig. 2), and 2) smaller-scale upwards-coarsening cycles averaging 92 feet (28 meters) in thickness (EDIGER 1986; Text-fig. 3). Two complete large scale cycles are preserved, as well as the top and bottom portions of two others; each large cycle is composed of about 30 of the smaller cycles. If these cycles are controlled by orbital forcing as OLSEN (1986) has demonstrated for the Newark Basin of New Jersey and Pennsylvania, the ratio of 30: 1 comes closest to the 40,000-50,000-year cycle of the obliquity of the earth's axis and the 1.6-million-year cycle recognizable in the Lockatong and Passaic formations of the Newark Basin.
Text-fig. 2
Our understanding of the palynology of the Richmond Basin sequence has greatly improved over previous knowledge from the study of isolated outcrop localities, whose stratigraphic relationships could not be tested. The palynofloral history of the Horner No. 1 reflects the cyclic waxing and waning of large fresh-water lakes, and the progradation of large deltaic complexes (Text-fig. 2; CORNET & OLSEN 1985). A graph of the relative percentage of amorphous kerogen (mostly algal debris) in the Horner samples records major lacustrine cycles as zones of high amorphous kerogen content (Text-fig. 2: column six). A second graph (Text-fig. 2: column seven) shows the relative abundance of palynomorphs in the palynological preparations (i.e. number of palynomorphs per traverse of a slide). That graph tends to track the curve for amorphous kerogen; the correlation between the curves reflects the finer grain size of the sediments yielding the higher concentrations of kerogen and palynomorphs. Higher than normal percentages of palynomorphs occur in prodeltaic facies underlying prograding deltaic complexes and in swamp facies that lie on top of deltas. A third graph (Text-fig. 2: column eight) tracks the relative percentage of pollen versus spores in the Horner No. 1; intervals dominated by spores reflect either swampy or lacustrine facies, while intervals dominated by pollen reflect either prodeltaic or fluvio-deltaic facies. Swampy conditions correlate with the presence of coals, while strictly fluvial conditions correlate with very low palynomorph abundances, a strong dominance by pollen, and an abundance of sandstone.
A fourth graph (Text-fig. 2: column 10) gives a summary of lacustrine transgressions and regressions in proximity to the Horner No. 1 well, based on the data in Text-fig. 2. Deltas prograding in one part of the basin may be replaced by lacustrine or prodeltaic facies in another part; the deltaic complex present in the Horner No. 1 near the top of the Vinita Beds, for example, is represented by shallow lacustrine and delta-margin deposits with high palynomorph abundance in the Bailey No. 1 well.
Along with the transgression/regression curve are ten palynozones based on palynomorph species content (not given). These zones are numbered according to palynofloral similarity, with palynozone 1 generally being dominated by cryptogam spores and monosulcate pollen; palynozone 2 having a high percentage of articulate spores and saccate gymnosperm pollen; palynozone 3 having a high diversity and abundance of pollen morphotypes; and palynozone 4 being dominated by a lower diversity of bisaccate and circumsaccate pollen with increasing spore content in older zones. These sequential facies-controlled palynozones repeat themselves through the section: Only the top of sequence "a" is present at the base of the section (Bailey No. 1); sequences "b" and "C' are relatively complete, indicating little time lost in the Horner No. 1 at the projected "unconformity" near their mutual boundary; while sequence "d" is represented only by the spore-dominated lower zone.
Aratrisporites scabratus, A. fimbriatus, Calamospora nathorstii, and Laricoidites spp. make up the dominant cryptogam elements of palynozone Ib, while Osmundacidites spp., Baculatisporites spp. and Granulatisporites spp. fluctuate in dominance with articulate spores (e.g. Laricoidites sp. and Pilasporites sp.) in palynozones Ic and Id (CORNET & OLSEN 1985). However, articulate spores strongly dominate the upper half of zone Id. The percentage of red beds increases upwards in the section, supporting the changing cryptogam assemblages from ones of high diversity in older strata to ones of lower diversity near the top of the section. Angiosperm-like pollen is present throughout most of the palyniferous sections in both the Horner and Bailey wells (cf Text-fig. 2), but preferentially occurs in near-shore lacustrine, swamp, and delta-margin facies - an indication that it probably did not travel far from its source. Angiosperm-like pollen diversity drops significantly above the middle unconformity, supporting the overall floral trend of decreasing diversity upwards, and indicating a general preference of the plants producing angiosperm-like pollen for wetter tropical conditions.
Richmond Basin AgeThe palynoflora of the Richmond Basin changes in composition more with changes in facies and climate than with age. Most of the age-diagnostic species persist throughout the stratigraphic sequence, with the youngest palynoflorules having more quantitative than qualitative differences from the oldest palynoflorules (CORNET & OLSEN 1985). Although some reworking is suspected above an angular unconformity that developed during basin filling (middle unconformity, Text-fig. 2), younger palynoflorules in the basin come from sediments that blanket or overlie buried (positive) structure. Overall, the age of the Richmond Basin sediments (excluding the Otterdale Sandstone) appears to range from earliest Carnian to late middle Carnian (early Late Triassic), and does not represent much more than three million years of deposition (DUNAY & FISHER 1974; CORNET 1977; CORNET & OLSEN 1985; EDIGER 1986). Such a duration is in agreement with the 65+ obliquity cycles preserved in the basin, giving a minimum duration of 2.6 to 3.25 million years, depending on whether the smaller Richmond Basin cycles are 40,000 or 50,000 years in duration (cf OLSEN 1986). The oldest coal-bearing strata contain the last abundant appearance of Aratrisporites spp., which has its last acme zone in the late Ladinian of Europe (EDIGER 1986), while the youngest Triassic sediments in the basin lose age diagnostic palynomorphs (e.g. Striatoabieites aytugii) restricted to middle Carnian or older strata in Europe. The presence of Vallasporites ignacii, Patinasporites toralis/densus, Camerozonosporites rudis, and Lagenella martinii in the oldest strata of the Richmond Basin (i.e. Productive Coal Measures and Lower Barren Beds) indicates an age no older than Cordevolian, or basal Carnian (BRUGMAN 1983). The uniformity in palynofloral taxa through the section is paralleled by an unchanging fossil fish fauna, dominated by Dictyopyge spp. (SCHAEFFER & MCDONALD 1978), a subholostean fish which is not Present in younger Newark strata containing phytosaur remains. The oldest phytosaurs have been dated worldwide as late Carnian (CORNET & OLSEN 1985).
Text-fig. 3. Schematic summary of changing paleoenvironmental distribution of angiosperm-like and polyplicate pollen taxa in the Richmond Basin, VA. Read discussion of data quality in Materials and Methods. Some of the repetative transgressive-regressive lacustrine cycles in the Richmond Basin (gamma ray and shallow resistivity logs) are used to portray the changing vertical composition and facies distribution of angiosperm-like pollen through the Vinita Beds. Representative sequences for three common types of cycles, and their relative position within a deltaic system; A. "Shoreface" siltstones and mudstones coarsening upwards into a bar-finger sandstone (Horner 5,440-5,570'); B. Deltaic plain mudstones, shales, and thin coal beds with interbedded cravasse subdeltaic sandstones of destructional marsh sequence on top of an abandoned deltaic lobe (Bailey 4,120-4,350'); C. Three prograding distributary mouth bar and point bar sandstone cycles within a shoal water lobe complex (Horner 4,175-4,545'). Sequences B and C correlate with one another as shown. The distribution of taxa is based on all known occurrences, and does not represent any particular sequence within a well or outcrop (individual occurrences are too sporadic or rare). Large TYPE indicates two or more occurrences in similar parts of analogous depositional cycles, while small type indicates only one record of an occurrence. Schematic drawing of deltaic system modified from Galloway (1968). Do = Dicrinopollis operculatus; Md = Monocrinopollis doylei; Mi = M. microreticulatus; Mu = M. mulleri; Mw = M. walkeri; Pg = Pentecrinopollis gemmatus; Pm = Polycolpopollis magnificus; Pt = Pentecrinopollis traversei; Tm = Tricrinopollis minutus; Po = P. olsenii; Sh = Steevesipollenites hemiplicatus; Za = Zonacrinopollis anasulcatus. Dot pattern = gray to buff sandstone; clear pattern = gray to red siltstone and mudstone; dash line pattern = fissile gray to black shale; horizontal bar = thin coal bed or carbonaceous shale. Relative percentages of spores are given for these examples of sequences A-C, with percentages positioned at the top of each 20-30 ft. sample interval. Vertical scale in 100 ft. intervals.
Materials and MethodsAll specimens and holotypes used in the systematic portion of this study come from outcrop locality VB-4 (Goodwin et al., 1985, Stop 6a) of the Richmond Basin, Virginia (Text-fig. 1). Strew slides were prepared for outcrop samples and well cuttings of the basin, and were used for the stratigraphic distribution and environmental occurrence of described taxa (Text-fig. 2).
Most specimens (including holotypes) used in this study exist as single grain mounts (279 slides), while the remainder exist as multiple grain mounts (17 slides containing 221 specimens). All single and multiple grain mounts were picked from strew preparations and photographed using a Zeiss photomicroscope. Palynological residues were prepared using standard chemical and mechanical (centrifuge) techniques of rock sample maceration in HF, heavy liquid separation using zinc bromide, and oxidation with Schultze's solution. The specimens were stained with Safranin O.
Lithological, palynological, and kerogen analyses were conducted on cuttings samples from the Horner No. 1 and Bailey No. 1 wells (Text-figs. 1-2). Electric log correlations provided the initial means of correlation between the wells, and along with dipmeter control established the presence of a number of small faults and at least one large fault crossing each borehole (faults are represented by horizontal gaps in the lithologic columns: Text-fig. 2); palynological correlation later substantiated the electric log correlation, and provided a biostratigraphic basis for interpreting depositional facies. Sandstone, siltstone, shale, and coal percentages were averaged over 50 foot cuttings intervals in order to show major facies changes within the wells (Text-fig. 2). Both palynological and kerogen studies were conducted on the same cuttings intervals, which ranged from 10 feet to 30 feet.
Palynofacies and environmental interpretations for the sediments producing angiosperm-like pollen was possible using cuttings because of the separation and stratigraphic distribution of palyniferous shales and because of the low percentages of angiosperm-like pollen in any one sample. Upwards-coarsening depositional cycles, like those reported for the Newark Basin in New Jersey and Pennsylvania (OLSEN 1986), are the most useful tool for well correlation in the Richmond Basin. At least 65 such cycles have been identified by the author, with each containing the darkest organic-rich shales near or at their base (Text-fig. 3). The cycles range from about 50 to 150 feet (15-45 meters) in thickness, with organic-rich shale intervals usually separated by more than 30 feet (9 meters) and typically by at least 60 feet (18 meters) of sandstone and siltstone. Caving during drilling was monitored at lithologic breaks (by CORNET & WEISBRICH, wellsite geologists), rarely exceeded 10-15% 10 feet (3 meters) below, and rarely persisted in detectable quantities more than 30 feet (9 meters) below the lithologic break. Caving from higher in the well was usually less than 5% when it did occur. Since the volume of shale cuttings for each shale break was usually good, the relative percentage of shale contamination from higher units was typically diluted to under 5%.
Identifying the shale interval from which angiosperm-like pollen probably came was relatively simple because the lagged sample interval usually was less than the spacing of shale beds. Since angiosperm-like pollen abundance was typically less than 1% and frequently less than 0.5 % of any given sample (1 count in 150-200 palynomorphs), the relative percentage of caved angiosperm-like pollen would be less than 0.1% (1 count in 1000), making it highly unlikely that caved specimens were a significant problem in evaluating the stratigraphic occurrences of angiosperm-like pollen in the wells studied. The environmental distribution of described taxa was based on all known occurrences (See Text-fig. 3), because the distribution of individual taxa was sporadic and rare, and because the repetitive nature of the sedimentary cycles allowed the identification of the same or analogous environments in each cycle. Text-fig. 3 is an attempt to show 1) the cyclical nature of the fluvial-deltaic facies within the Richmond Basin, 2) the more frequent occurrence of angiosperm-like pollen within organic-rich quiet-water shales overlying abandoned delta lobes, and 3) the changing vertical composition and environmental distribution of angiosperm-like taxa within the Vinita Beds. Because depositional environments are repetitive, the most likely explanation for such change is probably biotic rather than sedimentary.
Systematic PalynologyAll palynomorph specimens illustrated herein or used in the systematic part of this study are deposited in the palynological collections of the U. S. Geological Survey, National Center, Reston, VA, U. S. A. The slides containing the holotypes have been appropriately labeled and designated in the text and plates.
The following list contains all the spore and pollen taxa identified in palynoflorule VB-4. A comprehensive systematic treatment of the entire palynoflora has not been undertaken, as most of the recorded taxa (DUNAY & FISHER 1974; CORNET 1977; CORNET & OLSEN 1985) have been adequately described and systematically treated elsewhere (SCHULTZ & HOPE 1973; DUNAY & FISHER 1979; FISHER & DUNAY 1984; EDIGER 1986). Those taxa which are given detailed systematic treatment are marked with an asterisk.
Alisporites aequalis MÄDLER 1964
Alisporites opii DAUGHERTY 1941
Alisporites ovatus (BALME & HENNELLY) JANSONIUS 1962
Alisporites parvus DE JERSEY 1962
Alisporites toralis (LESCHIK) CLARKE 1965
Aratrisporites saturnii (THIERGART) MÄDLER 1964
Calamospora nathorstii (HALLE) KLAUS 1960
Callialasporites sp. -(cf. SCHULTZ & HOPE 1973)
Camerosporites pseudoverrucatus SCHEURING 1970
Camerosporites secatus LESCHIK 1955
Colpectopollis cf. C. ellipsoideus VISSCHER 1966
Converrucosisporites cameronii (DE JERSEY) PLAYFORD & DETTMANN 1965
Convolutispora affulens (BOLCHOVITINA) SCHULTZ & HOPE 1973
Cornetipollis cf. C. reticulata POCOCK & VASANTHY 1988
Cycadopites spp. (six unidentified species)
Deltoidospora toralis LESCHIK 1955Dicrinopollis operculatus n. gen. et sp.*
Dictyophyllidites harrisii COUPER 1958
Duplicisporites granulatus LESCHIK 1955
Echinitosporites sp. (new species)
Enzonalasporites vigens LESCHIK 1955 emend. SCHEURING 1970
Equisetosporites spp. (Three new species)
Granulatisporites infirmus (BALME) CORNET & TRAVERSE 1975
Guthoerlisporites cancellosus PLAYFORD & DETTMANN 1965
Laevigatosporites sp.
Lagenella martinii (LESCHIK) KLAUS 1960
Laricoidites intragranulosus BHARADWAJ & SINGH 1963
Lycospora imperialis JANSONIUS 1962
Microcachryidites doubingeri KLAUS 1964
Monocrinopollis doylei n. gen. et sp.*
Monocrinopollis microreticulatus n. gen. et sp.*
Monocrinopollis mulleri n. gen. et sp.*
Monocrinopollis walkeri n. gen. et sp.*
Osmundacidites senectus BALME 1963
Ovalipollis ovalis KRUTZCH 1955
Paracirculina scurrilis SCHEURING 1970
Parillinites pauper SCHEURING 1970
Patinasporites densus LESCHIK 1955
Pentecrinopollis traversei n. gen. et sp.*
Pentecrinopollis gemmatus n. gen. et sp.*
Perotriletes sp.
Pityosporites devolvens LESCHIK 1955
Pityosporites inclusus LESCHIK 1955
Pityosporites neomundanus LESCHIK 1955
Pityosporites scaurus (NILSSON) SCHULZ 1967
Placopollis koobii n. gen. et sp.*
Platysaccus triassicus (MALJAVKINA) DUNAY & FISHER 1979
Plicatisaccus badius PAUTSCH 1971
Polycolpopollis magnificus n. gen. et sp.*
Protohaploxypinus sp.
Protohaploxypinus arizonicus FISHER & DUNAY 1984
Pseudoenzonalaporites summus SCHEURING 1970
Pyramidisporites traversei DUNAY & FISHER 1979
Raistrickia grovensis SCHOPF 1944
Rugubivesiculites proavitus FISHER & DUNAY 1984
Steevesipollenites hemiplicatus sp. nov.*
Striatoabieites aytugii VISSCHER 1966
Sulcatisporites Kraeuselii MÄDLER 1964
Tetrad type 39 (CORNET 1977: PI. 18, Figs. 5-6)
Triadispora verrucata (SCHULZ) SCHEURING 1970
Tricrinopollis olsenii n. gen. et sp.*
Tricrinopollis minutus n. gen. et sp.*
Umbrosaccus keuperianus MÄDLER 1964
Vallasporites ignacii LESCHIK 1955
Vitreisporites pallidus (REISSINGER) NILSSON 1958
Zonacrinopollis anasulcatus n. gen. et sp.*
At least seventy three palynomorph taxa are present in palynoflorule VB-4 of the Richmond Basin, VA (Text-fig. 1). Based on a count of 390 palynomorphs, 80.5% are pollen and 19.5% are spores. The assemblage was recorded according to morphotype (or presumed taxonomic grouping in the case of articulate spores, lycopod spores, and angiosperm-like pollen):
Striate bisaccates .................................................................………..... 0.3%
Large bisaccates (>40 microns) ...........................................………... 40.0%
Small bisaccates (<40 microns) ...........................................……….... 5.1%
Circumsaccates (e.g. Patinasporites) ......................................…….. 14.9%
Dispersed tetrads (e.g. Placopollis) ......................................………. 2.6%
Monosulcates (excl. angiosperm-like types) ..........................………. 12.0%
Angiosperm-like morphotypes ......…..........................................……. 2.0%
Circumpolles (e.g. Camerosporites) ...........................................……. 3.6%
Articulate spores (e.g. Laricoidites) ...........................................…….. 0.8%
Lycopod spores (e.g. Aratrisporites ..........................................……… 0.5%
Psilate spores (e.g. Dictyophyllidites) .........................................……. 1.8%
All other sculptured spores ............................................……………....16.4%
Total: 100.0%
The Crinopolles Group
Definition: A group of pollen morphotypes united by their typically (but not exclusively) reticulate-columellate exine structure, the presence of two or more sulci (or furrows) which are restricted to the distal and equatorial sides of a grain, the absence of apertures on the proximal side, and the presence in most taxa of a dimorphic sculptural pattern which resembles that found in monocots, especially the Liliaceae and the fossil formgenus, Liliacidites (DOYLE 1973; WALKER & WALKER 1984). This resemblance does not necessarily indicate that crinopolles pollen was produced by monocots, or for that matter by angiosperms. The strong resemblance to monocot pollen, however, probably should not be ignored or minimized, and is therefore reflected here in a name that suggests morphological similarity but not affinity.
Etymology: The Crinopolles Group is designated for fossil pollen grains whose generic names contain the ending, -crinopollis, which means lily-like pollen. This name and ending in no way imply affinity, just as crinoids are not monocots.
Pentecrinopollis n. gen.Type species: Pentecrinopollis traversei CORNET, n. sp.
Diagnosis: Pollen grains pentasulcate or pentaplicate with usually five sulci or aperture-like furrows (range 4-6 sulci or furrows) positioned on distal and equatorial sides of grain, and a non-apertural proximal zone or patch; corpus oblong or elliptical, rarely round; sulci usually separate, not joined; exine composed of a nexine bearing large (sexinal) gemmae or large prominent clavae whose heads are joined either by a reticulum or imperforate tectum; clavae on ridges separating furrows or sulci arranged in rows; clavae on proximal patch randomly spaced.
Etymology: Pente - Greek, meaning five; crino - derived from crinum, Greek, meaning lily, lily-like; pollis - Latin, meaning pollen.
Pentecrinopollis traversei n. sp.Holotype: SGM-P1, Locality VB4, Richmond Basin, VA, U.S.A.: pi. 1, Figs. 1-2; dimensions overall 81 X 55 microns.
Diagnosis: Pollen grains pentasulcate with five sulci positioned on distal and equatorial sides of grain, and a non-apertural proximal zone or patch (Pl. 1, Figs. 5-6); corpus elliptical to oblong; sulci usually separate, not joined, each centrally positioned within a broad tapering furrow; ridges separating furrows about 5-8 microns wide. Exine composed of a 1.0-1.5 micron thick nexine bearing large prominent clavae whose heads are joined by a delicate reticulum that abruptly becomes an imperforate tectum along the sides of the furrows containing the sulci (Pl. 1, Figs. 4; 7-9). Clavae arranged in rows on ridges separating sulci; clavae crowded and randomly spaced on proximal patch; clavae 2.25-4.75 microns tall; heads shorter than wide, usually 2.25-4.75 microns in diameter; necks 1.25-2.50 microns tall. Reticulum joins clavae at junction of head and neck. Non-apertural proximal patch sometimes connected apically at both ends to the distal ridges by a narrow band of clavate sexine. A pair of equatorial sulci closely approach one another apically, more so than the three distal sulci, and their furrows usually join to isolate proximal patch at one or both ends.
Dimensions (8 specimens): 66-(av. 78)-88 microns in length; 42-(av. 48)-55 microns in width; non-apertural proximal patch about 30-40 microns wide: See Text-fig. 4. Etymology: traversei - named after Dr. ALFRED TRAVERSE, Professor of palynology at The Pennsylvania State University, University Park, PA, for his contributions to our understanding of Triassic palynology and for his support, both professional and through his NSF grant, during the early phases of this study. Text-fig. 4.
Remarks: Pentecrinopollis traversei n. sp. possesses all of the essential characteristics belonging to the Crinopolles Group described in this paper: multiple sulci restricted to the distal and equatorial sides of the grain; columellae attached to a footlayer and supporting a reticulate tectum. The reticulum is attached to the base of the swollen heads of the clavae (Pl. 1, Fig. 4), making the heads supratectal sculptural elements perched on top of the reticulum. Such a configuration is reminiscent of the crotonoid pattern found in the monosulcate, Stellatopollis barghoornii DOYLE, from the Lower Cretaceous (DOYLE et al., 1975). The reticulum of P. traversei n. sp. is much smaller, however, while the reticulum of S. barghoornii is organized into large lumina ringed by supratectal elements, which are each supported by many short columellae rather than one large columella. Just as the sculptural pattern and large size of Stellatopollis (36-73 microns in length) is surprising to find in the Lower Cretaceous (DOYLE et al., 1975), the reticulate-clavate pattern, polysulcate condition, and large size of P. traversei n. sp. is surprising to find in the Upper Triassic amongst pollen of the Crinopolles Group whose morphology is more typical of angiosperms.
Age: Late Triassic: Early Carnian.
Occurrence: In the Richmond Basin, P. traversei n. sp. has been recorded only at outcrop locality VB-4. The relative percentage of P. traversei n. sp. amongst angiosperm-like pollen in sample VB-4 is 2.4%, or about 0.05% (5/10,000) of the entire palynoflorule. No specimens were encountered in a routine slide count of 390 grains, nor in routine counts (usually 100-250 grains) of slides made from cuttings samples in either the Horner No. 1 or Bailey No. 1 wells (Text-figs. 1-2). One specimen was found, however, in outcrop locality T20 from near the top of the Falling Creek Member of the Doswell Formation in the Taylorsville Basin, VA (WEEMS 1980b). The type Falling Creek Member correlates with the Vinita Beds of the Richmond Basin.
Its pattern of occurrence cannot be determined because of too little data. P. traversei n. sp. does occur in thin black lacustrine shales overlying abandoned delta lobes or crevasse splay deposits (See Text-fig. 3 and discussion in Materials and Methods).
Pentecrinopollis gemmatus n. sp.PI. 1, Figs. 10-13; Pl. 8, Figs. 97-100
Holotype: SGM-Q1; Locality VB-4, Richmond Basin, VA, U.S.A.: PI. 1, Figs. 12-13; dimensions overall 32 X 20 microns.
Diagnosis: Pollen grains usually pentaplicate with four to six plications positioned on distal and equatorial sides of grain, and a non-apertural zone or patch on proximal side; corpus mostly elliptical, occasionally round. Furrows shallow, lacking a median rent or sulcus; ridges separating furrows bearing usually a single row of gemmae; proximal patch protruding slightly (Pl. 1, Figs. 11; 13) and bearing 7-12 randomly spaced gemmae. Exine about 1.0-1.5 microns thick; tectum either lacking or joined to nexine; surface of exine between gemmae sparsely scabrate. Gemmae usually 2.25-3.75 microns in diameter, 3.0-4.5 microns tall with constricted bases; an enlarged gemma or auricula, 5.25-9.0 microns in diameter, sometimes present at one or both apical ends of grain (Pl. 1, Fig. 10; Pl. 8, Figs. 97-98; 100).
Dimensions (20 specimens): 30-(av. 39)-45 microns in length; 19-(av. 29)-41 microns in wide: See Text-fig. 4.
Etymology: gemmatus - Latin, meaning buds or gems.Remarks: P. gemmatus n. sp. is included in Pentecrinopollis, because it possesses the basic construction of P. traversei n. sp., even though it lacks a reticulum and has furrows instead of sulci. The generic diagnosis accepts such variation, because 1) P. gemmatus n. sp. is closer in morphology to P. traversei n. sp. (compare Text-figs. 7A; 7B) than it is to Steevesipollenites hemiplicatus n. sp., with which it also compares, and 2) P. gemmatus n. sp. and P. traversei n. sp. are close enough morphologically to have been produced by related plants. The occasional presence of auriculae or enlarged gemmae on P. gemmatus n. sp. provides a link or morphological bridge between P. traversei n. sp. and S. hemiplicatus n. sp., whose variation includes forms that approach P. gemmatus n. sp. (e.g. Pl. 8, Fig. 104). The absence of a reticulum and the presence of polyplicate furrows and occasional auriculae in P. gemmatus n. sp. are characters interpreted here as less derived than the presence of a reticulum and sulci, and the absence of auriculae.
Similar morphotypes have been recorded amongst angiosperms: Disulcate (operculate) clavate pollen resembling P. gemmatus n. sp. was recorded by G. R. FOURNIER in the Eocene (Pl. 8, Fig. 95); this morphotype probably came from a monocotyledonous plant (cf. THANIKAIMONI 1970), whose relatives produced normal reticulate-columellate pollen. Auriculae are present on pollen of some extant angiosperms (e.g. Bomarea lycina: Amaryllidaceae: P1. 8, Fig. 96), even though other members of the same family produce normal reticulate-columellate pollen, suggesting that the presence of auriculae is not a valid reason for excluding P. gemmatus n. sp. from the Crinopolles Group. In addition, the presence of furrows instead of sulci is a variation in aperture morphology found in the extant Araceae (e.g. Spathiphyllum spp.: THANIKAIMONI 1969; TREVISAN 1980).
Age: Late Triassic: Early Carnian.
Occurrence: Pentecrinopollis gemmatus n. sp. has been recorded thus far only in the Richmond Basin. The relative percentage of P. gemmatus n. sp. amongst angiosperm-like pollen in sample VB-4 is about 6.1% or about 0.12% (12/10,000) of the entire palynoflorule. No specimens were encountered in a routine slide count of 390 grains; specimens were found in cuttings interval 5090-5110 ft./1152/1558 m. (two in 69 count) in the Horner No. 1 well, and in cuttings interval 5370-5410 ft./1634-1649 m. (one in 209 count) in the Bailey No. 1 well (Text-figs. 1-2).
Its pattern of occurrence suggests that the plant producing P. gemmatus n. sp. may have preferred fluvial and deltaic sandstone and levee environments, because it is restricted to thin shales interbedded within deltaic sandstones, and to black lacustrine shales overlying abandoned delta lobes and crevasse splay deposits (See Text-fig. 3 and discussion in Materials and Methods).
Tricrinopollis n. gen.Type species: Tricrinopollis olsenii CORNET n. sp.
Diagnosis: Pollen grains normally with one distal sulcus flanked by a pair of equatorial or lateral sulci oriented nearly parallel to the distal sulcus; occasionally one equatorial sulcus missing or an additional sulcus present on distal side; corpus elliptical to oblong, rarely subrounded; sulci separate, not joined. Sculpture differentiated, finely reticulate or foveolate distally and coarsely reticulate proximally; sulci all located within area of finely reticulate-foveolate distal sculpture; muri of reticulum psilate. Proximal exine thicker with a footlayer supporting well-developed columellae; columellae much reduced to granules and short rods on distal side where footlayer absent; endexine present, continuous, not poly-laminated as in gymnosperms, and noticeably thicker under sulci or where footlayer absent.
Etymology: Tri - Greek, meaning three, in reference to three sulci; crino - derived from crinum, Greek, meaning lily, lily-like; pollis - Latin, meaning pollen.
Remarks: Tricrinopollis n. gen. is very different from Eucommiidites ERDTMAN 1948, which was once thought to represent pre-Cretaceous angiosperm pollen, but which is now recognized as gymnospermous (See DOYLE et al., 1975). The reticulate-columellate exine, lack of obvious endexinal laminations, and dimorphic sculpture of T. olsenii n. sp. indicate no close relationship with Eucommiidites, which is absent from most Newark Supergroup palynofloras. Trisulcate Pretricolpipollenites DANZÉ-CORSIN & LAVEINE 1963 is present in the Richmond Basin palynoflora, but differs from Tricrinopollis n. gen. by having an imperforate psilate sculpture and thin faintly intra-punctate exine with two lateral sulci positioned on the distal rather than equatorial side (i.e. closer to the median sulcus: BALME 1970). No intermediate morphotypes were encountered that would suggest a derivation from Pretricolpipollenites, but intermediates (cf. Text-fig. 7) were found that suggest a derivation from other morphotypes of the Crinopolles Group. Tricrinopollis n. gen. compares with trisulcate variants of normally tricolpate Nelumbo pollen (extant Nymphaeidae: KUPRIANOVA 1979). When Nelumbo pollen is trisulcate, its tetrad arrangement is tetrahedral, as it is for 7: olsenii n. sp.
Tricrinopollis olsenii n. sp.Pl. 2, Figs. 14-24; Pl. 8, Figs. 108-109; PI. 9, Fig. 112
Holotype: SGM-I21; Locality VB-4, Richmond Basin, VA, U.S.A.: Pl. 2, Figs. 17-18; dimensions overall 48 X 30 microns.
Diagnosis: Pollen grains normally with one median distal sulcus flanked by a pair of equatorial sulci oriented nearly parallel to the distal sulcus; occasionally one equatorial sulcus missing; corpus elliptical to oblong; sulci separate, not joined. Proximal exine coarsely reticulate-columellate, 1.9-4.0 microns thick; distal exine foveo-reticulate (Pl. 2, Fig. 23), 0.6-1.1 microns thick; all apertures restricted to area with foveo-reticulate sculpture.
Proximal columellae 2.0-3.0 microns tall, markedly decreasing in height equatorially; columellae reduced to granules and short rods under area with finer sculpture (Pl. 8, Fig. 108). Lumina of proximal reticulum variable in size and heteromorphic, decreasing in size in equatorial transition zone (Pl. 2, Fig. 24); larger lumina 3.0-10.5 microns in maximum dimension; muri of reticulum psilate. Exine two-layered with a well-developed footlayer proximally; distal ectexine much thinner than proximal ectexine; footlayer 0.15-0.21 microns thick proximally, disappears equatorially and distally under finer sculpture; endexine present, continuous, probably not laminated, and noticeably thicker under sulci and where footlayer absent (Pl. 8, Fig. 109; Pl. 9, Fig. 112). Dimensions (37 specimens): 42-(av. 46)-53 microns in length; 25-(av. 29)-39 microns in width: See Text-fig. 5. Etymology: olsenii - named after Dr. PAUL E. OLSEN, Professor of geology, Lamont-Doherty Earth Observatory of Columbia University, Palisades, NY, for his extensive contributions to our knowledge of Newark Supergroup geology and vertebrate paleontology, as well as for his support and aid in palynological studies of the Newark Supergroup. Text-fig. 5.
Remarks: The discovery of a tetrad of T. olsenii n. sp. pollen provides proof that the coarsely reticulate-columellate side is proximal, or facing the inside of the tetrad, and that the foveo-reticulate side bearing the sulci is distal (Pl. 2, Figs. 14-16). The tetrad is tetrahedral (Text-fig. 6A), rather than tetragonal; a tetrahedral arrangement is required for the evolution of radial symmetry. The polar axis appears to pass through the symmetrical center of the grain as in monosulcate pollen. The endexine in one TEM cross section appears to be homogenous (Pl. 9, Fig. 112), while in another (Pl. 8, Fig. 109) it split in a manner that suggests the presence of a layered structure on the proximal side of the grain. At best, only two layers can be recognized on the proximal side, and the outer layer appears to belong to the footlayer (compare footlayer thickness in Pl. 8, Fig. 109 and Pl. 9, Fig. 112). On the distal side the endexine is thicker, possibly vacuolated, and clearly not laminated. Since the endexine of Monocrinopollis doylei n. sp. is similar (possibly vacuolated) on both proximal and distal sides (Pl. 9, Fig. 13), it may have been undergoing radical change in the Crinopolles Group.
Age: Late Triassic: Early to middle! Carnian.
Occurrence: Tricrinopollis olsenii n. sp. has been recorded at outcrop localities BB-1, VB-4, and PCM4 in the Richmond Basin, VA (Text-fig. 1). The relative percentage of T. olsenii n. sp. amongst angiosperm-like pollen in sample VB-4 is about 11.3%, or about 0.23% (23/10,000) of the entire palynoflorule. One specimens was encountered in a routine slide count of 390 grains in palynoflorule VB-4. A specimen was found in cuttings inverval 5800 - 5830 ft./1768 - 1777 m. (one in 112 count) in the Horner No. 1 well (Text-figs. 1-2). T. olsenii n. sp. also occurs in the Taylorsville Basin, VA: At outcrop locality T22 (WEEMS 1980a; CORNET 1977: Doswell) in the Falling Creek Member of the Doswell Formation, and at Locality T5 (WEEMS 1980b: p. 33, unit 72; CORNET 1977: M'b) located above the type Falling Creek Member, based on palynological correlation. T. olsenii n. sp. is found mainly in the Vinita Beds and Productive Coal Measures of the Richmond Basin, but may range slightly higher into the overlying unit (provided that it is not reworked).
Its pattern of occurrence suggests that the plant producing T. olsenii n. sp. may have preferred fluvial and deltaic sandstone and levee environments, because it is restricted to dark gray to black shales interbedded within thick fluvial or deltaic sandstones, sometimes containing coal seams, and to black lacustrine shales overlying abandoned delta lobes and crevasse splay deposits (See Text-fig. 3 and discussion in Materials and Methods).
Tricrinopollis minutus n. sp.Holotype: SGM-JI; Locality VB-4, Richmond Basin, VA, U.S.A.: PI. 3, Figs. 36-37; dimensions overall 30 X 20 microns.
Diagnosis: Pollen grains normally with one median distal sulcus flanked by a pair of equatorial sulci oriented nearly parallel to the distal sulcus; occasionally equatorial sulci positioned more proximally as in a tricolpate configuration (Pl. 3, Fig. 41); sometimes an additional sulcus present between median distal and equatorial sulci (Pl. 3, Figs. 38-39); corpus elliptical to oblong; sulci separate, not joined. Proximal exine thick, coarsely reticulate-columellate; distal exine thin with a foveo-reticulate sculpture (Pl. 3, Fig. 36); all apertures restricted to area with foveo-reticulate sculpture. Proximal columellae 0.8-1.5 microns tall, markedly decreasing in height equatorially; columellae much reduced or absent on distal side. Lumina of proximal reticulum relatively uniform in size except in equatorial transition zone, where lumina decrease in size; lumina relatively uniform in shape: pentagonal to rounded, sometimes irregular; larger lumina 1.5-4.5 microns in maximum dimension; muri of reticulum psilate. Exine two-layered with a well-developed footlayer proximally; endexine probably present but not observed.
Dimensions (21 specimens): 24-(av. 31)-38 microns in length; 19-(av. 22)-27 microns in width; see Text-fig. 5.
Etymology: minutus- Latin, meaning little, small.
Text-fig. 6.
Age: Late Triassic: Early Carnian.
Occurrence: Tricrinopollis minutus n. sp. has been recorded at outcrop localities VB-1 and VB-4 in the Richmond Basin, VA (Text-figs. 1-2). The relative percentage of T. minutus n. sp. amongst angiosperm-like pollen in sample VB-4 is about 6.4 %, or about 0.12% (12/10,000) of the entire palynoflorule. One specimen was encountered in a routine slide count of 390 grains in palynoflorule VB-4. No specimens were encountered in routine counts (usually 100-250 grains) of slides made from cuttings samples of either the Horner No. 1 or Bailey No. 1 wells (Text-figs. 1-2). Its pattern of occurrence suggests that the plant producing T. minutus n. sp. may have preferred fluvial and deltaic sandstone and levee environments, because it is restricted to thin black shales interbedded within thick fluvial or deltaic sandstones, and to black lacustrine shales overlying abandoned delta lobes and crevasse splay deposits (See Text-fig. 3 and discussion in Materials and Methods). Text-fig. 7. 
Type species: Monocrinopollis doylei CORNET n. sp.
Diagnosis: Pollen grains usually monosulcate, but with aperture formed by two closely-spaced sulci separated by a narrow operculum; occasionally an anomalous sulcus present in equatorial position; corpus oblong to spherical, usually elliptical; round or spherical specimens usually with a trichotomosulcate aperture. Proximal exine finely to coarsely reticulate-columellate, distal exine foveo-reticulate to faintly pitted (almost psilate); all apertures restricted to area with foveo-reticulate sculpture. Exine two-layered with well-developed footlayer proximally; ectexine thinner distally with footlayer discontinuous or missing and columellae reduced to granules and short rods under area with finer sculpture; endexine, if present, vacuolated, non-laminated, and thicker under distal aperture.
Etymology: Mono - Greek, meaning one, or a single apertural area; crino - derived from crinum, Greek, meaning lily, lily-like; pollis Latin, meaning pollen.
Remarks: The classification of the aperture as monosulcate is based on its resemblance to the apertures of other monosulcate pollen. If it were not for the numerous characteristics which link the genus to the Crinopolles Group, the origin of this type of monosulcus from two closely-spaces sulci probably would have gone unrecognized (Text-fig. 7J-L). Whether or not the aperture of other monosulcate grains evolved in a similar manner is beyond the scope of this paper, but the compound nature of the aperture is not unique to the Crinopolles Group: The compound distal aperture is quite common among extant monocots (THANIKAIMON1 1970; CHANDA & GHOSH 1976; CHANDA et al. 1978).
Monocrinopollis doylei n. sp.
