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Species Globorotalia crassaformis Galloway & Wissler 1927 | ||||||
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| Diagnosis / Definition: | ||||||
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Bolli & Saunders (1985): Opinions are divided on the origin of Globorotalia crassaformis and related taxa and on their evolutionary trends and usefulness as stratigraphic indices within the Pliocene and Pleistocene. Comparison of published work actually shows a reversal of trends depending on the authority. Certain authors regard crassaformis as the end form of an evolutionary development, others as the initial species from which other morphologically distinguishable taxa have developed. Evolution of the non carinate crassaformis from distinctly carinate ancestors has been suggested, but also the view that crassaformis gave rise to keeled forms has been stated. There is also no general agreement on ranges of individual taxa. The use and acceptance of taxa of the crassaformis plexus as index forms in biostratigraphy thus remains incompletely understood, controversial, and largely limited to restricted areas, such as the Mediterranean or the Caribbean. Since the erection of G. crassaformis (Galloway & Wissler) in 1927 from the Pleistocene of California, several other taxa regarded as closely related have been proposed. G. crassaformis is known to be a cosmopolitan form, occurring in both warm and temperate waters and displaying considerable variability through time and in different environments; this has led to the erection of related taxa. Morphological changes in the closely related taxa are fluid and their clear differentiation therefore difficult. Stainforth et al. (1975), are of the opinion that 'distinctions between adjacent forms are tenuous and arbitrary and not expressible in objective terms'. They therefore restrict themselves to describing and figuring only G. crassaformis with G. aemiliana and G. ronda as recognizably more primitive and more advanced forms, respectively. Opinions on how valid the crassaformis plexus is for biostratigraphy are divided. Data from different regions indicate that in geographically and paleoenvironmentally restricted areas, certain taxa of the plexus may successfully be applied as index forms and zonal markers within the PliocenePleistocene. It is for these reasons that the species and subspecies and their evolutionary trends as described in particular for New Zealand, Italy and the Caribbean are here briefly discussed. Proposed lineages The following bioseries or evolutionary trends have been proposed: Kennett (1966) for New Zealand: G. miozea G. conomiozea G. crassaformis. Colalongo & Sartoni (1967) for Italy: G. hirsuta ( G. margaritae) G. aemiliana G crassaformis. Conato & Follador (1967) for Italy: G. crotonensis G. crassacrotonensis G. crassaformis. Blow (1969) general: G. crassaformis crassaformis G. crassaformis rondo G. crassaformis oceanica. Blow (1969) general: G. crassaformis crassaformis G. crassula conomiozea G. crassula crassula G. crassula viola. Lamb& Beard (1972) Gulf of Mexico, Caribbean, Italy: G. aemiliana G. crassacrotonensis G. crassaformis. The conflict in evolutionary trends postulated from different areas is apparent from the above list. It is in part because morphological changes within the plexus were controlled by different and regionally restricted environmental conditions. A study by Lidz (1972) of Late Pleistocene G. crassaformis populations from different latitudes has shown these to be largely controlled by temperature. Some of the conflicting views are difficult to reconcile even when taking the above controls into account, and in our opinion require revision or further investigation. One of them is the view of Blow (1969), who regarded the non carinate and pustulose G. crassaformis as the ancestor of the fully carinate and smooth surfaced G. conomiozea, which he considered to have branched off from it in the uppermost Miocene. In addition to his lineage crassaformis conomiozea crassula viola, Blow proposed a second line of non carinate forms, crassaformis ronda oceanica from which in turn developed G. tosaensis tosaensis and eventually G. truncatulinoides pachytheca. Kennett (1966) believed that in this bioseries the ancestors of the non carinate crassaformis are the fully keeled and smooth Late Miocene G. miozea and G. conomiozea with the latter restricted to the uppermost Miocene where it develops into crassaformis. This view remains problematical and is in contrast to Blow's opinion. Investigations on Pleistocene specimens (Lidz, 1972) have shown that a trend to form an imperforate rim or keel occurs in warm water low latitude specimens, with tests still retaining their pustulose surface character. The lineage from G. aemiliana to G. crassaformis proposed by Colalongo & Sartoni (1967) from the Mediterranean area seems to be the most straightforward and therefore acceptable; it is based on a gradual increase in height of the umbilical side. Later in 1967 Conato & Follador proposed the same lineage using the additional names G. crotonensis and G. crassacrotonensis which are now considered as junior synonyms of G. aemiliana and G. crassaformis respectively. The sequence of taxa given by Lamb & Beard (1972) for the Gulf of Mexico, and Italy (aemiliana crassacrotonensis crassaformis) is the same as that used by the Italian workers. The difference lies in the earlier appearance of the series (within the Early Pliocene Globorotalia margaritae Zone) as compared with the Italian authors, whose sequences begin stratigraphically later; that is, in the Middle Pliocene. Rögl (1974) closely followed the distribution of the crassaformis plexus in the extended Middle Pliocene to Holocene section of DSDP Site 262 in the Timor Trough (hit. 1 l' S). The fact that the ranges given by him differ in part from those for the Caribbean can probably be attributed to different environmental conditions that existed in the two areas. Stratigraphic significance Considerable discrepancies among authors also exist in their interpretation of ranges of individual taxa. Except for Blow, according to whom the crassaformis plexus originates in the Late Miocene, all other authors place this event either at the base or within the Early Pliocene Globorotalia margaritae margaritae Zone or, in the Mediterranean area, somewhat later; that is in the mid Pliocene. Ranges of all the taxa distinguished by Blow run from the Late Miocene or basal Pliocene to Holocene and are thus of no stratigraphic significance within this interval. Data from a number of DSDP Caribbean sections (Bolli, 1970; Bolli & Premoli Silva, 1973) indicate for that region a much more restricted distribution of the subspecies viola and hessi. The taw recognized as evolutionary stages by Italian workers, and adapted by Lamb & Beard (1972) are also stratigraphically restricted. From the ranges reported it can he concluded that the G. crassaformis plexus is limited to the Pliocene Holocene and that certain subspecies are significant for stratigraphically restricted intervals at least within certain areas. G. crassaformis and subspecies have been proposed as zonal markers by a number of authors. Several Italian workers (see Lamb & Beard, 1972) subdivide the Middle Pliocene into a Globorotalia aemiliana Zone (first occurrence of zonal marker to first occurrence of G. crassaformis) and a Globorotalia crassaformis Zone (first occurrence of zonal marker to first occurrence of G. inflata). In Chapter 8 of this volume Iaccarino combines these two zones into the Globorotalia aemiliana Zone (first occurrence of G. aemiliana to first occurrence of G. inflata). Based on evidence from several DSDP sites of Legs 4 and 15, Bolli & Premoli Silva (1973) introduced a Globorotalia crassaformis viola Subzone (first G. truncatulinoides truncatulinoides to first G. crassaformis hessi) and a Globorotalia crassaformis hessi Subzone (first zonal marker to first G. calida calida), subdividing the Early Pleistocene in the Caribbean. Coiling trends The preferred Coiling direction in the crassaformis plexus is sinistral. Swings to dextral coiling are rare and mostly limited in time; locally they may, however, be of stratigraphic significance. In the Pacific realm temporary dextral coiling occurs in the Late Pliocene of New Zealand (Jenkins, 197 1), and in the Middle Pliocene of Java (Bolli, 1966b). Coiling directions have been followed in several Caribbean DSDP sites by Bolli (1970) and Bolli & Premoli Silva (1973). All taxa of the plexus recognized show a nearly exclusive preference for sinistral coiling throughout the Pliocene and Pleistocene. There are only a few instances of brief swings to dextral coiling: G. crassaformis hessi in the upper part of the Pleistocene in Site 30; G. crassaformis crassaformis in the upper part of the Globorotalia margaritae evoluta and lower part of the Globigerinoides trilobus fistulosus zones in the Early to Middle Pliocene and G. crassaformis cf. viola within the Globorotalia tosaensis Zone in the Late Pliocene, both in Site 148. Lidz (1972) in her study on Late Pleistocene Atlantic/ Caribbean G. crassaformis specimens from piston cores at three different latitudes (5, 15, 34° N) concluded that 'coiling direction is not influenced by temperature and appears to be neither consistent nor interregionally correlative among the cores discussed'. Her text figure I 'Percentage of right coiled specimens of Globorotalia crassaformis' shows a preference for sinistral coiling. It is interrupted in the 5' latitude core by only one brief swing to nearly 100% dextral. More frequent dextral forms recurring within shorter intervals are present in the 15' latitude core, and still more in that from 34'. Contrary to Lidz' conclusions these patterns therefore might rather be interpreted as reflecting fluctuations related to temperature, i.e. a distinct preference for sinistral coiling in warmer and a trend towards dextral coiling in cooler waters. |
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| Discussion / Comments: | ||||||
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Chaisson & Leckie (1993): Similar species: Globorotalia crassiformis has fewer chambers and a more lobate equatorial outline than G. tosaensis. |
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| Synonym list: | ||||||
| Bolli & Saunders (1985): 1985 Globorotalia crassaformis Galloway & Wissler. - Bolli & Saunders : p.230
Vincent & Toumarkine (1990): 1927 Globigerina crassaformis Galloway & Wissler. - Galloway & Wissler : p. 41 pl. 7, fig. 12
1990 Globorotalia crassaformis Galloway & Wissler. - Vincent & Toumarkine : p. 834 pl. 5, fig. 11
Chaisson & Leckie (1993): 1927 Globigerina crassaformis Galloway & Wissler. - Galloway & Wissler : p.41 pl. 7; fig. 12
1983 Globorotalia (Truncorotalia) crassaformis Galloway & Wissler. - Kennett & Srinivasan : p.146 pl. 34; fig. 6-8
1985 Globorotalia crassaformis crassaformis Galloway & Wissler. - Bolli & Saunders : p.230 fig. 36.6-7
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| Stratigraphy - absolute ages: | ||||||
| FAD: 4.5 ± 0 [Ma], Berggren et al. (1995) FAD: 3.58 ± 0 [Ma], Berggren et al. (1995) Mediterranean RAP: 33.5 ± 0 [Ma], Berggren et al. (1995) Mediterranean S-D: 3.26 ± 0 [Ma], Berggren et al. (1995) Mediterranean D-S: 3.17 ± 0 [Ma], Berggren et al. (1995) Mediterranean S-D: 3 ± 0 [Ma], Berggren et al. (1995) Mediterranean D-S: 2.92 ± 0 [Ma], Berggren et al. (1995) Mediterranean |
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| References: | ||||||
Galloway,J.J. and Wissler,S.G. (1927): Kennett,J. and Srinivasan,M.S. (1983): Bolli,H.M. and Saunders,J.B. (1985): Vincent,E. and Toumarkine,M. (1990): Chaisson,W.P. and Leckie,R.M. (1993): Berggren,W.A.; Hilgen,F.J.; Langereis,C.G.; Kent,D.V.; Obradovich,J.D.; Raffi,I.; Raymo,M.E. and Shackleton,N.J. (1995): |
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| Anonymous: Unedited TaxonConcept data | ||||||
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