TY - JOUR
T1 - Taxonomy and biogenicity of Archaean spheroidal microfossils (ca. 3.0 Ga) from the Mount Goldsworthy-Mount Grant area in the northeastern Pilbara Craton, Western Australia
AU - Sugitani, Kenichiro
AU - Grey, Kathleen
AU - Nagaoka, Tsutomu
AU - Mimura, Koichi
AU - Walter, Malcolm R.
PY - 2009/9
Y1 - 2009/9
N2 - Microstructures recently reported from an Archaean sedimentary succession (ca. 3.0 Ga) in the Mount Goldsworthy-Mount Grant area in the northeastern Pilbara Craton meet the criteria for compelling evidence of biogenicity [Sugitani, K., Grey, K., Allwood, A., Nagaoka, T., Mimura, K., Minami, M., Marshall, C.P., Van Kranendonk, M.J., Walter, M.R., 2007. Diverse microstructures from Archaean chert from the Mount Goldsworthy-Mount Grant area, Pilbara Craton, Western Australia: microfossils, dubiofossil, or pseudofossils. Precambrian Res. 158, 228-262]. The structures are morphologically diverse. Although they were tentatively classified into five major morphological types (thread-like, film-like, small (<15 μm) and large (>15 μm) spheroidal, and spindle-like), the possible taxonomic significance of these groups was not discussed. Building on our earlier analysis, we focus on the morphology of the larger spheroids, as well as presenting further evidence relating spindles and several bizarre forms, and attempt to group them taxonomically and adduce additional evidence for their biogenicity. Taphonomic features were identified in each of the various morphological groups, but the range of morphological diversity of the spheroids cannot be attributed solely to taphonomic alteration. Four subdivisions of spheroids are proposed: (1) simple single-walled spheroids, (2) thin-walled spheroids having a diffuse envelope, (3) thick-walled spheroids, and (4) spheroids having an extensively folded wall. Simple single-walled spheroids, 15-60 μm in diameter, with various wall textures but commonly lacking envelopes or appendages form the dominant subgroup. Other complex morphologies are present and include aligned or associated bodies of thin-walled spheroids with diffuse envelopes, and spindle-like structures containing inner spheroidal bodies. The degree of morphological complexity and associations between structures suggest the presence of reproductive phases. If correct, this implies that the early Earth (ca. 3.0 Ga) showed a higher level of biodiversity than is currently postulated.
AB - Microstructures recently reported from an Archaean sedimentary succession (ca. 3.0 Ga) in the Mount Goldsworthy-Mount Grant area in the northeastern Pilbara Craton meet the criteria for compelling evidence of biogenicity [Sugitani, K., Grey, K., Allwood, A., Nagaoka, T., Mimura, K., Minami, M., Marshall, C.P., Van Kranendonk, M.J., Walter, M.R., 2007. Diverse microstructures from Archaean chert from the Mount Goldsworthy-Mount Grant area, Pilbara Craton, Western Australia: microfossils, dubiofossil, or pseudofossils. Precambrian Res. 158, 228-262]. The structures are morphologically diverse. Although they were tentatively classified into five major morphological types (thread-like, film-like, small (<15 μm) and large (>15 μm) spheroidal, and spindle-like), the possible taxonomic significance of these groups was not discussed. Building on our earlier analysis, we focus on the morphology of the larger spheroids, as well as presenting further evidence relating spindles and several bizarre forms, and attempt to group them taxonomically and adduce additional evidence for their biogenicity. Taphonomic features were identified in each of the various morphological groups, but the range of morphological diversity of the spheroids cannot be attributed solely to taphonomic alteration. Four subdivisions of spheroids are proposed: (1) simple single-walled spheroids, (2) thin-walled spheroids having a diffuse envelope, (3) thick-walled spheroids, and (4) spheroids having an extensively folded wall. Simple single-walled spheroids, 15-60 μm in diameter, with various wall textures but commonly lacking envelopes or appendages form the dominant subgroup. Other complex morphologies are present and include aligned or associated bodies of thin-walled spheroids with diffuse envelopes, and spindle-like structures containing inner spheroidal bodies. The degree of morphological complexity and associations between structures suggest the presence of reproductive phases. If correct, this implies that the early Earth (ca. 3.0 Ga) showed a higher level of biodiversity than is currently postulated.
KW - Archaean
KW - Biodiversity
KW - Microfossils
KW - Mount Goldsworthy-Mount Grant
KW - Pilbara Craton
UR - http://www.scopus.com/inward/record.url?scp=67650757265&partnerID=8YFLogxK
U2 - 10.1016/j.precamres.2009.02.004
DO - 10.1016/j.precamres.2009.02.004
M3 - Article
AN - SCOPUS:67650757265
SN - 0301-9268
VL - 173
SP - 50
EP - 59
JO - Precambrian Research
JF - Precambrian Research
IS - 1-4
ER -