These proposed biozones
Seeley named were subdivided further by
Robert Broom between 1906 and 1909.[8]Broom proposed the following
biozones (from oldest to youngest):
These
biozone divisions were approved by paleontologists of the time and were left largely unchanged for several decades.[9] The Lystrosaurus Assemblage Zone was first named by
Robert Broom in 1906.[10] Initially Broom had subdivided the existing Lystrosaurus zone into the Lystrosaurus and Procolophon Assemblage Zones respectively. The
biozone was later revised in 1976 by
James Kitching where Kitching assimilated the Procolophon zone into the Lystrosaurus zone due to discovering that fossils of the small
parareptileProcolophon were likewise found throughout the Lystrosaurus zone.[11][12]
The boundary is defined by a change in the
sedimentary rock types. The changing rock types across the boundary reveal a change in the
fluvial environment, from
meandering high sinuosity
river channels composed of greenish-grey
siltstones and
mudstones found in the underlying
Daptocephalus Assemblage Zone.[16][17][18] From the start of the Palingkloof Member the predominant presence of
mudstone and
siltstone show that meandering river channels were present, however, in
arid and warmer conditions due to change in colour of the rocks to reddish-brown and maroon.[19][20] These are inter-spaced with
claystones, olive to grey fine-grained
sandstone, and reddish-brown to maroon
shales. In the overlying Katberg Formation,
alluvial fans containing
braided low sinuosity
river channels comprising mainly coarse-grained
sandstone appear. These
sandstones form either single and multi-storey channel
sandstones and
crevasse-splaysandstones.[21] The dominance of sandstones is diagnostic of the Katberg Formation. The
sandstones are interspersed by reddish-brown
siltstones and
mudstones which were deposited as
silt sediments washed down the
braided channels further down the
Karoo Basin.[22] The
mudstones here often contain cracks which are infilled with
sandstone.[23] The domination of sandstone in the Lystrosaurus Assemblage Zone shows that the
climate at the time had become more
arid, where rainfall was unpredictable and the shallow, braided rivers would seasonally dry up.[24] When the rivers flowed again after the rains, due to being shallow, they would frequently
flood their banks, hence the presence of
crevasse-splays.
Conglomerates are also found in eastern outcrops, which are indicative of
erosion occurring due to die-offs of plant
ecosystems. There is in addition a notable gap in
coal deposits at this time as a result.
Siltstone and
mudstoneoutcrops are less common, with the majority of
outcrops of these being found in the lower sections within the Palingkloof Member and in its uppermost section within the Burgersdorp Formation.
Noduleconglomerates comprising
pedogenicnodules and intrabasinal
clasts are also found.[25][26]
^Keyser, A. W., & Smith, R. M. H. (1978). Vertebrate biozonation of the Beaufort Group with special reference to the western Karoo Basin. Geological Survey, Department of Mineral And Energy Affairs, Republic of South Africa.
^Rubidge, B. S. (ed.) 1995b. Biostratigraphy of the Beaufort Group (Karoo Supergroup). South African Committee of Stratigraphy. Biostratigraphic Series 1. Pretoria, Council for Geoscience.
^Smith, R.M.H. (1995-08-01). "Changing fluvial environments across the Permian-Triassic boundary in the Karoo Basin, South Africa and possible causes of tetrapod extinctions". Palaeogeography, Palaeoclimatology, Palaeoecology. 117 (1–2): 81–104.
Bibcode:
1995PPP...117...81S.
doi:
10.1016/0031-0182(94)00119-S.
ISSN0031-0182.
^BOTHA, JENNIFER; SMITH, ROGER M. H. (2007-04-08). "Lystrosaurus species composition across the Permo-Triassic boundary in the Karoo Basin of South Africa". Lethaia. 40 (2): 125–137.
doi:
10.1111/j.1502-3931.2007.00011.x.
ISSN0024-1164.
^Broom, R. (1906). V.—On the Permian and Triassic Faunas of South Africa. Geological Magazine, 3(1), 29-30.
^Kitching, J. W. (1977). The distribution of the karroo vertebrate fauna: with special reference to certain genera and the bearing of this distribution on the zoning of the Beaufort Beds, Bernard Price Institute for Palaeontological Research, University of the Witwatersrand.
^Kitching, J. W. (1984). A reassessment of the biozonation of the Beaufort Group. Paleo News, 4(1), 12-13.
^Rubidge, B. S. (ed.) 1995b. Biostratigraphy of the Beaufort Group (Karoo Supergroup). South African Committee of Stratigraphy. Biostratigraphic Series 1. Pretoria, Council for Geoscience.
^Viglietti, Pia A.; Smith, Roger M.H.; Angielczyk, Kenneth D.; Kammerer, Christian F.; Fröbisch, Jörg; Rubidge, Bruce S. (2016-01-01). "The Daptocephalus Assemblage Zone (Lopingian), South Africa: A proposed biostratigraphy based on a new compilation of stratigraphic ranges". Journal of African Earth Sciences. 113: 153–164.
Bibcode:
2016JAfES.113..153V.
doi:
10.1016/j.jafrearsci.2015.10.011.
ISSN1464-343X.
^Viglietti, Pia A.; Smith, Roger M.H.; Rubidge, Bruce S. (2018-02-01). "Changing palaeoenvironments and tetrapod populations in the Daptocephalus Assemblage Zone (Karoo Basin, South Africa) indicate early onset of the Permo-Triassic mass extinction". Journal of African Earth Sciences. 138: 102–111.
Bibcode:
2018JAfES.138..102V.
doi:
10.1016/j.jafrearsci.2017.11.010.
ISSN1464-343X.
^Smith, R.M.H. (1995-08-01). "Changing fluvial environments across the Permian-Triassic boundary in the Karoo Basin, South Africa and possible causes of tetrapod extinctions". Palaeogeography, Palaeoclimatology, Palaeoecology. 117 (1–2): 81–104.
Bibcode:
1995PPP...117...81S.
doi:
10.1016/0031-0182(94)00119-S.
ISSN0031-0182.
^Viglietti, Pia A.; Smith, Roger M.H.; Compton, John S. (2013-12-15). "Origin and palaeoenvironmental significance of Lystrosaurus bonebeds in the earliest Triassic Karoo Basin, South Africa". Palaeogeography, Palaeoclimatology, Palaeoecology. 392: 9–21.
Bibcode:
2013PPP...392....9V.
doi:
10.1016/j.palaeo.2013.08.015.
ISSN0031-0182.
^Viglietti, Pia A.; Smith, Roger M.H.; Rubidge, Bruce S. (2018-02-01). "Changing palaeoenvironments and tetrapod populations in the Daptocephalus Assemblage Zone (Karoo Basin, South Africa) indicate early onset of the Permo-Triassic mass extinction". Journal of African Earth Sciences. 138: 102–111.
Bibcode:
2018JAfES.138..102V.
doi:
10.1016/j.jafrearsci.2017.11.010.
ISSN1464-343X.
^Smith, R., Rubidge, B., & Van der Walt, M. (2012). Therapsid biodiversity patterns and paleoenvironments of the Karoo Basin, South Africa. Forerunners of Mammals: Radiation, Histology, Biology. Indiana University Press, Indianapolis, Indiana, 30-62.
^Viglietti, Pia A.; Smith, Roger M.H.; Compton, John S. (2013-12-15). "Origin and palaeoenvironmental significance of Lystrosaurus bonebeds in the earliest Triassic Karoo Basin, South Africa". Palaeogeography, Palaeoclimatology, Palaeoecology. 392: 9–21.
Bibcode:
2013PPP...392....9V.
doi:
10.1016/j.palaeo.2013.08.015.
ISSN0031-0182.
^Smith, Roger M.H.; Botha-Brink, Jennifer (2014-02-15). "Anatomy of a mass extinction: Sedimentological and taphonomic evidence for drought-induced die-offs at the Permo-Triassic boundary in the main Karoo Basin, South Africa". Palaeogeography, Palaeoclimatology, Palaeoecology. 396: 99–118.
doi:
10.1016/j.palaeo.2014.01.002.
ISSN0031-0182.
^Viglietti, Pia A.; Smith, Roger M.H.; Compton, John S. (2013-12-15). "Origin and palaeoenvironmental significance of Lystrosaurus bonebeds in the earliest Triassic Karoo Basin, South Africa". Palaeogeography, Palaeoclimatology, Palaeoecology. 392: 9–21.
Bibcode:
2013PPP...392....9V.
doi:
10.1016/j.palaeo.2013.08.015.
ISSN0031-0182.
^Smith, R.M.H. (1995-08-01). "Changing fluvial environments across the Permian-Triassic boundary in the Karoo Basin, South Africa and possible causes of tetrapod extinctions". Palaeogeography, Palaeoclimatology, Palaeoecology. 117 (1–2): 81–104.
Bibcode:
1995PPP...117...81S.
doi:
10.1016/0031-0182(94)00119-S.
ISSN0031-0182.
^Smith, Roger M.H.; Botha-Brink, Jennifer (2014-02-15). "Anatomy of a mass extinction: Sedimentological and taphonomic evidence for drought-induced die-offs at the Permo-Triassic boundary in the main Karoo Basin, South Africa". Palaeogeography, Palaeoclimatology, Palaeoecology. 396: 99–118.
doi:
10.1016/j.palaeo.2014.01.002.
ISSN0031-0182.
^Viglietti, Pia A.; Smith, Roger M.H.; Rubidge, Bruce S. (2018-02-01). "Changing palaeoenvironments and tetrapod populations in the Daptocephalus Assemblage Zone (Karoo Basin, South Africa) indicate early onset of the Permo-Triassic mass extinction". Journal of African Earth Sciences. 138: 102–111.
Bibcode:
2018JAfES.138..102V.
doi:
10.1016/j.jafrearsci.2017.11.010.
ISSN1464-343X.
^Botha-Brink, Jennifer; Huttenlocker, Adam K.; Modesto, Sean P. (2013-09-21), "Vertebrate Paleontology of Nooitgedacht 68: A Lystrosaurus maccaigi-Rich Permo-Triassic Boundary Locality in South Africa", Early Evolutionary History of the Synapsida, Vertebrate Paleobiology and Paleoanthropology, Springer Netherlands, pp. 289–304,
doi:
10.1007/978-94-007-6841-3_17,
ISBN9789400768406
^BOTHA, JENNIFER; SMITH, ROGER M. H. (2007-04-08). "Lystrosaurus species composition across the Permo-Triassic boundary in the Karoo Basin of South Africa". Lethaia. 40 (2): 125–137.
doi:
10.1111/j.1502-3931.2007.00011.x.
ISSN0024-1164.
^Viglietti, Pia A.; Smith, Roger M.H.; Compton, John S. (2013-12-15). "Origin and palaeoenvironmental significance of Lystrosaurus bonebeds in the earliest Triassic Karoo Basin, South Africa". Palaeogeography, Palaeoclimatology, Palaeoecology. 392: 9–21.
Bibcode:
2013PPP...392....9V.
doi:
10.1016/j.palaeo.2013.08.015.
ISSN0031-0182.
^Smith, Roger M.H.; Botha-Brink, Jennifer (2014-02-15). "Anatomy of a mass extinction: Sedimentological and taphonomic evidence for drought-induced die-offs at the Permo-Triassic boundary in the main Karoo Basin, South Africa". Palaeogeography, Palaeoclimatology, Palaeoecology. 396: 99–118.
doi:
10.1016/j.palaeo.2014.01.002.
ISSN0031-0182.
^Hammer, W. R.; Cosgriff, J. W. (1981). "Myosaurus gracilis, an Anomodont Reptile from the Lower Triassic of Antarctica and South Africa". Journal of Paleontology. 55 (2): 410–424.
JSTOR1304227.
^Smith, Roger; Botha, Jennifer (2005-09-01). "The recovery of terrestrial vertebrate diversity in the South African Karoo Basin after the end-Permian extinction". Comptes Rendus Palevol. 4 (6–7): 623–636.
doi:
10.1016/j.crpv.2005.07.005.
ISSN1631-0683.