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Paleosols of Late Pennsylvanian cyclic strata, New Mexico*
Article first published online: 14 JUN 2006
Volume 35, Issue 5, pages 777–803, October 1988
How to Cite
GOLDSTEIN, ROBERTH. (1988), Paleosols of Late Pennsylvanian cyclic strata, New Mexico. Sedimentology, 35: 777–803. doi: 10.1111/j.1365-3091.1988.tb01251.x
Samples designated with UW1779/X are on repository at the University of Wisconsin-Madison.
- Issue published online: 14 JUN 2006
- Article first published online: 14 JUN 2006
- revision 12 September 1986 revision 15 February 1988
Cyclically deposited siliciclastic and carbonate rocks of the Late Pennsylvanian (Virgilian, Holder Formation) of south-central New Mexico were deposited on a narrow shelf between the Pedernal uplift and the Orogrande basin. In the Dry Canyon area, Sacramento Mountains, shelf-to-basin palaeotopography is indicated by onlapping beds and primary dips. Calcareous alteration zones are developed on the tops of major carbonate units. These detailed studies confirm earlier interpretations that alteration zones represent subaerial exposure events and provide new evidence for and further documentation of a paleosol environment. The paleosols contain: (1) rhizoliths; (2) tangential needle fibres of calcite; (3) five types of alveolar texture; (4) upward oriented ‘ribbon spar’; (5) brownish and clear isopachous spar; (6) blackened grains; (7) random needle fibres of calcite; (8) coated grains; (9) micritized grains; (10) glaebules; (11) desiccation cracks; (12) possible Microcodium; and (13) well-developed laminated crusts. Isopachous cements, upward-oriented cements (which mark the former tops of capillary fringes), dark colour and shallow depth of penetration of rhizoliths (less than 1 m) indicate significant paleosol formation in waterlogged (hydromorphic) and drier conditions. Pennsylvanian palaeohydrogeology of the system is reflected in the type of paleosol alteration.
Paleosols developed on subtidal strata and paleosols which drape tens of metres of palaeotopography indicate cyclic sedimentation was not controlled by delta lobe switching. Local tectonic up and down movement would be an unlikely mechanism to explain the repeated tens of metres of relative sea-level fluctuation. Eustatic sea-level fluctuations, induced by Late Pennsylvanian Gondwana glaciation, probably were of the correct magnitude and frequency to have caused the Holder cycles.