Aptian, Early

Fig. 9.8 Stratigraphic presentation of 813C values for organic material extracted from the Arundal clay formation, Maryland. Error bars reflect the standard deviation for three replicate analyses. The dashed line represents the boundary between the early and middle Aptian eras ( 125 to 112 megayears BP) established from the geological record. The gray arrow highlights the isotope shift of interest (Reprinted from Jahren, A. H. et al., Earth Planet. Sci. Lett. 236, 691, (2005), Copyright 2005, with permission from Elsevier)...

Bralower T. J., Sliter W. V., Arthur T. J., Lekie R. M., Allard D. J., and Schlanger S. O. (1993) Dysoxic/anoxic events in the Aptian-Albian (Early Cretaceous). In The Mesozoic Pacific Geology, Tectonics, and Volcanism, American Geophysical Union Monograph 77 (eds. M. S. Pringle, W. W. Sager, W. V. Sliter, and S. Stein), pp. 5-37. 

Cooper basin sediments consist of glaciofluvial, fluvio-lacustrine and deltaic elastics (Fig. 2) (Bat-tersby, 1976 Thornton, 1979). The Jurassic section of the Eromanga basin sequence was deposited in an intercratonic basin sag, and is made up of non-marine elastics deposited under fluvial, deltaic and lacustrine conditions. The Early Cretaceous Murta Member to Cadna-Owie Formation (Fig. 2) show deposition changing from lacustrine to marine, with marine conditions prevailing from the Aptian until the Upper Albian, when a return to paralic and fluvio-lacustrine conditions is indicated (Senior et al., 1978 Armstrong Barr, 1986). 

Dumitrescu, M. and Brassell, S.C., 2005. Biogeochemical assessment of sources of organic matter and paleoproductivity during the Early Aptian Oceanic Anoxic Event at Shatsky Rise, ODP Leg 198. Org. Geochem., 36 1002-1022. 

Towards the end of the early Cretaceous, two more subfamilies branched off the main tetrarhynchiine stem the Albian to Maastrichtian Viarhynchiinae (subsphaerical, uniplicate, densely costate, with crura transitional between canaliform and raduliform) and the Aptian to Maastrichtian Cretirhynchiinae (dorsibiconvex, finely and densely costellate, with subrectangular uniplication and distally concave raduliform crura). 

A Boreal brachiopod fauna of five species was found in Okutadami, central Japan Ammonaria sp., Kochiproductus sp., Yakovlevia sp., Spiriferella sp. and Attenuatella sp., indicating a late Middle Permian (Midian) age. The Okutadami fauna is the first documented Permian Boreal brachiopod fauna in Japan. The occurrence of the Boreal brachiopod fauna from Okutadami suggests that the fossil-bearing rocks were formed at the northernmost part of Japan in the Middle Permian, and afterwards moved relatively to the central part by the large-scale left-lateral strike-slip faulting in Cretaceous, probably late Early Cretaceous (Aptian-Albian), time. 

The split between Magnolia and the two monocot taxa (node 32) was constrained at 123 myr. Magnohales (stem group Winteraceae) and monocots are both documented from the Late Barremian or Early Aptian (Doyle, 2(X)0, Friis, 2004). 

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