Influence of subsidence on the anatomy of marine siliciclastic sequences and on the distribution of shell and bone beds

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Abstract
Skeletal concentrations are common foci for palaeontological collecting, yet vary widely in their expected levels of taphonomic bias depending on whether they are comparatively simple event-concentrations, more complex accretionary accumulations of either normal or condensed thickness, or residual lags that mark horizons of significant erosional/corrosional truncation of the record (Table 1). These different types and their intermediates also have different potential for use in basin analysis, for example as marker beds, bathymetric indicators, and clues to hiatuses. The stratigraphy and taphonomy of marine siliciclastic sequences from a spectrum of basin types have been examined to determine the extent to which shell and bone beds are linked to physical stratigraphic features such as discontinuity surfaces and transgressive-regressive cycles at various scales, and thus the extent to which physical processes might influence palaeontological data. This series of basin-scale studies has also provided an opportunity to assess the practical utility of skeletal concentrations in reconstructing basin history and to investigate subsidence-related variation both in skeletal accumulation and in the anatomy of siliciclastic sequences. Field studies have been restricted to post-Palaeozoic, primarily Neogene sections in warm temperate to subtropical palaeolatitudes and have focused on marine facies tracts developed in shelf and shallower water depths during phases of ‘coastal onlap’. (Sequence stratigraphic terms are used here to describe physical aspects of the record, and do not imply any particular chronostratigraphic value or genetic, i.e. eustatic, origin.) The results of this work indicate that: (a) skeletal concentrations are distributed fairly systematically within marine sequences, both in