Cool-water shell bed taphofacies from Miocene-Pliocene shelf sequences in New Zealand: utility of taphofacies in sequence stratigraphic analysis

Abstract

An investigation of the taphonomy, palaeoecology and stratigraphy of cool-water skeletal concentrations (shell beds) of the Matemateaonga Formation (Late Miocene-Early Pliocene) of Wanganui Basin, New Zealand, has provided the basis for the classification of taphofacies presented here. Two taphofacies described from transgressive systems tracts include the amalgamated shell bed and sediment starved shell bed taphofacies, representing skeletal concentration dominated by wave and current agitation, and sediment starvation, respectively. A further five taphofacies described from highstand and regressive systems tracts exhibit a gradient of sedimentological, taphonomic and palaeoecological properties that result from variation in storm event and fair-weather wave processes across the palaeoshelf bathymetric gradient. A principal components analysis of semi-quantitative data (53 observations) from sequences in Manutahi-1 well core demonstrates that taphonomic properties may be limited to particular systems tracts in some cases, but can also be repeated in different system tracts where the depositional environments are similar. Taphofacies, which are contained within siliciclastic-dominated portions of sequences (highstand and regressive systems tracts) possess little direct relevance to sequence stratigraphic analyses, but do provide valuable information on environmental conditions, in particular, depth relative to storm and fair-weather wave base, and proximity to shoreline.

Decomposing Lithification Bias: Preservation of Local Diversity Structure in Recently Cemented Storm-Beach Carbonate Sands, San Salvador Island, Bahamas

“…This may result from the intrinsic differences in (1) the diagenetic pathways between carbonate and siliciclastic rocks, (2) hydrogeological and climatic circumstances, or simply from (3) longer diagenetic history of older Cenozoic rocks affected by diverse postdepositional processes. In either case, the degree of diagenetic alteration seems to be stronger in shell beds sampled by Hendy (2009), often characterized by maceration of aragonitic shell material (Hendy et al, 2006), compared to the levels observed in the present study.…”

Heterozoan carbonates: When, where and why? A synthesis on parameters controlling carbonate production and occurrences

“…Nutrient-enriched, high-energy shelves host bioclastic accumulations the occurrence of which is controlled by seabottom topography and hydrodynamics (e.g. , case studies 52, 53, 92; (Hendy et al, 2006), case study 88). A large array of heterozoan carbonate deposits exists within these highly hydrodynamic settings but modern analogues of such sedimentary processes can be grouped into (i) upwelling systems such as the NW African shelf (case study 121), (ii) localized bioclastic bodies such as sand dunes off the coast of Scotland (case study 114), (iii) shell beds within terrigenous systems such as the Wanganui Shelf (case study 106) and (iv) "shaved shelves" and distal accumulations of the famous Great Australian Bight (case study 126).…”

Neogene molluscs, shallow marine paleoenvironments, and chronostratigraphy of the Guajira Peninsula, Colombia

“…14b). Nevertheless, the regular concentrations of shells, the thickness of shell beds, and evidence of sea-level rise upward through the stratigraphy of these shell beds are more likely the result of reduced sedimentation rate and condensation associated with high-frequency marine transgressions (e.g., Kidwell 1989;Brett 1995;Hendy et al 2006;Brett et al 2011).…”