Post-glacial sea-level control and sequence stratigraphy of carbonate–terrigenous sediments, Wanganui shelf, New Zealand

Gillespie, Jeanette L.; Nelson, Campbell S.; Nodder, Scott D.

doi:10.1016/s0037-0738(98)00109-2

Cited by 18 publications

(7 citation statements)

References 36 publications

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“…Step 1: Attritional Accumulation in Freshwater Aquatic Basins.-First, with regard to pond/ lake microfossil bonebeds, data are consistent with the in situ accumulation of skeletal debris via attritional mortality in long-lived aquatic ecosystems characterized by relative ly low rates of net sedimentation. Ground truth for this attritional mode of accumulation comes from marine records, where hiatal concentrations of shell debris and vertebrate hardparts are documented (e.g., Sykes 1977;Kidwell 1993;Macquaker 1994;Brett 1995;Abbott 1998;Gillespie et al 1998;Kondo et al 1998;Conkin et al 1999;Turner et al 2001;Allulee and Holland 2005;Irmis et al 2007;Pyenson et al 2009). In marine settings, the supply of skeletal debris generated during hiatus apparently counteracts the negative aspects of delayed permanent burial.…”

Section: Revised Model For Microfossil Bonebedsmentioning

confidence: 99%

Origins of microfossil bonebeds: insights from the Upper Cretaceous Judith River Formation of north-central Montana

Rogers¹,

Brady²

2010

Paleobiology

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Microfossil bonebeds are multi-individual accumulations of disarticulated and dissociated vertebrate hardparts dominated by elements in the millimeter to centimeter size range (≤75% of bioclasts ≤5 cm maximum dimension). Modes of accumulation are often difficult to decipher from reports in the literature, although predatory (scatological) and fluvial/hydraulic origins are typically proposed. We studied the sedimentology and taphonomy of 27 microfossil bonebeds in the Campanian Judith River Formation of Montana in order to reconstruct formative histories. Sixteen of the bonebeds examined are hosted by fine-grained facies that accumulated in low-energy aquatic settings (pond/lake microfossil bonebeds). Eleven of the bonebeds are embedded in sandstones that accumulated in ancient fluvial settings (channel-hosted microfossil bonebeds). In lieu of invoking separate pathways to accumulation based on facies distinctions, we present a model that links the accumulation of bioclasts in the two facies. We propose that vertebrate material initially accumulates to fossiliferous levels in ponds/lakes and is later reworked and redeposited as channel-hosted assemblages. This interpretation is grounded in reasonable expectations of lacustrine and fluvial depositional systems and supported by taphonomic data. Moreover, it is consistent with faunal data that indicate that channel-hosted assemblages and pond/lake assemblages are similar with regard to presence/absence and rank-order abundance of taxa.This revised model of bonebed formation has significant implications for studies of vertebrate paleoecology that hinge on analyses of faunal data recovered from vertebrate microfossil assemblages. Pond/lake microfossil bonebeds in the Judith River record are preserved in situ at the scale of the local paleoenvironment, with no indication of postmortem transport into or out of the life habitat. Moreover, they are time-averaged samples of their source communities, which increases the likelihood of capturing both ecologically abundant species and more rare or transient members of the paleocommunity. These attributes make pond/lake microfossil bonebeds excellent targets for paleoecological studies that seek to reconstruct overall community membership and structure. In contrast, channel-hosted microfossil bonebeds in the Judith River record are out of place from a paleoenvironmental perspective because they are reworked from preexisting pond/lake assemblages and redeposited in younger channel facies. However, despite a history of exhumation and redeposition, channel-hosted microfossil bonebeds are preserved in relatively close spatial proximity to original source beds. This taphonomic reconstruction is counter to the commonly held view that microfossil bonebeds are biased samples that have experienced long-distance transport and significant hydrodynamic sorting.

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Section: Revised Model For Microfossil Bonebedsmentioning

confidence: 99%

Origins of microfossil bonebeds: insights from the Upper Cretaceous Judith River Formation of north-central Montana

Rogers¹,

Brady²

2010

Paleobiology

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“…6C) that are each characterised by basal obliqueparallel and chaotic reflections infilling smooth channels (facies F1). On such a shallow depositional platform as the Wanganui shelf (e.g., Nodder, 1995;Gillespie et al, 1998), these channel-fill deposits are interpreted as the remnants of lateral accretion bedding, infilling fluvial or estuarine channels (e.g., Lericolais et al, 2001;Proust et al, 2001b). These deposits are overlain by thin to transparent, fairly continuous, sub-parallel reflections (F2) that complete the infilling and drape the channel incisions.…”

Section: Seismic Unitmentioning

confidence: 99%

Sedimentary architecture of a Plio-Pleistocene proto-back-arc basin: Wanganui Basin, New Zealand

Proust

Lamarche

Nodder

et al. 2005

Sedimentary Geology

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“…To the west of the nearshore wedge, the uppermost semiopaque layer above reflector B becomes progressively buried (up to 15 ms deep) and more transparent in character (Figure 5b). This layer overlies buried sand ridges on the inner continental shelf, which are opaque units with a smoothly undulating, strong reflector at their upper surface [e.g., Gillespie et al , 1998].…”

Section: Resultsmentioning

confidence: 99%

Characterizing earthquake recurrence parameters for offshore faults in the low‐strain, compressional Kapiti‐Manawatu Fault System, New Zealand

et al. 2007

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[1] Seafloor fault scarps and near-surface deformation of late Quaternary seismic reflectors occur along the eastern margin of the Wanganui Basin, 200 km behind the active Hikurangi subduction front, southern North Island, New Zealand. The offshore scarps are associated with the low-strain, compressional Kapiti-Manawatu Fault System (KMFS), which comprises high-angle (>60°) reactivated reverse and normal faults oriented NE-SW, highly oblique to the coast. Seafloor scarps range from <10 to 50 km in length with vertical seafloor offsets of 2 to 30 m. The longest structure is the Mascarin Fault, with maximum late Quaternary vertical slip rates of 3 mm a À1 (where a is years). Other faults in the KMFS have typical rates of <1 mm a À1 , comparable to long-term estimates. Three zones of recent deformation are identified: faults in the north and south of the KMFS are characterized by high scarps (>10 m high) and moderate to long fault seafloor rupture lengths, and those in central parts of the fault system are characterized by low scarps (<5 m high), variable slip rates, and short to moderate fault lengths. Empirical equations indicate that KMFS faults may generate earthquakes with moment magnitudes (M w ) of 5.7-7.5 (mean 6.9 ± 0.3, ±1 standard deviation, for sources with M w ! 6.5). Estimated recurrence intervals that are generally >10,000 a, suggest that the seismic hazard of the Kapiti-Manawatu region is relatively low. Incorporation of these new geological data, however, is likely to increase slightly the expected seismic hazard in southern North Island. The method of determining the earthquake recurrence parameters of offshore faults has potentially wider applications elsewhere.

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Post-glacial sea-level control and sequence stratigraphy of carbonate–terrigenous sediments, Wanganui shelf, New Zealand

Cited by 18 publications

References 36 publications

Origins of microfossil bonebeds: insights from the Upper Cretaceous Judith River Formation of north-central Montana

Origins of microfossil bonebeds: insights from the Upper Cretaceous Judith River Formation of north-central Montana

Sedimentary architecture of a Plio-Pleistocene proto-back-arc basin: Wanganui Basin, New Zealand

Characterizing earthquake recurrence parameters for offshore faults in the low‐strain, compressional Kapiti‐Manawatu Fault System, New Zealand

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