Shallow-Water Foraminiferal Taphocoenoses at Site 821: Implications for the Pleistocene Evolution of the Central Great Barrier Reef Shelf, Northeast Australia

Abstract

Reworked shallow-water foraminifers that settled on the upper slope of the central Great Barrier Reef at Site 821 (water depth, 212.6 m) were used as indicators of the paleoclimatic and paleoenvironmental conditions that have controlled the Pleistocene evolution of the adjacent platform. Throughout the 400-m-thick sequence drilled, the nature, composition, and distribution of the shallow-water foraminiferal assemblages studied indicate that (1) all the species recorded are at present living in diverse tropical, reef-related areas of the Indo-Pacific and Atlantic provinces; (2) the composition of the microfaunal taphocoenoses is almost identical between the different stratigraphic intervals studied and the modern Great Barrier Reef environments; (3) inner-neritic, tropical environments have continued to develop since the middle Pleistocene; (4) high-to moderate-energy platform edges occurred repeatedly throughout Pleistocene time. These factors may suggest that, since the beginning of the Pleistocene, several reef-like tracts have grown successively on the central area of the northeastern Australian shelf edge. These tracts probably had a sufficiently evolved morphological zonation to act as shelters for foraminiferal biocoenoses of high species diversity.

The initiation of the southern central Great Barrier Reef: New multiproxy data from Pleistocene distal sediments from the Marion Plateau (NE Australia)

“…The simultaneous rise in the proportion of HMC and aragonite versus LMC indicates an increased importance of platform supply, also supported by a higher amount of reefal bioclasts observed in the same core (Cotillon et al, 1994). Scattered reefs already existed throughout the Pleistocene and earlier on the Queensland and Marion Plateaus, and most likely acted as precursors to the modern GBR system (Montaggioni and Venec-Peyre, 1993). However, the large carbonate banks from the Marion Plateau have never recovered from being exposed and subsequently drowned in the middle Miocene and early Pliocene.…”

Revisiting the Quaternary development history of the western New Caledonian shelf system: From ramp to barrier reef

“…By contrast, flattened Amphistegina radiata, large soritids and miliolids are best represented in deeper and quieter environments, along euphotic foreslopes and in lagoonal bottoms. These free-living forms occur as epiphytes or colonizing hard or sandy substrates (Debenay, 1985;Hallock and Glenn, 1986;Hottinger, 1983;Montaggioni, 1981;Montaggioni and Vénec-Peyré, 1993;Reiss and Hottinger, 1984;Renema, 2010;Vénec-Peyré, 1991). They are generally associated with smaller foraminiferal forms, including miliolids, cymbaloporids, rotaliids, elphidiids, nodosariids, among others.…”

“…After disintegration, the relevant fragments are block-shaped or form irregularly surfaced rods. As a result, these have a low buoyancy ability and therefore are not displaced very far from their habitats (Mackenzie et al, 1965;Montaggioni and Vénec-Peyré, 1993). Thus, the biological composition of Facies 1, 2 and 4 appears to be related to both hard and soft substrates and are consistent with deposition at water depths less than 40 m. Their textural characteristics, changing from grainstone to packstone and wackestone, indicate that deposition has occurred in different parts of an open, outer carbonate shelf, exposed to varying water agitation.…”

Nature and biological composition of the New Caledonian outer barrier reef slopes

“…Their aspect in debris and the presence of planktonic and relatively deep benthic (amphisteginids, soritids, nummulitids) foraminifera in sediments indicate that they were probably reworked in relatively deep sediments. In the Mascareignes archipelago, the amphisteginids and soritids range from the surface to 50 m and nummulitids from the surface to 70 m (Montaggioni, 1981;Montaggioni and Venec-Peyré, 1993). …”