Sedimentology and lithostratigraphy of Upper Eocene sponge‐rich sediments, southern Western Australia

Abstract

Late Eocene time in the Bremer and western Eucla Basins of southern Western Australia was a period of terrigenous clastic and abundant, unusual, biosiliceous sponge sedimentation. The Pallinup Formation (revised) consists of five units; 1 and 2 are basal sandstones, 3 and 4 are variably spiculitic mudstones, whilst the uppermost unit is spiculite and spongolite, and formalised as the Fitzgerald Member (new). The Pallinup Formation, plus coeval spiculites in palaeovalleys and carbonates in the western Eucla Basin, accumulated during one large-scale, transgressive-regressive relative sea-level cycle. Drowned, low-gradient rivers supplied mud but little sand. Instead, sand was locally sourced via transgressive shoreface erosion of deeply weathered regolith. Regression terminated shoreface erosion, eliminated the sand source, and resulted in a river-supplied, clay-dominated shallow-marine depositional system. The unit 2-3 sandstone-mudstone transition, which would normally be interpreted as transgressive drowning, is in this case the result of regressive cessation of sand supply. The peak relative sea-level (highstand) horizon thus lies within unit 2 sandstones, a facies that would usually be considered wholly transgressive, and no highstand systems tract was deposited. The maximum flooding and downlap surfaces are the same horizon and cap the transgressive systems tract. They formed coincidentally or subsequent to peak relative sea-level, but prior to initiation of unit 3 mudstone deposition. Upper unit 2 plus unit 3 represent a condensed section systems tract, and unit 4 plus the Fitzgerald Member comprise a regressive systems tract.

Cenozoic uplift of south Western Australia as constrained by river profiles

“…2 and 3). We calibrated m and vo using the deposition age (~33.5--36.5 Ma) and present--day elevation range (100--250 m) of the Upper Eocene shallow--marine deposits of the Pallinup and Princess Royal Spongolite Formation (Gammon et al, 2000). This geological constraint implies that the cumulative uplift for the Young, Phillips, and Gardiner rivers should be between 100 and 250 m since ~36.5--33.5 Ma (white box in Fig.…”

Mixed carbonate–siliciclastic sequence stratigraphy of a Paleogene transition zone continental shelf, southeastern USA

“…This warming culminated in the short-lived (2 my) Paleocene-Eocene thermal maximum. This event is associated with a widespread global extinction in both the marine and terrestrial realms, turnover from thermohaline to stenohaline ocean circulation, and a global negative 13 C isotope shift at the Paleocene/ Eocene boundary, perhaps triggered by dissociation of methane hydrates or increased tropical weathering (Zachos et al, 1994;Berggren et al, 1998;Bralower et al, 2002;Gammon et al, 2000). By the end of the Paleocene, the Supersequence 1 inner-shelf break had prograded up to 15 km seaward of the preceding uppermost Cretaceous terminal inner-shelf break, indicating sedimentation well in excess of accommodation on the shelf.…”

A new species and a new record of endobenthic Clavagellidae (Bivalvia: Anomalodesmata: Clavagelloidea) from the Oligocene and Miocene of New Zealand

“…They joined southern endemic species to form a distinctive blended fauna (Darragh & Kendrick 1980, 2000 such as is found today in the Pallinup Formation of south-western Western Australia. The Pallinup Formation of the Bremer Basin (Gammon et al 2000) was deposited on the shallow, inner continental shelf (Darragh & Kendrick 1980) and the cooccurrence here of S. pallinupensis and in the Wharekuri Greensands of southern New Zealand suggests a similar shallow-water habitat. With the Oligocene, there was a general decline in South Pacific sea temperatures (Shackleton & Kennett 1975) and opening of the Drake Passage facilitating the circum-Antarctic circulation in the Southern Ocean (Beu et al 1997).…”