High resolution sequence biostratigraphy: examples from the Gulf of Mexico Plio-Pleistocene

The Hampden Beach section is a well-exposed and near-complete 256.5 m thick Paleogene succession of moderately to well-exposed claystone, siltstone, and glauconitic sandstone of Moeraki, Kurinui, and Hampden Formations that spans over 20 m.y. from Teurian to Kaiatan Stages (Paleocene to late Eocene). The sequence was deposited on a passive margin at shelf (Moeraki Formation) to deep upper bathyal (Kurinui Formation) and outermost shelf to upper bathyal paleodepths (Hampden Formation). Paleocirculation was restricted to the north, placing the site under a marginally neritic watermass.The lowest 30 m of the section consists of non-calcareous mudstone of upper Moeraki Formation which is dated as Teurian (Paleocene) by an assemblage of long-ranging, agglutinated foraminifers. Kurinui Formation (30-134.8 m) comprises non-calcareous basal greensand overlain by a fining-upwards succession of slightly calcareous siltstone and claystone. The formation spans the Waipawan, Mangaorapan, and Heretaungan Stages (early to early middle Eocene). The first occurrence of Elphidium hampdenense at 59.7 m marks the base of the Heretaungan Stage. Hampden Formation (134.8-256.5 m) consists of a moderately calcareous basal greensand, grading up into a calcareous siltstone. Hampden Formation contains the Bortonian boundary stratotype which overlies an incomplete or very condensed Porangan interval within the basal greensand, as defined by the presence of the key index species Elphidium saginatum. Bortonian strata are identified by the first appearance of Globigerinatheka index 0.7 m above the base of the formation. The Bortonian/Kaiatan boundary is identified 5.5 m below the top of the section (at 251.0 m) by the highest occurrence of Acarinina primitiva. Revised age control on Acarinina primitiva implies that the top of the Bortonian Stage may be lowered by 2 m.y. to 39 Ma, which represents a significant reduction in the duration of the Bortonian and a tripling in the duration of the Kaiatan Stage-from 1 to 3 m.y. Other abundant microfossils in the section provide scope for further integrated biostratigraphy.

Section: Sedimentary Cyclesmentioning

confidence: 98%

Late Paleocene to middle Eocene foraminiferal biostratigraphy of the Hampden Beach section, eastern South Island, New Zealand

Morgans

2009

“…7, 8E, H). McGowran & Li (1993, 1996 and Li & McGowran (1994) considered that this group of upper water, spinose globigerinids was commonly associated with cool, nutrientrich water in the neritic Early Miocene sequence in southeastern Australia. In their scenario, cool episodes associated with proximity to the Subtropical Convergence would be marked by increases in Globigerina bulloides, while Globigerina woodi group declined.…”

Section: Nannofossilsmentioning

confidence: 99%

“…9) is the strong spike between 9.5 and 23.1 m (Z14/f297-298). In sequence stratigraphy, such specimen spikes are used to indicate sediment starvation and the presence of condensed sections (Armentrout 1996). Low sediment flux is regarded as a primary cause of the specimen spike c. 9.5-23.1 m but not as the sole factor.…”

Section: Datum (Lad) Chiasmolithus Altus)mentioning

confidence: 99%

Integrated stratigraphy of the lower Altonian (Early Miocene) sequence at Tangakaka Stream, East Cape, New Zealand

Morgans

Scott

Edwards

et al. 2002

The biostratigraphy of a rapidly deposited, deep bathyal, lower Altonian (Early Miocene) sequence through Whakai Formation, East Cape, is presented. We interpret the depositional milieu, identify and describe foraminiferal and nannofossil bioevents potentially useful in biostratigraphy, and relate these to the magnetostratigraphy, 40 Ar/ 39 Ar ages, and ages using the Sr isotope sea-water curve. Although lower and upper contacts of the 623 m section through Whakai Formation are obscured, a high (c. 0.9 m/ka) flux of muddy sediment has produced an amplified record of most of the lower Altonian Globorotalia incognita Zone and the base of the overlying Globorotalia zealandica Zone. No significant breaks were identified. Benthic foraminiferal paleodepth proxies suggest that the site was on the lower slope (>1000 m) throughout, but the moderate abundance of planktonic taxa shows that it was not in fully oceanic water. Planktonic assemblages identify warm-temperate water masses. Abundance data for both nannofossils and planktonic G00062;

“…Maximum flooding surfaces separating transgressive systems tract and highstand systems tract sequence units can be characterised by microfossil abundance and diversity peaks (Armentrout 1996;Mancini & Tew 1997) which, given stable biotic productivity, reflect decreases in sediment flux at highstands. At Bluecliffs there is a well-defined series of foraminiferal abundance peaks (Fig.…”

Section: Sedimentary Cyclesmentioning

confidence: 99%

Integrated stratigraphy of the Waitakian‐Otaian Stage boundary stratotype, Early Miocene, New Zealand

Morgans¹,

Edwards²,

Scott³

et al. 1999

The base of the type section of the Otaian Stage at Bluecliffs, South Canterbury, is recognised as the stratotype for the boundary between the Waitakian and Otaian Stages. Principal problems with the boundary are the restriction of existing bioevent proxies to shelf and upper slope environments and its uncertain age. These topics are addressed by a multidisplinary study of a 125 m section about the boundary, which examines its lithostratigraphy, depositional setting, biostratigraphy, correlation, and geochronology.The lower siltstone lithofacies (0-38.5 m) was deposited at upper bathyal depths (200-600 m) in a marginal basin which was partially sheltered from fully oceanic circulation by a submarine high and islands. The site was covered by cool-temperate water and was probably adjacent to the Subtropical Convergence. This unit is succeeded by the banded lithofacies (38.5-106 m) and the upper siltstone lithofacies (basal 19 m studied). Paleodepth probably declined up-sequence, but deposition at shelf depths is not definitely indicated. A cyclic pattern of abundance spikes in benthic and planktonic foraminifera commences 9 m above base and extends to 73 m in the banded lithofacies. Oxygen isotope excursions (up to 2.08%o) in Euuvigerina miozea and Cibicides novozelandicus are greatest within the interval containing the abundance spikes. The stage boundary occurs in the banded lithofacies at the highest abundance spike (73 m). Although condensed intervals might affect the completeness of the section, they are not associated with sedimentary discontinuities, and we consider that the section is suitable as a biostratigraphic reference.Spores, pollens, dinoflagellates, calcareous nannofossils, foraminifera, bryozoans, and ostracods are preserved near the boundary, but molluscs principally occur higher, in the shallower upper siltstone lithofacies. Siliceous microfossils are rare. There is considerable scope for further biostratigraphic research.The primary event marking the boundary at 73 m is the appearance of the benthic foraminifer Ehrenbergina marwicki. This is a distinctive and widely distributed event but is restricted to shelf and upper bathyal environments. Supplementary events in planktonic foraminifera and calcareous nannofossils were researched. Highest occurrences of Globigerina brazieri and G. euapertura are recorded at 47 and 58 m. There is a marked decline in relative abundance of Paragloborotalia spp. at 62 m. Helicosphaera carteri becomes more abundant than H. euphratis between 56 and 87 m. These events are not exact proxies for the boundary but they may usefully indicate proximity to it. They occur in the interval of prominent spikes in foraminiferal abundance.The Waitakian-Otaian boundary is dated at 21.7 Ma by strontium isotopes. Stable primary remanence could not be determined in a pilot paleomagnetic study of Bluecliffs specimens. However, specimens trended towards reversed polarity, and remagnetisation great circle analysis will allow directions to be calculated in future collections.