Physical Sciences and Mathematics Commons^™

Early Lake Ontogeny Following Neoglacial Ice Recession At Glacier Bay, Alaska, Daniel R. Engstrom, Sherilyn C. Fritz

Department of Earth and Atmospheric Sciences: Faculty Publications

This study explores the environmental forces controlling lake ontogeny at Glacier Bay as a model for early Holocene lake evolution in north temperate lakes worldwide. Long-term chemical and biological changes in lakes are investigated with two complementary research strategies: (1) limnological conditions are compared among 32 lakes of known age and in different stages of primary catchment succession and (2) sediment cores from these same lakes are analyzed stratigraphically for fossil diatoms to ascertain developmental trends in pH, alkalinity, algal composition, and trophic status at individual sites.

Trends in water chemistry inferred from the chronosequence approach include a progressive loss …

Calcareous Nannofossil Biostratigraphy From Leg 101, Northern Bahamas, David K. Watkins, Joost W. Verbeek

Department of Earth and Atmospheric Sciences: Faculty Publications

Leg 101 of the Ocean Drilling Program drilled 19 holes at 11 sites to investigate the geology of the Straits of Florida and the northern Bahamas. Drilling at Site 626 indicated that the Gulf Stream has had significant flow through the Straits of Florida for at least the last 24 million years. Winnowed, foraminiferal grainstones and packstones with sparse nannofossil assemblages and the reworking of older nannofossils suggest strong bottom-current activity throughout this interval. Drilling north of Little Bahama Bank and in Exuma Sound documents the growth of platform slopes during the late Cenozoic. Nannofossil biostratigraphy of the upper Cenozoic …

Pliocene-Pleistocene Variations In Aragonite Content And Planktonic Oxygen-Isotope Record In Bahamian Periplatform Ooze, Hole 633a, André W. Droxler, Christopher H. Bruce, William W. Sager, David K. Watkins

Department of Earth and Atmospheric Sciences: Faculty Publications

Hole 633A was drilled in the southern part of Exuma Sound on the toe-of-slope of the southeastern part of Great Bahama Bank during ODP Leg 101. The top 55 m, collected as a suite of six approximately 9.5-m-long hydraulic piston cores, represents a Pliocene-Pleistocene sequence of periplatform carbonate ooze, a mixture of pelagic calcite (foraminifer and coccolith tests), some pelagic aragonite (pteropod tests), and bank-derived fine aragonite and magnesian calcite. A 1.6-m.y.-long hiatus was identified at 43.75 mbsf using calcareous nannofossil biostratigraphy and magnetostratigraphy.

The 43.75-m-thick periplatform sequence above the hiatus is a complete late Pliocene-Quaternary record of the past …

Oligocene Calcareous-Nannofossil Biostratigraphy From Leg 101, Site 628, Little Bahama Bank Slope, Michael J. Moran, David K. Watkins

Department of Earth and Atmospheric Sciences: Faculty Publications

Drilling at Hole 628A, Leg 101 of the Ocean Drilling Program, recovered a thick, relatively complete Oligocene section of nannofossil-foraminifer chalk and ooze. Sediments from Cores 101-628A-16H through 101-628A-29X were examined using the light microscope to provide information about biostratigraphy of calcareous nannofossils. Several authors noted a problem in distinguishing the first appearance of species within the Sphenolithus predistentus-S. ciperoensis lineage of the mid-Oligocene, particularly Sphenolithus ciperoensis, because of the gradual evolution of its members. Successful separation of species in this lineage is critical for accurately dating relative age of mid- and upper-Oligocene nannofossil sediments. Length and taper of …

Paleontological Results From Ocean Drilling Program Leg 101, David K. Watkins, Eric Fourcade, R. Mark Leckie, Allan J. Melillo, Amanda A. Palmer, Joost W. Verbeek, Jacques Butterlin, Renée Damotte, Claude Guernet, Edwige Masure, Michael J. Moran

Department of Earth and Atmospheric Sciences: Faculty Publications

Leg 101 of the Ocean Drilling Program recovered Albian through Holocene sediments from a variety of carbonate depositional environments. Data from four microplanktonic groups (calcareous nannofossils, planktonic foraminifers, radiolarians, and dinoflagellates) and four benthic groups (larger foraminifers, smaller benthic foraminifers, ostracodes, and sponge spicules) yield a biostratigraphic and paleoecologic framework for these varied sediments. Winnowed, skeletal-planktonic foraminiferal packstones and grainstones from the central Straits of Florida (Site 626) reflect a late Oligocene to Holocene history of sporadic sedimentation greatly influenced by strong bottom-current activity. Neogene to Quaternary sediments from two carbonate-slope transects (Sites 627 to 633) indicate significant slope accretion …

Leg 101--An Overview, James A. Austin Jr., Wolfgang Schlager, Amanda A. Palmer, Paul A. Comet, André Droxler, Gregor Eberli, Eric Fourcade, Raymond Freeman-Lynde, Craig S. Fulthorpe, Gill Harwood, Gerhard Kuhn, Dawn Lavoie, Mark Leckie, Allan J. Melillo, Arthur Moore, Henry T. Mullins, Christian Ravenne, William W. Sager, Peter Swart, Joost W. Verbeek, David K. Watkins, Colin Williams

Department of Earth and Atmospheric Sciences: Faculty Publications

During Leg 101, the inaugural leg of the Ocean Drilling Program, the JOIDES Resolution drilled 19 holes at 11 sites in the Bahamas. Grids of high-resolution seismic profiles provided information crucial for both site selection and regional stratigraphic interpretations. The first major scientific objective was to understand the long-term evolution of the bank-and-basin pattern that currently characterizes the Bahamas archipelago. Drilling and seismic surveys have indicated considerable platform expansion and retreat rather than stationary upward growth. Upbuilding in the Late Jurassic-Early Cretaceous was followed by drowning and retreat in the mid-Cretaceous and by renewed expansion in the Cenozoic. At Site …

10. Evidence For Continuous And Discontinuous Alteration In Dsdp Hole 418a Basalts And Its Significance To Natural Gamma-Ray Log Readings, Mary Anne Holmes

Department of Earth and Atmospheric Sciences: Faculty Publications

During Ocean Drilling Program Leg 102, the Schlumberger natural gamma-ray spectrometry tool measured high potassium levels in one interval of DSDP Hole 418A basalts. Samples from that hole were examined by X-ray diffraction, SEM, and EDS analyses in order to identify mineral species responsible for the high readings. The results indicate that high K readings observed on wireline logs run in basement can be attributed to extensive low-temperature oxidative alteration resulting in formation of palagonite and K-rich clays (celadonite, potassic nontronite, and mixed-layer celadonite/ nontronite). Where these readings are accompanied by high porosity, low density, and low velocity readings, a …