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Bass Rive Site Report; ODP Leg 174X (fwd)



Hi all,
        Thought the part of this report about the
K/T boundary and the evidence for the Chixulub Impact would be of
interest.


Ray McAllister, Prof (Emeritus) Ocean Eng., FAU, Boca Raton, FL 33064
Diving Dinosaur, Geologist/Oceanographer/Ocean Engineer, 44 years SCUBA
mcallist@gate.net (954) 426-0808, Author Diving Locations, Boynton/Dania


---------- Forwarded message ----------
Date: Thu, 30 Jan 1997 17:01:56 CDT
From: Linda_Weatherford@odp.tamu.edu
Reply-To: Ocean Drilling Program Open Discussion List
     <ODP-L@TAMVM1.TAMU.EDU>
To: Multiple recipients of list ODP-L <ODP-L@TAMVM1.TAMU.EDU>
Subject: Bass Rive Site Report; ODP Leg 174X

The following is a summary of the latest borehole in the New
Jersey Coastal Plain Drilling Project.  Data from this hole will
complement the data which will be gathered on ODP Leg 174A.
****************************************************************

CRETACEOUS/TERTIARY BOUNDARY
The Bass River borehole recovered a remarkable Cretaceous/
Tertiary (K/T) boundary succession.  We identified a ~6 cm thick
spherule layer overlying the K/T boundary (1260.25 ft; 384.2 m)
resulting from fallout of ballistic ejecta from Chicxulub Crater
in Yucatan, Mexico.  This layer represents extremely rapid
deposition (with settling though the water column of 100 m
beginning at ~10 minutes after impact).  This is the furthest
from the impact that a distinct spherule layer has been
identified (some 2500 km from the crater) and is the first
confirmed non-turbidite spherule bed (i.e., > 1cm) outside the
Gulf of Mexico.  This discovery provides constraints on the
amount and direction of ejecta derived from the impact and the
size and direction of the impactor.  Because the K/T boundary in
NJ is far enough from "ground zero," it allows clear
identification of the K/T boundary and its relationship to the
effects of the impact.

Our initial biostratigraphic studies have confirmed that
deposition was continuous at Bass River across the K/T boundary.
Uppermost Cretaceous strata (calcareous nannofossil Micula
prinsii Zone) are overlain by lowermost Tertiary planktonic
foraminiferal Zone P0 (Fig. 5), indicating that deposition was
continuous on a scale of 10's of thousands of years. Continuous
deposition was interrupted by the abrupt fallout of the ejecta
layer, an abrupt extinction of marine planktonic organisms, and
disappearance of burrowing organisms, indicating a major
environmental disruption.  Overlying the spherule layer at Bass
River is a zone of clay clasts and sparse Tertiary fossils that
may have formed, in part, as a tsunami deposit.