title: Tectonomorphic evolution of Marie Byrd Land - Implications for Cenozoic rifting activity and onset of West Antarctic glaciation

authors: Spiegel, Cornelia

subjects: Science & Technology

abstract: The West Antarctic Rift System is one of the largest continental rifts on Earth. Because it is obscured by the West Antarctic Ice Sheet, its evolution is still poorly understood. Here we present the first low-temperature thermochronology data from eastern Marie Byrd Land, an area that stretches ~ 1000 km along the rift system, in order to shed light on its development. Furthermore, we petrographically analysed glacially transported detritus deposited in the marine realm, offshore Marie Byrd Land, to augment the data available from the limited terrestrial exposures. Our data provide information about the subglacial geology, and the tectonic and morphologic history of the rift system. Dominant lithologies of coastal Marie Byrd Land are igneous rocks that intruded (presumably early Paleozoic) low-grade meta-sedimentary rocks. No evidence was found for un-metamorphosed sedimentary rocks exposed beneath the ice. According to the thermochronology data, rifting occurred in two episodes. The earlier occurred between ~ 100 and 60 Ma and led to widespread tectonic denudation and block faulting over large areas of Marie Byrd Land. The later episode started during the Early Oligocene and was confined to western Pine Island Bay area. This Oligocene tectonic activity may be linked kinematically to previously described rift structures reaching into Bellingshausen Sea and beneath Pine Island Glacier, all assumed to be of Cenozoic age. However, our data provide the first direct evidence for Cenozoic tectonic activity along the rift system outside the Ross Sea area. Furthermore, we tentatively suggest that uplift of the Marie Byrd Land dome only started at ~ 20 Ma; that is, nearly 10 Ma later than previously assumed. The Marie Byrd Land dome is the only extensive part of continental West Antarctica elevated above sea level. Since the formation of a continental ice sheet requires a significant area of emergent land, our data, although only based on few samples, imply that extensive glaciation of this part of West Antarctica may have only started since the early Miocene.

text: Tectonomorphic evolution of Marie Byrd Land - Implications for Cenozoic rifting activity and onset of West Antarctic glaciation The West Antarctic Rift System is one of the largest continental rifts on Earth. Because it is obscured by the West Antarctic Ice Sheet, its evolution is still poorly understood. Here we present the first low-temperature thermochronology data from eastern Marie Byrd Land, an area that stretches ~ 1000 km along the rift system, in order to shed light on its development. Furthermore, we petrographically analysed glacially transported detritus deposited in the marine realm, offshore Marie Byrd Land, to augment the data available from the limited terrestrial exposures. Our data provide information about the subglacial geology, and the tectonic and morphologic history of the rift system. Dominant lithologies of coastal Marie Byrd Land are igneous rocks that intruded (presumably early Paleozoic) low-grade meta-sedimentary rocks. No evidence was found for un-metamorphosed sedimentary rocks exposed beneath the ice. According to the thermochronology data, rifting occurred in two episodes. The earlier occurred between ~ 100 and 60 Ma and led to widespread tectonic denudation and block faulting over large areas of Marie Byrd Land. The later episode started during the Early Oligocene and was confined to western Pine Island Bay area. This Oligocene tectonic activity may be linked kinematically to previously described rift structures reaching into Bellingshausen Sea and beneath Pine Island Glacier, all assumed to be of Cenozoic age. However, our data provide the first direct evidence for Cenozoic tectonic activity along the rift system outside the Ross Sea area. Furthermore, we tentatively suggest that uplift of the Marie Byrd Land dome only started at ~ 20 Ma; that is, nearly 10 Ma later than previously assumed. The Marie Byrd Land dome is the only extensive part of continental West Antarctica elevated above sea level. Since the formation of a continental ice sheet requires a significant area of emergent land, our data, although only based on few samples, imply that extensive glaciation of this part of West Antarctica may have only started since the early Miocene.

year: 2016

title: Flat primes and thin primes

authors: Broughan, Kevin A.

subjects: flat prime

abstract: A number is called upper (lower) flat if its shift by +1 ( −1) is a power of 2 times a squarefree number. If the squarefree number is 1 or a single odd prime then the original number is called upper (lower) thin. Upper flat numbers which are primes arise in the study of multi-perfect numbers. Here we show that the lower or upper flat primes have asymptotic density relative to that of the full set of primes given by twice Artin’s constant, that more than 53% of the primes are both lower and upper flat, and that the series of reciprocals of the lower or the upper thin primes converges.

text: Flat primes and thin primes A number is called upper (lower) flat if its shift by +1 ( −1) is a power of 2 times a squarefree number. If the squarefree number is 1 or a single odd prime then the original number is called upper (lower) thin. Upper flat numbers which are primes arise in the study of multi-perfect numbers. Here we show that the lower or upper flat primes have asymptotic density relative to that of the full set of primes given by twice Artin’s constant, that more than 53% of the primes are both lower and upper flat, and that the series of reciprocals of the lower or the upper thin primes converges.

year: 2010

title: Horowaewae

authors: Maxwell, Te Kahautu

abstract: Horowaewae is dedicated to Horowaewae Maxwell a Te Matatini Lifemember. Horowaewae is from the Rotorua area and the Te Arawa iwi. He is a foundation member of the champion kapa haka Ngāti Rangiwewehi. Horowaewae has been a performer, a male leader, the Te Arawa delegate to the Te Matatini National Committee. He has served kapa haka in its development since the inception of Te Matatini in 1972 and prior to this performing in the tourism industry in Rotorua. Horowaewae was performed by Ōpōtiki Mai Tawhiti at the 2013 Te Matatini World Championship Kapa Haka Competition.

text: Horowaewae Horowaewae is dedicated to Horowaewae Maxwell a Te Matatini Lifemember. Horowaewae is from the Rotorua area and the Te Arawa iwi. He is a foundation member of the champion kapa haka Ngāti Rangiwewehi. Horowaewae has been a performer, a male leader, the Te Arawa delegate to the Te Matatini National Committee. He has served kapa haka in its development since the inception of Te Matatini in 1972 and prior to this performing in the tourism industry in Rotorua. Horowaewae was performed by Ōpōtiki Mai Tawhiti at the 2013 Te Matatini World Championship Kapa Haka Competition.

year: 2012-09-13